The four major spawning tributaries where native fluvial Yellowstone Cutthroat Trout spawn in the South Fork Snake River system are Burns, Pine, Rainey, and Palisades creeks. IDFG will operate and maintain the modified fish weirs and traps on all four tributaries through the spring spawning runs from mid-March through mid-July annually. Each of the tributaries have a barrier to fish migration adjacent to an upstream fish trap. Pine, Rainey, and Palisades creeks have electrical barriers and Burns Creek incorporates both a waterfall and a velocity barrier. Migrating trout will be forced into the fish trap where IDFG will hand sort individual fish on a daily basis. Cutthroat Trout will be placed upstream of the barrier and Rainbow Trout and Rainbow x hybrid trout will be removed and transported to a nearby kids fishing pond. Cutthroat Trout passed upstream will be marked with PIT tags or fin punches. Near the end of the spawning run, IDFG will capture fluvial-sized trout upstream of the fish weirs and inspect each fish for marks. The percentage of marked fish will be used as a measure of trapping efficiency. With the newly modified weirs, trapping efficiencies have been high, and we anticipate high efficiencies to continue. In order to maintain high trapping efficiencies, periodic maintenance such as slight channel modifications, removal of sediment, and replacement or repair of damaged equipment or software will be required to keep the weirs  functional.


The second part of this contract pertains to entrainment of Yellowstone Cutthroat Trout into irrigation canals. Rainey Creek in Swan Valley is the only major spawning tributary with more than one irrigation diversion, and it is the most impacted by water withdrawals. Rainey Creek is also the only tributary where Yellowstone Cutthroat Trout spawning runs have not increased since the operation of weirs was initiated. It is possible that the fluvial run of Yellowstone Cutthroat Trout in Rainey Creek has passed a bottleneck which the population may have difficulty recovering from. Thus, we will quantify the effects of entrainment on fry migrating downstream and assess the use of eyed-egg stocking to determine if it is a feasible way to compensate for entrainment and move the Rainey Creek fluvial population back toward historical run numbers.