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Basin-Scale Variation in the Spatial Pattern of Fall Movement of Juvenile Coho Salmon in the West Fork Smith River, Oregon
Citation:
Hance, D., L. Ganio, K. Burnett, AND Joe Ebersole. Basin-Scale Variation in the Spatial Pattern of Fall Movement of Juvenile Coho Salmon in the West Fork Smith River, Oregon. TRANSACTIONS OF THE AMERICAN FISHERIES SOCIETY. American Fisheries Society, Bethesda, MD, 5(145):1018-1034, (2016).
Impact/Purpose:
Many stream fishes move between seasonal habitats, seeking shelter, foraging opportunities, spawning habitat, or other specific habitat needs that may not be uniformly distributed within watersheds. Managing and protecting habitats for fish in streams could be made more efficient and effective if we better understood how and when fish move between seasonal habitats. In the Pacific Northwest, several species of salmon have been recorded moving between mainstem and tributary habitats during the transition from the summer dry season to the winter wet season. In this paper, we describe basin-scale variability in movement between mainstem and tributary habitat for juvenile coho salmon. We found a diversity of movement patterns that differed across the watershed. This basin-scale variation in patterns of immigration and emigration demonstrates complexity in the connectivity of juvenile coho salmon seasonal habitats within a stream network. The diversity of movements and habitat use patterns may help salmon ‘spread the risk’ of habitat stress if not all fish are subject to the same stressors at the same time, thus contributing to population resilience. These findings have implications for restoration planning and watershed management. Restoration actions may be most effective if they allow connectivity of summer rearing and overwintering habitat throughout a stream network. This work contributes to an FY 16 deliverable under SSWR 3.01C, Watershed Resilience, Recovery Potential and Sustainability.
Description:
For several species of salmonids (Oncorhynchus and Salvelinus spp.) inhabiting Pacific coastal temperate streams, juvenile fish have been recorded moving between mainstem and tributary habitats during the transition from the summer dry season to the winter wet season. Movement connecting summer and winter habitats may be particularly important for coho salmon (O. kisutch) because availability of overwintering habitat can limit freshwater survival for this species. Here, we describe basin-scale variability in movement between mainstem and tributary habitat for juvenile coho salmon tagged in the summer with passive integrated transponders (PIT) and detected in the fall at four stationary detection sites at tributary-mainstem confluences of the West Fork Smith River, Oregon. We used odds ratios to evaluate spatial patterns in tributary-mainstem movement across tributary junctions at upper-river, mid-river, and lower-river locations. Three types of movement were assessed: 1) emigration out of tributaries into the mainstem, 2) immigration into a tributary from the mainstem downstream of the tributary junction, and 3) immigration from the mainstem upstream of the tributary junction. Likelihood of emigration had a distinct spatial pattern. Only at the two upper-river detection sites were juvenile coho salmon more likely to emigrate than immigrate. Fish immigrating into a mid-river tributary were more likely to originate from the mainstem downstream of the confluence, whereas fish immigrating into two lower-river tributaries were more likely to originate from the mainstem upstream of the confluence. This basin-scale variation in patterns of immigration and emigration demonstrates complexity in the connectivity of juvenile coho salmon seasonal habitats within a stream network. We conclude that effective restoration planning and watershed management should account for spatial pattern of connectivity of summer rearing and overwintering habitat throughout a stream network, and consider the full diversity of movement patterns that may be required for fish to access seasonal habitats.
