Center of Expertise in Marine Mammalogy

Scientific Research Report
2015-2017

Table of Contents

• Complete Text
• Introduction
• Using aerial infrared images to count ringed seals on ice
• The use of unmanned aerial vehicles (UAV)
• 2017: A Marine Mammal Odyssey, Eh!
• Mark-recapture analysis from long-term study on Sable Island identifies changes in demographic rates in northwest Atlantic Grey Seals
• OTN – Using grey seals (Halichoerus grypus) as bioprobes to estimate phytoplankton biomass
• Northwest Atlantic International Sightings Survey (NAISS) of Marine Megafauna on the Continental Shelf From Northern Labrador to the Bay of Fundy
• Monitoring Movements of Whelping Seals on Drifting Pack Ice
• Marine Mammal Genomics Research in the Central and Arctic Region
• OTN and predator-prey interactions
• Listening in on the Deep: Passive Acoustic Monitoring of Whales off Nova Scotia
• Sharing Meals Keeps Killer Whale Families Together: Provisioning relatives maintains long-term social bonds and helps pass on shared genes
• New developments in the use of fatty acids to determine marine mammal diets
• More than a mouthful – unlocking bowhead whale foraging and reproductive histories from baleen
• Observing walrus behaviour at haulout sites in quasi real-time
• Moving towards automated counting
• References

Mark-recapture analysis from long-term study on Sable Island identifies changes in demographic rates in northwest Atlantic Grey Seals.

Cornelia E. den Heyer, Fisheries and Oceans Canada
W. Don Bowen, Fisheries and Oceans Canada
Damian Lidgard, Dalhousie University
Shelley Lang, Fisheries and Oceans Canada

The grey seal breeding colony on Sable Island is the largest grey seal breeding colony in the world, and in 2016 produced 85% of the total grey seal pup production in Canadian waters. After more than three decades of growth at 13%, the rate of increase has declined to about 4% since 1997. Large, long-lived vertebrates facing resource limitation are hypothesized to exhibit reduced juvenile survival first, followed by natality and finally adult survival. To monitor and better understand the changes in demographic rates and the effect of changing demographic rates on population dynamics, we need long-term studies. Since 1969, some 7000 grey seals were uniquely and permanently marked at weaning on the Sable Island breeding colony. Each year during the December to February breeding season, DFO science staff and collaborators systematically survey the entire colony for marked adults.

These data provide individual resighting histories that allow us to estimate age- and sex-specific survival for juveniles and adults. Average adult survival was high, but male Grey Seals had lower survival at all ages (Fig. 1). Because of the high fidelity of grey seals to breeding colony, we can also estimate reproductive rates using the resighting histories of female grey seals. Only females with pups are sighted at the breeding colony; females that skip breeding are unobservable (temporary emigration). A new multi-state, open robust design model was used to estimate the transition probabilities between breeding and non-breeding states from 1992 to 2016. Females that gave birth had on average an 85% probability of pupping in the following year. However, females that did not give birth had a 56% probability of giving birth in the following year, suggesting that female quality plays a role in breeding probability. Although breeding probability varied among years, there was no trend over time. Thus, neither adult survival nor reproductive rates have contributed to the reduced rate of increase in pup production. To date, the reduced growth rate appears to be driven by a large reduction in juvenile survival from 0.74 (1985-89 cohorts) to 0.33 (1998-2002 cohorts). Recently marked cohorts (2014-2016) will provide future estimates to test how vital rates vary as the population nears environmental carrying capacity.