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Frantz 1
Blair Frantz
Dr. Tamsen Byfield
Marine Protected Areas: Management Techniques & Policies
SFS 3510
June 23, 2014
Email: [email protected] or
Abundance and Biodiversity of Queen Conch (Strombus gigas) in Marine Reserves vs. Non-
Reserves
1. Introduction:
The mollusk, known internationally as the Queen Conch or Pink Conch, and scientifically
as Strombus gigas of the Strombidae family, is a Caribbean marine animal of great importance to
the diet and livelihood of thousands of families throughout the Caribbean. Conch are found in
shallow, clear water at depths generally less than 30 meters. Conch are limited to that depth
range by limits in seagrass and algae cover, as food sources. Seagrass meadows, coral rubble,
algal plains, and sandy substrates are the preferred habitat for conch (McCarthy, 2007).
Queen Conch has high commercial fishery value and is commercially threatened. The
large beautiful shell has been prized by tourists in recent years, but was previously valued more
for its meat. Queen Conch have provided a staple meat source in the Caribbean region for
centuries and in recent times have been extensively overfished for this reason. Their flesh is also
used as fishing bait and the shells can be sold for the tourist trade. The tendency of conch to
aggregate in shallow waters in order to spawn in the summer months has made the species
vulnerable. The increase in fishing pressure caused by its rising commercial value since the
1970's has caused Queen Conch populations to decline throughout their distribution range. This
is largely due to the slow maturation growth cycle (three to four years) of the Queen Conch. At
this rate, conch populations are unable to offset the development of fisheries technical
enhancements allowing them to catch larger quantities and at previously unobtainable depths
(Gascoigne, 2005).
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Queen Conch face many other threats such as habitat loss, poaching, habitat management
and critical depensation threshold and tourist potential. Damage to key areas of habitat,
particularly mangrove and seagrass beds have reduced the availability of nursery areas for young
conch. Poaching, in combination with legal take can prevent populations of conch from
recovering. Habitat management for juvenile conch is very specific, therefore making
management difficult. Juvenile conch habitat is suspected to be shallow, with turtle grass,
Thalassia testudinum beds. Critical depensation threshold: when Queen Conch populations drop
below a critical density point, reproduction ceases to be effective. Queen Conch rely on high
density breeding populations for successful breeding. An unsustainable conch population cannot
be considered healthy until population density has significantly increased above current levels. If
an unsustainable population should ever fall below the critical depensation threshold, intensive
restoration management will be required for basic stock maintenance. The final threat involves
tourist potential. As availability of conch becomes limiting, demand for conch meat and shell
products may be expected to become greater (Queen conch Strombus gigas, 2010).
The Queen Conch is listed on Appendix II of the Convention on International Trade in
Endangered Species (CITES), thus requiring an export permit for trade to occur. In 1996, the
countries within this conch’s range recognized the importance of the species and adopted an
International Queen Conch Initiative to promote a common international management strategy
for the queen conch resource in the Caribbean region. It has been suggested that harvesting limits
or marine reserves will allow the species to recover from overfishing (Gascoigne, 2005). There is
sufficient evidence that over fishing negatively affects ecosystems, therefore a reduction in
fishing is the mainstay of fisheries- model case studies predicting that the establishment of
marine protected areas (MPAs), especially for overexploited populations, can mitigate ecosystem
effects of fishing; reserve protection should increase biomass and density (“Marine Fishing
Strombus Gigas”, 2013).
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Specifically, in South Caicos of Turks and Caicos Islands (TCI) reef degradation and
depletion of fisheries has impacted the livelihood of the local community. Presently the South
Caicos economy is based on tourism and fisheries- primarily conch. Unsustainable and
destructive fishing practices in combination with increased human activity threaten coastal
habitats and the organisms and industries that they support. Increased tourism and the creation of
the infrastructure that supports this industry often have deleterious effects on the environment.
An increase in tourism and coastal development will lead to increased demand for marine
resources such as the Queen Conch. In addition, climate impacts on local ecosystems will greatly
impact the fishing industry. The TCI has an extensive network of 34 protected areas including
Tuckers Reef and Admiral’s Aquarium. These marine reserves in South Caicos are established to
ensure the sustainability of natural and historic resources- such as the Queen Conch. However,
lack of scientific knowledge, local understanding and personal and environmental stewardship
hinders effective management of resources and the effectiveness of these protected areas (“Turks
and Caicos”, 2014).
