EGG QUALITY AND FEMALE CONDITION IN VENDACE (COREGONUS-ALBULA L) BEFORE AND DURING SPAWNING

The fat content of muscle, liver and eggs of vendace (Coregonus albula L.) were measured during the maturation of ovaries in summer. The fat content of eggs was at its highest in July and that of muscle in August during the optimal feeding season. Significant differences were not found in fat content between lakes Suvasvesi and Southern-Kallavesi in central Finland. There were no essential differences in fatty acid composition between muscle, liver and eggs of Lake Suvasvesi vendace. During the last month before spawning in October the gross energy and fat contents of eggs decreased in Lake Suvasvesi vendace. The fat and vitamin C contents of muscle as well as the liver index of females decreased during this time also. In males the corresponding decrease did not occur, indicating that spawning is a greater stress for females than for males. The egg quality and condition of Lake Inarijarvi vendace were about the same as those of Lake Suvasvesi vendace. The unfavourable conditions of Lake Inarijarvi, located in northern Finland, are reflected in the size of ovaries, which is known to be smaller (gonadosomatic index < 20%) than in Lake Suvasvesi (GSI 26-27%). Vendace, then, maintain the quality of eggs at the expense of their number.