Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8524
Title: A life-table model estimation of the parr capacity of a late 19th century Puget Sound steelhead population
Author: N. Gayeski, G. R. Pess, T. J. Beechie
Publication Year: 2016
Journal: FACETS
Volume: 1
Pages: 83-104
Keywords: steelhead,habitat capacity,life cycle assessment

An age-structured life-cycle model of steelhead (Oncorhynchus mykiss) for the Stillaguamish River in Puget Sound, Washington, USA, was employed to estimate the number of age-1 steelhead parr that could have produced the estimated adult return of 69,000 in 1895.  We then divided the estimated parr numbers by the estimated area of steelhead rearing habitat in the Stillaguamish River basin in 1895 and under current conditions to estimate density of rearing steelhead then and now.  Scaled to estimates of total wetted area of tributary and mainstem shallow shoreline habitat, our historic estimates averaged 0.39-0.49 parr · m-2, and ranged from 0.24 to 0.7 parr · m-2.  These values are significantly greater than current densities in the Stillaguamish (mainstem average:  0.15 parr · m-2, tributaries:  0.07 parr · m-2), but well within the range of recent estimates of steelhead parr rearing densities in high-quality habitats.  Our results indicate that modest improvement in the capacity of mainstem and tributary rearing habitat in Puget Sound rivers will yield large recovery benefits if realized in a large proportion of the area of river basins currently accessible to steelhead.

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Theme: Habitats to Support Sustainable Fisheries and Recovered Populations
Foci: Characterize relationships between habitat and ecosystem processes, climate variation, and the viability of organisms.