Contributions to the comparative physiology and genetics of the European Salmonidae

Abstract

1. The temperature resistance measured by the ultimate upper lethal temperature was determined in salmon seatront and browntrout, alevin, fry and parr. 2. The temperature resistance increases with the age from the alevin to the parr stage. 3. The individual temperature resistance of the yearlings is in each form positively correlated with the individual standard length and weight. 4. The salmon is caracterised by a higher temperature resistance as distinct from trout at the three considered age classes. 5. These interspecific differences in temperature resistance decrease from the alevin (1 months old) to the parr stage (32 months old). 6. No significant differences were found between seatrout and browntrout. 7. The differences in temperature resistance, measured by the ultimate upper mean lethal temperature, indicate that the salmon is possibly more thermophilic than the trout. This has been confirmed by the data on the embryonic developmental rate, viability and growth, reported by Spaas & Heuts (1958). From slight differences in embryonic developmental rate between seatrout and browntrout can be supposed that the seatrout is more thermophilic than the browntrout. 8. The ecological distribution does not match the experimental classification with respect to thermal adaptation.