Ringold Springs Hatchery Test Facility

A multi-year evaluation was conducted at Ringold Springs Hatchery (RSH) to determine if the U. S. Army Corps of Engineers (COE) should build additional rearing vessels at the hatchery as part of the required John Day mitigation. The fall Chinook salmon used in this study were initially reared at the Oregon Department of Fish and Wildlife’s (ODFW) Bonneville Hatchery, then transported to RSH, and reared in either raceways (treatments) or a large earthen pond (control) for several weeks before being released in the Columbia River at RSH in June. Phase 1 of the project utilized passive integrated transponder (PIT) tags in juvenile fall Chinook salmon released from the control or treatment groups at RSH to compare migration speed and detection rates at one or more of the downstream dams. Phase 2 compared smolt-to-adult returns (SARs) of control and treatment groups as determined by total estimated recoveries of coded-wire tags (CWTs) from all recovery locations. This report covers the tenth and final year of the study, and the final analyses of Phase 2 (adult recoveries and return rates).

Results from weekly juvenile growth monitoring and documentation of release size, and downstream migration tracking (survival and timing) through the use of PIT tags were previously presented in annual progress reports. In summary, smolts released from the rearing pond generally had higher downstream migrant survival rates, had shorter migration times, and smolts generally appeared more �"smolted” (i.e. more silvery in color) than smolts reared in the raceways.

In 2006, staff hired temporary workers and security guards for the capture, processing, and security of returning fall Chinook salmon to RSH. A total of 117 adults and 1 jack fall Chinook salmon were captured in the trap facility. Four adults were recovered with CWTs but none of the snouts recovered in 2006 were from the study groups.

The regional CWT database was queried, and all recoveries of study fish were tallied. Significantly more adult fall Chinook salmon returned from the rearing pond group in three of the five brood years of the study as compared to the treatment raceways. Overall, about 35% more adult fall Chinook salmon returned from the rearing pond group over the course of the study. In addition, significantly fewer (P = 0.025) age 3 adult fall Chinook salmon, and significantly more age 5 (P = 0.005) adult fall Chinook salmon returned from the control group as compared to the treatment groups. Mean length at return between the groups was not significantly different.

In conclusion, fall Chinook salmon reared and released from the rearing pond had higher overall survival rates than those reared in concrete raceways. However, bird predation in the rearing pond can be significant (believed by RSH hatchery staff to be as high as 30% in one year) and should be considered as part of a cost-benefit analysis to determine which rearing method is better for the program. Based on this study, I would recommend construction of 1-2 additional rearing ponds with avian predator netting at RSH. This would provide the greatest number of adult returns back to the Columbia River system to support the mitigation fishery. Further, predator control netting should also be installed on the existing rearing pond to maximize fall Chinook salmon survival to release.