Remote sensing to measure the physiology and foraging ecology of North Atlantic right whales in the Gulf of St. Lawrence, Canada
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Date
2024-12
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University of New Brunswick
Abstract
Despite modern-day conservation efforts, many populations of baleen whales have not fully recovered since exploitation by commercial whaling. A better understanding of the physiology and foraging ecology of baleen whales would improve population monitoring, and the development of remote sensing technology offers non-invasive tools for collecting pertinent datasets on wide-ranging whales and their prey. My thesis used remote sensing to measure the physiology and foraging ecology of critically endangered North Atlantic right whales (Eubalaena glacialis, NARWs) in the southwestern Gulf of St. Lawrence (swGSL), Canada, where occupancy by NARWs increased around 2011 following an ocean regime shift. First, I developed, calibrated, and applied a method using drone-based infrared thermography to assess the internal body temperatures of NARWs. With this method, I established the first baselines of intranasal temperature for free-swimming baleen whales: 26.9 ± 1.7ºC in NARWs (n = 21). Second, I evaluated several methods for conducting drone-based photogrammetry with suboptimal photographs of NARWs. This helped me produce the first analysis of NARW body condition in the swGSL (summertime), which was significantly greater than in Cape Cod Bay (springtime) (p < 0.001). Across habitats, standardized widths of adult males (0.166 ± 0.012) and calves (0.170 ± 0.010) were significantly greater than those of lactating females (0.139 ± 0.001) (p < 0.024). Meanwhile, adult females in the Bay of Fundy two decades ago had considerably higher standardized widths (0.18 ± 0.02). Third, I provided context for this variation in body condition by describing prey field conditions associated with groups of foraging NARWs in the swGSL. Conditions were diverse, explained by the diel behaviors, life histories, and relative concentrations of three copepod prey species, including Calanus hyperboreus, which is less abundant in more southerly foraging habitats. Maximum prey concentrations occurred anywhere from 18 m deep to just above the seafloor, implying that NARWs likely alter their dive behavior to target different prey layers in the swGSL depending on the time of day and year. Overall, my thesis provides information for assessing change to the NARW population over time, which is essential for forecast modelling and effective management of this critically endangered species.