Changes in eggs of brown trout, rainbow trout, and grayling during short-term storage

Short-term storage of the eggs of rainbow trout Oncorhynchus mykiss, brown trout Salmo trutta, and grayling Thymallus thymallus was investigated to examine factors that limited egg viability and to compare storage with and without ovarian fluid. Egg viability was similar after 2 h, but after 4 h, egg fertilization rate was lower by 14-26% for eggs stored in ovarian fluid and lower by 23-51% in eggs stored without ovarian fluid. Substitution of a buffered physiological saline solution for ovarian fluid was tested for brown trout and grayling but did not improve egg viability. The wet weight of eggs during storage without ovarian fluid decreased significantly. Water influx during hardening was higher for eggs stored without ovarian fluid than in controls and eggs stored with ovarian fluid. However, water loss due to storage could not be completely compensated, so the wet weight of hardened eggs that had been stored without ovarian fluid remained lower. Ovarian fluid pH and activities of protease during egg storage with ovarian fluid significantly increased, and peptide levels decreased.