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Global Vision International, Seychelles - Mahé Report Series No. 124
ISSN 1751-2255 (Print)
GVI Seychelles – Mahé
Marine Conservation Expedition
July - December 2012
GVI Seychelles – Mahé / Marine Conservation Expedition Report July - December
2012
Submitted in whole to
Global Vision International
Seychelles National Parks Authority (SNPA)
Produced by
Lee Cassidy – Science Coordinator
Sam Howlett – Science Coordinator
And
Rowana Walton Expedition Leader Christophe Mason-Parker Country Director
Elizabeth Harris Expedition Staff Emily Allen Dive Instructor
Joe Daniels Expedition Staff Grace Frank Science Coordinator
Emily Shelton Scholar Kate Downes Expedition Staff
Chris Petchey Scholar Elizabeth Martin Scholar
Thank you also to our hardworking volunteers for the collection of all data;
Sage Roberts, Afnan Kumosani, Johanna Sollenberg, Michael Pollard, Rebecka Porse Shalin, Kate
Poss, Christopher Sharwood, Mai Al-Marzoogi, Sophie May, Sarah Meek, Russell Keen, Christin
Staerz, Daniel Walker, Thae Saatvedt Brekke, Suzanne Schoales, Carmen Kowarik, Pieter Van
Altena, Stewart Clarke, Leah Andrews, Faris Radwan, Noa Homolka, Paolina d’Avack, Laura
Halbach, Anita Futterer, Nadia Aswani, Melainie Cordes, Zainab Saigol, Amer Alseiari, Lizzie
Southall, Derry Tanzil, Katie Leggett, Sara Stekla, Samantha Gough, Naomi Trepanier, Cody
Thomason, Mina Janeska, Sheena Weller,, Samuel Koolman, Carl Brown-Kenyon, Joe Lander, Kim
Seymour, Clara Graefin Von Luckner, Jessica, Hehir, Johannes Renz, Lara Thompson, Thomas
Ellis, Eva Paulus, Steph Gardner, Laetitia, Brun, Roya Allemann, Hunter Ring, Laura Rickwood,
Manuel Spescha, Lucy Stratton, Lina Lundberg, Paul Mancuso, Katy Kelsoe, Laura Boggeln, Finbarr
O’Mahony, Lina Kehlenbeck, Nick Taylor, Juliette Delacroix, Troy Gallant, Guido Staubesand,
Sandra Haessig & Lance Williams.
GVI Seychelles – Mahé / Marine Conservation Expedition
Address: GVI c/o SNPA, PO Box 1240, Victoria, Mahé, Seychelles
Email: [email protected] Web page: http://www.gvi.co.uk and http://www.gviusa.com
Abstract
2
This report summaries all data collected during the July to December 2012 survey period of
coral reef monitoring; at all 24 survey sites across the North West Mahé coastline. Surveys
were conducted to analyse the rate of Scleractinian coral recruitment, density of both reef
and commercial fish species and the abundance of key mobile invertebrate species.
Coral recruitment monitoring found that the mean recruit density to be 15.3 recruits per m2
(SE ± 0.35), finding 40 coral genera from 14 family groups. Significantly, pre 2011, it was
thought that the density of coral recruits had stabilised at around 12 – 14 recruits per m2
however the changes seen for 2011/2012 shows that recruit density has continued to
increase. Family density changes were focused on for this report and noted that once data
had been normalised, to account for number of genus in each family, the Poritidae family
found highest relative abundance from 2005. However if the percentage composition of the
total recruit density is analysed, which can indicate overall recruitment rates, the
Acroporidae family has increased from 10.2% in 2005 up to 18.5% in 2012; whereas the
Poritidae family has fallen from 32.9% in 2005 to 28.0% in 2012. Indicating that if current
trends persist the Acroporidae family could become the dominant family group in future
recruitment surveys.
Monitoring of the reef and commercial fish densities through the survey program shows
continuation of trends seen in recent years. Whereas overall density had remained
relatively stable, diversity has increased across most sites by an average of 6.38 (±1.65
SE) from 2012. The most significant trend in the feeding guild analysis is the increase in the
coralivore and corallivore/invertivore fish species. This is a primary indicator of the
continued recovery of the structure and overall diversity of the reefs. Monitoring of the
Marine Protected Areas (MPAs) continued this year again showing higher densities within
these protected areas with both the reef and commercial fish species, highlighting again the
need to maintain correct management of these critical areas.
Invertebrate density surveys show the Short-spine (Echinothrix sp.) and long-spine
(Diadema sp.) urchins are dominating. Substrate type analysis shows that density of short
spine urchins is decreasing; but at a very slow rate, on both substrates yet long spines are
stable. Density of the coralivorous Drupella snail has continued to increase but still remains
at levels which cannot inflict significant damage to the reefs overall.
3
Contents
1. Introduction......................................................................................................................8
1.1. Survey Sites...........................................................................................................10
2. Aims...............................................................................................................................11
2.1. Species Lists..........................................................................................................12
2.1.1. Coral...............................................................................................................12
2.1.2. Fish.................................................................................................................12
2.1.3. Invertebrates...................................................................................................13
2.2. Training..................................................................................................................13
2.2.1. Dive / Science Training...................................................................................13
2.2.2. Survey Methodology.......................................................................................13
3. Methodology..................................................................................................................14
3.1. Coral......................................................................................................................14
3.1.1 Coral Recruitment Quadrat.............................................................................14
3.2. Fish........................................................................................................................14
3.2.1 Stationary Point Count....................................................................................14
3.2.2 50m Belt Transects.........................................................................................15
3.3. Invertebrates..........................................................................................................16
3.3.1 50m Belt Transect..........................................................................................16
3.4. Environmental Parameters....................................................................................17
4. Results...........................................................................................................................18
4.1. Surveys Completed...............................................................................................18
4.2. Coral Recruitment Surveys....................................................................................18
4.2.1. Scleractinian Coral Recruitment Density........................................................18
4.2.2. Coral Recruit Size Class Comparison............................................................20
4.2.3. Coral Recruitment; Granitic versus Carbonate Substrate Composition.........21
4.2.4. Coral Recruitment; Deep versus Shallow Zonation........................................22
4.2.5. Coral Family Density and Diversity.................................................................23
4.3. Fish Density Surveys.............................................................................................26
4
4.3.1. Mean Commercial and Reef Fish Species Density........................................26
4.3.2. Combined Fish Density 2005 – 2012.............................................................26
4.3.3. Fish Densities with regards to Feeding Guilds...............................................28
4.3.4. Influence of Marine Protected Areas on Fish Densities 2005 – 2012............29
4.3.5. Fish Species Diversity....................................................................................30
4.3.6. Commercial Fish Sizing Results.....................................................................32
4.4. Invertebrate Densities............................................................................................33
4.5. Sea Cucumber Densities.......................................................................................35
5. Discussion.....................................................................................................................36
5.1. Coral Recruitment Surveys....................................................................................36
5.2. Fish Surveys..........................................................................................................37
5.3. Invertebrate surveys..............................................................................................41
6. Additional Ecosystem Monitoring..................................................................................42
6.1. Turtles....................................................................................................................42
6.1.1. Incidental Turtle Sightings..............................................................................42
6.1.2. Beach Patrols for Nesting Turtles...................................................................44
6.1.3. In-water Surveys of Turtle Behaviour.............................................................44
6.1.4. Photo Identification of Turtles.........................................................................46
6.2. Crown of Thorns....................................................................................................47
6.3. Cetacean Sightings................................................................................................47
6.4. Whale Shark Sightings..........................................................................................47
6.5. Plankton Sampling.................................................................................................48
7. Non-survey Programmes...............................................................................................49
7.1 Extra Programmes.................................................................................................49
7.1.1 Internships......................................................................................................49
7.2 Community Development......................................................................................49
7.2.1 International School Seychelles (ISS)............................................................49
7.2.2 GVI Charitable Trust.......................................................................................49
7.2.3 National Scholarship Programme...................................................................50
5
8. References....................................................................................................................51
9. Appendices....................................................................................................................53
Appendix A. Details of sites surveyed by GVI Seychelles – Mahé, year round. Sites in
bold-type text are located within Marine Protected Areas................................................53
Appendix B. Scleractinian coral genera surveyed by GVI Seychelles - Mahé..............54
Appendix C. Fish families, genera and species surveyed by GVI Seychelles - Mahé.....55
Appendix D. Fish feeding guilds analysed by GVI Seychelles – Mahé............................58
Appendix E. Fish species lists divided into commercial and reef species analysed by GVI
Seychelles – Mahé...........................................................................................................59
Appendix F. List of invertebrate species surveyed on 50m belt transects by GVI
Seychelles – Mahé...........................................................................................................60
Figures List
FIGURE 1.1. LOCATION AND SUBSTRATE TYPE OF GVI SURVEY SITES...............................................................11
FIGURE 3.3.1. LAYOUT OF CORAL RECRUITMENT SURVEYS AT EACH SURVEY SITE, WHERE THE SHORELINE IS
REPRESENTED BY THE TOP OF THE FIGURE AND THE DISTANCE FROM SHORE INDICATES INCREASING
DEPTH.......................................................................................................................................................16
FIGURE 3.3.2. LAYOUT OF FISH SPC AND BELTS, AND 50M INVERTEBRATE TRANSECTS AT EACH SURVEY SITE,
WHERE THE SHORELINE IS REPRESENTED BY THE TOP OF THE FIGURE AND THE DISTANCE FROM SHORE
INDICATES INCREASING DEPTH................................................................................................................17
FIGURE 4.2.1. MEAN CORAL RECRUITMENT DENSITY ACROSS ALL SITES FOR EACH SURVEY PERIOD FROM
2002 – 2012..............................................................................................................................................19
FIGURE 4.2.3. A COMPARISON OF THE MEAN RECRUITMENT DENSITY PER M2 OF SCLERACTINIAN CORALS
FOUND ON GRANITIC VERSUS CARBONATE SITES ACROSS NORTH-WEST MAHÉ, 2005 – 2012...............21
FIGURE 4.2.4. MEAN CORAL RECRUITMENT DENSITY PER M2 ON DEEP AND SHALLOW DEPTH RANGES ACROSS
ALL SURVEY SITES OF NORTH-WEST MAHÉ, 2005 – 2012.........................................................................22
FIGURE 4.2.5. RECORDED MEAN CORAL RECRUITMENT DENSITIES PER M2 OF SCLERACTINIAN FAMILIES
ACROSS ALL SURVEY SITES OF NORTH-WEST MAHÉ, 2005 – 2012)..........................................................23
FIGURE 4.2.6. NORMALISED RELATIVE ABUNDANCE OF CORAL RECRUITMENT DENSITIES FOUND PER M2 OF
SCLERACTINIAN FAMILIES ACROSS ALL SURVEY SITES OF NORTH-WEST MAHÉ, 2005 – 2012 (DATA
NORMALISED TO ACCOUNT FOR NUMBER OF GENUS WITHIN EACH FAMILY)........................................24
FIGURE 4.2.7. NORMALISED RELATIVE ABUNDANCE OF CORAL RECRUITMENT PER M2 OF THE 5 MOST
ABUNDANT SCLERACTINIAN FAMILIES ACROSS ALL SURVEY SITES OF NORTH-WEST MAHÉ, 2005 – 2012
(DATA NORMALISED TO ACCOUNT FOR NUMBER OF GENUS WITHIN EACH FAMILY).............................24
6
FIGURE 4.2.8. PERCENTAGE COMPOSITION OF RECRUIT FAMILIES OF THE RELATIVE ABUNDANCE ACROSS ALL
SURVEY SITES OF NORTH-WEST MAHÉ, 2005 – 2012 (DATA NORMALISED TO ACCOUNT FOR NUMBER
OF GENUS WITHIN EACH FAMILY)............................................................................................................25
FIGURE 4.3.1. MEAN DENSITY PER M² OF ALL SURVEYED FISH SPECIES ACROSS ALL SURVEY SITES, 2005 -
2012.........................................................................................................................................................27
FIGURE 4.3.2. A COMPARISON OF MEAN DENSITY PER M² OF ALL SURVEYED FISH SPECIES BETWEEN
CARBONATE AND GRANITIC SUBSTRATE SITES, 2005 - 2012....................................................................27
FIGURE 4.3.3. COMPARISON OF FISH FEEDING GUILDS THROUGH DENSITY PER M² ACROSS ALL SITES, 2005 -
2012.........................................................................................................................................................28
FIGURE 4.3.4. COMPARISON OF FEEDING GUILDS THROUGH DENSITY PER M² ACROSS ALL SITES, 2005 –
2012, DISREGARDING HERBIVORES..........................................................................................................29
FIGURE 4.3.5. OVERALL MEAN DENSITY PER M OF FISH INSIDE AND OUTSIDE MARINE PROTECTED AREAS,
NOV-DEC 2005 TO JULY-DEC 2012...........................................................................................................29
FIGURE 4.3.6. MEAN DENSITY OF FISH PER M² ON CARBONATE SUBSTRATE SITES INSIDE AND OUTSIDE
MARINE PROTECTED AREAS, NOV-DEC 2005 TO JULY-DEC 2012.............................................................30
FIGURE 4.3.7. MEAN DENSITY OF FISH PER M ON GRANITIC SUBSTRATE SITES INSIDE AND OUTSIDE MARINE
PROTECTED AREAS, NOV-DEC 2005 TO JULY-DEC 2012...........................................................................30
FIGURE 4.3.8. SPECIES-RICHNESS (NUMBER OF FISH SPECIES FOUND) ACROSS ALL SURVEY SITES ALONG NW
MAHÉ, 2012. GREEN DENOTES SITES WITHIN MARINE PROTECTED AREAS AND BLUE DENOTES NON-
PROTECTED SITES.....................................................................................................................................31
FIGURE 4.3.9. A COMPARISON OF SPECIES-RICHNESS (NUMBER OF FISH SPECIES) BETWEEN THE SAME SITES
OF NW MAHÉ IN 2005 AND IN 2012.........................................................................................................32
FIGURE 4.4.1. MEAN DENSITY PER M2 OF ALL SURVEYED INVERTEBRATE SPECIES ACROSS NORTH-WEST
MAHÉ, JULY – DECEMBER 2012................................................................................................................33
FIGURE 4.4.2. A COMPARISON OF THE MEAN DENSITY PER M2 OF SHORT SPINE (ECHINOTHRIX SPP.) AND
LONG SPINE (DIADEMA SPP.) URCHINS ON GRANITIC VERSUS CARBONATE SUBSTRATE ALONG NORTH-
WEST MAHÉ, 2009 TO 2012.....................................................................................................................34
FIGURE 4.4.3. MEAN DENSITY PER M2 OF CUSHION SEASTAR (CULCITA SPP.), CROWN OF THORNS
(ACANTHASTER PLANCI) AND THE GASTROPODS DRUPELLA SPP.............................................................34
FIGURE 4.4.4. MEAN NUMBER OF SEA CUCUMBERS RECORDED PER SITE FROM 2006 -2012..........................35
FIGURE 4.4.5. DENSITY PER M2 OF INDIVIDUAL SEA CUCUMBER SPECIES ACROSS ALL SURVEY SITES OF
NORTH-WEST MAHÉ, 2008 – 2012...........................................................................................................35
7
1. Introduction
Global Vision International (GVI) Seychelles comprises of two expeditions based on the
granitic inner islands of Seychelles. One on Mahé, the largest and most heavily populated
island in the Seychelles group, located at the Cap Ternay Research Centre in Baie Ternay
National Park and one on Curieuse Island within the Curieuse National Marine Park,
located north of Praslin. The marine parks at which both GVI bases are located are
controlled and managed by the Seychelles National Parks Authority (SNPA). All of GVI’s
scientific work in the Seychelles is carried out on behalf of our local partners and at their
request, using their methodology; GVI supplies experienced staff, trained volunteers and
equipment to conduct research in support of their on-going work. GVI’s key partner is the
conservation and research section of the SNPA. Additional local partners include the
Marine Conservation Society Seychelles (MCSS) and the Seychelles Fishing Authority
(SFA).
