|DAVIDSON III, JOHN - Freshwater Institute|
|GOOD, CHRISTOPHER - Freshwater Institute|
|WELSH, CARLA - Freshwater Institute|
|SUMMERFELT, STEVEN - Freshwater Institute|
Submitted to: Aquacultural Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/30/2011
Publication Date: 11/12/2011
Citation: Davidson III, J.W., Good, C.M., Welsh, C., Summerfelt, S.T. 2011. Abnormal swimming behavior and increased deformities in rainbow trout Oncorhynchus mykiss cultured in low exchange water recirculation aquaculture systems. Aquacultural Engineering. 45(3):109-117.
Interpretive Summary: Optimizing performance of fish cultured in water recirculating aquaculture systems (WRAS) requires observing and quantifying a variety of indicators of fish health and welfare. Throughout several grow out studies conducted at low and near-zero water exchange rates we observed and quantified swimming speeds, prevalence of “side swimming” behavior, spinal deformities, survival, and a variety of other abnormal fish behaviors. Measures of several key water quality parameters were observed to be correlated to various fish health and welfare metrics. Specifically key findings include: Rainbow trout cultured within low water exchange (0.26% of the total recycle flow) exhibited increased swimming speeds and a greater incidence of "side swimming" behavior as compared to trout cultured in high exchange WRAS. An increased percentage of rainbow trout deformities, as well as increased mortality and a variety of unusual swimming behaviors were observed within WRAS with the highest feed loading rates and least water exchange (hydraulic retention time > 94 days). A stringent review of reported toxicities, associations of water quality concentrations to rainbow trout swimming speed, deformities, and other health and welfare metrics suggests that accumulating dissolved copper, nitrate nitrogen, and/or dissolved potassium are highly correlated with deteriorating fish health and welfare. Identifying and controlling the factors that negatively contribute to fish health and welfare will improve opportunities to increase fish performance in WRAS.
Technical Abstract: Two studies were conducted to determine if accumulating water quality parameters would negatively impact rainbow trout Oncorhynchus mykiss health and welfare within water recirculation aquaculture systems (WRAS) that were operated at low and near-zero water exchange, with and without ozonation, and with relatively high feed loading rates. During the first study, rainbow trout cultured within replicated 9.5 cubic meter WRAS operated with ozone and with low water exchange (0.26% of the total recycle flow) exhibited increased swimming speeds as well as a greater incidence of “side swimming” behavior as compared to trout cultured in high exchange WRAS. During the second study, when the replicated WRAS were operated at near-zero water exchange, an increased percentage of rainbow trout deformities, as well as increased mortality and a variety of unusual swimming behaviors were observed within WRAS with the highest feed loading rates and least water exchange (hydraulic retention time >/= 94 days). A wide range of water quality variables were analyzed, including 27 dissolved metals/elements (including copper, zinc, iron, potassium, and selenium), total ammonia nitrogen, unionized ammonia, nitrite nitrogen, nitrate nitrogen, total suspended solids, biochemical oxygen demand, heterotrophic bacteria, carbon dioxide, as well as ozone and its byproducts (bromide, bromine, and bromate). Although the causative agent could not be conclusively identified, a review of reported toxicities, as well as associations of water quality concentrations to rainbow trout swimming speed, deformities, and other health and welfare metrics suggested that accumulating nitrate nitrogen and/or dissolved potassium could have created the problems identified. These findings suggest the need for further controlled studies to examine rainbow trout chronically exposed to nitrate nitrogen or potassium within WRAS.