Dilemma: do marine reserves really work? How can we best ensure sustainable fisheries?
This study focusses on conch dispersal, biodiversity, maturation, depth and habitat in reserve
areas vs. non reserve areas within the South Caicos area of TCI. The marine reserve in South
Caicos where this research was conducted was East Harbour Lobster and Conch Reserve. The
results from this field work can be used by scientists to better protect the high densities of native
adult Queen Conch using methods such as marine protected reserves, and more. The Queen
Conch (S. gigas) will be protected, be more abundant and have greater biodiversity in marine
reserve areas vs. non marine reserves provided effective resource management and conservation
programs, which include networks of sustainable protected areas are effectively maintained
throughout the TCI and entire Caribbean region. It is also hypothesized that the density of conch
outside marine reserves will not be high enough for mating to occur because there are not enough
Frantz 4
adult conch as a result of overfishing, and most adult conch will be found in seagrass areas or
algal cover habitats, as identified in previous studies as their preferred habitat due to essential
grazing needs.
2. Method:
The objective of this study was to assess the status of Caicos Bank benthic communities in
protected vs. non-protected sites in South Caicos. The field work was conducted at marine
reserve sites (East Harbour Lobster and Conch Reserve) which included Admirals Aquarium,
Tuckers Reef and HDL. The three non-marine reserve sites surveyed included AJ11, the south
end of Long Cay and Dryers Reef (Figure 1). This study was conducted by students from The
School for Field Studies (SFS) over a two-day period from June 19 – 20, 2014.
Figure 1. Map of surveyed areas of South Caicos.
During team field research vertebrates, invertebrates and the habitat organisms were
studied. Some key macro- invertebrates observed and recorded included sea urchins: Diadema
antillarus and Tripneustes ventricosus. Conch observed and recorded included the Queen Conch
and Strombus costatus. Lobster observed and recorded included Panulirus argus. If Queen
Conch was observed it was noted and recorded if the conch had a flared or roller lip. The
Frantz 5
significance of this observation was used for determining maturity of the conch. In younger
specimens of Queen Conch, the absence of a flared lip was an indication that the observed
animal had not reached sexual maturity (Figure 2).
Figure 2. Image of Queen Conch (Strombus gigas) exhibiting flared lip.
From: http://www.fishwatch.gov/seafood_profiles/species/conch/species_pages/queen_conch.htm
The type of habitat where these invertebrates were observed and found was also recorded.
The five classes of habitat noted in our observations included sandy plain, algal plain, seagrass,
coral and rubble (Figure 3).
Figure 3. Image of Queen Conch (Strombus gigas) in seagrass.
From: http://www.fishwatch.gov/seafood_profiles/species/conch/species_pages/queen_conch.htm
Frantz 6
Data were collected using visual belt transects and quadrat surveys. Quadrat surveys and visual
belt transect surveys were used to collect ecological data in a standardized way. These sampling
methods provided more accurate data than random sampling or simply guessing; they also took
less time than counting every specimen within a specific area. Both transects and quadrats were
used to determine the diversity and quantity of organisms in a specific area. A transect was
stretched 50 x 3 meters over the area we intended to study. A quadrat (0.5 meter by 0.5-meter
square) was used every 5 meters while swimming down the transect, based on the habitat
present, with visual observations recorded on an underwater dive slate. We estimated the
percentage of habitat cover within the quadrat. While quadrat tools were being utilized to
observe habitat on one side of the transect another observer swam along the 50 meter transect
recording all invertebrates observed and the habitat they were found in (i.e., sandy plain, algal
plain, seagrass, coral or rubble). Start and end depths of a specific site were recorded using a dive
computer. The information gathered during sampling would be used for the estimation of the
diversity and quantity of organisms within the habitat. The results of total population count for
Queen Conch within marine reserves vs. non-marine reserves, as well as counts of flared vs.
roller lip conch by survey location were organized in an Excel spreadsheet. Data was analyzed,
using mean calculations where appropriate to validate the existence of observed frequencies and
patterns of Queen Conch in protected vs. non-protected reserves.
