Spring outmigration of wild and hatchery chinook salmon and steelhead trout211 smolts from the Imnaha River, Oregon, February 6, 1995-June 20, 1995

摘要

For the second consecutive year, the Nez Perce Tribe, in conjunction with the211u001eFish Passage Center, participated in the smolt monitoring program in the Imnaha 211u001eRiver. A rotary screw trap was used to collect emigrating wild and hatchery 211u001echinook salmon (Oncorhynchus tshawytscha) and steelhead trout (Oncorhynchus 211u001emykiss) smolts from February 6 to June 20, 1995. We PIT tagged and released 421 211u001ewild chinook salmon smolts, 747 hatchery chinook salmon smolts (445 HxW and 302 211u001eHxH), 227 wild steelhead trout smolts and 1,296 hatchery steelhead trout smolts. 211u001eCumulative interrogation rates at mainstem Snake and Columbia River dams were 211u001e78.4% for wild chinook salmon, 58.9% for hatchery chinook salmon (HxW), 56.6% for 211u001ehatchery chinook salmon (HxH), 76.2% for wild steelhead trout, and 69.2% for 211u001ehatchery steelhead trout. Peak outmigration of NPT tagged wild Imnaha River 211u001echinook salmon smolts occurred from early to mid-May at Lower Granite, Little 211u001eGoose, and Lower Monumental Dams. Median and 90% passage dates for wild chinook 211u001esalmon smolts at Lower Granite Dam were May 1 and May 11, respectively. 211u001eContinuous spill at Lower Granite Dam was initiated on May 3 and lasted for 51 211u001edays. The 90% passage date of wild chinook salmon smolts at Lower Granite Dam 211u001e(May 11) preceded peak Snake River and Lower Granite (June 6) flows by 26 days. 211u001eAlthough hatchery chinook salmon exhibited a shorter outmigration period through 211u001ethe Snake River than their wild counterparts, peak arrival for both groups 211u001eoccurred at approximately the same time. Median and 90% passage dates at Lower