River features associated with chum salmon spawning areas: a method to estimate habitat capacity

Abstract

Diminishing returns of salmon and years of poor commercial and subsistence fishing in western Alaska are a cause for concern. Management tools which recognize the intricate life histories of salmon and incorporate environmental conditions at each particular life stage are needed. Toward that goal a study of spawning habitat for chum salmon Oncorhynchus keta was conducted from 2002 to 2005 on the Tuluksak River in western Alaska. Small-scale river features were measured during two summers of field work. Large-scale river features were identified using remote sensing. Principal components analysis (PCA) denoted an association between spawning sites and channel intersections, gravel bars, islands, and areas of accelerated channel change, forming the basis for a predictive habitat model. Two models were developed that combined them habitat assessment with chum salmon redd size and spatial requirements at three spawning densities. The first model, based on field observations in 2002 and 2003, estimated a greater spawning capacity than the second model, based on large-scale river features. Spawning capacity estimates from both models were consistent with historic escapement data and should be used as a starting point for further research. This study represents progress toward a management strategy that is sensitive to habitat-dependent production potential.