| Aquaculture/Fisheries Center Research Highlights |
| Catfish (2006) |
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Optimizing Techniques for
Artificial Spawning of Catfish Catfish farming represents the largest aquaculture industry in the United States but spawning practices for catfish remain relatively uncontrolled and can be highly variable in producing fry and fingerlings. Artificial spawning and out of season spawning are techniques being explored to enhance the production of hybrid catfish (blue catfish- channel catfish) fingerlings as artificial spawning techniques are required for this practice. Indoor wet laboratory facilities designed to maintain catfish broodstock under controlled photoperiods and controlled water temperatures are under construction and the first experiments are scheduled to commence in early 2007. Effect of Soybean Oil, Menhaden Oil, and Flaxseed Oil
Supplements on the Growth, Feed Utilization, Health and Sensory
Characteristics of Channel Catfish Reared at 22șC. The objective was to determine the effects of different supplemental lipids on performance and product quality of channel catfish fingerlings maintained at 22oC. Catfish (1/4 lb = 113 g each) were stocked into three independent recirculating systems and fed a 32%-protein commercial floating pellet supplemented with 2% soybean oil (SBO), menhaden oil (MFO), or flaxseed oil (FLX) once daily to satiation for 90 days. There was no difference in feed conversion ratio, weight gain or survival among treatments. Lysozyme was higher in fish fed diets enriched with n-3 fatty acids (FLX or MFO). The n-3 fatty acids were higher in muscle of catfish fed FLX or MFO diets. However, sensory evaluation showed that the overall acceptability of the fillet was lower for catfish fed FLX or MFO diets compared to fish fed the SBO diet. This gives producers more options to control fish performance and product quality under different temperature regimes. Growth and Survival Comparison of Channel Catfish, Ictalurus
punctatus, Fry Fed Diets Containing all Plant Protein Versus
Standard Diets Containing Animal Protein. The objective was to compare the effects of a commercial 36% protein diet with animal proteins (poultry+fish) to a 36% protein all-plant diet on growth and survival of catfish fry.There was no significant difference in growth rates for the two diets. However, diet analysis showed that the diets also differed in total protein. Therefore, experiments will be repeated using isonitrogenous diets differing in protein quality.A full scale study is planned to evaluate the effects of 36% and 45% all-plant-protein diets against 36% and 45% animal+plant-protein diets on channel catfish fry growth and survival. Results could lead to reduced fish meal use and lower feed costs in channel catfish production. Evaluation of Cuphea Meal as an Ingredient Replacement in
Channel Catfish Diets. The objective was to evaluate the effectiveness of cuphea meal at replacing wheat in catfish diets in order to lower feed costs or provide additional benefits for fish performance. Channel catfish fingerlings were fed a control diet containing wheat or two experimental diets containing 7.5% cuphea meal, or 12.5% cuphea meal for eight weeks to determine if cuphea meal could replace wheat products in catfish diets. Weight gain did not differ by diet. Whole-body protein of fish fed the cuphea diets (13.3 ± 0.66 and 14.5 ± 0.21%) was significantly (P < 0.05) higher than that of fish fed the wheat diet (12.7 ± 0.44%). Cuphea meal enhanced body composition of juvenile channel catfish without affecting growth or survival. Therefore, cuphea meal is a promising candidate for replacement of wheat bran at the levels tested. Evaluation of a
Confinement System for the Production of Channel Catfish A confinement system for the production of channel catfish Ictalurus punctatus was evaluated at the University of Arkansas at Pine Bluff Aquaculture Research Station. This research was carried out for two separate growing seasons each with its own unique experiment. Each study consisted of ten 0.1-ha ponds. A barrier was constructed in five of these ponds to partition the pond into 1/3 and 2/3 sections. The other five ponds were left as traditional open ponds and used as controls. When fingerlings were physically separated from larger carryover fish, significantly greater yields of fingerling (stocker) fish were achieved. There were no significant differences in survival, feed conversion ratio, or growth. The partial budget analysis revealed a positive net change of $367/ha or $38,125 for a 104 ha catfish farm at a market price of $1.54/kg of additional stockers produced. Yields, feed conversion ratios, and daily growth of food fish were significantly lower in the confinement system in the Year 2 single-batch study. Seining efficiency was significantly greater for the confinement system. The partial budget analysis showed a change in revenue of -$2,186.00/ha or -$227,334.00 across a 104-ha farm at a foodfish market price of $1.54/kg. The confinement system improved profits over the traditional multiple-batch system by taking advantage of maintaining different sizes of fish separately. However, yields were not as high as in the open-pond stocker single-batch system. Further research is needed to identify the best way to utilize the confinement system in a commercial setting. Testing the Efficacy of a
