Habitat associations and diet of young-of-the-year Pacific cod (Gadus macrocephalus) near Kodiak, Alaska

The influence of environmental variables and habitat on growth and survival of juvenile gadoid species in the Atlantic has been clearly demonstrated; conversely, in the North Pacific little is known about the habitat and ecology of juvenile Pacific cod (Gadus macrocephalus Tilesius). The hypothesis that density of young-of-the-year (YOY) Pacific cod in nearshore habitats is predicted by shallow depth and the presence of eelgrass and macroalgae was tested in a variety of nearshore habitats adjacent to commercial fishing grounds near Kodiak Island, AK. From 10 to 22 August 2002, a beach seine and small-meshed beam trawl were used to capture YOY Pacific cod (n = 254) ranging from 42 to 110 mm fork length. Depth, water temperature, salinity, sediment grain size, and percent cover by emergent structure (i.e. tube-dwelling polychaetes, sea cucumber mounds, macroalgae) were measured prior to fishing. Density of YOY Pacific cod was highest in areas of moderate depth (15-20 m) and positively and linearly related to percent cover by sea cucumber mounds and to salinity. No previous studies have documented fish utilizing sea cucumber mounds as habitat. Furthermore, eelgrass and macroalgae were inconsequential to cod distribution. Diets consisted mainly of small calanoid copepods, mysids, and gammarid amphipods and were significantly related to cod length and depth. This work provides important information on previously undocumented factors that affect distribution and feeding of YOY Pacific cod, which ultimately influence growth and survival in this species.