Location: Warmwater Aquaculture Research Unit2012 Annual Report
1a. Objectives (from AD-416):
The overall objective of this project is to improve the profitability of channel catfish by improving farm-level production efficiency. This will be accomplished by addressing key production inefficiencies over a broad range of issues (nutrition, production system design, and product quality) affecting production in all post-hatchery production phases (fingerling production, foodfish production, and post-harvest). Over the next 5 years, we will accomplish the following objectives: Objective 1: Explore alternative feed ingredients to reduce production costs of catfish. Objective 2: Improve culture methods for fry and fingerling production. Objective 3: Develop new and improve existing production strategies for large catfish. Objective 4: Determine the relationship between pre-harvest, harvest, and post-harvest practices and product quality.
1b. Approach (from AD-416):
Catfish aquaculture was a profitable and rapidly growing industry in the southeastern United States prior to 2003. Since that time, profitability has declined due primarily to competition from imports and increased feed prices. Although these macroeconomic issues are difficult to address, new technologies can improve farm production efficiency and help restore profitability. This project addresses key production inefficiencies in fish nutrition, production system design, and product quality. Objective 1 will address the rising cost of catfish feed by finding suitable replacements for traditional feed ingredients that have recently increased dramatically in price. Objective 2 will evaluate the use of natural feeds and different stocking densities on growth and survival of catfish fry, with the goal of reducing feed costs and improving growth of fish from fry to fingerling stage. Objective 3 will evaluate ways to reduce feed-input costs by providing food-sized catfish with forage fish as a secondary source of food. A second subobjective proposes to alter pond design to overcome production limitations related to loading limitations of traditional earthen ponds. Objective 4 will address the large number of fish rejected for processing due to product-quality issues. Fish rejected for processing has become an important inefficiency for foodfish producers. The benefits of this project will be development of techniques to enhance economic performance, improve global competitiveness, and allow domestic aquaculture to reduce dependence on imports to meet the U.S. demand for seafood.
3. Progress Report:
Digestibility trials were conducted to determine apparent digestibility coefficients (ADCs) for several alternative protein sources including corn gluten feed, distillers dried grains with soluble, canola meal, poultry by-product meal, and hydrolyzed feather meal as compared with that of soybean meal. ADCs for protein ranged from 70 to 87%, lower than 94% for soybean meal. ADCs for energy ranged 52–59% for plant feedstuffs and 79–82% for animal feedstuffs as compared with 79% for soybean meal. Lysine in plant feedstuffs was 67–79% available and that in animal feedstuffs was 61–72% available to catfish, lower than 94% for soybean meal. These ADC values can be useful in formulating cost-effective feeds using these feedstuffs. A pond study was conducted to evaluate the use of corn gluten feed and cottonseed meal to replace 25, 50, 75 and 100% soybean meal in the control diet. Results demonstrate that a maximum of 50% of the soybean meal in channel catfish diets may be replaced by a combination of corn gluten feed and cottonseed meal without markedly affecting physical quality of feed pellets, fish growth, processed yield, and body composition. At current feedstuff prices, the use of a combination of corn gluten feed and cottonseed meal to partially replace soybean meal and corn reduces feed cost for catfish producers. A second pond study was conducted to examine the use of distillers dried grains with solubles (DDGS) in catfish feeds. Results showed no significant differences in production characteristics among fish fed DDGS at levels up to 20%. No obvious yellow pigmentation was observed in fillets of fish fed the DDGS diets. However, processed yield significantly decreased with increasing levels of DDGS, which is likely caused by reduced digestible protein, an imbalance in essential amino acids, or high fat content in DDGS. Studies on stocking different ages of fry have been completed. Stocking hatchery-fed fry resulted in 41.6% survival, stocking swim-up fry resulted in 7.1% survival, and stocking sac fry resulted in 4.5% survival. The final recommendation is to continue feeding fry in the hatchery before stocking to improve survival rates. In forage fish studies, the addition of threadfin shad to catfish ponds did not improve catfish growth or feed conversion. Threadfin shad did reduce algae-caused off-flavor in summer but caused fishy flavors in the winter. Presence of fathead minnows had no effect on production or fillet quality. Overall the use of forage fish to increase production efficiency does not appear effective. Recirculation flow rates and aeration requirements have been established for the split pond systems based on desired minimum dissolved oxygen concentration, maximum fish biomass, and water temperature. Daytime flow rate through the system (gallons per minute) = [(maximum pounds)(0.8)] ÷ (lowest desired dissolved oxygen). Nighttime aeration requirement (using standard paddlewheel aerators, in horsepower) = (maximum pounds of fish)(0.0002).
Mischke, C.C., Li, M.H., Oberle, D.F. 2011. Can reduced stocking rates and natural forage utilization produce market-sized catfish from fingerlings in one growing season. Journal of Applied Aquaculture. 23:271-278.