Seychelles National Parks Authority (SNPA): A local organisation partly funded by the
government, encompassing the conservation and research section and the Marine Parks
Authority (MPA). These organisations have the respective aims of carrying out marine
research in the Seychelles along with managing and protecting the marine parks. The
coral and fish monitoring carried out for the SNPA constitutes the majority of the work
conducted by the volunteers.
Marine Conservation Society Seychelles (MCSS) is a local non-governmental organisation
(NGO) that carries out environmental research in the Seychelles, currently monitoring
whale sharks, cetaceans and turtles around Mahé. GVI assists with all three of these
research programmes by documenting the presence or absence of turtles on every dive
throughout the phase, conducting in-water turtle behaviour survey dives and also turtle
nesting surveys. Along with the turtle work GVI reports incidental sightings of cetaceans
and whale sharks and undertakes weekly plankton sampling to aid with year round
monitoring of plankton levels in conjunction with the arrival of whale sharks to Mahé Island.
Seychelles Fishing Authority (SFA) is the governing body which oversees the management
and regulation of commercial and artisanal fisheries in the Seychelles. This government
agency is directly concerned with setting the catch, bag and seasonal limits that apply to
local stocks on an annual basis, as well as managing the international export industry that
is generated from the harvest of fisheries across the Seychelles Exclusive Economic Zone
(EEZ).
8
In 1998, a worldwide coral bleaching event decimated much of the coral surrounding the
inner granitic islands of the Seychelles, with hard coral mortality reaching 95% in some
areas (Spencer et al. 2000). It is thought that this was caused by the high ocean
temperatures associated with an El Nino Southern Oscillation event at that time. Efforts to
monitor the regeneration of reefs in the Seychelles were initiated as part of the Shoals of
Capricorn, a three year programme started in 1998 and funded by the Royal Geographic
Society in conjunction with the Royal Society. The Conservation and Research section of
the SNPA was set up by the Shoals of Capricorn in an effort to ensure continuation of the
work started, as well as to assist the Marine Parks Authority (MPA) with the management of
the existing marine parks. The predominant objective for the Seychelles GVI expedition is
to aid this monitoring programme and thereby assist in the construction of management
plans that will benefit the future recovery of coral reefs in the area.
Between 2000 and the beginning of the GVI expedition in 2004 the Seychelles marine
ecosystem management program (SEYMEMP) took place, this was the most
comprehensive assessment of the coral reefs within the inner islands of the Seychelles to
date. Eighty one carbonate and granitic reef sites throughout the inner islands were
monitored using fine scale monitoring techniques. Monitoring efforts were continued by
Reefcare International, a non-governmental organisation based in Australia. The protocols
established by Reefcare International provided a foundation for those adopted by GVI.
Although GVI’s logistical constraints restrict monitoring efforts to the north-west coast of
Mahé at sites selected by SNPA.
The survey data collected by GVI volunteers allows for analysis of trends in coral reef
health seen over the past 14 years of monitoring. Along with this core research GVI
Seychelles also endeavours to aid in any of the other projects undertaken by all their
partners where it can; as it is hoped that with this help they will be able to increase their
capacity to monitor, manage and ultimately conserve the marine environment of the
Seychelles for the future.
The GVI expedition comprises of survey programs that are four, eight or twelve weeks long,
running continuously throughout the year from January - December. Within the 12 months
fish and invertebrates are surveyed continuously at all survey sites in set time periods. Line
Intercept Transects and Coral Diversity transects are undertaken in the first 6 months to
evaluate coral coverage and site diversity, and Coral Recruitment monitoring is conducted
within the second 6 months to survey newly recruited colonies and gain a picture of site
recovery.
9
Health and Safety: The safety of all volunteers is paramount. All volunteers are given a
health and safety brief upon arrival and conservative diving guidelines are adhered to for
the duration of the expedition. In addition, volunteers complete the PADI Emergency First
Response first aid course, and are taught how to administer oxygen in the event of a diving
related incident.
1.1. Survey Sites
GVI surveys a maximum of 24 separate sites across the north-west coastline of Mahé (Fig
1.1.). The 24 sites are surveyed twice a year; once in the first 6 months and then again in
the second half of the year. All sites are now listed as ‘core sites’ (see Appendix A for site
details). The sites are evenly divided between carbonate and granitic reefs and they
represent varying degrees of exposure to wave action and currents. Six of the sites are
within Marine Protected Areas (MPAs) where restrictions on all fishing as well as
regulations on the recreational use of the park are in place.
Figure 1.1. Location and Substrate Type of GVI Survey Sites.
10
Each survey site is divided into ‘shallow’ and ‘deep’ zones, where the shallow zone is
defined by the depth range 1.5– 5.0m and the deep zone is defined by the depth range
5.1– 15.0m. Each site has a central point, marked by a distinctive landmark on the
coastline, and is further divided into left, centre and right areas (Fig 3.3.1.). These areas are
loosely defined as such by their position with respect to the centre marker of the site. All
depths are standardised with respect to tidal chart datum so as to eliminate tidal influence.
2. Aims
The focus of July to December 2012 was on surveying commercial and reef fish species as
well as hard coral coverage around North-West Mahé. The specific aims of the phase were;
Assess diversity and density of fish species across all survey sites
Estimate size of commercially important fish species
Assessing the rate of hard coral recruitment
Monitor coral predation and algal grazing pressures through density estimates of
hard coral predators, sea urchins
Assess abundance and diversity of commercially targeted invertebrate species
including sea cucumbers, lobster and octopus
2.1. Species Lists
2.1.1. Coral
The list of surveyed scleractinian corals covers 50 separate genera (See Appendix B for
the complete species list). Corals are identified to genus level only as in situ identification
beyond genus level is not possible in the case of some corals, and is also beyond the
requirements of the project aims. Volunteers are also encouraged to record the genus as
‘unknown’ if they are not able to confidently identify a coral beyond the family level, and
similarly to record ‘unknown hard coral’ where even the family is not determinable with a
level of confidence.
2.1.2. Fish
The fish species chosen for surveys are those that are likely to indicate status of the reefs
along with fishing pressure, but are not overly difficult to locate, identify and count as
specified by SCMRT. For example, Surgeonfish are herbivores and grazers and thus would
influence the algal – coral dynamics within the reef ecosystem. Reef-associated species of
commercial concern are also surveyed. This data can be used to help determine the status
11
of the reefs and of the fisheries especially when compared with the data from previous
phases.
Fish are surveyed to the highest taxonomic resolution practicable, with most identified to
species level. The resolution depends on difficulty of identification, and also the species’
characteristics and the data requirements of our partners. The taxonomic level needed
varies according to the ecological function of the species within the ecosystem; for
example, if different species within a genus feed on different types of food, it is highly
desirable to distinguish them to species. However, volunteers are instructed to record only
to the level to which they are confident of the identification, thus if they are sure of the
family but not genus or species, they record only as an “unknown species” of that family.
See Appendix B for the list and taxonomic resolution of fish species surveyed.
2.1.3. Invertebrates
Invertebrate species which influence and can indicate the health and conditions of coral
reefs are surveyed, along with commercially viable species which are targeted by the local
fishing industry. A full list of surveyed invertebrate species is included in Appendix E.
2.2. Training
2.2.1. Dive / Science Training
All volunteers must be at least PADI Open Water qualified to join the expedition.
Volunteers then receive the PADI Advanced Open Water course covering Boat, Peak
Performance Buoyancy, Navigation, Underwater Naturalist, and Deep dives. Particular
attention is paid to buoyancy as surveys are conducted in water as shallow as two metres
and over delicate reef ecosystems.
Volunteers are required to learn either hard coral, fish species or invertebrate identification.
Training is initially provided in the form of presentations, workshops and informal discussion
with the expedition staff. Self-study materials are also available in the form of electronic
and hard copy flashcards, as well as Indian Ocean identification publications. Knowledge
is tested using pictures on land, for which a 95% pass mark is required. Volunteers are
taken on identification dives with staff members for in-water testing; their responses are
recorded and the dives continue until the volunteer has demonstrated accurate
identification of all necessary species/genera.
2.2.2. Survey Methodology
12
Volunteers receive on land briefings and lectures, navigation practice and in-water training
in the skills required to conduct reef surveys. Participants complete the PADI Coral Reef
Research Diver (CRRD) course, which is specifically developed for GVI and offered in only
one other marine expedition in the world, Mexico. All are trained in the use of a delayed
surface marker buoy and tape reels, plus any other survey equipment specific to the
research they will be conducting. The course also includes a series of lectures on various
aspects of the marine environment. Before completing any Underwater Visual Census
(UVC) independently, volunteers participate in practice UVCs in which they are taught and
supervised by a member of staff.
Improvements to the quality of species identification training materials are an ongoing and
extremely important component to this marine expedition. Photographs taken locally of
species underwater are the best materials to use – they are accurate and portray how the
organism appears underwater. New electronic and hardcopy flashcards are produced to
enhance the self-study materials available and to develop the exams by the same means.
Volunteers are encouraged to donate their underwater pictures to add to the library.
3. Methodology
3.1. Coral
1.1.1 Coral Recruitment Quadrat
Reef regeneration around north-west Mahé was investigated by counting and identifying to
genus level recently recruited scleractinian corals within the survey sites. Recent 'recruits'
were defined as any coral smaller than 5cm in height and diameter, and then further
divided into two size classes of 0- 2cm and 2.1- 5cm. 1m2 quadrats were used to define the
area within which the recruits were to be counted. At each site, the coral recruits in a
minimum of fifteen shallow and fifteen deep quadrats were identified to genus and counted.
To ensure even coverage of the reef, quadrats were divided equally between the left,
centre and right areas of each site (Fig 3.3.1). To ensure random placement of the quadrats
the diver descends to a section of reef within the target depth and area, then swims for five
fin-kick cycles in any direction and drops the quadrat from a height of 1m above the
substrate, the quadrat will settle on an area of the reef not specifically selected by the diver.
13
3.2. Fish
1.1.2 Stationary Point Count
The stationary point count is a commonly used UVC technique (Kulbicki 1998, Engelhardt
2004) employed by well-respected reef assessment programs such as the Atlantic and Gulf
Rapid Reef Assessment (AGGRA) and the Florida Keys National Marine Sanctuary Coral
Reef Monitoring Program (FKNMS CRMP) (Hill & Wilkinson 2004). Variations of the method
have been used as part of several studies in the Seychelles (Jennings et al. 1995; Spalding &
Jarvis 2002; Engelhardt 2004; Graham et al. 2007) where the lack of spear fishing increases the
reliability of this technique (Jennings et al. 1995). The post-bleaching surveys conducted by
Reefcare International as part of the Seychelles Marine Ecosystem Management Project
(SEYMEMP) used 7 minute long stationary point counts and defined the area for the point
count with a 7m radius (Engelhardt 2001; 2004); 7– 7.5m radius circle has been shown to
create an area of the most suitable size for the size groups into which coral reef fish
typically fall (Samoilys & Gribble 1997). When GVI assumed responsibility for the
continuation of this assessment in 2005, the same methodology was adopted.
At each site eight stationary point counts were carried out. Four stationary point counts
were done in each of the shallow and deep zones, two centre, one left and one on the right
(Fig. 3.3.2.). Divers recorded depth at the centre of each point count and start time for each
survey. A tape measure was used to delineate the circle radius, laid in any direction along
the reef. This allows for visual reference for the census boundary, increasing accuracy for
density calculations. Point counts were conducted by buddy pairs of divers where each was
responsible for counting a different selection of surveyed fish, thus reducing the number of
fish one person is required to count. During the last minute both divers swam around the
circle to attempt to ensure that more cryptic fish were counted.
1.1.3 50m Belt Transects
Colvocoresses and Acosta (2007) reported that Belt Transect surveys can cover more area
with a similar observer effort than Point Count surveys, although behavioural avoidance of
fish towards divers was frequently noted and, possibly as a result, lower densities of fish
have been recorded on Belt Transects than on Point Counts. We decided to introduce Belt
Transects in addition to the Stationary Point Counts, but to incorporate mechanisms to
reduce behavioural avoidance. Variety in methodologies also has the advantages of adding
to the skills set of the Expedition Members and enhancing their experience.
