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

New developments in the use of fatty acids to determine marine mammal diets

Shelley Lang, Fisheries and Oceans Canada
Connie Stewart, University of New Brunswick
Don Bowen, Fisheries and Oceans Canada
Sara Iverson, Dalhousie University

Determining the diet of marine mammal species is difficult because most feeding occurs while they are diving at remote locations in the ocean and thus cannot be observed directly. Traditional methods using prey hard parts recovered from feces or stomach can provide useful information, but known sources of error and bias have motivated the development of new methods to determine marine mammal diets. Quantitative fatty acid analysis (QFASA) is one of these new methods.

Fatty acids are the building blocks of fat. In the ocean, there are about 67 such building blocks in the fats of most marine fish and invertebrate species such as Atlantic cod and squids, respectively. Although the same fatty acids occur in most species, their relative abundances differ greatly providing a fingerprint by which, for example, cod can be distinguished from herring and other fish and invertebrate species. An important feature of prey fatty acids is that they are deposited in predator fat stores in a predictable way. Thus, by comparing the predator’s fatty acid profile with a library of prey species fatty acids, we can estimate how much of each prey species must have been eaten to produce the predator profile. From this the diet composition of the predator can be estimated.

Although the method has been used for more than a decade, improvements continue to be made. Principle among these concern the library of prey species fatty acids and the calibration coefficients needed to account for predator metabolism of prey fatty acids. Although 87 prey species are represented in the fatty acid library, 21 species are now used to estimate the diet of grey seals on the Scotian Shelf. Estimates are now based on a subset of dietary fatty acids (i.e., those that can only come from the diet and cannot be synthesized by the predator) that are reliably estimated. Finally, the calibration coefficients that are associated with these 28 fatty acids have been tested for how well they work by comparing model results against diets fed to captive harbour and grey seals. These improvements in QFASA should provide more accurate estimates of not only the diets of grey seals but other marine mammals.