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Title: Use of avoidance response by rainbow trout to carbon dioxide for fish self-transfer between tanks

Author
item CLINGERMAN, JASON - CONSERVATION FUND FRESWAT
item Bebak, Julie
item MAZIK, PATRICIA - USGS WEST VIRGINIA UNIVER
item SUMMERFELT, STEVEN - CONSERVATION FUND FRESHWA

Submitted to: Aquacultural Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/11/2007
Publication Date: 11/1/2007
Citation: Clingerman, J., Bebak, J.A., Mazik, P.M., Summerfelt, S.T. 2007. Use of avoidance response by rainbow trout to carbon dioxide for fish self-transfer between tanks. Aquacultural Engineering. 37(3): 234-251.

Interpretive Summary: Convenient, economical, and reduced labor fish harvest and transfer systems are required to realize operating cost savings that can be achieved with the use of much larger and deeper circular culture tanks. To achieve these goals, we developed a new technology for transferring fish based on their avoidance behavior to elevated concentrations of dissolved carbon dioxide (CO2). We observed this behavioral response during controlled, replicated experiments that showed dissolved CO2 concentrations of 60-120 mg/L induced rainbow trout (Oncorhynchus mykiss) to swim out of their 11 m3 “growout” tank, through a transfer pipe carrying a flow with less than or equal to 23 mg/L dissolved CO2, into a second 11 m3 “harvest” tank. Results indicate that the CO2 avoidance technique can provide a convenient, efficient, more economical, and reduced labor approach for fish transfer, especially in applications using large and well-mixed circular culture tanks.

Technical Abstract: Convenient, economical, and reduced labor fish harvest and transfer systems are required to realize operating cost savings that can be achieved with the use of much larger and deeper circular culture tanks. To achieve these goals, we developed a new technology for transferring fish based on their avoidance behavior to elevated concentrations of dissolved carbon dioxide (CO2). We observed this behavioral response during controlled, replicated experiments that showed dissolved CO2 concentrations of 60-120 mg/L induced rainbow trout (Oncorhynchus mykiss) to swim out of their 11 m3 "growout" tank, through a transfer pipe carrying a flow with less than or equal to 23 mg/L dissolved CO2 into a second 11 m3 "harvest" tank. The research was conducted using separate cohorts of rainbow trout held at commercially relevant densities (40-60 kg/m3). The average weight of fish ranged from 0.15 to 1.3 kg during the various trials. In all trials that used a constant flow of low CO2 water (less than or equal to 23 mg/L entering the growout tank from the harvest tank, approximately 80-90% of the fish swam from the growout tank, through the transfer pipe, and into the harvest tank after the CO2 concentration in the growout tank had exceeded 60 mg/L. The first that remained in the growout tank stayed within the area of relavtively low CO2 water at the entrance of the transfer pipe. However, the rate of fish transfer from the growout tank to the harvest tank was more than doubled when the diameter of the transfer pipe was increased from 203 mm to 406 mm. To consistently achieve fish transfer efficiencies of 99%, water flow rate through the fish transfer pipe had to be reduced to 10-20% of the original flow just before the conclusion of each trial. Reducing the flow or relatively low CO2 water about the entrance of the fish transfer pipe, and provided the stimulus for all but a few remaining fish to swim out of the growout tank. Results indicate that the CO2 avoidance technique can provide a convenient, efficient, more economical, and reduced labor approach for fish transfer, especially in applications using large and well mixed circular culture tanks.