Spatial and temporal distribution of coho salmon carcasses in a stream in the Pacific Northwest, USA

During two consecutive spawning seasons, the movement and distribution of naturally occurring coho salmon (Oncorhynchus kisutch) carcasses were monitored, and the effectiveness of large woody debris (LWD) in retaining carcasses in a stream was evaluated. In both seasons studied, the proportion of carcasses trapped by LWD increased as the season progressed. Densities of salmon carcasses were higher in slow waters such as stream edges and backwaters throughout the study periods. The average distance drifted by carcasses was 19.5 m in the first season and 32.1 m in the second season. These results support the notion that LWD contributes to retention of salmon carcasses and enhances availability of salmon-derived nutrients for organisms near salmon spawning grounds.