The transect belts were 50m long by 5m wide, a standard area often used for reef
assessments (Samoilys & Gribble 1997; Hill & Wilkinson 2004). Surveys were conducted by
14
buddy pairs with each diver responsible for counting a different selection of fish. Four belt
transects were completed at each site, 2 in the deep zone and 2 in the shallow (Fig. 3.3.2.).
A measuring tape was laid parallel to the shoreline on the reef by one diver while the other
swims in front counting fish. Samoilys and Gribble (1997) recommend this technique of
simultaneously counting fish and laying the transect tape as it avoids disturbing the fish
prior to counting. After completion of the outward stage of the transect, the observers
hover away from the end of the tape for 3 minutes to allow fish to return to the survey area
before beginning the return leg. On the return journey, the second diver swims back along
the tape counting the other fish while the buddy reels in the tape behind them.
3.3. Invertebrates
1.1.4 50m Belt Transect
Extent of hard coral predation was measured as the density of two types of sea star;
cushion stars (Culcita spp.) and Crown of Thorns (Acanthaster planci), and gastropods in
the genus Drupella at each survey site, all of which are hard coral predators. Algal grazing
pressure was measured as the density of sea urchins. Two 50m transects were laid out at
each site, using polyprophelene reel tape measures. The transects start at the shallow
centre point and head out at opposing 45˚ angles towards the deep zone, thus covering the
whole depth range of 1.5– 15.0m and the spread of the site (Fig 3.3.1.)Target species within
2.5m either side of the tape were recorded (see Appendix F).
15
Coral recruitment density quadrat Invertebrate diversity belt
Stationary point countFish belt transectInvertebrate belt
Figure 3.3.1. Layout of coral recruitment surveys at each survey site, where the shoreline is represented by the top
of the figure and the distance from shore indicates increasing depth.
3.4. Environmental Parameters
During each survey dive the boat captain records abiotic factors pertaining to the
environmental conditions during the dive.
16
B A
Figure 3.3.2. Layout of fish SPC and belts, and 50m invertebrate transects at each survey site, where the shoreline is
represented by the top of the figure and the distance from shore indicates increasing depth.
Turbidity is recorded using a Secchi disk
Cloud cover is estimated in eighths
Sea state is evaluated using the Beaufort scale, a copy of which is kept on the boat
Surface and bottom sea temperatures are recorded using personal dive computers
17
4. Results
4.1. Surveys Completed
During July to December 2012 coral reef monitoring was completed across survey sites
along the North - West coast of Mahé. The surveys conducted monitored hard coral
recruitment, reef and commercial fish densities and mobile invertebrate densities. All
surveys were successfully completed across the 24 survey sites with the exception of one
invertebrate survey at Conception Central East Face. Bad weather conditions prevented
the final invertebrate survey being completed. At each site all stationary point counts, fish
belts, coral recruitment quads and invertebrate belt transect were completed; except for the
missing invertebrate belts at Conception Central East Face. This created a total of 192
SPCs, 96 fish belts (53,556m²), 861 coral recruitment quadrats (861m2) and 46 invertebrate
density belts (11,500m²) across the 24 completed sites.
In addition to the core surveys, in-water behavioural turtle surveys were conducted weekly
as well as turtle nesting surveys. Data was also collected on incidental sightings of mega-
fauna including turtles, cetaceans, sharks, rays and invertebrates of commercial
importance.
4.2. Coral Recruitment Surveys
4.2.1. Scleractinian Coral Recruitment Density
Overall mean Scleractinian coral recruitment density across all sites in the October to
December 2012 was 15.3 recruits per m2 (SE ± 0.35), finding 40 coral genera from 14
family groups. The dominant families at all sites were Faviidae, Poritidae and Acroporidae.
Highest recruit density was found at survey site 18. Lilot North Face with 26.69 per m2 with
lowest density at 10. Baie Ternay North West with 8.00 per m2; showing a high range in the
mean density of 18.69 per m2.
Diversity analysis showed that overall 10 individual genera were present at all 24 survey
sites and site specific analysis showed a maximum diversity of 28 genera from 13 families
found at 13B. Anse Major Point. 12A. Anse Major Reef came out with lowest diversity of 19
genera within 10 families.
18
Engelhardt 2002
Aug-Sept 05
Jan-Mar 06
July-Sept 06
Jan-Mar 07
July-Sept 07
Jan-Mar 08
July-Sept 08
Jan-Mar 09
Oct-Dec 09
Oct-Dec 10
Oct-Dec 11
Jul-Dec 12
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
18.0M
ea
n R
ecr
uit
De
nsi
ty (
m-2
±S
E)
Figure 4.2.1. Mean coral recruitment density across all sites for each survey period from 2002 – 2012.
Figure 4.2.1. shows mean coral recruitment density has decreased slightly since 2011 by
0.24 recruits per m2, 2011 still remains the density maxima for the whole monitoring
program. Previous to 2011 it was thought that the density of coral recruits had stabilised at
around 12 – 14 recruits per m2 however the change seen for 2011/2012 shows that overall
recruit density is continuing to increase. Results from 2012 show a significant increase in
density since the initial recruitment survey carried out in 2002 (Engelhardt 2004), from 7.47
recruits per m2 up to 15.3 recruits per m2 respectively. It is important to note that the 2002
survey covered a larger area than currently surveyed by GVI; a total of 1600m2 in 2002
compared to the current total area of 861m2. Also the extra area covered during the 2002
survey was on the eastern side of Mahé island (Engelhardt 2004) where the coral
abundance is lower than sites surveyed by GVI; this would affect direct comparisons made
to this data set. It is included in this report as a reference to early coral recruitment data
taken after the 1998 bleaching event.
19
4.2.2. Coral Recruit Size Class Comparison
Aug-Sept 05
Jan-Mar 0
6
July-Sept 06
Jan-Mar 0
7
July-Sept 07
Jan-Mar 0
8
July-Sept 08
Jan-Mar 0
9
Oct-Dec 09
Oct-Dec 10
Oct-Dec 11
Jul-Dec 12
0.0
2.0
4.0
6.0
8.0
10.0
12.0
0 - 2 cm
2 - 5 cm
Me
an
Re
cru
it D
en
sity (
m-2
± S
E)
Figure 4.1.2. Mean coral recruitment density per m2 for 0 -2 and 2 – 5 size classes on all survey sites across north-
west Mahé, 2005 – 2012.
Surveyed coral recruits are divided into two size classes, 0-2 cm and 2-5 cm, with respect
to both height and diameter; 0-2cm size category representing the most recently settled
coral juveniles to the reef. Results from 2012 found density of the recruits in the 2-5cm size
class (9.57 per m2) to be higher than density of the 0-2cm size class (5.96 per m2); this
trend is seen since surveys began in 2005.
The 2 – 5cm recruit density has continued to increase in 2012 reaching its current maxima
for the program. This is opposed to the 0 – 2cm recruit density which has decreased this
year to a similar density to that which was found in 2010. The separation between small
and large recruits has returned to similar values to that found previously in the program
(Fig. 4.2.2).
20
4.2.3. Coral Recruitment; Granitic versus Carbonate Substrate Composition
Engelhardt 2002
Aug-Sept 05
Jan-Mar 06
July-Sept 06
Jan-Mar 07
July-Sept 07
Jan-Mar 08
July-Sept 08
Jan-Mar 09
Oct-Dec 09
Oct-Dec 10
Oct-Dec 11
Jul-Dec 12
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
18.0
20.0
Granitic
Carbonate
Me
an
Re
cru
it D
en
sity
(m
-2 ±
SE
)
Figure 4.2.3. A comparison of the mean recruitment density per m2 of scleractinian corals found on granitic versus
carbonate sites across north-west Mahé, 2005 – 2012
Results of recruitment density divided by substrate type showed that on carbonate reefs a
mean of 13.24 per m2 (SE± 0.05) was found and on granitic sites recruitment was higher at
17.05 per m2 (SE ± 0.48). This trend of higher recruitment density has been seen on granitic
sites since the survey period began, with the exception of 2010 (Fig. 4.2.3.).
This year’s results show a decrease in the density on both substrate types however the
decrease is more pronounced on the granitic substrate which dropped by 0.44 recruits per
m2; compared to the decrease on carbonate of only 0.12 recruits per m2. However these
decreases only result in a minor change in overall density.
21
4.2.4. Coral Recruitment; Deep versus Shallow Zonation
Aug-Sept 05
Jan-Mar 06
July-Sept 06
Jan-Mar 07
July-Sept 07
Jan-Mar 08
July-Sept 08
Jan-Mar 09
Oct-Dec 09
Oct-Dec 10
Oct-Dec 11
Jul-Dec 12
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
DeepShal-low
Me
an
Re
cru
it D
en
sity
(m
-2 ±
SE
)
Figure 4.2.4. Mean Coral recruitment density per m2 on deep and shallow depth ranges across all survey sites of
north-west Mahé, 2005 – 2012.
Depth specific recruitment densities at each of the sites for the current survey 2012 are
14.18 per m2 (SE ± 0.47) for the shallow surveys (1.5 – 5.0m) and 16.41 per m2 (SE ±0.52)
for the deep surveys (5.1 – 15m plus CD). Shallow surveys again show lower mean
densities than that of the deep ranges; a pattern confirmed by all depth comparisons from
this survey's history. Since 2010 recruitment has steadily increased within the shallow
depth range opposed to the significant fluctuation seen in the deep range which reached its
maximum density found in 2011 and subsequently decreased in the results from 2012 (Fig.
4.2.4.).
22
4.2.5. Coral Family Density and Diversity
Favii
dae
Poritidae
Acroporid
ae
Pocilloporid
ae
Agaric
iidae
Sider
astre
idae
Fungii
dae
Mussi
dae
Astroco
eniid
ae
Oculin
idae
Pectiniid
ae
Mer
ulinidae
Euphyll
idae
Dendro
phylliid
ae
Unidentified
0.0
1.0
2.0
3.0
4.0
5.0
6.02005
2006
2007
2008
2009
2010
2011
2012Mea
n Co
ral R
ecru
it D
ensi
ty (m
2)
Figure 4.2.5. Recorded mean coral recruitment densities per m2 of scleractinian families across all survey sites of
north-west Mahé, 2005 – 2012).
Recorded densities of coral recruits when focusing on the comparison between families
show the same three groups dominating the abundance levels in previous surveys years
from 2008. Faviidae remain at the highest density at 5.44 per m2 this dominance has been
maintained throughout the survey program. The second most dominant coral family,
Poritidae, with recruit density of 3.40 per m2 and finally the Acroporidae family found a
density of 2.24 per m2 for 2012. These three coral families have remained dominant since
2008 when the Acroporidae family increased in density above the Pocilloporidae family and
has remained so from that year. All other family groups show relatively stable density levels
consistently lower than the top three.
This type of analysis however does not account for the number of coral genus within each
family. For example the Faviidae family consists of 12 individual coral genus; this would
naturally give a higher density result as within each 1m2 quadrat there is a higher chance of
finding Faviidae genus as the genus are more numerous than within the other family
groups i.e. Poritidae and Acroporidae only have 3 genus within each family.
The following analysis of family abundance has been normalised; wherein total density is
divided by number of genus within the family, to give a more accurate representation of
changes in the overall abundance by negating the difference in genus number between
each family. Density units have been converted to relative abundance per m2 to give a
visual representation of coral family density changes with time.
23
Poritidae
Acroporid
ae
Favii
dae
Astroco
eniid
ae
Pocilloporid
ae
Oculin
idae
Agaric
iidae
Dendro
phylliid
ae
Sidera
streid
ae
Fungii
dae
Mussidae
Unidentified
Merulin
idae
Euphyll
idae
Pectiniid
ae0.0
0.5
1.0
2005
2006
2007
2008
2009
2010
2011
2012
Rele
tive
abu
ndan
ce o
f cor
al r
ecru
it fa
mili
es
(nor
mal
ised
)
Figure 4.2.6. Normalised relative abundance of coral recruitment densities found per m2 of scleractinian families
across all survey sites of north-west Mahé, 2005 – 2012 (data normalised to account for number of genus within each
family).
Figure 4.2.6. shows that once the number of genus within the family is accounted for the
Poritidae family becomes the most abundant, this is constant throughout the survey
program. The second most abundant family is Acroporidae which has remained at this level
since 2008 when the abundance increased above the following families. The next three
families Faviidae, Astroceoniidae and Pocilloporidae have obtained similar abundance
levels for 2012.
2005 2006 2007 2008 2009 2010 2011 20120
0.5
1
Poritidae
Acroporidae
Astrocoeniidae
Faviidae
Pocilloporidae
Re
leti
ve a
bu
nd
ance
of
cora
l fam
ilie
s (n
orm
alis
ed
) p
er
m2
Figure 4.2.7. Normalised relative abundance of coral recruitment per m2 of the 5 most abundant scleractinian families
across all survey sites of north-west Mahé, 2005 – 2012 (data normalised to account for number of genus within each
family).
24
Figure 4.2.7. focuses on the 5 most abundant coral families; this shows clearly how the
density of the Acroporidae recruits has increased significantly over the monitoring program.
Increases are seen in the Faviidae, Pocilloporidae and Astroceoniidae families but at a
much slower rate than the other dominant families.
2005 2006 2007 2008 2009 2010 2011 20120%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%Pectiniidae
Euphyllidae
Merulinidae
Unidentified
Mussidae
Fungiidae
Siderastreidae
Dendrophylliidae
Agariciidae
Oculinidae
Pocilloporidae
Faviidae
Astrocoeniidae
Acroporidae
Poritidae
Figure 4.2.8. Percentage composition of recruit families of the relative abundance across all survey sites of north-
west Mahé, 2005 – 2012 (data normalised to account for number of genus within each family).
