Spawning Success of Hatchery Spring Chinook Salmon Outplanted as Adults in the Clearwater River Basin, Idaho, 2001.

摘要

The study described in this report evaluated spawning distribution, overlap with naturally-arriving spawners, and pre-spawning mortality of spring chinook salmon, Oncorhynchus tshawytscha, outplanted as adults in the Clearwater River Subbasin in 2001. Returns of spring chinook salmon to Snake River Basin hatcheries and acclimation facilities in 2001 exceeded needs for hatchery production goals in Idaho. Consequently, management agencies including the U.S. Fish and Wildlife Service (FWS), Idaho Department of Fish and Game (IDFG) and Nez Perce Tribe (NPT) agreed to outplant chinook salmon adults as an adaptive management strategy for using hatchery adults. Adult outplants were made in streams or stream sections that have been typically underseeded with spawners. This strategy anticipated that outplanted hatchery chinook salmon would spawn successfully near the areas where they were planted, and would increase natural production. Outplanting of adult spring chinook salmon from hatcheries is likely to be proposed in years when run sizes are similar to those of the 2001 run. Careful monitoring of results from this year's outplanting can be used to guide decisions and methods for future adult outplanting. Numbers of spring chinook salmon outplanted was based on hatchery run size, hatchery needs, and available spawning habitat. Hatcheries involved in outplanting in the Clearwater Basin included Dworshak National Fish Hatchery, Kooskia National Fish Hatchery, Clearwater Anadromous Fish Hatchery, and Rapid River Fish Hatchery. The NPT, IDFG, FWS, and the National Marine Fisheries Service (NMFS) agreed upon outplant locations and a range of numbers of spring chinook salmon to be outplanted (Table 1). Outplanting occurred mainly in the Selway River Subbasin, but additional outplants were made in tributaries to the South Fork Clearwater River and the Lochsa River (Table 1). Actual outplanting activities were carried out primarily by the NPT with supplemental outplanting done in the Lochsa basin by IDFG. Fish were trucked from the hatcheries to outplant sites.