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Submitted to: Aquaculture Research
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 11/12/2009 Publication Date: 8/23/2010 Citation: Green, B.W., Rawles, S.D. 2010. Comparative growth and yield of channel catfish and channel x blue hybrid catfish fed a full or restricted ration. Aquaculture Research. 41:e109-e119. Interpretive Summary: When a female channel catfish is mated with a male blue catfish the resulting offspring are hybrids known as channel x blue hybrid catfish. Catfish farmers are very interested in growing this fish because it 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. However, the performance of the hybrid catfish compared to the purebred channel catfish appears to be affected by the strain of maternal catfish and requires investigation. Fish feed prices increased dramatically in past 2 years and this has impacted negatively the profitability of catfish farming because feed costs comprise about half of the total production costs. Thus, modification of catfish feeding practices with the goal of reducing feed-related costs needs to be investigated. An experiment was conducted to compare the production characteristics of the channel x blue hybrid catfish and purebred channel catfish, both of which shared the Jubilee strain of channel catfish as the maternal parent, during the April-November growing season. Each group of fish was fed in one of two ways: each day fish were fed as much feed as they could consume in 20 minutes or 80% of that amount. When fed as much as they could eat, the quantity of fish harvested and the average size were larger for the channel x blue hybrid catfish compared to the purebred channel catfish because the hybrid catfish consumed a greater percentage of its body weight at each feeding. Restricting the daily amount of feed offered to fish resulted in lower quantities of fish harvested and smaller fish sizes. In fact, nearly half of the fish from these ponds were too small to process and would require additional growth to reach market weight. The results of this study provide farmers with fish performance information that they can use to guide their decision as to the most appropriate fish to stock in production ponds. Furthermore, the results of this study show that even a modest reduction in the quantity of feed fed to fish daily impacts fish production negatively. Technical Abstract: Growth and yield (kg ha-1) of the channel catfish (Ictalurus punctatus, Rafinesque, 1818) and the channel x blue hybrid catfish (I. punctatus female x I. furcatus [Lesueur, 1840] male), which shared the Jubilee strain of channel catfish as the maternal parent, were compared in 16 0.1-ha earthen ponds (14,852 fish ha-1) during the April to November growing season. Each fish genetic group was fed a commercially formulated 32% protein feed daily to apparent satiation or at 80% of the mean daily satiation ration. Net yield and individual weight were higher for channel x blue hybrid catfish compared to channel catfish and for fish fed a full ration compared to a restricted ration. When fed a full ration, the channel x blue hybrid catfish grew faster from May to September than did the purebred channel catfish because the hybrid catfish consumed a greater percentage of its body weight at each feeding. Net yield within each fish genetic group was lower when feed ration was restricted. The percent reduction in net yield in response to feed restriction was similar for each fish genetic group. |
