Visually estimating substrate composition at potential spawning sites for trout in mountain streams

Self-sustaining trout populations in mountain streams depend on the presenc e of suitable spawning habitat. However, current watershed-scale habitat in ventory techniques do not assess trout spawning habitat. A spawning substra te evaluation technique is a logical component of such inventories because it would provide data on spatial patterns of suitable substrate across wate rsheds. We evaluated a visual technique designed to assess substrate suitab ility for trout spawning. Comparisons of visual assessments of potential sp awning sites to those using a single-probe freeze-core were made. The visua l method of evaluating spawning substrate was nearly as good as the freeze- core method. Considering the time, labor, and cost efficiency of visual sub strate assessment, this visual technique is a reasonable alternative when e valuating trout spawning substrate at the watershed scale.