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

OTN and predator-prey interactions

Don Bowen, Fisheries and Oceans Canada
Damian Lidgard, Dalhousie University
Sara Iverson, Dalhousie University

The Canadian Ocean Tracking Network (OTN Canada) was a 7-year integrative research program which began in 2010 to understand changing continental shelf marine ecosystems across Canada in relation to important issues in fisheries and resource management. The program was funded by the Canadian Foundation for Innovation, Natural Science and Engineering Research Council, and DFO. One of the themes of OTN concerned the spatial and temporal characteristics of foraging by predators and the role they play in structuring trophic interactions and understanding ecosystems. Using newly developing acoustic technology, this study set out to test hypotheses concerning predator impacts on prey populations.

In eastern Canada, grey seals fitted with satellite tags and acoustic transceivers were used to examine the spatial and temporal pattern of encounters between seals and Atlantic cod. Grey seals were fitted with instruments in each year of the 7-yr study (115 at Sable Island and 20 in the Gulf of St. Lawrence). During the same period, acoustic tags were surgically placed in ~1200 Atlantic cod (800 on the Scotian Shelf, 400 in the southern Gulf of St. Lawrence). Species tagged by other investigators that co-occurred with grey seals included bluefin tuna and Atlantic salmon.

Acoustic detections occurred both among the acoustically tagged seals and fish species, mainly Atlantic cod. Seals tended to encounter other tagged seals at offshore banks, presumably were most feeding occurred (Fig. 9). There was no evidence that seals travelled together to these feeding sites, rather seals used the same limited number of feeding hotspots. Of the 104 seals from which data were recovered, only 25% detected tagged cod even though the movements of 70% of these seals overlapped with known cod distribution, underscoring the difficulty in using overlap as the basis for inferring predation rate. Most detection of cod were of short duration (~5 min compared to > several hours if the tag where ingested) and, thus, did not appear to represent predation events. The distribution of cod detected by grey seals on the Scotian Shelf and in the Gulf of St. Lawrence are illustrated in Fig. 10. Overall, these data demonstrate the feasibility of studying predator-prey interactions in the open ocean, but also underscore the importance of tagging large number of prey to have confidence in estimates of prey encounter rate and predation events.