| Abstract |
We tagged 4,505 hatchery steelhead from Dworshak National Fish Hatchery (NFH), with Passive Integrated Transponder (PIT) tags to evaluate factors contributing to residualism. Steelhead lengths from typical growth ponds (System I) averaged 8 mm less than those in System II and travel times were two days faster. Steelhead were released into Clear Creek, South Fork Clearwater River and directly from Dworshak NFH; detection rates were 75.7%, 77.9%, and 76.4%, respectively. The mean detection rates of steelhead by rearing system were 75.8%, 78.4%, and 74.7% for System I, System II, and System III. We PIT tagged an additional 1,131 hatchery steelhead in the North Fork and mainstem Clearwater rivers between April 9 and September 19. In the four tributaries sampled, 85 steelhead were PIT tagged and released, 57.6% were detected emigrating downstream. A total of 149 coded-wire tags were recovered; 18 were tagged at Dworshak NFH in 2000 and two in 1999. Additionally, 20 were released from the Clearwater Fish Hatchery and nine were released in Oregon. Although sample sizes were small, we were able to verify that at least 52 residual steelhead survived the winter to persist in the Clearwater River. These 52 steelhead were PIT tagged in 2000 and detected at Lower Granite Dam emigrating in 2001. Based on this years data, the majority of steelhead, which do not emigrate during the first couple of weeks after release, are unlikely to emigrate. Final analysis will also include influences of water flow and temperature in emigration success. This information needs to be compared over several years for meaningful analysis. |