Figure 4.2.8. shows the percentage composition of recruits, by family, within the total
density recorded for each year across the reefs . This is a better indicator of the recruitment
rate when focused at the family level. Although relative abundance shows a continual
increase in the Poritidae recruits, percentage composition shows that in 2005 Poritidae
represented 32.9% of all the recruits recorded and in 2012 this had fallen to 28.0%. This
indicates that although the density has increased through the monitoring program, the
Poritidae recruits are actually making up a smaller proportion of the total recruits found.
This is opposed to the Acroporidae family which has increased from 10.2% in 2005 up to
18.5% in 2012. This would indicate that the recruitment rate of Acroporidae colonies is
greater than that of the Poritidae family. This is equally seen in the Astrocoeniidae family
were the proportion of recruits has been increasing although at a slower rate. All other
family groups show a stable recruit composition and rate of recruitment.
25
4.3. Fish Density Surveys
4.3.1. Mean Commercial and Reef Fish Species Density
Overall abundance for all surveyed commercial and reef fish species using both point count
and belt methodologies came to 13,346 individuals across a total survey area of 53,556m2,
giving an average fish density of 0.25 individuals per m2. Per specific survey site, the
highest total abundance levels were found at Baie Ternay Centre with 809 individuals (0.36
per m2). The site with second highest overall density was Baie Ternay Lighthouse with 783
individuals (0.35 per m2). The lowest abundance levels were found at Anse Major Reef with
300 individuals (0.13 per m2), and Baie Ternay Reef North West with 339 individuals (0.15
m2).
Baie Ternay Centre, the site with the highest density, is central in location to GVI’s survey
area and is also a Marine Protected Area (MPA). Although liable to high levels of traffic
from both tourist charters and dive boats, the protection from fishing within this site is
arguably the highest compared to all marine protected areas around north-west Mahé. It is
unsurprising then that the two sites with the highest densities are located here. It is
suprising, however, that one of the lowest densities is also found within this MPA. This is
due to the fact that Baie Ternay North West is characterised by extensive rubble substrate
where corals struggle to colonise. Where this section of the Bay may have supported as
diverse coral communities as the rest of the Bay prior to the 1998 bleaching event, the lack
of stable substrate has obviously hindered recovery and the limited presence of corals
subsequently means a less diverse and abundant community of fish.
4.3.2. Combined Fish Density 2005 – 2012
The data used to analyse fish abundance over all sites is taken from the stationary point
count surveys, as the belt transect was only introduced into GVI’s set survey methodology
in 2009. The analysis of all data 2011 has also been modified to adapt to the new surveyed
species list revised in 2009 and 2010, and all pre-existing data from 2005 onwards has
been adapted to represent this. This finally allows for correct interpretation of the feeding
guilds and total fish density across all of the survey years, and hence any relevant
fluctuations in density or predominance of guilds can be accurately seen.
The mean density of fish for July to December 2012 was found to be 0.25 individuals per
m2, similar to the findings from 2011. Minor fluctuations in density are present across all
26
years of surveys, however the density has never been seen to rise or fall outside of 0.25
and 0.35 per m2 since 2005 (Fig. 4.3.1.).
2005 2006 2007 2008 2009 2010 2011 20120
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
Trend in mean density of fish surveyed in Stationary Point Counts
Me
an
de
nsit
y o
f fi
sh
pe
r m
2
Figure 4.3.1. Mean density per m² of all surveyed fish species across all survey sites, 2005 - 2012.
When dividing the densities between site substrate (granitic vs. carbonate) the results from
2012 show an insignificant difference between the two; granitic sites had a density of 0.30
compared to 0.29 per m2 within the carbonate sites (Fig.4.3.2.). This finding is in tune with
previous results; as minor fluctuations in substrate relative richness have occurred across
all years and the predominance of either site switches. This is interesting in itself, as the
two substrate compositions have greatly differing environments and food resources for fish
species and so would theoretically harbour varying levels of fish density per m².
2005 2006 2007 2008 2009 2010 2011 20120
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
Carbonate Granitic
Survey Year
Mea
n d
ensi
ty o
f fi
sh p
er m
2
Figure 4.3.1. A comparison of mean density per m² of all surveyed fish species between carbonate and granitic
substrate sites, 2005 - 2012.
27
4.3.3. Fish Densities with regards to Feeding Guilds
All data on the abundance of fish species can be analysed using feeding guilds; determined
by the primary food source of individual species. These feeding guilds and the species that
fall within them are taken from Obura and Grimsditch (2009), and further adapted to the
specific species found within Seychelles in agreement with our partners. A full list of the
relative guilds and the divided species can be found in appendices C. Along with fish
density results, the density of feeding guilds is also only taken from the stationary point
counts to allow for standardised comparison regardless of the change in survey
methodology in 2009.
The most dominant feeding guild across all sites is the herbivores (Fig. 4.3.3.), comprising
surgeonfish (Acanthuridae), rabbitfish (Siganidae) and parrotfish (Scaridae). This guild has
remained at a relatively stable abundance during all survey years, increasing slowly in
density from 2006 to 2010. 2011 saw the first drop in herbivores for a number of years,
however the results for 2012 show that the rate of decrease is slowing.
2005 2006 2007 2008 2009 2010 2011 20120
0.05
0.1
0.15
0.2
0.25
PlanktivoresPiscivorousCorallivoresVaried dietInvertivoresHerbivoresCorallivore / HerbivoreCorallivore / Invertivore
De
nsi
ty o
f Fis
h S
pe
cie
s p
er
m2
Figure 4.3.3. Comparison of fish feeding guilds through density per m² across all sites, 2005 - 2012.
Figure 4.3.4. reveals the greatest change in density that has occurred for any feeding
guilds across all survey years. Once again the corallivores, a feeding guild consisting of
obligate coral feeders within the butterflyfish family (Chaetodontidae), is the guild which has
displayed the greatest change in abundance across the survey years, from 0.001 in 2005 to
0.037 per m2 in 2012.
28
2005 2006 2007 2008 2009 2010 2011 20120
0.01
0.02
0.03
0.04
0.05
0.06
CorallivoresPiscivorousVaried dietCorallivore / HerbivoreCorallivore / InvertivoreInvertivoresPlanktivores
Survey Phases
De
nsi
ty p
er
m2
Figure 4.3.4. Comparison of feeding guilds through density per m² across all sites, 2005 – 2012, disregarding
herbivores.
4.3.4. Influence of Marine Protected Areas on Fish Densities 2005 – 2012
In analysing the data between the mean density of fish per m2 within marine protected
areas (MPAs) and unprotected areas there is a consistently higher density within MPAs
(Fig. 4.3.5.). With the exception of the Jan - Mar 2010 survey phase, MPAs have had an
average greater density of 0.049 per m2 ± 0.004 SE.
Nov-Dec
05
Apr-Ju
n 06
Oct
-Dec
06
Apr-Ju
n 07
Oct
-Dec
07
Apr-Ju
n 08
Oct
-Dec
08
Jul-S
ept 0
9
Jan-M
ar 1
0
Jul-S
ept 1
0
Jan-M
ar 1
1
Jul-S
ept 1
1
Jan-Ju
n 12
Jul-D
ec 1
200.05
0.10.15
0.20.25
0.30.35
0.40.45
0.5
Overall Protected Overall Unprotected
Survey Phases
Me
an D
en
sity
s o
f fi
sh (
pe
r m
2)
Figure 4.3.5. Overall mean density per m of fish inside and outside marine protected areas, Nov-Dec 2005 to July-
Dec 2012.
Carbonate sites within MPAs have always held a higher density of fish since 2005, with the
July to December 2012 phase containing a mean density of 0.307 per m2 within MPAs
compared to 0.242 per m2 in the carbonate sites outside protected zones (Fig. 4.3.6.).
29
Nov-Dec
05
Apr-Jun 0
6
Oct-Dec
06
Apr-Jun 0
7
Oct-Dec
07
Apr-Jun 0
8
Oct-Dec
08
Jul-S
ept 0
9
Jan-M
ar 1
0
Jul-S
ept 1
0
Jan-M
ar 1
1
Jul-S
ept 1
1
Jan-Ju
n 12
Jul-D
ec 1
20.00
0.10
0.20
0.30
0.40
0.50
0.60
Carbonate Protected Carbonate Unprotected
Survey Phase
Me
an D
en
sity
of
Fish
pe
r m
2
Figure 4.3.6. Mean density of fish per m² on carbonate substrate sites inside and outside marine protected areas,
Nov-Dec 2005 to July-Dec 2012.
Granitic sites have had a much less significant difference between the years, continuously
fluctuating in relevant densities. The July to December 2012 results show that mean
density within granitic protected sites is currently slightly higher at 0.297 per m2 compared
with 0.281 per m2 outside protected zones (fig. 4.9.3.).
Nov-Dec
05
Apr-Ju
n 06
Oct
-Dec
06
Apr-Ju
n 07
Oct
-Dec
07
Apr-Ju
n 08
Oct
-Dec
08
Jul-S
ept 0
9
Jan-M
ar 1
0
Jul-S
ept 1
0
Jan-M
ar 1
1
Jul-S
ept 1
1
Jan-Ju
n 12
Jul-D
ec 1
20
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
Granitic Protected Granitic Unprotected
Survey Phase
Me
an D
en
sity
of
Fish
pe
r m
2
Figure 4.3.7. Mean density of fish per m on granitic substrate sites inside and outside marine protected areas, Nov-
Dec 2005 to July-Dec 2012.
30
4.3.5. Fish Species Diversity
Diversity refers to the species-richness, or number of separate species, within the survey
site as opposed to the relative abundance, or count, of individual fish. The three sites with
the highest diversity in 2012 were Baie Ternay Reef Centre, Therese North End and
Conception North Point, all with 40 species (Fig. 4.3.8.). The lowest diversity was found at
Anse Major Reef with 23 species and Willie’s Bay Reef and Therese North East with 28
species (Fig. 4.3.8.). It is interesting but unsurprising that the sites that show the highest
(Baie Ternay Centre) and the lowest (Anse Major Reef) abundance also show the highest
and lowest diversity also. In addition, comparing sites inside Marine Protected Areas to
those outside revealed that MPAs contained a higher number of species on average than
non-protected areas with 36.3 species within the MPAs and 34.2 species outside MPAs.
L'ilo
t
White
Vill
a
Corsai
re R
eef
Auberge
Ree
f
Site
X
Whal
e Rock
Ray's
Point
Anse M
ajor R
eef
Anse M
ajor P
oint
Will
ie's
Bay R
eef
Will
ie's
Bay P
oint
Site
Y
Baie T
ernay
Nort
h East
Secr
et B
each
Baie T
ernay
Cen
tre
Baie T
ernay
Nort
h Wes
t
Baie T
ernay
Ligh
thouse
Port La
unay So
uth R
eef
Port La
unay W
est R
ocks
Conception N
orth P
oint
Conception C
entr
al Ea
st Fa
ce
Ther
ese N
orth En
d
Ther
ese N
orth Ea
st
Ther
ese S
outh0
5
10
15
20
25
30
35
40
45
No.
of
indi
vidu
al s
peci
es s
urve
yed
Figure 4.3.8. Species-richness (number of fish species found) across all survey sites along NW Mahé, 2012. Green
denotes sites within Marine Protected Areas and blue denotes non-protected sites.
A comparison of species-richness between the same sites surveyed in 2005 and the results
from 2012 reveal a significant increase in the number of surveyed fish species present
across all areas (Fig. 4.3.9.); with a mean increase of 6.38 species (± 1.65 SE) over all sites.
The only exception of this rise was Therese North End, Baie Ternay North West and
Therese North East survey sites which saw a recorded a drop of 1, 2 and 3 species
respectively.
31
White
Vill
a
Corsai
re R
eef
Site
X
Whal
e Rock
Anse M
ajor R
eef
Site
Y
Baie T
ernay
Nort
h East
Baie T
ernay
Cen
tre
Baie T
ernay
Nort
h Wes
t
Baie T
ernay
Ligh
thouse
Port La
unay So
uth R
eef
Port La
unay W
est R
ocks
Conception N
orth P
oint
Conception C
entr
al Ea
st Fa
ce
Ther
ese N
orth En
d
Ther
ese N
orth Ea
st0
5
10
15
20
25
30
35
40
45
2005
2012
No
. of
surv
eye
d s
pe
cie
s p
rese
nt
Figure 4.3.9. A comparison of species-richness (number of fish species) between the same sites of NW Mahé in
2005 and in 2012.
4.3.6. Commercial Fish Sizing Results
All volunteers are assessed on their ability to estimate size of the commercial fish species
when sighted underwater. Assessment was carried out by use of on-land training, where
volunteers are asked to size objects from varying distances and instant feedback is given.
On-land testing is also given by sizing a line with artificial fish attached from a distance of
no closer than 2m. In-water assessment was carried out using a line with sections of
polyurethane piping of known length. Volunteers estimate the lengths underwater and
results and feedback are given after each dive. Along with practice methodology,
assessment is also undertaken within the fish survey practice methodology under the
supervision of a staff member. All volunteer’s sizings are checked against the staff’s
recording. Only when a volunteer displayed 100% accuracy in sizing fish to the 10cm
bandwidth on both in-water piping assessment and the practice surveys were they allowed
to conduct surveys. All volunteers from the past survey phase could accurately define the
size of all commercial fish species to within the 10cm bandwidth required.
32
4.4. Invertebrate Densities
In total 46 invertebrate abundance belts were completed across all the 23 sites surveyed,
covering a total area of 11,500m2. The trends in density levels found during 2012 continue
those found with all previous survey phases. Short-spine (Echinothrix sp.) at 0.32 per m2
SE ±0.03 and long-spine (Diadema sp.) at 0.16 per m2 SE ±0.05 (Fig. 4.4.1.) still show the
highest abundance of all the surveyed invertebrates; significantly higher than all other
invertebrate species found with the exception of Drupella snails.
Short
Spin
e Urc
hin
Long S
pine U
rchin
Pencil
Urc
hin
Flower
Urc
hin
Mat
hae’s
Urchin
Cake U
rchin
Other
urc
hins
Cushio
n seas
tar
Crown o
f Thorn
s
Other
seas
tars
Drupell
a
Giant C
lams0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
Invertebrate Species
Me
an d
en
sity
pe
r m
2
Figure 4.4.1. Mean density per m2 of all surveyed invertebrate species across north-west Mahé, July – December
2012.
