Ecological biogeography of deap-sea fishes within eastern Canadian and Arctic frontier areas

Devine, Brynn M. (2019) Ecological biogeography of deap-sea fishes within eastern Canadian and Arctic frontier areas. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

The lack of deep-sea sampling – particularly through in-situ observations - limits our understanding of factors that influence deep-sea fish distributions and the relative importance of different habitats in the deep ocean. Through five research cruises sampling multiple marine ecoregions, data presented in this dissertation offer novel insight into benthic and mesopelagic fish assemblages in the Northwest Atlantic and Canadian Arctic, improving knowledge of fish distributions and their environmental drivers. Over 200 hrs of baited camera video footage were analyzed from remote regions in the eastern Canadian Arctic to detect significant differences in fish and invertebrate assemblages among regions. Patterns were attributed to variations in depth and temperature, and validated the utility of using baited cameras to detect the presence of benthic taxa when deployed over fine-grain sediments, requiring fewer deployments compared to fishing gear. These videos yielded the first fisheries-independent estimates of Greenland shark local abundances in Arctic waters, visually identifying 142 individuals and exploring potential extrapolated densities using an established theoretical abundance model. Remotely-operated vehicle transects along the Flemish Cap and Orphan Seamount covering a distance of 55 km documented over 6,900 fish-habitat observations, comprising at least 45 taxa. Fishes were not randomly distributed, with unique assemblages defined by depth zones and particular complex physical and biological habitats. In the pelagos, fish assemblages are largely shaped by changes in hydrography and large-scale oceanographic features. Examination of over 6,000 fishes collected from mid-water trawls along transects through anti-cyclonic eddies in the North Atlantic eddy field revealed distinct assemblages inside eddy waters, as well as significant differences between upper- and mid-mesopelagic sampled depths. Together these results contribute new data on fish distributions and habitat associations in three remote, understudied deep environments.

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