We estimated the hooking mortality of spring Chinook salmon Oncorhynchus tshawytscha that were caught and released to determine whether selective fishing on hatchery Chinook salmon would reduce harvest mortality of wild fish in a sport fishery in the lower Willamette River, Oregon. Hooking mortality in the fishery was estimated from hooking mortality rates for each of five anatomical locations (jaw, 2.3%; tongue, 17.8%; eye, 0.0%; gills, 81.6%; and esophagus–stomach, 67.3%) and from the frequency of these anatomical locations in the sport fishery (jaw, 81.5%; tongue, 5.1%; eye, 0.4%; gills, 5.1%; and esophagus–stomach, 7.8%). Mortality rates by anatomical location were estimated from recaptures of 869 tagged fish that were experimentally angled and of 825 tagged controls that were trapped in a nearby fishway. Anatomical hook locations in the lower Willamette River sport fishery were determined with creel surveys. We estimated hooking mortality rates of 12.2% for wild Chinook salmon caught and released in the sport fishery and 3.2% for the entire run of wild Chinook salmon based on a mean encounter rate of 26%. Hook location was the primary factor affecting recapture of hooked fish, but fish length, gear type, bleeding, and the elapsed time to unhook fish were also significant factors. A selective sport fishery in the lower Willamette River can be used to reduce harvest mortality on runs of wild Chinook salmon while maintaining fishing opportunity on hatchery Chinook salmon. The effect of selective fisheries for Chinook salmon in other rivers would depend on the frequency distribution of anatomical hook locations and on river‐specific encounter rates.

No abstract

Juvenile hatchery summer steelhead Oncorhynchus mykiss were treated with the hormone 17α‐methyltestosterone by methods developed for rainbow trout O. mykiss in an attempt to obtain sterile returning adults. Our objective was to determine if sterile steelhead would return to a target stream at frequencies high enough to provide recreational fisheries while providing fishery managers with a tool for reducing steelhead interactions with wild fish. From three brood years of treated releases, only one sterile adult steelhead returned to the collection hatchery on the South Santiam River, Oregon. Gonads were absent in this fish at the end of spawning in February. Other returning adults from treatment groups were 80% male and 20% female. Adults from control groups were 49% male and 51% female. Males from treatment groups developed secondary sexual characteristics similar to controls but contained deformed gonads at the end of spawning. Gonads of treated females appeared normal, but only one ripened by the end of spawning. Although sperm from treated males was viable, based on crosses with eggs from control females, our inability to hand‐strip milt from 81% of the treated males suggest that occluded sperm ducts would prevent many from spawning naturally. The mean return frequency of treatment groups was 0.5%, which was 24% of the mean return frequency of control groups. Treatment groups may have had higher mortality after the juveniles were released, or sterile fish may have survived but not returned to the hatchery. Treating juvenile steelhead with 17α‐methyltestosterone by the methods we used was not effective in producing sterile returning adults, although sterile individuals may have remained in the ocean.