When dividing the two most abundant invertebrates by substrate type some interesting
trends can be observed (Fig 4.4.2.). Short-spine sea urchins show a preference to granitic
substrate, indicated by the higher density levels on these reefs; whereas long-spine sea
urchins display similar density levels over both substrate types; not indicating any
preference. Short spine urchins show a continual decrease in density on the carbonate
reefs. On Granitic reefs Short Spine urchins increased significantly in 2010 but from that
stage have decreased steady. Results from 2012 show that the density of short spine
urchins, on the granitic sites, has returned to a level similar to 2009; negating the gains of
2010. Long spine urchins however have maintained similar density levels throughout the
monitoring program on both site substrata.
33
2009 2010 2011 20120.00
0.10
0.20
0.30
0.40
0.50
0.60
Long Spine Carbonate
Short Spine Carbonate
Long Spine Granitic
Short Spine GraniticM
ean
de
nsi
ty (
pe
r m
2)
Figure 4.4.2. A comparison of the mean density per m2 of short spine (Echinothrix spp.) and long spine (Diadema
spp.) urchins on granitic versus carbonate substrate along north-west Mahé, 2009 to 2012.
Studies of the trends in the corallivorous invertebrates show significant, almost alarming,
increases in abundances across the survey sites for the Drupella snails. Figure ??? shows
the density levels of the major corallivorous invertebrates of Crown of Thorns seastar
(Acanthaster planci), Cushion Starfish (Culcita spp.) and Drupella snails
Jan-M
ar09
Jul-S
ept0
9
Oct-Dec
09
Jan-M
ar10
Jul-S
ept1
0
Oct-Dec
10
Jan-M
ar 1
1
Jul-S
ept 1
1
Oct-Dec
11
Jan-Ju
n12
Jul-D
ec 1
20
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
Cushion seastarCrown of Thorns seastarDrupella
Survey Phase
Me
an d
en
sity
pe
r m
2
Figure 4.4.3. Mean density per m2 of Cushion Seastar (Culcita spp.), Crown of Thorns (Acanthaster planci) and the
gastropods Drupella spp.
Density levels of both the Crown of Thorns Seastar (Acanthaster planci) and the Cushion
Seastar (Culcita sp.) have remained at very low and stable densities. The density of
Drupella snails however have been increasing significantly since early 2010; reaching its
maximum for 2012 of 0.15 per m2.
34
4.5. Sea Cucumber Densities
The total number of sea cucumbers found across all survey sites along north-west Mahé
was 267 individuals for Jul – Dec 2012. Figure 4.4.4. shows the total number of sea
cucumbers found per site for each year of survey. This graph clearly displays that after the
initial rapid decrease in abundance of sea cucumbers seen in 2007 the populations are
increasing across all the survey sites
2006 2007 2008 2009 2010 2011 20120.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
No
. O
f C
uc
um
be
rs f
ou
nd
pe
r s
ite
su
rv
ey
ed
Figure 4.4.4. Mean Number of sea cucumbers recorded per site from 2006 -2012
Analysis of individual sea cucumber species reveals that both Stichopus sp. (0.012 per m2)
and Pearsonothurian graeffei (0.008 per m2) remain the most abundant sea cucumbers
across all sites (Fig. 4.4.5.). Both show significant increases in their density through the
monitoring program although Stichopus sp. has seen the larger rise from 0.007 per m2 in
2008 to its current maxima for the program, 2012. The results show clearly that the
abundance of the commercially valuable species of sea cucumbers is significantly lower
than that found for the non-valuable species of Stichopus sp., Pearsonothurian graeffei and
Bohadshia sp.
2008 2009 2010 2011 20120.000
0.002
0.004
0.006
0.008
0.010
0.012
0.014Stichopus sp.
Pearsonothurian graeffei
Bohadschia sp.
Holothuria atra
Actinopyga sp.
*Actinopyga mauuritiana
*Thelenota ananas
Holothuria edulis
*Holothuria nobilis
*Holothuria fuscopunctata
*Holothuria fuscogilva
*Holothuria sp. (Pentard)
Thelenota anax
Me
an
De
nsi
ty (
ind
ivid
ua
ls p
er
m2
)
Figure 4.4.5. Density per m2 of individual sea cucumber species across all survey sites of north-west Mahé, 2008 –
2012.
35
5. Discussion
This report combines the data on coral recruitment, fish density and invertebrate
abundance from the most recent survey period with that from the previous years’ studies to
analyse any trends identified throughout the monitoring program.
5.1. Coral Recruitment Surveys
Coral recruitment monitoring for 2012 indicates that conclusions made in 2010; that mean
recruit density had stabilised at around 12.0 – 14.0 recruits per m2, doesn’t seem to be
continuing through 2011/2012 as average density for these years has increased to 15.5 per
m2. Obviously this is a very positive sign for the continual growth in the coral communities
on the reefs within the survey area and indicates towards increased resilience to possible
future degradation event. As the coral recruitment rate is one of the most important aspects
of regeneration of reefs after disturbance (Connel 1997, Hughes & Tanner 2000, Syms & Jones
2000, Hughes et al. 2003).
When looking at the other aspects of coral recruitment; such as substrate preference,
density of recruits with regard to size class and most notably for this report the trends in
density and relative abundance of the coral families, additional information and conclusions
can be drawn above that of overall mean density.
Coral recruit density with regards to substrate type (granitic vs. carbonate) shows a
decrease from the density maxima on both substrates in 2011. The decrease on granitic
reefs however is more pronounced. Although, when looking at the trend over time, density
changes are seen year on year and with such a minor change this year it is of little concern.
What has remained stable is the continual dominance of the granitic reefs in terms of
recruit density. This is to be expected as the granitic reefs provide a more suitable
environment for coral recruitment, in terms of increased substrate availability and greater
exposure to offshore currents due to their position, providing clear offshore waters and
stable temperature / salinity gradients.
Recruit size class analysis shows that the larger more dominant size category 2-5cm has
increased in density following a similar trend seen in recent years. However the smaller
size class decreased this year back in levels seen in 2010. As the smaller size class
indicates early settlement of coral juveniles. This drop in the smaller size class could
indicate a reduction in the spawning of adult colonies during 2012. It will be interesting to
see in the results from the next survey period, 2013, if the drop in small size class density
36
of this year will have an effected on the survivorship of recruits which can be drawn from
the density of the larger size class in 2013, but this remains to be seen.
For 2012 the changes in family density were analysed, in detail, using differing analysis
techniques to try to identify changes in the recruitment density and composition at the
family level. Recorded family density followed trends seen in recent years with the family
groups of Faviidae, Poritidae and Acroporidae dominating. However this way of looking at
the results doesn’t account for the number of genus within each family. For further analysis
of the family density all data was then normalised and converted to relative abundance to
give a better visual representation of changes in family density. This analysis shows that
the Poritidae family has highest relative abundance and has remained so since the surveys
began. This is a very positive sign in terms of overall reef growth as the Porites genus
within the Poritidae family is one of the principle reef building scleractinian corals
contributing heavily to the structure of the reef. Acroporidae has had the biggest change in
relative abundance increasing to the second most abundant coral family group from 2008,
showing a faster rate of increase than the Poritidae family.
The second type of analysis used to look at changes in family density is the percentage
composition of total recorded density. This type of analysis can indicate relative recruitment
rates. Analysis has shown that the Acroporidae family is making up a larger proportion of all
recruits found, increasing from 10.2% in 2005 to 18.5% in 2012, which is the greatest
increase seen across all family groups. Opposed to this is the reduction in the percentage
composition of the Poritidae family which although still remaining the dominant family group
has decreased in overall composition from 32.9% in 2005 to 28.0% in 2012. Although
overall recruit density is increasing this indicates that if current trends remain stable the
Acroporidae family could make up the greater proportion of the total recruits found in future
surveys.
5.2. Fish Surveys
This section of the report contains results from fish surveys conducted between July to
December 2012, focusing on the abundance and diversity of both reef and commercial fish
species. The majority of the analysis is undertaken using the Stationery Point Count (SPC)
data as this is the survey method used since the beginning, allowing for relevant long term
comparisons. The belt transect methodology was introduced in 2009 and is therefore only
used in the overall abundance analysis. This ongoing data set; comprising results from 12
years worth of collection; is invaluable as it provides significant insights into the health of
37
coral reefs around the inner islands of the Seychelles, as well as contributing information
towards the status of coral reef knowledge around the world.
One of the greatest impacts on Seychelles’ fish populations after the coral bleaching in
1998 was in species-richness, or in the variety of different species found at each site
(Graham et al. 2006). The immediate loss of live coral cover and physical structure of the
reef eliminated resources for fish; both physical habitats and prey. With the lack of
resources, the ability to provide for a range of species was diminished and the diversity of
all sites declined dramatically.
Based on this theory, one approach to viewing the relative health of survey sites is to
compare the species-richness of the areas both to one another and over time. High
species-richness indicates a reef which can support the needs of varying species and an
associated complex food web. Comparing current diversity results at all sites to initial
diversity recording in 2005 has shown an average improvement across all sites of +6.38
species, with the exception of only two sites (Fig. 4.3.9.).
Many studies have highlighted the positive correlation of species-richness of both fish and
other targeted organisms to the structural complexity of the reef substrata of a site
(Chabanet et al. 1996, Luckhurst & Luckhurst 1978, Talbot et al. 1978, Roberts & Ormond 1987).
Analysis of the trend in reef structural complexity shows a shift towards a much more
diverse habitat (Cassidy 2012). Initial data analysis in 2005 shows a reef system dominated
by encrusting and massive lifeforms as these consist of families such as Porites and
Faviidae which are slow growing corals and typically more resilient to bleaching events.
The data show a steady increase in branching and a gradual increase in submassive
lifeforms. This increase in coral diversity provides a greater variety in resources to be
exploited, thereby resulting in a greater diversity in higher trophic level reef species.
There is a constant and steady increase in corallivores throughout the history of the data
set (Fig 4.3.4.). Obligate corallivores are predators who feed solely on coral polyps,
therefore numbers of these individuals are linked directly to the health and diversity of the
coral reef (Jones & McCormick 2002). This strong linkage has led to many corallivore species
being used as ‘indicator species’ in different coral ecosystems about the world, allowing
researchers to gather a picture of the health of a reef area by only recording the distribution
and specific abundance of corallivorous species. There is also a steady increase in
38
corallivore/invertivores (Fig. 4.3.4.), indicating a diverse reef system that is able to support a
variety of species.
The data since 1998 shows a steady rise in the corallivore guild from the initial density
recordings of 0.001 to 0.038 fish per m². This rise has mainly been due to the increase in
two butterflyfish species; Chaetodon trifascialis (Chevroned) and Chaetodon trifasciatus
(Indian Redfin). When overlaid with the rise in percentage hard coral cover through the
survey years (Cassidy 2012), corallivore density perfectly mirrors that of coral coverage.
Herbivores have always been the most abundant feeding guild in the history of the data set,
reflecting their trophic level as primary consumers. The importance of healthy populations
of herbivores on the reef has been documented in a number of studies (Miller 1998, Sluka &
Miller 2001) due to the role they play in mediating the competition between benthic algae
and slow growing corals (Sluka & Miller 2001). If macroalgae were not removed by
herbivores then this would out compete corals and inhibit coral diversity (Hughes 1994).
Research conducted on the Great Barrier Reef immediately following the 1998 bleaching
event also solidified the importance of herbivory; with experimental manipulations removing
herbivores from degraded areas causing a dramatic explosion in macroalgae which in turn
suppressed the fecundity, recruitment, and survival of corals (Hughes et al. 2007).
Herbivores gradually and constantly increased in number for 4 years between 2006 and
2010, but then numbers took a downturn following this (Fig. 4.3.3.). There are a number of
ecological theories as to why densities of herbivores fluctuate and rarely remain stable.
One possibility is that they have reached their carrying capacity for some sites, therefore
numbers will fluctuate around this maximum. Another theory is based upon the Lotka-
Voltera cycle (Berryman 1992), describing the relationship between predators and prey
whereby prey numbers are controlled by the number of predators. A rise in prey will
generally result in an increase in related predators as there is more food available. This
increase in predators puts more pressure on prey populations and the population drops,
causing a drop in availability of food and a subsequent drop in the number of predators.
This drop in predator numbers relieves some of the pressure on prey populations, and the
population increases again starting the cycle over. Corresponding peaks and troughs are
generally more pronounced in prey numbers than for predators, and are slightly delayed for
predators also. Throughout the data set piscivore numbers fluctuate at a density of around
0.02 individuals per m2 (Fig. 4.3.4.). A sharp decrease in piscivores in 2009 does show a
rise in herbivores the following year, however, while some potentially related peaks and
39
troughs can be found in the data this oscillating cycle cannot obviously be seen in the
trends for herbivores and piscivores. A study by Jennings & Polunin (1996) found that the
biomass of piscivorous fishes was not correlated with the biomass or diversity of their
potential prey, indicating that reef fish communities are not governed by a single, dominant
process. It may be that analysing the data in a yearly or 6 monthly timescale is too broad to
show such a relationship, or that predator numbers are not the primary influencing factor in
control of herbivore numbers, therefore further analysis is required into the relationships
between these two feeding guilds.
When analysing fish communities and assemblages it is important to factor in the affect of
Marine Protected Areas (MPAs). MPAs within the Seychelles are designated zones where
the removal of any species is illegal and the anchoring of boats and level of tourism is
monitored. These no-take zones have been developed to serve as both safe-houses for
targeted fish species and coral reefs, but also so that they may potentially benefit fish
stocks through the theory of ‘spillover’, the net export of adult fish, from an area of high
density to adjacent non-protected areas of lower fish density (Abesamis & Russ 2005).
