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DFO Pinniped Research Program
Pinniped Research Program
DFO Nanaimo, BC
Strahan Tucker
1
Pinniped Species in BC
1. Harbour seals
2. Steller sea lions
Breeding species: have pan-Pacific breeding distribution
2
Non-breeding species
1. Northern elephant seals
2. Northern fur seals
3. California sea lions
Photo: Brian Gisborne
Pinniped Research Program
Program Drivers:
• Species at Risk (SARA) considerations
Steller Sea Lions are designated as Special Concern based on
the limited number of breeding sites and concentrated breeding
aggregations (the bulk is on 1 site, Triangle Island)
links with Killer Whale Recovery Plans: understanding
competition with Resident Killer whales for prey resources
harbor seals are the main prey item for Biggs or Transient Killer
whales (threatened status)
• Fisheries Management: the contribution of predation to natural
mortality and implications for population benchmarks
3
Photo: Brian Gisborne
Pinniped Research Program: What we doObjective: understand the drivers of population trends of pinnipeds, their
feeding ecology and their influence on prey/predator population dynamics
Core activities:
• population assessments: provide current abundance data
1. Standardized aerial surveys since early 1970’s
2. GPS telemetry based correction factors (CF) to convert counts to
abundance
3. Contribution to US brand resight database (US animals)
• diet assessments: do pinnipeds have an impact on commercially/
culturally important species?
1. Scat analysis
4
Strait of Georgia: Index site
Harbour seal abundance: Strait of Georgia
• Highest density of seals ~40% of BC population
• Aerial surveys are undertaken every 5 years
• Last survey 2014; estimate of harbour seal
population in the Strait of Georgia was ~39,000
• Next survey planned for 2019
Majewski and Ellis unpublished
5
DFO. 2010. Population Assessment Pacific Harbour Seal (Phoca vitulina richardsi). DFO Can. Sci. Advis. Sec. Sci. Advis. Rep. 2009/011.
Harbour seal abundance: BC coast wide
• Since the late 1990’s all other areas of the coast have been
surveyed on a 5-10 year interval from which a coast wide
abundance estimate has been compiled.
• Last compilation 2008; total population size in BC waters
was approx. 105,000
• Last survey completed in 2018: final counts and results
targeted to be published in 2020
6
Steller Sea Lion
1913 estimates
• Aerial surveys undertaken during pupping season (July) for total
breeding population assessments
• Range wide surveys conducted on a 4 year interval in coordination
with US counterparts
• Latest population estimate (2013) in BC waters: 33,000-39,000
animals in summer rookeries and haulouts, approx. 48,500
animals in winter
• Last survey in 2017; final abundance estimates to be published
Fall 2019
Olesiuk 2018
7
California Sea Lions• Relative overwintering counts are made
opportunistically from winter surveys
• Updated counts of 2017 survey are expected to be
published Fall 2019
Southeast Alaska
Washington
Oregon
California
British Columbia
120°W
120°W
130°W
130°W
140°W
140°W
150°W
150°W
60°N 60°N
50°N 50°N
40°N 40°N
30°N 30°N8
Harbour seals: final abundance estimate is a 2 step process
1. Obtain a census from aerial surveys of haul-out sites
2. Apply an upward correction factor based on the proportion of
seals actually hauled out
Improvements in population assessment methodology
Aerial surveys undertaken during pupping season (summer) for total breeding population assessments
sample of telemetry-tagged seals
The last deployments were in the 90’s
9
Since the 1990’s…things have changed
Transient killer whale
Courtesy of Thomas Doniol-Valcroze, DFO
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
1973 1978 1983 1988 1993 1998 2003 2008 2014
Pro
port
ion o
f E
stim
ate
d A
bundance
NEGULF
NWGULF
GULFISL
HOWESD
FRASERR
BBAY
SGULF
Shifts in the relative distribution of harbour seals among the Strait of Georgia
subareas from 1973-2014.
• the harbor seal population is no longer increasing
• evidence for a redistribution of animals to North SoG
• major predator transient killer whales: are increasing
and more commonly observed in the area
• Harbor seals routinely haul out for hours at a time daily;
dependent on tides and time of day
• Observational evidence suggests that seals might
spend more time hauled out to avoid killer whale
predation
10
Harbour seals
• New deployments of GPS satellite tags planned for February 2019 in Strait of Georgia
• Multiyear project; deployments in other areas of BC
Improvements in population assessment methodology–
effort to update correction factors
Aerial surveys undertaken during pupping season (summer) for total breeding population assessments
?
11
Pinniped diets:
Context – Complex and changing ecosystems
• Marine ecosystems are complex
• Pinnipeds eat a variety of types of fish and
other prey
• Other animals compete with pinnipeds for
the same prey (e.g., whales, dolphins,
porpoise, seabirds, marine fish…).
