Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 1491
Title: Mechanisms affecting the relative competitive abilities of hatchery-reared and wild juvenile anadromous Pacific salmonids in fresh water
Author: C. P. Tatara, B. A. Berejikian
Publication Year: 2011
Journal: Environmental Biology of Fishes
Volume: 94
Pages: 7-19
DOI: 10.1007/s10641-011-9906-z
Keywords: competition, hatchery and wild, Pacific salmonids, freshwater life stage, relative competitive ability,

Avoiding negative effects of competition from released hatchery salmonids on wild fish is a primary concern for recovery efforts and fisheries management. Several factors affect competition among juvenile salmonids including: (1) whether competition is intra- or interspecific, (2) duration of freshwater cohabitation of hatchery and wild fish, (3) relative body size, (4) prior residence, (5) environmentally induced developmental differences, and (6) fish density. Intraspecific competition is expected to be greater than interspecific because of greater niche overlap between conspecific hatchery and wild fish. Competition is expected to increase with prolonged freshwater cohabitation. Hatchery smolts are often larger than wild, and larger fish are usually superior competitors. However, wild fish have the advantage of prior residence when defending territories and resources in natural streams. Hatchery-induced developmental differences are variable and can favor both hatchery and wild fish. Although all these factors influence competitive interactions, fish density of the composite population (wild + hatchery fish) in relation to habitat carrying capacity likely exerts the greatest influence. The extent of competition and relative competitive ability of wild and hatchery fish can be determined by additive and substitutive experimental designs, respectively, and the limited body of substitutive experiments suggests that the relative competitive ability of hatchery and wild fish is approximately equal when measured as growth. Conducting substitutive experiments becomes difficult as the spatial and temporal scales increase. Largescale experiments comparing supplemented and control reaches or streams hold some promise for quantifying the effects of released hatchery fish on wild fish behavior, growth and survival.


Review article about the factors affecting competition between juvenile Pacific salmon species during their juvenile life history phase, and a calculation of the relative competitive ability of hatchery fish when compared to wild fish

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Theme: Recovery, Rebuilding and Sustainability of Marine and Anadromous Species
Foci: Maximize effectiveness and minimize impacts of artificial propagation in recovery, rebuilding and stock sustainability