West Fork recently completed two studies testing the ability of cutthroat trout to ascend corrugated metal culverts using an experimental test flume. Results from these passage trials provided the empirical data necessary to describe the probability of successful passage over a range of hydraulic conditions (Peterson et al. 2013).

In order to broaden the applicability of these results, West Fork is currently validating passage probabilities through field-based passage testing in southwest Washington. The ability for a resident cutthroat trout population to pass through a culvert in situ is being tested by capturing, tagging, and releasing individuals in the vicinity of the culvert in order to track their movement. The research site is instrumented to record movement of PIT tagged individuals into and through the culvert as well as the stream stage and turbidity.

Initial findings have revealed the importance of high flow events in spurring movement and the conditions most likely to facilitate successful passage through the pipe. Results from this validation process will provide a greater context to previous experimental results, leading to broad applicability for headwater drainages across the Pacific Northwest.