Physiological and behavioural differences of hatchery and wild‐reared steelhead Oncorhynchus mykiss smolts of the same genetic origin
In many parts of the world release of hatchery‐reared smolts has long been used to mitigate for the deleterious effects of habitat loss and overfishing on salmonid populations. Of increasing concern is whether this may cause harm by spreading non‐native stocks and potentially releasing incompetent smolts. The objective of this study was to determine if smolt physiology and behavior of juveniles produced from a recently founded native broodstock differ from their wild (naturally‐reared) counterparts. In the fall of 2002 and 2003 juvenile wild steelhead were captured, PIT tagged, and returned (n = 1360 in 2002 and n = 2708 in 2003) to Abernathy Creek. In winter of 2003 and 2004 hatchery‐reared fish were PIT tagged and later released (n = 1100 in 2003 and n = 1400 in 2004) into Abernathy Creek. Gill biopsies were collected from wild and hatchery fish throughout the rearing and out‐migration season. The timing and speed of outmigration was assessed using two stationary PIT tag antennas (92–97% efficient). Hatchery migrants in 2003 were larger, had significantly lower gill Na+, K+‐ATPase activities, and migrated slower than wild fish. Results from the 2004 migratory season will also be presented. This study shows that hatchery rearing can result in smolts which are physiologically and behaviourally different from genetically similar wild fish. Whether these differences are critical enough to affect the rate of adult returns will be determined in future years.
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Document Type: Research Article
Affiliations: US Fish and Wildlife Service, Abernathy Fish Technology Center, 1440 Abernathy Creek Road, Longview, WA 98632, U.S.A.).
Publication date: 2004-12-01