Food and feeding habits of young saithe, Pollachius virens (L.), on the coast of western Norway
MetadataVis full innførsel
The stomach contents of young saithe (both I- and II-group, but mainly II-group) from two areas, denoted A and B, on the western coast of Norway have been analysed. When these juvenile saithe become two or more often three years old, they migrate from the coastal shallows to the North Sea. Nutrition may be an important factor governing or influencing this migration. In area A, the saithe had preyed almost exclusively upon plankton in the pelagic environment. The appendicularian Oikopleura dioica, the copepod Calanus finmarchicus, and the krill Thysanoessa inermis each dominated the nutrition at times. In the winter, when krill seemed to be the most important single food organism, the saithe showed clear signs of starvation. In area B, Calanus finmarchicus was the most common single prey. In this area the diversity of the stomach content was higher than in area A. Epifauna and hyperbenthos, consisting of isopods and amphipods attached to bottom vegetation, seemed to play an important role, especially when typical suitable plankton organisms were scarce. Larvae and yearlings of fish were at certain times important food for the saithe. Different species occurred in the diet at different times. Small differences in the length distribution throughout the sampling period are indicative of a gradual migration of the largest fish, mostly two-year-olds, away from the coast. In July-August almost all two-year-olds saithe disappeared from area B for a short time, while they were still present in area A. This behaviour did not seem to appear every year in the investigated areas. Intraspecific competition from younger age groups may be an explanation. The main migration of saithe away from the coast seems to take place during spring (after February, but before June) when the saithe are three years old. In the beginning of March, the saithe seemed to have preyed mostly on krill, and the observed transport of krill with the water masses away from the coast may have led the saithe to follow.
SerieFiskeridirektoratets skrifter, Serie Havundersøkelser
vol 18 no 6