dfo pinniped research program - frafs - fraser river aboriginal … · 2019-01-25 · harbour seal...

DFO Pinniped Research Program

Pinniped Research Program

DFO Nanaimo, BC

Strahan Tucker

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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

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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

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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Majewski and Ellis unpublished

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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

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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

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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

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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

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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

?

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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

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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

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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

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Case Study: Harbour Seals - Strait of Georgia

Non estuary

Estuary

2012-13

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Non estuary

Estuary

2012-13

Non estuary

Estuary

2014

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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

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18


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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


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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


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• Monthly collections at 5 index sites; opportunistic at others (sea lions)

Scat Sampling program 2018 and beyond

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• Monthly collections at index sites West Coast Vancouver Island and Queen Charlotte

Strait

Scat Sampling program 2018 and beyond

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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

dfo pinniped research program - frafs - fraser river aboriginal … · 2019-01-25 · harbour seal...

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