Aspects of Reproduction and Larval Biology of Arctic Cod (<i>Boreogadus saida</i>)

Abstract

Arctic cod (Boreogadus saida) were captured from Resolute Bay, Northwest Territories, shipped to Vancouver and reared in holding tanks for up to three years. Spawning and development of larvae were monitored in two separate years. Fish that were in the laboratory for less than one year spawned during the normal spawning period for wild fish, January to February. The timing of spawning was altered by water temperature and light regime. Elevated water temperature caused spawning to occur earlier, and increased mortality and rate of deformity in larvae. The absence of "light" and "dark" seasons may have caused spawning to deviate from the predicted time in successive years. Larvae hatched at 87-91 C days. The newly hatched planktonic larvae were 5-6 mm long (total length), non-pigmented, and had poor swimming ability, likely because of the large yolk sac (1.5 mm in length). Even though swimming ability remained poor for the entire rearing time (up to 100 days), it improved as the yolk dissipated. Yolk nutrition lasted 20 to 40 days after hatching. Healthy larvae remained within the top 15 cm of the water column, and fed on brine shrimp and barnacle nauplii, and oyster trochophores. Growth rate under laboratory conditions was similar to those for fish sampled from the field. Fish that were not near the surface did not grow.

Key words: Arctic cod, larvae, spawning, temperature, behaviour, growth