A PRELIMINARY STUDY ON THE POPULATION STRUCTURES OF SALMONOIDS MIGRATION IN SUIFEN RIVER

Multipopulation migration of salmonoid is very rare in China, one isfound in Suifen river. The multipopulation was made up by more than 1,000 indivi-duals of pink salmon (O. gorbusha). cherry salmon (O. mason) and chum salmon.The rate of each species was 33.4%, 12. 2% and 65.4% for pink, cherry and chumsalmon respectively in 1986. Their population structures were as follows: The ave-rage body length of pink salmon was 44.6 (35.0-60.0)cm and its average bodyweight was 1,145 (550-3250)g. They were all 2-year old individuals. Their avera-ge fecundity was 1,231 eggs. They migrated up stream in June to August andspawned in August to September. The average body length of eherry salmon was55.7 (49.0-70.0) cm and the average body weight was 2,595 (1,800-4,000)g.Population was made up by 2-3 years old individuals, in which 3 years old indivi-duals occupied 93.5%. The average fecundity was 3,232 eggs and migrated in Mayto August, spawned in August to September. The average body length of chumsalmon was 71.2 (34.0-82.0) cm and body weight was 4,150 (1,700-7,500)g.The population was formed by 2-4 years old individuals, in which 3-year indivi-duals was about 66.4%. The average fecundity was 4,260 eggs and the migratingand spawning seasons were the same in September to October. In exploitation andincrement of the resources of these valuable salmonoids, a large scale artificialreleasing of parr or smalt should be adopted.