Title: Minthorn Springs Creek Summer Juvenile Release and Adult Collection Facility; 1992 Annual Report.

The Confederated Tribes of the Umatilla Indian Reservation (CT'UIR) and Oregon Department of Fish and Wildlife (ODFW) are cooperating in a joint effort to supplement steelhead and re-establish salmon runs in the Umatilla River Basin. As an integral part of this program, Bonifer and Minthorn Acclimation Facilities are operated for holding and spawning adult steelhead and fall chinook salmon and acclimation and release of juvenile salmon and steelhead. Acclimation of 109,101 spring chinook salmon and 19,977 summer steelhead was completed at Bonifer in the spring of 1992. At Minthorn, 47,458 summer steelhead were acclimated and released. Control groups of spring chinook salmon were released instream concurrent with the acclimated releases to evaluate the effects of acclimation on adult returns to the Umatilla River. Acclimation studies with summer steelhead were not conducted in 1992. A total of 237 unmarked adult steelhead were collected for broodstock at Three Mile Dam from October 18, 1991 through April 24, 1992 and held at Minthorn. Utilizing a 3 x 3 spawning matrix, a total of 476,871 green eggs were taken from 86 females. The eggs were transferred to Umatilla Hatchery for incubation, rearing, and later release into the Umatilla River. A total of 211 fall chinook salmon were also collected for broodstock at Three Mile Dam and held at Minthorn. Using a 1:1 spawning ratio, a total of 195,637 green eggs were taken from 58 females. They were also transferred to Umatilla Hatchery for incubation, rearing, and later release into the Umatilla River. Personnel from the ODFW Eastern Oregon Fish Pathology Laboratory in La Grande took samples of tissues and reproductive fluids from Umatilla River summer steelhead and fall chinook salmon broodstock for monitoring and evaluation purposes. Cell culture assays for replicating agents, including IHNV virus, on all spawned fish were negative. One of 60 summer steelhead tested positive for EIBS virus, while all fall chinook tested we re negative for inclusions. One of 73 summer steelhead sampled for BKD had a high level of antigen, while all others had very low or negative antigen levels. All fall chinook tested had low or negative antigen levels. Regularly-scheduled maintenance of pumps, equipment and facilities was performed in 1992. The progress of outmigration for juvenile releases was monitored at the Westland Canal fish trapping facility by CTUIR and ODFW personnel. Coho and spring chinook yearlings were released in mid-March at Umatilla rivermile (RM) 56 and 60. The peak outmigration period past Westland (RM 27) was mid-April to early May, approximately four to seven weeks after release. Groups of summer steelhead were released from Minthorn (RM 63) and Bonifer (RM 81) in late March and into Meacham Creek near Bonifer in late April. The peak outmigration period past Westland for all groups appeared to be the first two to three weeks in May. Spring chinook yearlings released in mid-April from Bonifer and at Umatilla RM 89, migrated rapidly downriver and the peak outmigration period past Westland appeared to be within a week or two after release. Fall and spring chinook subyearlings released in mid-May at RM 42 and 60, respectively, also migrated rapidly downriver and the peak outmigration period was within days after release. Coded-wire tag recovery information was accessed to determine the contribution of Umatilla River releases to the ocean, Columbia River and Umatilla River fisheries. Total estimated summer steelhead survival have ranged from 0.03 to 0.61% for releases in which recovery information is complete. Coho survival rates have ranged from 0.15 to 4.14%, and spring chinook yearling survival rates from spring releases have ranged from 0.72 to 0.74%. Survival rates of fall chinook yearlings have ranged from 0.08 to 3.01%, while fall chinook subyearling survival rates have ranged from 0.25 to 0.87% for spring released groups.