Catfish Trawl as an Inventory Assessment Tools Commercial catfish farmers do not have efficient ways to assess the size distribution of their fish inventories. Current methods are mostly limited to computer models that estimate fish growth based on feeding and stocking rates. However, computer estimates often become inaccurate after several years of multiple batch cropping. Accurate size distribution estimates of fish inventories would help farm managers schedule fish harvests and manage cash flow. Research trials have been conducted on commercial catfish farms in Arkansas to test the efficacy of a catfish trawl as an inventory assessment tool for commercial catfish ponds. The catfish trawl was shown to easily capture large fish samples out of commercial catfish ponds but results also suggest discrepancies between the trawl samples and other sampling methods. More research will be conducted in 2007 to test other aspects of the trawl. Catfish Feeding Frequency
Study, Understocking with Large Stockers Twelve 0.10-ac ponds were each stocked with 2,000 lb/ac carryover fish (average weight of 0.88 lb) and 4,500 fingerlings (150 lb/1,000). Treatments were feeding either every day, every other day, or every third day, and fish were fed to apparent satiation on the days fed with a 32% protein floating catfish feed. Both stockers and carryover fish grew significantly better when fed every day. Yields of market-sized fish were 860 lb/ac greater when fed every day and 1,000 lb/ac more when fed every other day as compared to feeding every third day. Fillet dressout yields were significantly greater for fish fed every day. The feed conversion ratio was greater with every day feeding, but the additional revenue from the higher yields more than compensates for the improved feed conversion ratio of feeding less than every day. Winter Feeding of Channel
Catfish Ten 0.25-acre ponds were stocked with 880 lb/ac market-sized fish (>1.25 lb) and 2,640 lb/ac of stocker-sized fish (250-500 g). Treatments were either fed or unfed over the winter. The average weight at harvest of market-size fish was similar (931±58 g for fed fish; 958±45 g unfed) (P>0.05). Sub market-size catfish that were fed over the winter lost less weight on average than those not fed over the winter (P<0.05). Fed fish averaged 260±8 g at harvest while unfed fish averaged 245±139. However, this difference was not great enough to affect the overall net yield of fish harvested. Net yield at harvest averaged -250±93 kg/ha for fed ponds, and -375±195 kg/ha for unfed ponds. Survival averaged 95% for both treatments. Effect of Density of
Understocked Stocker Catfish on Production A multiple-batch study was conducted using stocker catfish (0.09 kg/fish) and carryover fish (0.39 kg/fish) to look at the effects of different stocker densities on fish production. Twelve 0.1 ha ponds were stocked with 7,400; 11,120; or 14,825 stockers /ha and equal weights of carryover fish (2,268 kg/ha). No significant differences were detected for gross, net, and net daily yields, growth (g/d), or survival. Sub-marketable yield (< 0.57 kg) increased as stocking density increased. However, marketable yields (> 0.57 kg) were not affected by density. Carryover fish in high-density ponds had a significantly lower (P < 0.05) mean weight at harvest, but mean stocker weight was not different across densities. The study indicated the possibility that stockers compete with large carryover fish, particularly at higher densities. Hybrid-103 Catfish Growout
Challenge Channel catfish (NWAC 103) and hybrid catfish (channel-blue) fingerlings (6-8 inches each) were stocked at 6,000/acre, five 0.25-acre ponds of each. There was no significant difference (P <0.05) due to the type of fish in growth, yield, total feed fed, survival, seinability, average weight at harvest, or dressout yield. Feed conversion ratio was significantly lower for the hybrids. A partial budget analysis revealed that benefits from the lower feed costs that result from the lower conversion ratio for the hybrids were less than the additional cost of purchasing the hybrid fingerlings.
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