Journal of Aquatic Animal Health 23:55–61, 2011 C  American Fisheries Society 2011 ISSN: 0899-7659 print / 1548-8667 online DOI: 10.1080/08997659.2011.574082 COMMUNICATION Assessing the Suitability of a Partial Water Reuse System for Rearing Juvenile Chinook Salmon for Stocking in Washington State Christopher Good,* Brian Vinci, and Steven Summerfelt The Conservation Fund’s Freshwater Institute, 1098 Turner Road, Shepherdstown, West Virginia 25443, USA Kevin Snekvik Washington Animal Disease Diagnostic Laboratory and Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Post Office Box 647010, Washington StateUniversity, Pullman, Washington 99164-7010, USA Ian Adams and Samuel Dilly Chelan County Public Utility District, 327 North Wenatchee Avenue, Wenatchee, Washington 98801, USA Abstract To assess the suitability of water reuse technology for raising Pa- cific salmon Oncorhynchus spp. for stocking purposes, fish health and welfare were compared between two groups of juvenile Chi- nook salmon O. tshawytscha from the same spawn: one group was reared in a pilot partial water reuse system (circular tanks), and the other group was reared in a flow-through raceway. This ob- servational study was carried out over a 21-week period in Wash- ington State. Reuse and raceway fish were sampled repeatedly for pathogen screening and histopathology; fin erosion and whole- blood characteristics were also evaluated. By the study’s end, no listed pathogens were isolated from either cohort, and survival was 99.3% and 99.0% in the reuse and raceway groups, respectively. Condition factor was 1.28 in raceway fish and 1.14 in reuse fish; this difference may have been attributable to occasional differences in feeding rates between the cohorts. Fin indices (i.e., length of the longest dorsal or caudal fin ray, standardized by fork length) were lower in reuse fish than in raceway fish, but fin erosion was not grossly apparent in either cohort. The most consistent histological lesion was gill epithelial hypertrophy in reuse fish; however, blood analyses did not suggest any corresponding physiological imbal- ances. Overall, results suggest that water reuse technology can be employed in rearing juvenile anadromous salmonids for stocking purposes. Each year, the Chelan County Public Utility District (PUD) in Washington State produces over 4 million juveniles of anadro- mous and resident Pacific salmon Oncorhynchus spp. for stock- *Corresponding author: c.good@freshwaterinstitute.org Received December 3, 2009; accepted February 14, 2011 ing the upper Columbia River and surrounding waters. These fish are currently raised in a series of facilities that employ traditional flow-through rearing units; however, as water us- age and discharge permits in the region become increasingly restricted, Chelan County PUD managers are considering the adoption of new technologies, such as partial water reuse sys- tems that use circular tanks, for raising the fish. Such water reuse systems are capable of conserving water, concentrating waste for ease of removal, and increasing overall production capacity (Summerfelt et al. 2004; Vinci et al. 2004). However, before traditional raceway units can be replaced by new technologies, pilot studies must be able to demonstrate that satisfactory fish performance and health can be achieved when employing a new reuse system to raise anadromous salmonids obtained from par- ticular stocks. The Chelan County PUD therefore commissioned the construction of a pilot partial water reuse system for pur- poses of evaluating the feasibility of this technology for raising quality salmonids to be used in stocking. Although water reuse technology has been successfully adopted in whole or in part at numerous flow-through facilities throughout the United States, observational investigations comparing the health of salmonids raised in water reuse and flow-through environments have been limited. During the winter of 2008, a partial water reuse system was installed at the Eastbank Hatchery in Wenatchee, Washington. 55