Seasonal feeding ecology of cod (Gadus morhua l.) on the norwegian skagerrak coast

Abstract

Cod (Gadus morhua L.) is the most important species for the coastal fishery of southern Norway, but the feeding habits of cod in this area are virtually unknown. We studied the seasonal feeding ecology of cod from two locations on this coast, the Risorfjord and Flodevigen areas, during the period 1986-1989.The diet of cod, expressed as frequency of occurrence of prey items, varied seasonally.During the winter, larger cod (> 15 cm) preyed mainly on caridean shrimp, anomuran crabs, and fish. Prey fish were predominantly gobiids, and, to a lesser extent, gadids.During the spring and summer less shrimp and fish, and more brachyuran crabs, were taken. Fish and brachyuran crabs were both taken frequently during the autumn. Small cod (< 15 cm) ate a variety of zooplanktonic organisms, but included fish in the diet during autumn. Diets of larger cod differed between the two study areas. Fish from the Flodevigen area preyed on a broader spectrum of prey than Risorfjord cod. Stomach fullness varied little seasonally, but cod from the Flodevigen area tended to have more food in their stomachs than those from Risorfjord. Availability and diversity of prey were probably greater in the Flodevigen area, although there was no indication that food availability was critically low in the Riserfjord area. © 1992 Oxford University Press.