Effects of temperature and food availability on the survival and growth of larval Arctic cod (Boreogadus saida) and walleye pollock (Gadus chalcogrammus)

Arctic cod (Boreogadus saida) is an ecologically significant species that is uniquely adapted to occupy ice edges, but warming and loss of sea ice are hypothesized to favour more facultative gadids, such as walleye pollock (Gadus chalcogrammus). To test this hypothesis, we experimentally measured the growth and survival of Arctic cod and walleye pollock at two larval stages across a range of temperature and food conditions in the laboratory. Results indicated early and late-stage Arctic cod larvae have a competitive growth and survival advantage over walleye pollock at low temperatures. However, these advantages are lost under warmer, food-productive conditions where walleye pollock larvae survived and experienced accelerated growth rates. Growth models developed from this study emphasize the need to account for both species- and stage-specific differences in the thermal response of closely related marine fish larvae. More broadly, these new vital rate data provide a mechanistic framework to forecast spatial-temporal shifts of gadids at the Arctic-boreal interface resulting from climatic warming and altered productivity regimes.