Monitoring salmon habitat in small streams using streambed profiling and the importance of large woody debris for juvenile chinook salmon habitat in small Yukon streams

Thalweg profiles are longitudinal profiles of the streambed elevation measured along the deepest portion of the stream. This technique has recently been advocated as a tool to monitor fish habitat in streams because profiles can provide useful information on such habitat, and measurements are both repeatable and independent of stream flow. However, a relation between fish abundance and metrics calculated from thalweg profiles has not been established. To test this relation, I surveyed thalweg profiles and sampled juvenile chinook salmon (Oncorhynchus tshawytscha) density in 14 reaches of small, undisturbed streams in the Yukon Territory. Chinook salmon density was correlated with three thalweg metrics. Two of these metrics—length in residual pools and mean residual pool depth—provided useful information on chinook salmon habitat. Thalweg metrics differed between these undisturbed streams and reaches in streams affected by placer gold mining. These results suggest that thalweg profiling provides a useful tool to monitor fish habitat in small streams.