Carbon and nitrogen utilization in developing eggs and larvae of cod ( Gadus morhua, L.) and variation among different parents

Abstract

Measurements of total carbon and nitrogen were made on single fertilized eggs and larvae of cod ( Gadus morhua, L.). Eggs from ripe females were fertilized by sperm from males taken at the same locality and depth. Four different groups of siblings, a total of 700 eggs and larvae, were investigated. The eggs were kept at 4°C in closed, aerated incubators containing filtered seawater. The larvae were kept in stagnant water without being fed. Five different stages of embryos and six yolk-sac stages of larvae were investigated. Newly-fertilized eggs contained about 43 μg C and 9.6 μg N per individual, decreasing to about 37 μg C and 7.6 μg N just before hatching, and further to about 27 μg C and 3.9 μg N in newly-hatched larvae. During the 7 days following hatching, the starving larvae used about 18% of their total carbon, but without significant decrease in nitrogen. Nine to eleven days after hatching, the yolk sac became exhausted and the larvae contained about 16.4 μg C and 3.4 μg N. The average carbon and nitrogen utilization from fertilization to yolk resorbtion was 48 and 60%, respectively. Carbon and nitrogen measurements seems to be a worthy tool in the study of factors affecting the metabolism in developing embryos and larvae of fish.