2011 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.
Trials were conducted using fingerling channel catfish to determine nutrient and energy digestibility for corn gluten feed, distillers dried grains with solubles (DDGS), canola meal, poultry by-product meal, and hydrolyzed feather meal. Fecal samples are being analyzed. A pond study evaluated using corn gluten feed and cottonseed meal to replace 25, 50, 75 and 100% soybean meal in control diet for channel catfish. Fish production, carcass and fillet yield, and fillet protein and fat levels decreased and feed conversion ratio increased as soybean meal replacement levels increased. A maximum of 50% of soybean meal in catfish diets may be replaced by a combination of corn gluten feed and cottonseed meal (up to 20% of each in the diet). A second pond study was initiated in 2011 to evaluate DDGS in catfish feeds. Four 28%-protein diets were formulated with 0, 10, 15, and 20% DDGS as a partial replacement of soybean meal, and the study is underway.
A study was conducted to determine the optimum age for stocking fry into nursery ponds. Stocking hatchery-fed fry (8 days-old) resulted in 41.6% survival, swim-up fry had 7.1% survival, and sac fry had 4.5% survival. The logistical burden of holding fry in the hatchery is offset by improved fry survival.
Thirty ponds were stocked with catfish and either threadfin shad, fathead minnows, or no forage fish. Presence of shad or fathead minnows had no positive effect on catfish production, but filter-feeding by shad decreased abundance of cyanobacteria and improved catfish flavor quality. The new, 1.8-ha split-pond aquaculture system was stocked with 45,000 hybrid catfish fish (0.4 kg/fish) in April; fish were harvested in late October. Daytime water flow was 57 m3/min and the dissolved oxygen concentrations were maintained above 3.5 ppm. Fish harvest weight was 35,000 kg (19,000 kg/ha), which is 2-3 times production achieved in traditional ponds.
Stocking catfish fry. Holding catfish fry in the hatchery and feeding commercial starter diets for a week or more is the common practice in commercial catfish farming. Holding fish in the hatchery is, however, labor intensive and expensive. Previous studies in small ponds showed that fry could be stocked into nursery ponds at very young ages with no reduction in survival or growth. If this is true when larger ponds (as on commercial farms) are used, reducing residence time in the hatchery would reduce costs and benefit fingerling producers. However, ARS and Mississippi State University scientists at the National Warmwater Aquaculture Center, Stoneville, MS, showed that stocking fry early leads to poor survival. 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. Without some means of protecting fry from predators, early stocking is too risky for commercial producers.
Co-stocking planktivorous fish. Co-stocking small planktivorous fish could increase efficiency of channel catfish production by providing natural forage and reducing cyanobacteria originating off-flavors. Scientists at the National Warmwater Aquaculture Center, Stoneville, MS, evaluated the effects of co-stocking fathead minnows and threadfin shad with channel catfish. Stocking fathead minnows was not beneficial to water quality or fish production, but the filter-feeding habits of threadfin shad changed the plankton community beneficially by reducing the abundance of blue-green algae. This caused a marked improvement in catfish flavor quality. Co-stocking ponds with threadfin shad appear to be an effective tool to reduce off-flavor incidence in channel catfish production ponds.
Split-pond aquaculture system. A split-pond aquaculture system has been developed that potentially can increase channel catfish production by 2 or 3 times that achieved in traditional earthen ponds. The new system splits an existing earthern pond into two unequal sections with an earthen levee and then links the two systems by circulating water that is pumped with a large, efficient, slow-turning paddlewheel. Fish are held in the small section and the larger section provides waste treatment and oxygen production. The new, full-size (4.5-acre) system studied by ARS scientists at the National Warmwater Aquaculture Center, Stoneville, MS, produced 77,000 pounds of fish (17,000 pouynds/acre) at a feed conversion ratio of 1.8. Based on these results, several hundred acres of split-ponds have been built by commercial farmers in Mississippi and Arkansas.
Alternative feeding ingredients. Prices of soybean meal and corn, the two most commonly used traditional feed ingredients in channel catfish diets, have increased dramatically in recent years. Using less-expensive alternative feed ingredients to partially replace soybean meal and corn will reduce feed cost. ARS scientists at the National Warmwater Aquaculture Center, Stoneville, MS, investigated the use of corn gluten feed and cottonseed meal, two promising alternative feedstuffs, as replacements for soybean meal and corn in diets for pond-raised channel catfish. The study showed that a maximum of 50% of the soybean meal in channel catfish diets may be replaced (soybean meal was reduced from 51.4% to 25.7%) by a combination of corn gluten feed and cottonseed meal (up to 20% of each in the diet) without markedly affecting the physical quality of feed pellets, fish growth, processed yield, and body composition. Results are bing used by catfish feed mills to reduce feed costs while providing a nutritionally complete feed for commercial catfish farming.
Mischke, C.C., Griffin, M.J. 2011. Mass culture of Dero digitata in the laboratory. North American Journal of Aquaculture. 73:13-16.
Robinson, E.H., Li, M.H. 2010. Channel catfish Ictalurus punctatus size and feed conversion ratio. Journal of the World Aquaculture Society. 41:829-833.
Li, M.H., Robinson, E.H., Bosworth, B.G., Oberle, D.F., Lucas, P.M. 2010. Effects of varying dietary compositions using common feed ingredients on growth and feed efficiency of pond raised channel catfish. Aquaculture Research. 41:1133-1139.