Overall, protected areas have been found to positively affect fish density and diversity at
the sites surveyed on North-West Mahé. Apart from one survey phase within January –
March 2010, throughout the data set MPAs have held a higher mean density of fish across
all sites (Fig. 4.3.5.). In 2012 MPAs held an average density of 0.66 individuals per m2 as
opposed to a density of 0.57 individuals per m2 outside the MPAs. Protected areas also
held on average 2 species more than unprotected areas, showing that MPAs increase
diversity. Protection has a much more pronounced affect on carbonate reefs than on
granitic (Fig. 4.3.6., Fig 4.3.7.).
High levels of fishing pressure can have knock-on effects on fish communities. Studies in
Marine Reserves in Kenya have shown that intense fishing pressure can have strong direct
and indirect impacts on herbivore assemblage structure, herbivory intensity and resulting
benthic community structure (McClanahan & Shafir 1990, McClanahan 1994, McClanahan et al.
1994). For example, removal of species such as the Emperors (Lethrinidae) that predate
upon herbivorous invertebrates such as urchins (Diadema sp.) can mean that the numbers
of these individuals could go unchecked and therefore over graze and exclude other
herbivorous species such as the Surgeonfish (Acanthuridae). Future analysis breaking
down the affect of MPAs on feeding guilds could help to highlight exactly how MPA’s affect
reef fish assemblages across the North-West of Mahé.
40
5.3. Invertebrate surveys
Invertebrates have been studied as biological indicators within terrestrial and aquatic
ecosystems extensively, including coral reef habitats. Their importance lies in their
interactions with the reef habitat, and density may reflect changes in reef composition and
structure. For the 50m abundance and diversity belts three groups are focused on; algal
grazers, coral predators and commercially important invertebrates.
Algal grazers control the algal / coral dominance on the reefs, the key invertebrates which
control this are the Echinoidea (sea urchins) (Hughes 1994). Abundance of sea urchins have
been continuously dominated by two genus, the Echinothrix (Short Spine urchins) and
Diadema (Long Spine urchins). Echinothrix show a reduction in their numbers with time,
however density levels have only fallen by a very small amount which shouldn’t have a
major effect on algal density on the reefs. Diadema numbers have remained stable. All
other Echinoidea are found in extremely low densities, and so would contribute little to the
algal/coral dynamics of the reefs.
Coralivorous invertebrates surveyed consist of the Acanthaster planci (Crown of Thorns
seastar), Culcita spp. (Cushion Starfish) and Drupella snails. The density of the two
coralivorous Sea Stars have remained at very low stable densities throughout the
monitoring program. However density of the drupella snails has increased significantly over
the past two years. The continued increase in this species could be having an effect on the
recruitment of the coral, Acropora spp. as this is their preferred food source; however
although the densities are increasing they still remain relatively low at only 0.15 per m2. The
most likely explanation for the increase in the Drupella numbers is that it is coupled with the
increase in the adult branching Acropora spp., their preferred habitat and food source,
found from GVI’s benthic composition monitoring.
Commercial invertebrate monitoring is conducted by monitoring the Holothuroidea (Sea
Cucumbers) along with Lobster and Octopus numbers. Monitoring is conducted to look at
local coastal populations as they are highly valuable for the local fishing industry and
density changes could indicate changes in exploitation levels. Sea cucumber numbers
seem to be rising after the initial large reduction in overall abundance in 2007. If current
trends persist abundance will reach and maybe exceed these figures in the future. When
focussing on species diversity it is important to note that only the non-commercially
valuable species are found in any significant numbers across the survey sites. Lobster and
Octopus are consistently at very low densities.
41
6. Additional Ecosystem Monitoring
6.1. Turtles
Five species of marine turtles are found in the Seychelles EEZ waters: the leatherback
(Dermochelys coriacea), loggerhead (Caretta caretta), olive ridley (Lepidochelys olivacea),
hawksbill (Eretmochelys imbricata), and green (Chelonia mydas) (IUCN 1996). The
leatherback, loggerhead and olive ridley, although common to parts of the Western Indian
Ocean, are not thought to currently nest in the Seychelles and are rarely seen. In contrast,
the hawksbill and green are residents in coastal waters of the Seychelles, nest on the
beaches, and are commonly observed. All five species found in the Seychelles face the
combined threats of poaching, pollution and loss of nesting sites, and are listed by IUCN as
endangered or critically endangered. The Seychelles is considered one of the most
important sites for the critically endangered hawksbill turtle and is one of the only localities
in the world where they can be observed nesting during daylight hours.
GVI staff and volunteers are trained in turtle biology and the identification of the two
species commonly seen around north-west Mahé, C. mydas and E. Imbricata, through
lectures and PowerPoint presentations. Volunteers are also trained in survey methodology
for water based and land based turtle surveys.
6.1.1. Incidental Turtle Sightings
For every dive undertaken by GVI, a record of turtle observations is kept. The parameters
for each of GVI’s dives are logged, regardless of whether or not a turtle was seen, enabling
the calculation of turtle frequency per dive and thus effort-related abundance. The species,
carapace length, sex, distinguishing features and behaviour of all turtles sighted is recorded
wherever possible.
Incidental sightings of sea turtles are divided into three month periods to more accurately
view the fluctuations that occur in and outside of nesting season. Within the July to
September time period of this report phase, a total of 38 turtles were sighted on 130 boat
outings whereby dives were completed in that period (discounting dives that were
specifically looking for turtles as part of the focal behaviour study). 34 of these sightings
were identified as hawksbill turtles and 4 as green turtles, with an overall sighting frequency
for all dives of 22.6%. Within the October to December period following this, 70 turtles were
sighted on 152 dives; consisting of 57 hawksbills and 13 green turtles, giving a much higher
overall sighting frequency of 53% (Fig. 6.1.1).
42
Jul-S
ep 05
Jan-M
ar 06
Jul-S
ep 06
Jan-M
ar 07
Jul-S
ep 07
Jan-M
ar 08
Jul-S
ep 08
Jan-M
ar 09
Jul-S
ep 09
Jan-M
ar 10
Jul-S
ep 10
Jan-M
ar 11
Jul- S
ep 11
Jan - M
ar 12
Jul -
Sep 120
10
20
30
40
50
60
Hawksbill TurtlesGreen Turtles
Freq
uenc
y of
Sig
hting
(%)
Figure 6.1.1. Frequency (%) of hawksbill and green turtle sightings around north-west Mahé from Oct- Dec 2005 to
Apr- Jun 2012.
In analysing the sightings results the frequency found for the months within October to
December is comparatively higher than for those within July to September; a pattern that
can be observed for hawksbills throughout our recorded data. This increase in encounters
in the Seychelles’ coastal waters during this time can in part be explained by the
immigration of sexually mature turtles to these designated nesting areas (Witzell 1983;
Houghton 2003; Ellis & Balazs 1998). This can be seen by a 100% increase in sighting
frequency for adult hawksbills in October to December. Carapace length can be used as a
guide to the stage of sexual maturity of sea turtles, therefore for every turtle sighting the
curved carapace length (CCL) is estimated. The approximate minimum carapace length of
breeding-age female green and hawksbill turtles is 105cm and 80cm respectively
(Mrosovsky 1983). The mean estimated carapace length for hawksbill turtles during the
July to September and October to December period was 54.8cm (± 1.0 SE) and 55.1cm (±
1.0 SE) respectively (fig. 6.1.2.). This reveals a general steady population of sexually
immature sea turtles. There was only one recorded sighting of a male during both periods
and if males and females were occupying the bay randomly and equally, then we would
expect to see a similar increase in both males and females with an increase in sighting
frequency. This shows the increase in turtle activity within this time is largely due to the
arrival of adult females for the nesting season.
43
Jul-
Sep
t 0
5
Oct
-Dec
05
Jan
-Mar
06
Ap
r-Ju
n 0
6
Jul-
Sep
t 0
6
Oct
-Dec
06
Jan
-Mar
07
Ap
r-Ju
n 0
7
Jul-
Sep
t 0
7
Oct
-Dec
07
Jan
-Mar
08
Ap
r-Ju
n 0
8
Jul-
Sep
t 0
8
Oct
-Dec
08
Jan
-Mar
09
Ap
r-Ju
n 0
9
Jul-
Sep
t 0
9
Oct
-Dec
09
Jan
-Mar
10
Ap
r -
Jun
10
Jul -
Sep
10
Oct
- D
ec 1
0
Jan
- M
ar 1
1
Ap
r -
Jun
11
Jul -
Sep
11
Oct
- D
ec 1
1
Jan
- M
ar 1
2
Ap
r -
Jun
12
Jul -
Sep
12
Oct
-Dec
120
10
20
30
40
50
60
70
80M
ean
car
apac
e le
ngt
rh (
cm)
Figure 6.1.2. Mean carapace length of hawksbill turtles around north-west Mahé from Jan- Mar 2006 to Apr- Jun 2012.
6.1.2. Beach Patrols for Nesting Turtles
Beach patrols are conducted on north-west Mahé during the Hawksbill turtle nesting
season from October to March. This land-based turtle monitoring work includes beach
walks, documentation of nesting tracks, and investigation of newly hatched clutches. Beach
patrols are carried out weekly at beaches local to the Cap Ternay research station (Anse
du Riz and Anse Major) to monitor nesting turtle activity. The surveys are conducted on
foot, with the teams searching for signs of tracks or body pits walking along the upper
beach, on the main beach, and also within the coastal vegetation.
Within the October to December period 18 beach patrols were conducted on both Anse du
Riz and Anse Major beach. One nest which was not identified to species level was found
on Anse Major at the beginning of October, and one hawksbill was found successfully
nesting on Anse di Riz during November. Tracks were found on Anse du Riz on a separate
occasion with no obvious body pit. The difference in track width suggests that this was a
separate, smaller individual who may have attempted to nest elsewhere in the area.
6.1.3. In-water Surveys of Turtle Behaviour
In studies concentrating on the home ranges of sea turtles it has been found that normal
daily activities of sea turtles centre around areas of high food availability and resource
quality. When sufficient resources are available, individuals develop affinities for specific
areas (Makowski et al. 2006). Preliminary results from research conducted by Von Brandis
in the Amirantes, Seychelles, established that philopatric behaviour is common among
foraging hawksbill turtles, and extensive information on individuals and their energy
44
budgets can be gathered using relatively non-invasive sampling protocols (Von Brandis
pers. comm.). Focal behavioural studies work on the philosophy that an individual, when
followed and observed correctly, can provide a wealth of ecological information that would
otherwise be unnoticed in a simple point count survey.
Our objective is to document important interactions between hawksbill turtles and their
environment while obtaining information on feeding preferences and the number of
individuals displaying philopatric behaviour within the Baie Ternay Marine Reserve.
Expedition members use SCUBA equipment to undertake a U-shaped search pattern.
Divers look for focal animals and, upon finding an individual, follow and document all
behaviours observed. Environmental conditions can dictate at what distance accurate
observations are made without altering normal behaviour but in general a distance of no
closer than 5m is sufficient. A continuous time scale of data is used; divers stay with any
individual encountered for as long as possible even if another individual is located. In the
event that another turtle is found, the second member of the buddy pair may start to
document behaviour but at no time are buddy pairs to become separated by more than 2m.
Any characteristic markings should be documented and the use of underwater photography
is highly desirable for turtle identification and determining unknown prey items. Due to
logistical constraints, it is only possible for the study in Baie Ternay to be carried out on a
weekly basis, incorporating two 45 minute dives with most Expedition Members
participating in one dive; however it is an interesting addition to the routine for Expedition
Members, enhancing their skill set and appreciation for marine ecological fieldwork.
Between July to December of 2012, two turtle behavioural dives were conducted each
week; wherein a combined total of 25 turtle sightings over 38 separate dives. These
sightings comprised 16 hawksbill and 9 green turtle. The estimated mean carapace length
(CCL) of all turtles sighted was 61.2cm ± 21.01 SD. The range of sizes of turtles varied
from 35cm to 120cm, and most were accurately identified through photo-identification and
individual characteristics as being residential turtles of Baie Ternay Marine Park.
Of these turtles sighted in the previous phase, again the greatest frequency of sightings
occurred within the 0-10m depth class, with four sightings recorded outside of these depths
with 3 at 11m and one at 13.8m. The shallow reef slope of Baie Ternay Centre does bias
the results towards the shallower depth class, as the 0-10m range covers a larger area of
reef and therefore a larger area of foraging grounds. From the studies it was noted that
algae and soft coral were all common chosen food items.
45
Through the use of photo identification methods, spoken about in the following section, a
number of individual turtles have been seen returning to, or residing within, specific areas
of Baie Ternay marine park over a long time scale.
It is impossible to correctly determine the specific home range of sea turtles without the use
of remote telemetry, however one or more areas of disproportionately heavy use (i.e. core
areas) can be identified for some of the more frequently spotted turtles. Understanding the
spatial use patterns of sea turtles is fundamental to their conservation. This study reveals
that Baie Ternay remains an important habitat for both the endangered green and hawksbill
turtles; thus, further underscoring the need to develop and maintain conservation strategies
that address the impacts that threaten this region.
6.1.4. Photo Identification of Turtles
Throughout 2012 the use of photo identification methods for turtles was implemented into
all dives where volunteers or staff had an underwater camera. The post-ocular area of
scales on the left and right cheeks of both hawksbill and green turtles are unique to each
individual, allowing for comparisons to be made between identification shots taken on
different dives. Individuals can be recognised through analysis of the photographs, based
on a code defined from the localisation and the number of sides of each scale of the head
profile. This method has been taken from the Kelonia Observatory for Sea Turtles in
Reunion Island (Ciccione et al. n.d.).
The ability to recognise individuals in a population allows for reliable information to be
collected on distribution, habitat use, or life history traits. It is from the increased emphasis
on the importance of photographic identification that resident turtles have been accurately
re-identified, and their home ranges consequently estimated within Baie Ternay marine
national park. A number of individual turtles, both hawksbill and greens, have been
accurately re-identified over varying time scales within the MPA. From data collected from
these sightings it has been noted that many have distinct habitat preferences and feeding
and resting areas. Photo-identification has also been critical in identifying the reasons
behind the low trend in carapace length and any incidence of philopatric behaviour.
