Predation by Sculpins on Fall Chinook Salmon, 



Oncorhynchus ishawytscha, 



Fry of Hatchery Origin 



By 



BENJAMIN G. PATTEN, Fishery Biologist 



National Marine Fisheries Service Biological Laboratory- 

 Seattle, Wash. 98102 



ABSTRACT 



Predation was studied during migration of the fry towards the Columbia River 

 from two hatcheries — the Elokomin River Hatchery (13 km. upstream from the 

 Columbia) and the Oxbow Hatchery on Herman Creek (0.2 km. upstream). In 

 the Elokomin River the estimated loss of hatchery salmon to sculpins, Cottus spp., 

 was 3.9 percent of 1.5 million fry released in 1962 and 1.3 and 3.6 percent of 2.2 

 and 0.1 million fry, respectively, released in 1963. Loss was negligible among 2.3 

 million fry released in Herman Creek in 1962. 



Sculpins that preyed on hatchery salmon were coastrange sculpin, C. aleuticus; 

 prickly sculpin, C. asper; reticulate sculpin, C. perplexns, and torrent sculpin, C. 

 rhotheus; in the Elokomin River and prickly and reticulate sculpins in Herman 

 Creek. Predation was greatest by prickly sculpin (the largest species) and least 

 by coastrange sculpin (a species with a comparatively small mouth). 



Losses of salmon to sculpins may have been related to diet and to the size of 

 the releases. In the Elokomin River, predation was greater on salmon fed a wet 

 diet than on those fed moist pellets. The larger of the two releases in 1963 had 

 the smaller percentage loss. Improvement of hatchery procedures is probably the 

 best way to reduce losses of hatchery-reared salmon to sculpins. 



INTRODUCTION 



Artificial propagation of Pacific salmon, 

 Oncorhynchus spp., in hatcheries has been ef- 

 fective in increasing their survival until time 

 of release. Although the returns indicate eco- 

 nomic success, the number of salmon accounted 

 for (in the fishery and returning to a hatchery) 

 represents only a small fraction of the fish 

 released (Hublou, 1963). Biologists suspect 

 that the major cause of the loss is predation. 



Sculpins, Cottus spp., are known predators 

 of Pacific salmon fry released from hatcheries. 

 Hikita and Nagasawa (1960) reported about 

 5-percent predation of chum salmon, 0. keta, 

 by C. nozawae in a Japanese stream. Infor- 



mation on predation in North America is lim- 

 ited, but sculpins, salmon, and trout, Salmo spp., 

 are known to readily consume artificially reared 

 salmon. 



I studied predation by sculpins on fry of 

 fall chinook salmon, 0. tshmvytscha, that mi- 

 grated into the Columbia River from two 

 hatcheries — the Elokomin River Hatchery 

 (operated by the State of Washington Depart- 

 ment of Fisheries), which is 13 km. from the 

 lower Columbia River, and the Oxbow Hatchery 

 (operated by the State of Oregon Fish Commis- 

 sion, on Herman Creek, 0.2 km. from the 

 Columbia River. 



I analyzed the quantitative and qualitative 

 aspects of predation in the Elokomin River in 



