Growth and survival studies on 0-group plaice (Pleuronectes platessa L.) in a small basin with a closed ecosystem

Abstract

A growth and survival experiment on 0-group plaice was carried out in a small basin during the summer of 1976. The volume of the basin was about 25 m³, and the seawater was left stagnant during the summer. Of the initial 200 metamorphosed fry released, 154 survived, and a mean daily length increment of 0.28 mm was observed for a period of 105 days. The temperature was about 20°C for half of the experimental period. The main energy flow is supposed to have followed this simplified route: phytoplankton -> Mytilus edulis produced faeces -> detritus-eating crustaceae -> plaice fry. Calculations of food intake and gross growth efficiency have been carried out, applying the metabolic values earlier reported (EDWARDS, FINLAYSON and STEELE 1969), and the present data have been compared with their results. The basin appeared to be an ecosystem with a high production, giving better survival and growth than previous tank experiments. In spite of the extreme temperature during midsummer, the growth was comparable to that observed under natural conditions (Loch Ewe), but the survival was far better due to lack of predators in the basin.