Food uptake, growth and survival of capelin larvae (Mallotus villosus Müller) in an outdoor constructed basin

Abstract

An experiment with a population of capelin larvae was carried out in an outdoor basin of 2000 m³ 1979. Data on food uptake, growth and survival of capelin larvae were collected over a period of 127 days. The first sample from the basin showed that some larvae had been feeding at an age of 5 days. Under the same temperature conditions (8°C), the capelin larvae, kept in the laboratory, started to feed at age 4 days. Sea-caught larvae from 1971 had started to feed at the same development stage as in the laboratory experiment. The basin experiment indicated that capelin larvae fed upon the most dominant organism of an appropriate size: the larvae of Spionidae spp. for the first 60 days and the veligers of Littorina spp. for the last 60 days. Partial or total defecation of the gut content made it impossible to calculate the daily food uptake. The capelin larvae in the basin had their maximum increase in length a few days after the end of the yolk sac stage (EYS), (0.29 mm/day), decreasing slowly to 0.20 mm/day, giving a total specific growth rate of 4.1%. Similar growth was not observed in the feeding group in the laboratory. The length-weight relationship for the basin and the sea-caught larvae was nearly the same. The mass mortality period (age 20-40 days) of the capelin larvae in the basin experiment was delayed and prolonged compared to mass mortality (age 14-22 days) of the starving group in the laboratory. The results from the sea-caught larvae indicated a similar mass mortality as in the basin experiment. The basin experiment gave 2.1 % survival of the capelin larvae over a period of 127 days.