The duration of the first two yolk sac stages in herring (Clupea Harengus L.) larvae

Abstract

Artifically fertilized and naturally spawned herring eggs from the local herring stock in Lindåspollene, north of Bergen, Norway, were hatched at 9°C in 1978 and at 6°C in 1979. The purpose was to calculate the duration of the first two yolk sac substages. All the larvae hatched in 1978 were in substage la (DOYLE 1977). In 1979, however, 73% and 27% of the hatched larvae were in substages 1a and 1b, respectively. The duration of substage la is affected both by the amount of yolk present at hatching and by the temperature. The duration of substage 1a was 1 day in 1978 and 1.2 days in 1979. The duration of substage 1b is only affected by the temperature and was 1.2 days in 1978 and 3.3 days in 1979. Genetic differences between the Lindås herring and the Clyde herring may account for the different durations of the first two yolk sac substages. This experiment demonstrates the importance of hatching experiments in connection with spawning stock abundance investigations.