Kelt Reconditioning: A Research Project to Enhance Iteroparity in Columbia Basin Steelhead (Oncorhynchus mykiss), 2000 Annual Report.

Technical Report · Sat Dec 01 00:00:00 EST 2001

DOI:https://doi.org/10.2172/796201· OSTI ID:796201

Evans, Allen F; Beaty, Roy E; Hatch, Douglas R ^[1]

---

1. Columbia River Inter-Tribal Fish Commission, Portland, OR

Repeat spawning is a life history strategy that is expressed by some species from the family salmonidae. Natural rates of repeat spawning for Columbia River steelhead Oncorhynchus mykiss populations range from 1.6 to 17%. Increasing this repeat spawning rate using fish culture techniques could assist the recovery of depressed steelhead populations. Reconditioning is the process of culturing post-spawned fish (kelts) in a captive environment until they are able to grow and develop mature gonads. Kelt reconditioning techniques were initially developed for Atlantic salmon Salmo salar and sea-trout S. trutta. The recent Endangered Species Act listing of many Columbia Basin steelhead populations has prompted interest in developing reconditioning methods for local populations. The primary purpose of this project in 2000 was to test the general feasibility of collecting, feeding, and treating steelhead kelts in a captive environment. Steelhead kelts were collected from the Yakima River at the Chandler Juvenile Evaluation Facility (Rkm 48) from 12 March to 13 June 2000. Kelts were reconditioned at adjacent Prosser Hatchery in both rectangular and circular tanks and fed a mixed diet of starter paste, adult sized trout pellets, and freeze-dried krill. Formalin was used to control outbreaks of fungus, and we tested the use of ivermectin to control internal parasites (e.g., Salmincola spp.). Some the kelts that died during the reconditioning process were analyzed via pathology and gonad histology to ascertain the possible cause of death and to describe their reproductive development at the time of death. All surviving specimens were released for natural spawning on 12 December 2000. Overall success of the reconditioning process was based on the proportion of fish that survived captivity, gained weight, and on the number of fish that successfully underwent gonadal recrudescence. Many of the reconditioned kelts were radio tagged to assess their spawning migration behavior and success following release from Prosser Hatchery. In total, 512 kelts were collected for reconditioning at Prosser Hatchery. Captive specimens represented 37% (512/1,380) of the entire 1999-2000 Yakima River wild steelhead population, based on fish ladder counts at Prosser Dam. At the conclusion of the experiments ({approx}240 days from capture), 91 fish (18%) had survived and were released to spawn in the wild. Ultrasound examination--to determine sex and reproductive development--determined that 87 (96%) of 91 specimens were female, and we estimated 62 fish (12% of the total collected) had successfully reconditioned. Unfortunately, the majority (82%) of the kelts collected died during the experiment, with the bulk of the moralities occurring during the first 100 days of captivity. Much was learned from the mortalities and modifications were made to the facility to reduce loss for future projects. Overall, the kelts reconditioned during this project will substantially bolster the number of repeat spawners in the Yakima River. Knowledge regarding kelt husbandry, food type preferences, condition, and rearing environments were obtained during this research endeavor. Although the reconditioning success rate achieved (estimated at 12%) was substantially lower than we initially hoped yet still six times higher than the natural rate of respawning and the authors are encouraged by the results of this innovative project. Information collected during this feasibility study will be incorporated into the experimental design for the upcoming year of research and is expected to increase survival.

• Research Organization: Columbia River Inter-Tribal Fish Commission.
• Sponsoring Organization: United States. Bonneville Power Administration.
• DOE Contract Number: 00004185
• OSTI ID: 796201
• Report Number(s): DOE/BP-00004185-1; R&D Project: 200001700; TRN: US200214%%208
• Resource Relation: Other Information: PBD: 1 Dec 2001
• Country of Publication: United States
• Language: English

Related Subjects

13 HYDRO ENERGY
54 ENVIRONMENTAL SCIENCES
COLUMBIA RIVER
DIET
ENDANGERED SPECIES
EVALUATION
FEEDING
FISH PASSAGE FACILITIES
FISHERIES
FOOD
FORMALDEHYDE
GONADS
HISTOLOGY
PATHOLOGY
REARING
RIVERS
SALMON
TROUT
STEELHEAD (FISH) - SPAWNING - WASHINGTON (STATE) - YAKIMA RIVER WATERSHED
STEELHEAD (FISH) - FERTILITY - WASHINGTON (STATE) - YAKIMA RIVER WATERSHED
FISH STOCKING - WASHINGTON (STATE) - YAKIMA RIVER WATERSHED