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Distinct habitat use strategies of sympatric rorqual whales within a fjord system

TitleDistinct habitat use strategies of sympatric rorqual whales within a fjord system
Publication TypeJournal Article
Year of Publication2018
AuthorsKeen E.M, Wray J., Pilkington JF, Thompson K.L, Picard C.R
JournalMarine Environmental Research
Date Published2018/09
Type of ArticleArticle
ISBN Number0141-1136
Accession NumberWOS:000447579500019
KeywordsBalaenopmrct physalus; cetaceans; Critical habitat; Environmental Sciences & Ecology; Fin whale; fin whales; Fjord system; Habitat partitioning; habitat use; humpback whale; humpback whales; Kitimat fjord system; Marine & Freshwater Biology; Megaptera novaeangliae; megaptera-novaeangliae; minke; oceanographic domains; prey; random forest; sea; Site loyalty; stable-isotope analysis; Toxicology; western antarctic peninsula; whales

We used ecosystem sampling during systematic surveys and opportunistic focal follows, comparison tests, and random forest models to evaluate fin whale (Balaenoptera physallts) and humpback whale (Megaptera novaeonglicte)habitat associations within an inland feeding ground (Kitimat Fjord System, British Columbia, Canada). Though these species are sympatric and share a common prey source, they were attuned to different aspects of the local habitat, The fin whales were associated with habitat properties reminiscent of the open ocean. Humpback whales, in contrast, were associated with features more commonly associated with the inland waters of fjords. Fixed habitat features, such as seafloor depth and distance from the fjord mouth, were the most important predictors of fin whale presence, but fixed and dynamic variables, such as surface properties, predicted humpback whale presence with equal (moderate) success. With the exception of strong salinity gradients for humpback whales, habitat conditions were poor predictors of feeding state. Fin whales practiced a spatially confined, seasonally stable, and thus more predictable use of certain channels within the fjord system. These findings are compatible with site loyal behavior, which is interesting in light of the species' historical, unique use of this fjord system. The relatively lackluster performance of humpback-habitat models, coupled with the importance of oceanographic properties, makes the humpback's habitat use strategy more uncertain. The fact that two sympatric species sharing a common prey source exhibited different habitat use strategies suggests that at least one species was informed by something in addition to prey, Given that the two species are attuned to different aspects of the fjord habitat, their responses to habitat changes, including anthropogenic impacts, would likely be different in both nature and degree. Our findings highlight the value of comparative studies and the complexity of rorqual habitat use, which must be understood in order for critical habitat to be identified and protected.

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