Physiological changes in blood and seminal plasma during the spawning period of maturing rainbow trout held under different temperature and salinity regimes, and the effect on survival of the broodstock and the eyed eggs

Abstract

Maturing rainbow trouts reared in sea cages were transferred to tanks and kept under nine different temperature and salinity regimes. Blood and seminal fluids were regularly sampled from the fish, and different organic and inorganic components were measured. The survivel of both the broodstock and the eyed eggs were recorded. Dry matter of the eggs were measured as well. Sexual differences were noted according to the progressive changes of glucose, chloride, haematocrit and the survivel of the broodstock. Cold temperatures delayed the sexual maturation independent of salinity, and only few females spawned at these temperatures. The broodstock reared at cold temperatures in freshwater and seawater suffered from high mortality and high levels of blood chloride or blood glucose. Brackish water appeared to be the most favourable environment, especially for the broodstock reared at the warmer temperatures. The survivel of the broodstock and also of eggs from females stripped at this salinity was high. Analysis of the physiological components were more stable compared to fish reared at the other salinities.