Competition for food and predator-prey relationships among young cod (Gadus Morhua) and some other fish from shallow waters. In: Flødevigen rapportserie no 1, 1988

Abstract

Experiments were conducted to study food competition between young cod (20-30 cm) and some other fish from shallow waters. When food was dropped from the surlace the cod took much more than the other species, but goldsinny-wrasse, Ctenolabrus rupestris, and flounder. Platichthys flesus, also took considerable quantities. Competition belween small (15-17 cm) and larger (22-26 cm) cod was generally in favour of the larger fish. The first piece of food offered was often taken by the smallest fish. After that the big fish took most of the food till it was satisfied. Then the small fish could feed again. Experiments in aquaria and in large outdoor basins showed that cod of 20-50 cm length will eat small cod and whiting, Merlangius merlangus (7- 20 cm) even if other, natural or artificial, food is available. Small cod apparently have a better chance of survival in basins with macroalgae.