Carcass additions increase juvenile salmonid growth, condition, and size in an interior Columbia River Basin tributary

• Published in: Canadian journal of fisheries and aquatic sciences Vol. 77; no. 4; pp. 703 - 715
• Main Authors: Kaylor, Matthew J, White, Seth M, Sedell, Edwin R, Warren, Dana R
• Format: Journal Article
• Language: English
• Published: Ottawa NRC Research Press 01.04.2020; Canadian Science Publishing NRC Research Press
• Subjects: Anadromous fishes; Anadromous species; Aquatic ecosystems; Body size; Carcasses; Creeks & streams; Eggs; Emigration; Escapement; Fish; Fishes; Food supply; Freshwater; Freshwater ecosystems; Growth; Growth rate; Juveniles; Nursery grounds; Oncorhynchus; Oncorhynchus mykiss; Oncorhynchus tshawytscha; Rations; River basins; Rivers; Salmon; Salmonidae; Salmonids; Salmoniformes; Size; Snakes; Spawning grounds; Statistics; Survival; Tagging; Tributaries; Trout; Oregon; Columbia River; Canada, British Columbia, Columbia River
• ISSN: 0706-652X; 1205-7533
• DOI: 10.1139/cjfas-2019-0215

Numbers of anadromous fish returning to freshwater ecosystems have declined precipitously across much of western North America, reducing a potentially important resource subsidy for juvenile salmonids. We added carcasses to three sections of a Snake River tributary and assessed juvenile Chinook salmon (Oncorhynchus tshawytcha) and steelhead trout (Oncorhynchus mykiss) growth, body condition, size, and diet responses in summer and early fall. Juvenile salmonids consumed an abundance of eggs and carcass tissue, which increased energy rations. Within 3 weeks of carcass additions, juvenile Chinook and steelhead growth rates were 1.1–5 and 6–23 times greater in treatment reaches relative to control reaches, respectively. We used long-term tagging and detection data from this system to assess the relationship between juvenile Chinook size and emigration survival for two different juvenile life histories. The increased growth rates and body size in response to carcass additions, coupled with a positive relationship between body size and survival, suggest that juvenile salmonid rearing productivity and emigration survival may be limited by depressed returns of anadromous fishes in this system and potentially other tributaries of the Columbia Basin.