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Minke Whales in the Scope: Satellite Tracking, Chemical Tracers and Population Genomics

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Minke Whales in the Scope: Satellite Tracking, Chemical Tracers and Population Genomics

Using next-generation tracking, tracers, and genomics to advance understanding of migration, feeding, and population structure of minke whales in the St. Lawrence (2021-2024); in collaboration with Dr. Melissa McKinney (McGill University), Dr. Denis Roy (McGill University), Dr. Brian Kot (MICS), and Haley Land-Miller (PhD candidate, McGill University).

The goal of this project is to address gaps in knowledge in North Atlantic minke whale ecology; primarily, population structure, migration routes, and foraging ecology. Minke whales are among the most abundant cetaceans in the North Atlantic, and as generalist predators, can be valuable ecosystem sentinels. Through collaboration between Mériscope, McGill University and MICS, boat-based fieldwork in the Saint Lawrence Estuary and the gulf will be carried out to collect tissue samples via dart biopsies and to deploy satellite tags onto minke whales. Using next-generation genomics techniques and additional samples from minke whales in the Northeast Atlantic, high-resolution population structure, connectivity, and local adaptation will be assessed. Data from satellite tags will be used to identify hotspots, migration routes, and potential winter breeding grounds of minke whales, which are currently unknown, and movement patterns will be analyzed in connection to genetic markers. Chemical tracers, including stable isotopes of carbon, nitrogen and sulfur in skin and fatty acids in blubber, will also be analyzed from biopsies. Tracer analysis will be used as a proxy for diet and will indicate patterns in minke whale foraging, including in comparison to individuals from Greenland, Iceland, and Norway. Variation in dietary patterns across location and over the multi-year span of the project will be assessed and associations between diet, movement, and genetics will be evaluated. Overall, this project will greatly increase current understanding of North Atlantic minke whale ecology, and through the lens of St. Lawrence minke whales, the broader North Atlantic ecosystem.

Satellite tag deployment: A) Using an adjustable 13 mm bore CO2 injection rifle, B) specially designed airgun arrows, and low impact minimally percutaneous electronic transmitters with disinfected titanium anchors, C) satellite tags are deployed into the dorsal region of the whale, according to best practice guidelines for cetacean tagging (Andrews et al. 2019). A special trigger assembly with a 25 bar pressure manometer allows adjusting the pressure to the distance of the target animal, thus minimizing the impact. No transmitter will be deployed when the head or pectoral fins are exposed or at distances under 4 m or above 15 m. Deploying tags at shorter distances ensures that the tag gets anchored firmly in the blubber and sits tightly on the skin, thus reducing hydrodynamic pressure on the tag and potential tissue damage.

Remote biopsy sampling: several steps are involved in sampling a biopsy from a minke whale : A) Preparation of the crossbow with a sterilized dart, B) careful approach of the target animal and firing of the dart into the dorsal section of the whale, C) sterilization of the on-board lab equipment before extraction, D) careful extraction of the biopsy using a sterile pincette, E) conservation of the biopsy in a cryotube, and F) storage in a triple-layer cooler on board and subsequent transfer to a liquid nitrogen cryoshipper at the station.

Taking a biopsy from a minke whale is a real challenge: the time window is about two seconds, just after the last blow and before the dive, when the animal exposes the lower flank, at a distance of 8-25 meters and ideally at an angle of 90 degrees. Since we are using a crossbow and relatively bulky darts, we have to account for wind direction and speed when shooting. We normally take a biopsy after a detailed 30-minutes sample of the animal’s behavior, during which we measure dive duration, respiratory rate and velocity of the animal, to compare these to the same parameters during a post-biopsy behavioral sample. 80 % of the minke whales resume their normal behavior within less than 15 minutes after the biopsy.

Current knowledge of North Atlantic minke whale population structure and movement patterns is limited. There appears to be prominent sex segregation in summer feeding grounds, with females being more common at higher latitudes, a pattern which is consistent with movements of other baleen whales. In the Northern Hemisphere, only two studies have successfully tracked minke whales, and both in the Eastern North Atlantic. Together, these studies revealed early fall southward movements in several animals, in line with the previously proposed migration patterns. However, longer-term tracking of more animals would be extremely valuable in determining the species’ routes of migration, winter locations and movements, migratory sex segregation, and potential breeding grounds.

Minke whales are generalists who have demonstrated the ability to prey-switch in response to changes in abundance of prey species. This flexible diet could suggest their potential resilience to climate change, as generalists are often hypothesized to be the likely “winners” under future climate change scenarios because of their ability to adapt to rapid shifts. Their demonstrated shifts in diet that parallel dynamics in lower trophic level organisms, over both short and long time scales, highlights the species’ power as ecosystem indicators. Understanding the dynamics of this abundant predator species across a geographically diverse landscape will provide valuable insight into lingering mysteries in minke whale ecology, the health of varied ecosystems within its range, and the potential adaptability of generalist species under climate change.

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