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Response of channel x blue hybrid catfish to chronic diurnal hypoxia

Green, Batholomew W., Rawles, Steven D., Beck, Benjamin H.
Aquaculture 2012 v.350-353 pp. 183
Ictalurus furcatus, Ictalurus punctatus, body composition, body weight, catfish, citrate (si)-synthase, dissolved oxygen, exposure duration, feed intake, growing season, hybrids, hypoxia, lipids, oxygen, ponds, regression analysis, water temperature
Performance traits and metabolic responses of the channel×blue hybrid catfish (Ictalurus punctatus female×I. furcatus male) in response to chronic diurnal hypoxiawere evaluated in this 197-d study. Sixteen 0.1-ha earthen pondswere stocked with 15,169 hybrid catfish/ha (47 g/fish) and managed tomaintain the minimumdissolved oxygen concentration greater than 12%, 24%, 36%, or 48% of saturation. Growth and yield of channel×blue hybrid catfish were 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 oxygenminutes) proved to be a better independent variable for regression analysis than minimumnightly dissolved oxygen concentration. Gross and net yield andmean individualweight increased curvilinearly as dissolved oxygenminutes increased. Chronic nightly hypoxia affected daily feed consumption and channel×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 and with increasing total feed fed. 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 masswas 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 C) and at 36% saturation during the rest of the growing season.