Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 1902
Title: Dispersal and tributary immigration by juvenile coho salmon contribute to spatial expansion during colonisation
Author: J. H. Anderson, G. R. Pess, Peter M. Kiffney, T. R. Bennett, P. Faulds, T. P. Quinn
Publication Year: 2013
Journal: Ecology of Freshwater Fish
Volume: 22
Issue: 1
Pages: 30-42
Keywords: movement, reintroduction, parentage,

Anadromous fishes are frequently restricted by artificial barriers to movement such as dams and culverts, so measuring dispersal helps identify sites where improved connectivity could promote range expansion and population viability. We used a combination of DNA-based parentage analysis and mark-recapture techniques to evaluate dispersal by juvenile coho salmon of fish passage structures at a previously impassable dam on the Cedar River, WA, USA. The spatial distribution of individuals within maternal families revealed that dispersal was common. Among the offspring of radio-tagged mothers, 28 % were collected outside the spawning reach and dispersed up to 6.3 km (median = 1.5 km). Most juveniles captured in a tributary (Rock Creek, where few adults spawned) had immigrated from the Cedar River, and represented many different families. Juvenile dispersal therefore provided a secondary phase of spatial expansion following initial colonization by adults. Consistent with the condition dependent dispersal hypothesis, juveniles that dispersed farther upstream in the tributary were larger than fish collected near the tributary mouth. Overall, the results demonstrated widespread dispersal in a system with low coho salmon densities, and this might increase the rate of population growth if it reduces the effects of local density dependence. By implication, juveniles can take advantage of rearing habitats reconnected through barrier removal, even when such areas are located several km from adult breeding areas.

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Theme: Habitats to Support Sustainable Fisheries and Recovered Populations
Foci: Develop effective and efficient habitat restoration and conservation techniques.
Characterize the interaction of human use and habitat distribution, quantity and quality.