• Other animals depend on pinnipeds for food
(e.g., transient killer whales, sharks)
• Factors other than predation can affect fish
abundance (fishing, habitat quality, climate)Okey, T.A., H.M. Alidina, A. Montenegro, V. Lo, S. Jessen.
2012. Climate change impacts and vulnerabilities in
Canada’s Pacific marine ecosystems. CPAWS BC and
WWF-Canada, Vancouver, BC
12
Some facts on pinniped diet and
exploitation of key fisheries resources
• To varying degrees, these species utilize both pelagic and benthic habitats from
riverine estuaries to the oceanic zone beyond the continental shelf representing
a broad range of foraging strategies
• Each of the species tend to be opportunistic in their diets, exploiting seasonally
abundant prey, feeding on a mix of pelagic forage fish such as herring and
benthic fish such as rockfish
• However, explicit diet data for these species in BC are sparse and have been
taken opportunistically and irregularly
• Little is known about how key prey are partitioned both within and between species over varying spatial and temporal scales
13
Photo: Brian Gisborne
DFO has initiated new research to update knowledge of the temporal (monthly/annual)
and spatial (river-estuary and non-estuary sites) variation in pinniped diets using:
scat-based methods
• Samples are readily obtained
• hard-part identification and DNA-metabarcoding provide accurate species
composition of the diet and size-class of prey
• recent advances in DNA sequencing technology have revolutionized the field of
molecular diet analysis with high resolution
• DNA from the animal itself can be extracted from scat providing value added
information such as sex and population structure
Diet assessment
14
Case Study: Harbour Seals - Strait of Georgia
Non estuary
Estuary
2012-13
15
Case Study: Harbour Seals - Strait of Georgia
Non estuary
Estuary
2012-13
Non estuary
Estuary
2014
16
Case Study: Harbour Seals - Strait of Georgia
Non estuary
Estuary
2012-13
Non estuary
Estuary
2014
Non estuary
Estuary
2016-17
70 scats/month (April – November 2016 and April-May 2017)
1 estuary site (Cowichan Bay)
~ 400 samples
7 primary non-estuary sites
+ other non-estuary sites ~1300 harbour seal and ~300 sea lion samples
17
Case Study: Harbour Seals - Strait of Georgia
18
Case Study: Harbour Seals - Strait of Georgia
19
2012 2013 2014 2016 2017
Jun-Jul (54)
Aug-Sep (48)
Oct-Nov (35)
Apr-May (36)
Jun-Jul (40)
Aug-Sep (49)
Oct-Nov (43)
Apr-May (32)
Jun-Jul (35)
Aug-Sep (77)
Oct-Nov (133)
Dec (11)
Apr-May (22)
Jun-Jul (86)
Aug-Sep (78)
Oct-Nov (69)
Apr-May (65)
0
10
20
30
40
50
60
70
80
90
Year
Die
t %
Salmon in diet at Cowichan (2012-2017)
Interannual variability - Cowichan Bay
2012 2013 2014 2016 2017
Thomas et al. 2017 Nelson Current study
Case Study: Harbour Seals - Strait of Georgia
20
Conclusions
Site selection influences consumption estimates
• Salmon consumption inside vs. outside estuaries:
significantly higher in estuaries in the fall (Chum Vs
Chinook)
Annual and seasonal variability influence estimates
• Salmon in diet in estuaries follows an annual pattern
BUT
highly variable year to year and between seasons
Long-term monitoring is critical for assessing impacts of
predation
Brian Gisborne
Case Study: Harbour Seals - Strait of Georgia
21
• Monthly collections at 5 index sites; opportunistic at others (sea lions)
Scat Sampling program 2018 and beyond
22
• Monthly collections at index sites West Coast Vancouver Island and Queen Charlotte
Strait
Scat Sampling program 2018 and beyond
23
Summary
DFO BC Research Pinniped Program: Ecosystem perspective
Short term goals
1. Ongoing diet sampling at index sites within Salish Sea and Vancouver Island
2. Ongoing population assessments
3. Coordinated Salish Sea harbour seal population and diet surveys with US counterparts
4. Maximize information from scats
• sex markers
• population structure
• Individual specialization
• role of infectious agents in predation susceptibility
Longer Term goals
1. Applying alternate tools for diet estimation: by applying complementary methods of estimation we
gain a comprehensive picture of diet (stable isotopes and fatty acids)
2. Expanded geographic scope
3. Building and expanding linkages across disciplines:
• Fisheries & Oceanographic surveys: foodweb dynamics and quality
• trends amongst other predators: seabirds, sharks, salmon…
• Genomics (from diet assessment to population structure to functional genomics~physiology) 24