3. Results:
The data collected was used to determine the effect of marine reserves vs. non marine
reserves on the abundance and maturity of Queen Conch. A comparison of total population
counts of Queen Conch from marine reserves vs. non marine reserves showed higher total
populations within the marine reserves surveyed. A comparison of species maturity, using
population counts of total flared vs. roller lip conch showed higher numbers of roller lip conch
present within both the protected sites and the non-protected sites.
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Figure 4. - Total population counts of Queen Conch (Strombus gigas) with flared vs. roller
lip from protected and non-protected areas.
A comparison of the total populations of Queen Conch with flared vs. roller lip within
individual sites is shown in Figure 5. Marine reserves are hypothesized as fostering the growth
and stability of Queen Conch populations. Our observations tend to support this hypothesis. We
observed a total 46 Queen Conch (30 roller lip and 16 flared lip) within the protected quadrats,
with a mean number of 2.88 animals per quadrat, but with a fairly large standard deviation of
3.81 conch (see Table 1).
In contrast, the survey of unprotected waters resulted in much lower numbers of conch (19 total,
14 roller lip, and just 5 mature conchs. The mean number of total animals per quadrat was 1.19,
with a standard deviation of 1.68 conch (see Table 1).
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Table 1. – Total Queen Conch population counts in protected and non-protected areas.
Site
Queen
Conch
flared lip
(QCF)
Queen
Conch
unflared
lip (QCR)
Queen
Conch
Total
Site
Queen
Conch
flared lip
(QCF)
Queen
Conch
unflared
lip (QCR)
Queen
Conch
Total
Protected Unprotected
Admirals 1 2 3 AJ11 0 0 0
Admirals 2 8 10 AJ11 0 0 0
Admirals 1 3 4 AJ11 0 1 1
Admirals 8 5 13 AJ11 1 4 5
Admirals 1 3 4 AJ11 0 0 0
Admirals 0 5 5 AJ11 1 0 1
HDL 0 1 1 Dryers Reef 1 1 2
HDL 0 2 2 Dryers Reef 0 4 4
HDL 0 1 1 Dryers Reef 0 0 0
HDL 0 0 0 Dryers Reef 0 0 0
Tuckers Reef 0 0 0 SELC 0 0 0
Tuckers Reef 0 0 0 SELC 2 2 4
Tuckers Reef 3 0 3 SELC 0 1 1
Tuckers Reef 0 0 0 SELC 0 1 1
Tuckers Reef 0 0 0 SELC 0 0 0
Tuckers Reef 0 0 0 SELC 0 0 0
Observations 16 16 16 Observations 16 16 16
# of Conch 16 30 46 # of Conch 5 14 19
Mean 1.00 1.88 2.88 Mean 0.31 0.88 1.19
Std Deviation 2.07 2.39 3.81 Std Deviation 0.60 1.36 1.68
In the above tables mean and SE values are provided.
The value of marine reserves in aiding conch populations is evident in the survey,
however, the contribution from Admirals Aquarium was disproportional. Admirals Aquarium
accounted for 39 of the 46 conch observed in the protected quadrats, with a mean number of
animals per quadrat of 6.5. The other protected areas appeared to be less productive than the
unprotected quadrats, with a mean number of conch of only 0.70 per quadrat versus 1.19 for the
unprotected areas of the survey (see Table 2). This raises questions and a need for additional
research as to why Admirals is so much more productive than these other protected areas, or
what must be done to raise their productivity.
Frantz 9
Figure 5. - Population counts of Queen Conch (Strombus gigas) with flared and roller lip
from protected and non-protected areas.
Protected areas included: Admirals Aquarium, HDL and Tuckers Reef. Non-protected areas include: AJ11,
Dryers Reef and SELC.
Table 2. – Total Queen Conch population counts in marine reserve areas.
Site
Queen
Conch
flared lip
(QCF)
Queen
Conch
unflared
lip (QCR)
Queen
Conch
Total
Site
Queen
Conch
flared lip
(QCF)
Queen
Conch
unflared
lip (QCR)
Queen
Conch
Total
Protected (Others)
Protected (Admirals) HDL 0 1 1
Admirals 1 2 3 HDL 0 2 2
Admirals 2 8 10 HDL 0 1 1
Admirals 1 3 4 HDL 0 0 0
Admirals 8 5 13 Tuckers Reef 0 0 0
Admirals 1 3 4 Tuckers Reef 0 0 0
Admirals 0 5 5 Tuckers Reef 0 0 3
Tuckers Reef 0 0 0
Observations 6 6 6 Tuckers Reef 0 0 0
# of Conch 13 26 39 Tuckers Reef 3 0 0
Mean 2.17 4.33 6.50
Std Deviation 2.93 2.16 4.04 Observations 10 10 10
# of Conch 3 4 7
Mean 0.30 0.40 0.70
Std Deviation 0.95 0.70 1.06
In the above tables mean and SE values are provided.
