Technical Bulletin No. 0862: Influence of Culvert Crossings on Movement of Stream Dwelling Salmonids
Mark-recapture techniques were used to examine the effects of culvert crossings on fish movement over the course of a year on eight small streams in forested lands of the Cascade Mountains of Washington. Assessments were made of movements of resident and juvenile anadromous salmonids and cottids through culverts and control reaches situated upstream and downstream of road crossings. A total of 5273 fish (4409 salmonids and 864 cottids) were captured and marked during the study. Throughout the course of the study, 43% of all marked salmonids were recaptured. The majority of the recaptured salmonids (68%) were collected in the same reach in which they had been marked; the remaining 32% moved at least into the adjacent sample reach. Over 16% of the recaptured salmonids moved farther than 100 feet in either an upstream or downstream direction. The number of fish detected moving downstream through a control reach (207 fish) was more than double that of upstream detections (102 fish). A total of 52 recaptured fish (51 salmonids, 1 cottid) had moved upstream through a culvert. Thirty cutthroat trout were recaptured over 500 feet upstream of their point of initial capture and marking. Upstream fish movement through culverts was comparable to that of the natural control reaches. Immigration of unmarked fish into study reaches was similar both upstream and downstream of study culverts. The culverts investigated are technically considered barriers under the State of Washington’s culvert installation guidelines. Results indicate that reconsideration of the criteria used to determine the barrier status of culvert crossings during preparation of road maintenance and abandonment plans may be warranted.