Erbrütung der Eier von Dorsch (Gadus morhua), Flunder (Pleuronectes flesus) und Scholle (Pleuronectes platessa) unter kombinierten Temperatur- und Salzgehaltsbedingungen

Abstract

Eggs of Baltic cod (Gadus morhua L.), flounder (Pleuronectes flesus L.) and plaice (Pleuronectes platessa L.) have been reared under combined temperature and salinity conditions (0°-16° C, 7‰-42‰ S). Combined temperature and salinity influences on embryonic development were investigated. Optimum temperatures for the rearing of cod eggs range from 4° to 8° C, and optimum salinities from 20‰ to 33‰ S. Flounder eggs develop best at 4° C and in 33‰ S, and plaice eggs at 6° C and in 20‰ S. Suboptimum conditions result in lower percentages of larval hatching and survival, and increased morphological anomalies such as curvature of tail and body. Low salinities (20‰ and 15‰ S) cause swollen yolk sacs which, in experiments with flounder eggs, lead to jaw deformities. Rearing at low salinity decreases speed of development. Optimum salinity varies as a function of incubation temperature and influences variations in optimum rearing temperature. Extremely low salinities (20‰ and 15‰ S) are tolerated best at optimum or lower temperatures. From the results of these experiments it can be concluded that brackish water races of these fishes are likely to exist in the Baltic Sea. © 1970 Biologischen Anstalt Helgoland.