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In Figure 6 the effect of habitat depth on population counts is illustrated. Admirals
Aquarium, one of the shallowest areas surveyed exhibited the highest amount of Queen Conch.
Figure 6. - Effect of habitat depth on population counts of Queen Conch (Strombus gigas)
from protected and non-protected areas.
= Non-protected
= Protected
Table 3 summarizes habitat observations; the non-protected reserves were more diverse,
containing varying amounts of algal plain, coral, soft coral and plain sand. The habitat
composition of the three marine reserves surveyed consisted primarily of plain sand and coral,
and some rubble.
Table 3. – Habitat composition for surveyed marine reserve and non reserve sites.
Habitat Composition of Marine Reserve and Non-Reserve Sites
Location Status Observed Composition
Admiral Aquarium protected coral, plain sand
HDL protected coral, plan sand
Tuckers Reef protected coral, plain sand, rubble
Dryers Reef unprotected algal plain, coral
AJ11 unprotected soft coral
SELC unprotected coral, plain sand
Frantz 11
4. Discussion:
Overfishing has led to declines in populations of Caribbean queen conch Strombus gigas,
leading to its listing on CITES Appendix II. Marine Reserves such as the East Harbour Conch
and Lobster Reserve are increasingly being used as a conservation tool for protecting stocks and
sustaining fisheries. This study supports the hypothesis that more conch would exist in marine
reserves vs. non marine reserves. The higher populations of Queen Conch within the East
Harbour Lobster and Conch Reserve (EHLCR) demonstrate success in increasing the abundance
of conch populations, as well as density and diversity. For Queen Conch the establishment of
marine reserves is theoretically the best way to allow populations to recover. As ecological effect
results show, reserves are the best way to provide protection for this invertebrate species. The
invertebrate density trends and numerical values from this field work are positive, with diversity
and abundance for Queen Conch higher in reserves.
The presence of more juvenile conch rather than mature conch was also noted in the
marine reserves surveyed. This phenomenon could be due to habitat preference of juvenile conch
as EHLCR is an important nursery ground for juvenile conch. The habitat conditions within the
marine reserve are ideal for juvenile conch where they are able to thrive. One study showed that
within the EHLCR juvenile queen conch were most abundant in a unique coral habitat
overgrown with macroalgae and interspersed with seagrass. Within the same study the highest
number of juveniles were found in algal plains. These findings suggest that within EHLCR larval
settlement and juvenile survival may be highest in algal plains, possibly because the macroalgae
within this habitat induce settlement and provide a stable food source while the sandy substrate
allows juveniles to bury to avoid predation. Further analysis and studies of EHLCR suggest that
post settlement juveniles are moving from nursery ground into coral rubble areas. Small
juveniles may move from the nursery ground where they initially settle into the coral rubble
when they become larger and no longer need to bury to avoid predation or are better able to
Frantz 12
negotiate the terrain. As juveniles grow they require more food which might explain why they
are moving into the densely vegetated coral rubble habitat and why this researcher observed high
densities of juveniles in coral rubble during this field work. Regardless of why juvenile conch are
moving into coral rubble, it is clear that in EHLCR the successful recruitment of these
individuals into more suitable areas as they grow is dependent on the progression of these critical
juvenile habitats. Fortunately, in the case of EHLCR these habitats are within the reserve
boundaries and therefore protected. Based on this work it is reasonable to say that survival of
juveniles is higher in areas where food is abundant and the substrate is conductive to burial
(Rudd, 2001).
The protection of nursery grounds is critical, and the EHLCR could potentially support an
increase in the abundance of Queen Conch both inside and outside the reserve boundaries by
ensuring that a greater proportion of settled larvae reach maturity. Protection of juvenile conch
within the nursery ground could increase the abundance of adult and mature queen conch inside
the reserve. Increases in spawning stock would lead to an increase in larval export and the
spillover effect, thus generating fishery benefits.
