Habitat and Trophic Specialization Among Greenland Cod (Gadus ogac) Morphotypes in the Context of Climate Change...

Morphological variation is observed in many fish species; however, the direct ecological consequences of this variation in terms of specialists or generalists in resource use are rarely studied. Understanding the degree of specialist or generalist behavior among morphotypes has the potential to provide insight into the ability of Arctic fish species to adapt to ongoing climate change. Here, we estimated morphological variation and habitat-trophic metrics from carbon (δ ¹³C) and nitrogen (δ ¹⁵N) stable isotopes in Greenland cod (Gadus ogac) collected along the marine coast near Ulukhaktok, Northwest Territories (NT), in the western Canadian Arctic (n = 45). Principal component analysis (PCA) of linear morphometric measurements and subsequent k-means clustering categorized fish into two morphological groups driven primarily by head shape and body depth. Mean δ ¹³C and δ ¹⁵N values did not differ significantly between morphological groups; however, measures of individual specialization showed that the morphotype with the smaller head and slender body had lower habitat specialization and higher trophic specialization compared to the morphotype with the larger head and stockier body. This observed gradient suggests that morphotype-specific behaviors can be observed over a generalist-specialist gradient rather than as distinct groups and may benefit generalist populations in the future due to their ability to undergo resource shifts. The integrated approach used here informs our understanding of species' flexibility to competition and food web shifts with ongoing borealization. The findings highlight the importance of considering individual-level data and the degree to which a population exhibits specialization-generalization in fisheries co-management in the Arctic.