46
6.2. Crown of Thorns
Outbreaks of the coral predator, the Crown of Thorns starfish (Acanthaster planci), were
first reported in 1996 and were active until 1998, when the reefs suffered from the
bleaching-induced coral mortality (Engelhardt 2004). Normal density levels are less than one
individual per hectare (Pratchett 2007) and in these numbers A. planci can assist coral
diversity by feeding on the faster growing corals such as Acropora and Pocillopora, which
are its preferred prey items (Pratchett 2007) and early colonisers of degraded reefs that can
out-compete slower growing corals (Veron 2000). In high numbers however the level of
competition for food drives the starfish to eat all species of corals and reefs can become
severely degraded with coral cover reduced to as little as 1% (CRC Reef 2001). The causes
of outbreaks are still not completely understood; it may be connected to overfishing of A.
planci predators, such as the giant triton shell which is popular with shell collectors, or to
natural fluctuations (CRC Reef 2001). The most influential factor could be increased nutrient
levels in the oceans (Engelhardt pers. comm.), from agricultural, domestic or industrial
sources. A. planci are surveyed as part of the invertebrate abundance and diversity belts
and incidental sightings are also documented after every dive. There were 51 recordings of
A. planci across all sites during July and September and 29 seen during October to
December 2012. Most sightings of A. planci were at Anse Major Reef and the adjoining
Ray's Point. The greatest frequency of sightings for July to September occurred within the
month of August, whereas the most recorded sightings for October to December occurred
within November.
6.3. Cetacean Sightings
Cetaceans are considered to be under threat in many parts of the world and in response to
this threat, a national database of cetacean sightings, the Seychelles Marine Mammal
Observatory (SMMO), has been set up. GVI records all incidental cetacean sightings and
passes all data to MCSS for inclusion in the national database. Data recorded includes
date, time, location (including GPS coordinates where possible), environmental conditions,
number of individuals, distinguishing features, size, behaviour and species. There were
only 5 separate recordings of dolphin sightings within July to December 2012. Pod sizes
ranged from 4 to 8 individuals with one sighting of a solitary individual. One sighting
occurred during a dive and the rest were sighted from the boat.
6.4. Whale Shark Sightings
The Seychelles is famous for its seasonal fluctuations in the abundance of whale sharks
(Rhincodon typus). However despite their public profile, relatively little is known about their
47
behaviour or the ecological factors which influence their migratory patterns. A whale shark
monitoring programme was started by volunteers in 1996 and is now the cornerstone of a
eco-tourism operation run by MCSS. From 2001-2003, a tagging programme was initiated
to study migratory patterns as part of the Seychelles Marine Ecosystem and Management
Project (SEYMEMP); it is now clear that the sharks seen in the Seychelles are not resident,
but range throughout the Indian Ocean. The oceanographic or biological conditions that
determine the movements are unclear, it is possible however that the sharks follow
seasonal variations in the abundance of the plankton on which they feed. All sightings of
whale sharks are documented in as much detail as possible; including time, date, GPS
point, number, size of the individuals, sex, distinguishing features, behaviour and tag
numbers if present. Photographs are also taken whenever possible of the left and right
side of the thorax from the base of the pectoral fin to behind the gill area to be used as
identification in the global and regional database.
Within the July to December period there were two separate sightings of whale sharks. The
first sighting was a relatively small individual of 2.5m in Baie Ternay Centre on the
20/07/2012, an ‘early comer’ for the September to December season. The other was at
Lighthouse on the 05/08/12. All data collected, including any photographs taken, were sent
on to MCSS for inclusion into their database.
6.5. Plankton Sampling
MCSS initiated a plankton monitoring programme in conjunction with the tagging and
incidental recording surveys in an attempt to correlate the frequency of whale shark
sightings with plankton levels. Plankton sampling has been run by MCSS since 2003 in
conjunction with their on-going monitoring and tagging programmes. GVI started to assist
MCSS in the collection of plankton data in July 2004, and have since carried out the survey
on a weekly basis. Five plankton tows are carried out to the North West side of Grouper
Point, just outside of Cap Ternay, between 08:00 and 11:00 hours. The tows are carried
out along a North Westerly course from Grouper Point. In order to sample over a range of
depths the net is let out 5m every 30 seconds (up to 45m). Samples are collected in the
‘cod end’ of the net, decanted into a receptacle and preserved in formalin. After the survey
and the filtering process, they are sent to MCSS for measurement of wet weight and
species classification. Environmental conditions are also noted (sea state, cloud cover and
turbidity).
Plankton tows were successfully conducted each week from July to December and all
samples were sent on to MCSS for analysis.
48
7. Non-survey Programmes
7.1 Extra Programmes
7.1.1 Internships
GVI Seychelles currently runs a GVI internship and Divemaster Internship program in
conjunction with their marine research activities. Interns spend twelve weeks with GVI on
the marine expedition and then the divemaster interns will complete an additional twelve
weeks at a dive shop in the Seychelles gaining the PADI divemaster qualification. They
also complete the GVI internship training which included additional courses in biological
survey techniques and team leading.
7.2 Community Development
7.2.1 International School Seychelles (ISS)
The GVI Seychelles community education program works in conjunction with the
International School of the Seychelles (ISS). Lessons are held on Port Launay Beach,
within one of the National Marine Parks on Mahé, where children from ISS are taught about
the marine environment and marine conservation in a location that ignites and stimulates
their interest. This aspect of the expedition is key to the overall impact of our role within the
Seychelles. It also increases the extent to which volunteers are able to contribute on an
individual level, to help raise vital awareness of marine conservation issues related directly
to the Seychelles.
7.2.2 GVI Charitable Trust
As part of the GVI Charitable Trust, GVI Seychelles has partnered with the Presidents
Village Children’s Home in Port Glaud. The Presidents Village is part of The Children’s
Home Foundation, which has several children’s homes in the Seychelles. The Presidents
Village provides a home for abused, neglected and orphaned children and currently houses
56 children from birth to 18 years old. GVI Seychelles is successfully raising funds for the
Presidents Village to contribute towards the costs of housing and clothing the children as
well as purchasing special items not included in the children home’s budget. GVI
volunteers this phase have organized weekly snorkel trips to Port Launay Marine Park for
the children at Presidents Village. Some of the children were able swimmers so were
shown some of the fish and corals by the volunteers which they attempted to identify back
on the beach. Other children are new swimmers and the experience is an introduction to
water safety and an appreciation of the marine environment. These snorkelling trips
49
provide an opportunity for the children to interact with other members of their local
community and spend some time away from the Children’s home in a structured,
educational and fun activity.
7.2.3 National Scholarship Programme
As part of GVI’s local capacity program GVI runs a National Scholarship programme in
each country. The National Scholarship Programme is directly funded by GVI and aims to
increase long-term capacity building within the country. National recruits such as rangers,
researchers and students are selected by the local partner organisations and are brought
into the programme as volunteers. In order for SNPA to continue and build upon the
research conducted by GVI, scholars are invited to join every expedition from the pool of
SNPA staff. Unfortunately we did not have any applicants for the programme this phase.
50
8. References
Berryman, A. (1992), The Origins and Evolution of Predator-Prey Theory. Ecology, 73 (5), pp. 1530-1535.
Cassidy, L. (2011), GVI Phase Report 121 – Status of the Coral Reefs of North-West Mahé, Seychelles
Chabanet, P., Ralambondrainy, H., Amanieu, M., Faure, G. & Galzin, R., (1996), Relationships between coral reef substrata and fish, Coral Reefs 16, pp. 93-102
Ciccione, S., Jean, C., Ballorain, K. & Bourjea, J. (n.d.), Photo-identification of marine turtles: an alternative method to mark-recapture studies, Kelonia l’Observatoire des Tortues Marines, Region Reunion.
Connell, J.H., (1997), Disturbance and recovery of coral assemblages. Coral Reefs 16:S101-S113
Colvocoresses, J., Acosta A., (2007), A large scale field comparison of strip transect and stationary point count methods for conducting length-based underwater visual surveys of reef fish populations. Fisheries Research 85, 130-141
CRC Reef, (2001), Crown-of-thorns starfish on the Great Barrier Reef: Current state of knowledge: April 2001. Coral Reef Research Centre James Cook University, Townsville
Engelhardt, U., (2001), Interim Report No. 1 (December 2001): Report on scientific field studies and training activities conducted in June / July 2001. Seychelles Marine Ecosystem Management Project. Reefcare International Pty Ltd, Townsville
Engelhardt, U.M., Russell & Wendling, B., (2003), Coral Communities around the Seychelles Islands 1998–2002, p.212 – p.231
Engelhardt, U., (2004), The status of scleractinian coral and reef-associated fish communities 6 years after the 1998 mass coral bleaching event. Seychelles Marine Ecosystem Management Project. Global Environment Facility/Government of Seychelles/World Wildlife Fund, Victoria.
Ellis, D. M. & Balazs, G. H., (1998), Use of a generic mapping tools program to plot Argos tracking data for sea turtles, in S. P. Epperly and J. Braun (comp.) Proceedingsof the 17th Annual Symposium on Sea Turtle Biology and Conservation , NOAA Tech. Memo, NMFS-SEFSC-415, pp. 166–168
Graham, N.A.J., Wilson, S.K., Jennings, S., Polunin, N.V.C., Bijoux, J.P., & Robinson, J. (2006) Dynamic fragility of oceanic coral reef ecosystems, PNAS, 103, no. 22
Graham N. A. J., Wilson S. K., Jennings S., Polunin N. V. C., Robinson J., Bijoux J. P., Daw T. M., (2007), Lag Effects in the Impacts of Mass Coral Bleaching on Coral Reef Fish, Fisheries, and Ecosystems. Conservation Biology 21(Issue 5), 1291-1300
Hill J., Wilkinson C., (2004), Methods for Ecological Monitoring of Coral Reefs: Version 1. A Resource for Managers. Australian Institute of Marine Science, Townsville.
Houghton, J.D.R., Callow, M.J. & Hays, G.C. (2003) Habitat utilization by juvenile hawksbill turtles (Eretmochelys imbricata, Linnaeus, 1766) around a shallow water coral reef, Journal of Natural History, 37, pp. 1269–1280
Hughes, T.P., (1994) Catastrophes, phase shifts, and large-scale degradation of a Caribbean coral reef. Science 265: 1547–1551
Hughes, T.P., Tanner, J.E., (2000), Recruitment failure, life histories, and long-term decline of Caribbean corals. Ecology 81:2250–2263
Hughes T.P., Baird AH, Bellwood DR, Card M and 13 others (2003) Climate change, human impacts, and the resilience of coral reefs. Science 301:929–933
Hughes T.P., (2007), Phase Shifts, Herbivory, and the Resilience of Coral Reefs to Climate Change, Current Biology 17, pp. 360-365
Jennings S., Boulle D. P., Polunin N. V. C., (1995), Habitat correlates of the distribution and biomass of Seychelles reef fishes. Environmental Biology of Fishes 46, 15-25
51
Jennings, S & Polunin, N. V. C. (1997) Impacts of Predator Depletion by Fishing on the Biomass and Diversity of Non-target Reef Fish Communities. Coral Reefs. 16. 71-82. Jones, G.P. & McCormick, M.I., (2002) Numerical and energetic processes in the ecology of coral reef fishes, Sale P (ed) Coral reef fishes; dynamics and diversity in a complex ecosystem, Academic Press, San Diego, pp. 221–238.
Kulbicki M., 1998, How the acquired behavior of commercial reef fishes may influence the results obtained from visual censuses. Journal of Experimental Marine Biology and Ecology 222, 11-30
Luckhurst, B. & Luckhurst, K., (1978), Analysis of the influence of substrate variables on coral reef communities, Mar Biol 49, pp. 317-323
McClanahan, T. R. & Shafir, S. H. (1990) Causes and Consequence of Sea Urchin Abundance and Diversity in Kenyan Coral Reef Lagoons. Oecologia. 83. 362-370.
McClanahan, T. R. (1994) Kenyan Coral Reef Lagoon Fish; Effects of Fishing, substrate complexity and Sea Urchins. Coral Reefs. 13. Pp. 231-241.
McClanahan, T. R., Kamukuru, A. T. & Muthiga, N. A., Gilagabher, Y. M. & Obura, D. (1995) Effect of Sea Urchin Reductions on Algae, Coral and Fish Populations. Cons. Biol. 10. 136-154.
Miller, M. W. (1998) Coral/seaweed Competition and the Control of Reef Community Structure Within and Between Latitudes. Oceangr Mar Biol Annu Rev. 36. Pp. 65-96.
Mrosovsky, N., (1983). Conserving Sea Turtles. The British Herpetological Society, London, p. 4
Obura D. O., Grimsditch G., (2009). Resilience Assessment of coral reefs – Assessment protocol for coral reefs, focusing on coral bleaching and thermal stress. IUCN working group on Climate Change and Coral Reefs. IUCN. Gland, Switzerland.
Pratchett M.S., (2007), Feeding preferences of Acanthaster planci (Echinodermata: Asteroidea) under controlled conditions of food availability. Pacific Science 61 (Issue 1), 113-120
Samoilys M., Gribble N., (1997), Manual for Assessing Fish Stocks on Pacific Coral Reefs. Queensland Training Series. Department of Primary Industries, Brisbane.
Sluka, R. D. & Miller, M. W. (2001) Herbivorous Fish Assemblages and Herbivory Pressure on Laamu Atoll, Republic of Maldives. Coral Reefs, 20. Pp. 255-262.
Spalding M. D., Jarvis G. E., (2002), The impact of the 1998 coral mortality on reef fish communities in the Seychelles. Marine Pollution Bulletin 44, 309-321
Spencer, T., Telek, K.A., Bradshaw, C. & Spalding, M.D. (2000), Coral bleaching in the Southern Seychelles During the 1997 – 1998 Indian Ocean Warm Event, Marine Pollution Bulletin, 40 (Issue 7), pp. 569-586
Syms C, Jones GP (2000) Disturbance, habitat structure, and the dynamics of a coral-reef fish community. Ecology 81: 2714–2729
Veron, J.E.N., (2000) Corals of the World, Australian Institute of Marine Science, Townsville, Australia, Vol 1–3
Witzell, W. (1983) Synopsis of biological data on the hawksbill turtle, Eretmochelys imbricata (Linnaeus, 1766), FAO Fish, Synop., pp. 137
52
9. Appendices
Appendix A. Details of sites surveyed by GVI Seychelles – Mahé, year round. Sites in
bold-type text are located within Marine Protected Areas.
