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Population Biology of Fin Whales: Applying Demographic and Evolutionary Approaches to Studying Populations
Summary
This PhD thesis studied population dynamics and connectivity of fin whales using photo-identification and genetic tools, detecting a decline in the Gulf of St. Lawrence population. Fin whales face multiple pollution threats including microplastics and chemical contaminants that accumulate in large marine mammals.
Fin whales are the second largest mammals to roam across the oceans, often returning to the same feeding grounds every summer. In this PhD thesis, I used a different approach in each chapter to gain insight into how numbers, distribution, and connectivity of fin whales have changed over time. One approach to track fin whales over time is through the use of photo-identification, which identifies individuals based on unique pigmentation patterns and dorsal fin shapes. Based on the number of photographic recaptures, I detected a decline in the number of fin whales in the Gulf of St. Lawrence in eastern Canada from 2004 to 2016. This decline was likely the result of increased mortality or a shift in distribution. Another useful method to evaluate the extent of mixing among different groups of fin whales is the analysis of genetic profiles. For that purpose, over 1,500 genetic profiles from fin whales across the North Atlantic and Mediterranean Sea were compared. I found that differences in genetic profiles of fin whales increased with distance, suggesting that fin whales preferably mate with individuals from the same or neighbouring areas (albeit with exceptions). The composition of genetic profiles is also affected by historic events. Using this feature of genetic profiles, I described how past periods of extreme climatic fluctuations (e.g., during glaciation periods) influenced the amount of connectivity among fin whales from the Atlantic, Pacific, and Southern Ocean. Overall, this research highlighted the complex interplay between fin whale population trends and environmental conditions.
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