Regarding total population counts in the marine reserves surveyed there was more overall
Queen Conch in Admirals Aquarium versus the other two marine reserve sites. The unique
habitat and depth refugia in Admirals Aquarium are conducive for conch survivability. The depth
of Admiral Aquarium is not too deep, and not too shallow, making this habitat perfect for Queen
Conch to thrive and flourish. The population counts from this study support the belief that most
Queen Conch are found in depths of about 2.3 meters, with most of the Queen Conch in
Admirals Aquarium were found at or about this same depth. Queen Conch is herbivorous
therefore most are found in well lighted, photosynthetic algal regions where seagrass beds and
algal cover is present so they can graze. The habitat composition of Admiral Aquarium has
everything a Queen Conch needs to survive and thrive. There are other studies done in EHLCR
Frantz 13
identifying nursery grounds near Admirals Aquarium that possess some key characteristics that
induce the settlement of larvae, and in turn, are likely the source of a large proportion of
individuals that are eventually recruited into the adult segment of the population. Learning more
about the habitat requirements of small juvenile conch, and identifying key nursery grounds, is
important for the management of conch stocks and the design for protected areas for this species
(Population Assessment of Queen Conch, 2001).
For reproductive survival success high densities of conch are required. If the number of
conch continues to decrease in the fishery, soon conch may no longer recruit this reserve area.
During assessment, few conchs were found in fished areas, which is likely because of fishing
pressure. Other studies conducted in EHLCR show that illegal fishing takes place inside the
nursery habitats for Queen Conch within the reserve. This demonstrates that management of
these reserves is difficult to enforce, and scientists need to educate the community about
sustainable fishing and communicate more effectively about the value of the reserve to their
economy and the environment. Illegal fishing occurs when fisherman come to South Caicos and
stay for only a short time, and have no long term vested interest in the health of the fishery.
Typically, they fish mostly undersized, out of season or illegally taken conch. While the EHLCR
may be a successful reserve for all ages of conch, even with the presence of fishing pressure,
fishing management is difficult to enforce. Fishing management may never be completely
successful in this region, yet the EHLCR continues to provide a home for a significantly larger
amount of conch than do the fished areas. For more sustainable fishing, and protection of
exploited species I support the position that a network of reserves similar to the EHLCR in other
marine habitats experiencing problems would address some of the problems with over fishing. A
single reserve will never be sufficient to protect exploited species (Population Assessment of
Queen Conch, 2001).
There are many management plans and ideas for the future of TCI that can be put in place
Frantz 14
in an effort to prevent further declines of already overexploited resources and to ensure a
sustainable fishery in those areas that still have stable and healthy populations. Minimum size
restrictions can be put in place to limit the harvest to mature individuals in order to ensure a vital
spawning stock and to give all individuals a chance to breed. I would recommend and support
gear restrictions. Modern day gear used in Queen Conch fishery allows fishermen to harvest
more conch per hour and fishing trip. Moreover, the use of these gears also allows divers to
exploit populations which were normally not reached by free divers and which were formally
important spawning stock refugia. Limited entry into fishing areas would also be a good idea to
help protect the overexploited Queen Conch. Limited entry into the fishery is normally regulated
through restriction of the number or types of vessels and / or the number of divers that are
allowed to harvest conch. Such restrictions can help to reduce the overall fishing pressure and
may be a useful tool in areas where the fishery is rapidly expanding. Catch and export quotas-
restrictions on the overall catch and export by setting an annual quota or a quota per fishing
season can be another effective tool to manage fishing pressure. A rather simple quota is to
restrict the number of organisms that may be harvested per person or per boat. Improving the
monitoring of trade in Queen Conch meat and facilitating the regulation of non-commercial trade
in Queen Conch shells is also a large part of the management of this species. Management of the
Queen Conch can be improved by establishing an action plan and a team of experts. Scientists
need to increase awareness among stakeholders and communicate regularly with the
stakeholders. To be effective, any conservation action plan must take many factors into
consideration including science, state of the economy, nature of the harvest sector, and the
primary use of conch products, the community, long term consequences of Queen Conch harvest
(especially regarding genetics) and enforcement (Theile,2001).
Frantz 15
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