Site
NoSite Name GPS
Survey
StatusGranitic/Carbonate
1 Conception North Point S 04°39.583, E 055°21.654 Core Granitic
2 Conception Central East Face S 04°39.891, E 055° 22.258 Core Carbonate
4 Port Launay West Rocks S 04º39.416, E 055º23.382 Core Granitic
5 Port Launay South Reef S 04º39.158, E 055º23.695’ Core Carbonate
7 Baie Ternay Lighthouse S 04°38.373, E 055°21.993 Core Granitic
8 Baie Ternay Reef North East S 04°38.013, E 055°22.405 Core Granitic
9 Baie Ternay Reef Centre S 04°38.321, E 055°22.504 Core Carbonate
10 Baie Ternay Reef North West S 04°38.382, E 055°22.133 Core Carbonate
11 Ray’s Point S 04°37.347, E 055°23.145 Core Granitic
12 A Willie’s Bay Reef S 04°37.650, E 055°22.889 Core Carbonate
12 B Willie’s Bay Point S 04°37.589, E 055°22.776 Core Granitic
13 A Anse Major Reef S 04°37.546, E 055°23.121 Core Carbonate
13 B Anse Major Point S 04°37.509, E 055°23.010 Core Granitic
14 Whale Rock S 04°37.184, E 055°23.424 Core Granitic
15 Auberge Reef S 04°37.024, E 055°24.243 Core Carbonate
16 Corsaire Reef S 04°37.016, E 055°24.447 Core Carbonate
17 White Villa Reef S 04º36.935, E 055º24.749 Core Carbonate
18 L’ilot North Face S 04°38.652, E 055°25.932 Core Granitic
19 Site Y S 04°37.771, E 055°22.660 Core Granitic
21 Therese North End S 04°40.101, E 055°23.737 Core Granitic
22 Therese North East S 04°40.099, E 055°23.891 Core Carbonate
23 Therese South S 04°40.764, E 055°24.310 Core Granitic
24 Site X S 04°37.059, E 055°23.783 Core Granitic
N/A Secret Beach Reef N/A Core Carbonate
53
Appendix B. Scleractinian coral genera surveyed by GVI Seychelles - Mahé.
Acroporidae
Acropora
Fungiidae
Fungia
Astreopora Herpolitha
Montipora Diaseris
Pocilloporidae
Pocillopora Cycloseris
Stylophora Podabacia
Seriatopora Halomitra
Poritidae
Porites Polyphyllia
Goniopora
Faviidae
Favia
Alveopora Favites
Dendrophylliidae Turbinaria Montastrea
Siderastreidae
Siderastrea Plesiastrea
Pseudosiderastrea Goniastrea
Coscinaraea Echinopora
Psammocora Diploastrea
Mussidae
Lobophyllia Leptasrea
Symphyllia Cyphastrea
Acanthastrea Platygyra
Blastomussa Leptoria
Oculinidae Galaxea Oulophyllia
Euphyllidae Physogyra Astrocoeniidae Stylocoeniella
Pectinidae
Pectinia
Agaricidae
Pavona
Mycedium Leptoseris
Echinophyllia Gardineroseris
MerulinidaeMerulina Coeloseris
Hydnophora Pachyseris
54
Appendix C. Fish families, genera and species surveyed by GVI Seychelles - Mahé.
FamilyScientific
name
Common
nameFeeding guild
Relevance
(Engelhardt
2004)
Butterflyfish
(Chaetodontidae)
Chaetodon
vagabundusVagabond C/I Coral recovery
Chaetodon auriga Threadfin C/I Coral recovery
Chaetodon trifascialis Chevroned C Coral recovery
Chaetodon
melannotusBlack-backed C/I Coral recovery
Chaetodon mertensii Merten's C/I Coral recovery
Chaetodon
triangulumTriangular C Coral recovery
Chaetodon
trifasciatusIndian Redfin C Coral recovery
Chaetodon
interruptus
Indian Ocean
TeardropC/I Coral recovery
Chaetodon bennetti Bennett's C Coral recovery
Chaetodon lunula Raccoon C/I Coral recovery
Chaetodon kleinii Klein's C/I Coral recovery
Chaetodon citrinellus Speckled C/I Coral recovery
Chaetodon
guttatisimusSpotted C/I Coral recovery
Chaetodon lineolatus Lined C/I Coral recovery
Chaetodon falcula Saddleback C/I Coral recovery
Chaetodon meyersi Meyer's C Coral recovery
Chaetodon
xanthocephalusYellow-headed C/I Coral recovery
Chaetodon
zanzibariensis Zanzibar C Coral recovery
Forcipiger sp. Longnose sp. C/I Coral recovery
Angelfish
(Pomacanthidae)
Apolemichthys
trimaculatusThree-spot V Visual appeal
Pomacanthus
imperatorEmperor V Visual appeal
Pomacanthus
semicirculatusSemicircle V Visual appeal
Pygoplites diacanthus Regal V Visual appeal
Surgeonfish Acanthurus sp. Surgeonfish H Algae vs. coral
55
(Acanthuridae)Ctenochaetus sp. Bristletooths H Algae vs. coral
Naso sp. Unicornfish Pl Algae vs. coral
Zanclus cornutus Moorish idol V Visual appeal
Rabbitfish
(Siganidae)
Siganus puelloides Blackeye H Algae vs. coral
Siganus corallinus Coral H Algae vs. coral
Siganus stellatus Honeycomb H Algae vs. coral
Siganus argenteus Forktail H Algae vs. coral
Siganus sutor African Whitespotted H Algae vs. coral
Snappers
(Lutjanidae)
Lutjanus gibbus Paddletail Pi Fishing pressure
Lutjanus sebae Red emperor Pi Fishing pressure
Lutjanus fulviflamma Longspot Pi Fishing pressure
Lutjanus kasmira Blue-lined Pi Fishing pressure
Lutjanus bengalensis Bengal Pi Fishing pressure
Lutjanus monostigma Onespot Pi Fishing pressure
Lutjanus vitta Brownstripe Pi Fishing pressure
Lutjanus fulvus Flametail Pi Fishing pressure
Lutjanus
argentimaculatusMangrove jack Pi Fishing pressure
Lutjanus bohar Red Pi Fishing pressure
Lutjanus russelli Russell's Pi Fishing pressure
Macolor niger Black Pi Fishing pressure
Aprion virescens Green jobfish Pi Fishing pressure
Triggerfish
(Balistidae)
Balistoides
viridescensTitan I Sea urchins & COTs
Sufflamen
chrysopterusFlagtail I Sea urchins & COTs
Balistidae Other triggerfish I Sea urchins & COTs
Emperors
(Lethrinidae)
Monotaxis sp. Redfin/Bigeye bream I Sea urchins & COTs
Gymnocranius
grandoculis
Blue-lined large-eye
breamI Sea urchins & COTs
Lethrinus olivaceous Longnosed I Sea urchins & COTs
Lethrinus nebulosus Blue-scaled I Sea urchins & COTs
Lethrinus
rubrioperculatusRedear I Sea urchins & COTs
Lethrinus
xanthochilusYellowlip I Sea urchins & COTs
Lethrinus harak Thumbprint I Sea urchins & COTs
Lethrinus lentjan Pinkear I Sea urchins & COTs
Lethrinus obsoletus Orange-striped I Sea urchins & COTs
Lethrinus Yellowfin I Sea urchins & COTs
56
erythracanthus
Lethrinus mahsena Mahsena I Sea urchins & COTs
Lethrinus variegatus Variegated I Sea urchins & COTs
Groupers
(Serranidae)
Anyperodon
leucogrammicusSlender Pi Fishing pressure
Cephalopholis argus Peacock Pi Fishing pressure
Cephalopholis
urodetaFlagtail Pi Fishing pressure
Cephalopholis
miniataCoral Hind Pi Fishing pressure
Cephalopholis
sonneratiTomato Pi Fishing pressure
Epinephelus merra Honeycomb Pi Fishing pressure
Epinephelus
spilotocepsFoursaddle Pi Fishing pressure
Epinephelus
polyphekadionCamouflage Pi Fishing pressure
Epinephelus
caeruleopunctatusWhitespotted Pi Fishing pressure
Epinephelus
fuscoguttatusBrown-marbled Pi Fishing pressure
Epinephelus tukula Potato Pi Fishing pressure
Epinephelus fasciatus Blacktip Pi Fishing pressure
Aethaloperca rogaa Redmouth Pi Fishing pressure
Variola louti Yellow-edged Lyretail Pi Fishing pressure
Plectropomus laevis Saddleback Pi Fishing pressure
Plectropomus
punctatusAfrican Coral Cod Pi Fishing pressure
Sweetlips
(Haemulidae)
Plectorhinchus
orientalisOriental I Sea urchins & COTs
Plectorhinchus picus Spotted I Sea urchins & COTs
Plectorhinchus
gibbosusGibbus I Sea urchins & COTs
Parrotfish
(Scaridae)
Bolbometopon
muricatumBumphead parrotfish C/H Coral damage
Scaridae Other parrotfish H Algae vs. coral
Wrasse (Labridae)
Cheilinus trilobatus Tripletail I Sea urchins & COTs
Cheilinus fasciatus Redbreasted I Sea urchins & COTs
Oxycheilinus
digrammusCheeklined splendour I Sea urchins & COTs
Cheilinus undulatus Humphead I Sea urchins & COTs
Tetraodontidae Puffers I Sea urchins & COTs
Diodontidae Porcupinefish I Sea urchins & COTs
57
Holocentridae
Soldierfish Pl Upwelling areas
Squirrelfish Pl Upwelling areas
Appendix D. Fish feeding guilds analysed by GVI Seychelles – Mahé.
Code Feeding guild
Description (adapted from Obura and Grimsditch, 2009) Key species
Pl Planktivores
Resident on reef surfaces, but feed in the water column. Their abundance is related to quality of
reef habitat for refuge, and water column conditions.
Soldierfish, Squirrelfish, Unicornfish
Pi Piscivores
High level predators. Exert top-down control on lower trophic levels. Important fisheries species but very vulnerable to overfishing thus good indicators
of the fishing pressure on a reef.
Groupers, Snappers
C CorallivoresRelative abundance is an indicator of coral
community health
Butterflyfish (Chevroned, Triangular, Bennetts,
Indian Redfin, Meyers,
Longnose sp.)
V Varied diet
Feed on coral competitors such as soft corals and sponges. Relative abundances may be an indicator of abundance of these prey items and of a phase
shift.
Angelfish, Moorish Idol
I Invertivores* Second-level predators with highly mixed diets including small fish, invertebrates and dead
animals. Important fisheries species thus abundances are a good indicator of fishing
pressure.
Sweetlips, Emperors, Pufferfish,
Porcupinefish, Wrasse
(Tripletail, Redbreasted, Cheeklined Splendor,
Humphead), Triggerfish
(Titan, Flagtail,
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Other)
H Herbivores
Exert the primary control on coral-algal dynamics. Parrotfish, Surgeonfish, Bristletooth, Rabbitfish
May indicate phase shift from coral to algal dominance in response to mass coral mortality or
pressures such as eutrophication.
C/HCorallivore/Herbivore
Relative abundance is a secondary indicator of coral community health
Bumphead parrotfish
C/ICorallivore/Invertivore
Relative abundance can be a secondary indicator of coral community health
Butterflyfish (Vagabond, Threadfin,
Blackbacked, Mertens, Indian
Ocean Teardrop, Racoon, Kleins,
Speckled, Spotted, Lined,
Saddleback, Yellow headed,
Zanzibar)
Appendix E. Fish species lists divided into commercial and reef species analysed by
GVI Seychelles – Mahé.
Commercial Fish Species Reef Fish Species
Siganidae (Rabbitfish) Chaetodontidae (Butterflyfish)
Lutjanidae (Snappers) Pomacanthidae (Angelfish)
Lethrinidae (Emperors) Acanthuridae (Surgeonfish)
Serranidae (Groupers) Balistidae (Triggerfish)
Haemulidae (Sweetlips) Labridae (Wrasse)
Scaridae (Parrotfish) Tetradontidae (Pufferfish)
Diodontidae (Porcupinefish)
Holocentridae (Soldierfish & Squirrelfish)
Zanclus cornutus (Moorish Idol)
Bolbometopon muricatum (Bumphead Parrotfish)
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Appendix F. List of invertebrate species surveyed on 50m belt transects by GVI
Seychelles – Mahé.
Mollusca (Gastropoda) Drupella spp. Drupella
Mollusca (Bivalvia) Tridacnidae Giant Clam
Sea Stars (Asteroidea)
Culcita spp. Cushion Sea Star
Acanthaster planci Crown of Thorns Sea Star
Other Sea Stars
Sea Urchins (Echinoidea)
Diadema spp. Long Spine Urchin
Echinometra spp. Mathae’s Urchin
Echinothrix spp. Short Spine Urchin
Pencil Urchin
Toxopneustes pileolus Flower Urchin
Cake Urchin
Sea Cucumbers (Holothuroidea)
Holothuria artra Lollyfish
Holothuria fuscopunctata Elephant Trunk
Holothuria fuscogilva White teatfish
Holothuria nobilis Black teatfish
Holothuria sp.(undescribed) Pentard
Bohadschia spp. Bohadschia
Actinopyga spp. Actinopyga
Actinopyga mauritiana Yellow Surfish
Stichopus spp. Stichopus
Thelenota ananas Prickly Redfish
Pearsonothurian graeffei Flowerfish
Thelenota anax Royal
Holothuria edulis Edible Sea Cucumber
(Cephalopoda) Octopus spp. Common Reef Octopus
Lobsters (Palinura)Panulirus spp. Spiny Lobster
Parribacus spp./Scyllarides spp. Slipper Lobster
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