Predation of Juvenile Salmonids by Predatory Fishes in the Lower Cedar River, 1999

摘要

We sampled predatory fishes in the Cedar River (river kilometers 0-1.4). From February to June, 1999 to monitor how a flood control project affected predation levels of sockeye salmon fry (Oncorhynhucs nerka) and juvenile chinook salmon (O. tshawytscha). A wide variety of habitat changes occurred in the lower Cedar River, each modification apperared to have an effect on predator abundance or predator consumption rates of sockeye salmon fry. Becuase of the rarity of predation of juvenile chinook salmon, it was difficult to determine if there was any effect due to the flood control project. We used electrofishing equipment and beach seines to collect fish; however, the vast majority of fish sampled were collected with electrofishing equipment. We examined the stomach contents of 376 salmonids, 810 cottids and 8 other predatory fish. Data were compared to 1995 to 1996 pre-project sampling. Catch rates with beach seines were low. A total of 18 predator-suze fish was collected from 19 sets. Pre-project beach seining cath rates in 1995 and 1996 were substantially higher. Reduced catch in 1999 may have been due to reduced fishing efficiency of the beach seine or related to fish abundance.