Title: Response of channel x blue hybrid catfish to chronic diurnal hypoxia Authors
Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 29, 2012
Publication Date: June 7, 2012
Citation: Green, B.W., Rawles, S.D., Beck, B.H. 2012. Response of channel x blue hybrid catfish to chronic diurnal hypoxia. Aquaculture. 350-353:183-191. Interpretive Summary: Farmers devote great effort to managing dissolved oxygen concentration in catfish production ponds at night during the growing season because catfish performance is affected by the amount of oxygen contained within the pond water. Catfish farmers increasingly are interested in growing the hybrid catfish that is produced when a female channel catfish is mated with a male blue catfish because the hybrid is said to possess a number of positive attributes when compared to the purebred channel catfish, which is the fish most widely grown in the U.S. catfish industry. Although much is known about the response of channel catfish to dissolved oxygen concentration, no systematic study has been conducted for the hybrid catfish. Thus, we conducted a study to quantify the performance traits and metabolic responses of the hybrid catfish grown in ponds where the dissolved oxygen concentration in ponds was allowed to decline nightly to 12%, 24%, 36%, or 48% of the saturation concentration before mechanical aerators were activated to add oxygen to the pond water. Hybrid catfish performance in ponds was higher at higher nightly dissolved oxygen concentrations, an improvement that was attributable to higher feed consumption. Higher feed consumption increased yield with no loss in growth efficiency. The results of this study provide farmers with fish performance information that they can use to refine pond management practices to ensure pond dissolved oxygen concentration is maintained high enough to allow fast fish growth. Identifying an optimal pond dissolved oxygen management strategy is an important factor in ensuring sustainable catfish production in the United States.
Technical Abstract: Performance traits and metabolic responses of the channel x blue hybrid catfish (Ictalurus punctatus female x I. furcatus male) in response to chronic diurnal hypoxia were evaluated in this 197-d study. Sixteen 0.1-ha earthen ponds were stocked with 15,169 hybrid catfish/ha (47 g/fish) and managed to maintain the minimum dissolved oxygen concentration at approximately 12%, 24%, 36%, or 48% of saturation during the warmer months when aeration was necessary. Growth and yield of channel x blue hybrid catfish was significantly related to minimum nightly dissolved oxygen concentration. The cumulative effect of nocturnal dissolved oxygen concentration and the duration of exposure to hypoxia (termed dissolved oxygen-minutes) may be a more biologically meaningful independent variable for regression analysis than minimum nightly dissolved oxygen concentration. Gross and net yield and mean individual weight increased curvilinearly as dissolved oxygen-minutes increased. Chronic nightly hypoxia affected daily feed consumption and channel x blue hybrid catfish in the higher dissolved oxygen treatments grew faster because they consumed a greater percentage of their body weight at each feeding. Feed consumption increased linearly in response to dissolved oxygen-minutes during the peak production period (June-August), but curvilinearly over the entire study. Body compositional indices largely were unaffected by chronic nightly hypoxia. Lipid was the primary depot affected by hypoxia and lipid indices increased with increasing dissolved oxygen concentration. Citrate synthase activity was 14.6% higher in the highest compared to the lowest dissolved oxygen treatment and a strong inverse relationship between citrate synthase activity and fish body mass was observed in the highest dissolved oxygen concentration treatment. Results of this study suggest that pond dissolved oxygen concentration should be maintained at 48% saturation during the peak production period (water temperatures above 25 degrees C) and at 36% saturation during the rest of the growing season.