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

Abstract

Rearing the eggs of cod (Gadus morbua), flounder (Pleuronectesflesus) and plaice (Pleuroneetes platessa) under combined temperature and salinity conditions. Eggs of Baltic cod (Gadus morhua L.), flounder (Pleuronectes flesus L.) and plaice (Pleuronectes pIatessa L.) have been reared under combined temperature and satinity conditions (0°-16 ° C, 7 %-42 %0 S). Combined temperature and salinity influences on embryonic development were investigated. Optimum temperatures for the rearing of cod eggs range from 4 o to 80 C, and optimmn salinities from 20%0 to 33 %0 S. Flounder eggs develop best at 4 o C and in 33 %0 S, and plaice eggs at 6 o C and in 20 %o 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 %o and 15 %o 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 %0 and 15 %0 S) are tolerated best at optimum or lower temperatures. From the results of these experiments it can be concluded that bra&ish water races of these fishes are likely to exist in the Baltic Sea. EINLEITUNG UND FRAGESTELLUNG Temperatur und Salinit~it sind neben Sauerstoffgehalt und Licht die physiologisch wichtigsten Faktoren im Leben yon See-und Bra&wasserorganismen. Auf Grund zahlreicher Untersuchungen ist deutlich geworden, dai~ insbesondere Temperatur und Satini-t~it zusammen betrachtet werden miissen, wenn die Reaktion von Wasserorganismen auf Temperatur oder Salzgehalt ihrer Umwelt untersucht werden soll. Die komplexe Korrelation zwischen der biologischen Wirkung dieser beiden Faktoren wird besonders

The influence of temperature on the development of Baltic Sea sprat (Sprattus sprattus) eggs and yolk sac larvae

“…For example, flatfishes such as turbot (Psetta maxima), plaice (Pleuronectes platessa) and flounder (Platichthys flesus) or other fishes like cod (Gadus morhua), sprat (Sprattus sprattus) and herring (Clupea harengus) are distributed in the North Sea in an almost fully marine environment as well as in the brackish waters of the Baltic Sea. For this reason, stocks of the same species are specialised and adapted to prevailing hydrographical conditions in their habitat (Von Westernhagen 1970;Nissling andWestin 1991, 1997;Karås and Klingsheim 1997) and these adaptations are considered specific for the respective population as a result of long-term selection.…”

Early estimates of recruitment of the Belt Sea cod stock

“…Although the hydrographical situation in the western Baltic Sea is characterised by a high variability of the essential reproduction parameters salinity, temperature and oxygen content Matthäus et al, 1994Matthäus et al, , 2000, Bleil and Oeberst (2000) showed that the hydrographical conditions varied in ranges which did not influence the fertilisation and the development of spawned eggs negatively. According to Westernhagen (1970), Graumann (1974), Westin and Nissling (1991), Nissling et al (1994) and Nissling and Westin (1997), salinity is a major factor which influences the fertilisation of cod eggs in the Baltic Sea. Eggs spawned by the Belt Sea cod need a salinity of more than 14 PSU (marine condition).…”

Species assemblages of pelagic fish embryos in the southern North Sea between 1984 and 2000

“…Both are known to affect the spawning behaviour of adult fish and, in addition, have relevance to development, hatching success and vertical distribution of fish eggs (Westernhagen 1970). It is therefore likely that the occurrence of species in the samples was influenced by the hydrography.…”