Assessing the suitability of a partial water reuse system for rearing juvenile Chinook salmon Oncorhynchus tshawytscha for stocking in Washington State

Health and welfare of juvenile Chinook salmon Oncorhynchus tshawytsha reared in a pilot circular tank-based partial water reuse system in Washington State were evaluated in comparison to fish from the same spawn reared in a flow-through raceway, in order to assess the suitability of using water reuse technology for raising Pacific salmonids for stocking. This observational study was carried out over a 21-week period. Reuse and raceway fish were sampled repeatedly for pathogen screening and histopathology; fin erosion and whole blood parameters were also evaluated. By studyu0027s 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 (vs. 1.14 in reuse fish); occasional differences in feeding rates might have played a role in these values. Fin indices were lower in reuse fish, but fin erosion was not grossly apparent in either cohort. The most consistent histological lesion was gill epithelial hypertrophy in reuse fish; blood analyses, however, did not suggest any corresponding physiological imbalances. Overall, results suggest that water reuse technology can be employed for rearing juvenile anadromous salmonids for stocking purposes.