Prevalence of Bacterial Kidney Disease in Natural vs. Hatchery-Reared Adult Chinook Salmon Spawned in a Hatchery and in Nature Information Reports number 2009-06

Identification Information

Citation

Originator: Hoffnagle, T., G. O'Conner, R. Carmichael and S. Gee

Publish Date: September 2009

Online Link: None

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Contact Information

Agency: Oregon Department of Fish and Wildlife

Name: Cedric Cooney

Job Position: Natural Resources Data and Systems Manager

Telephone: 503-947-6094

E-Mail Address: cedric.x.cooney@odfw.oregon.gov

Description

Abstract: Bacterial kidney disease (BKD) is a major health problem of cultured Pacific salmon, Oncorhynchus sp. It has been particularly problematic in captive broodstock programs, where the interests of gene conservation and fish health can conflict when spawning females with signs of BKD. Not rearing those fish reduces the genetic diversity of an already depleted population, while rearing those fish may increase the prevalence of BKD in the natural population. We used data collected during spawning at Lookingglass Fish hatchery and on spawning ground surveys to examine the prevalence of BKD, based on enzyme-linked immunosorbent assay optical density (ELISA OD) values, to monitor the prevalence of BKD in natural and hatchery-reared Chinook salmon O. tshawytscha from Grande Ronde and Imnaha basin streams in northeast Oregon. Mean ELISA OD levels differed among all sampled streams from 2004-2008 and was lowest in the Imnaha River salmon (0.0839) and highest in the Minam River (0.1750). Salmon spawned at LFH had a lower mean ELISA OD level (0.086) than those collected from carcasses on spawning ground surveys (0.118). Natural salmon mean ELISA OD level was 0.1058 and 97% were from salmon with ELISA OD level <0.2 and in hatchery salmon, 96% had an ELISA OD level <0.2 and mean ELISA OD level was 0.1138, with no difference between the groups. Over 17 years in the Imnaha River we see no difference in mean ELISA OD levels between natural and hatchery Chinook salmon. There was no difference in mean ELISA OD levels between adult Chinook salmon from wilderness (0.1663) vs. supplemented (0.1184) streams. However, when comparing mean ELISA OD for only natural Chinook salmon carcasses recovered in these streams, we found that mean ELISA OD level was higher in the wilderness streams (0.1676) than in the supplemented streams. Returning adults from the Captive Broodstock F1 generation had a higher mean ELISA OD level (0.1349) than those of Conventional Hatchery Program offspring (0.0957). Annual mean ELISA OD level decreased over time in the Lostine River stock but did not change for any of the other stocks. The data for BKD in Chinook salmon from northeast Oregon streams and hatcheries show that this disease is not prevalent and we found no evidence that the release of hatchery salmon is causing an increase in BKD prevalence in the monitored streams. However, we will continue to monitor this disease.

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Geographic Extent: Lower Snake River

Status: Final

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Format: PDF File

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