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United States Department of Agriculture

Agricultural Research Service

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Location: Warmwater Aquaculture Research Unit

2009 Annual Report

1a.Objectives (from AD-416)
The objectives are to: 1)Discover, develop, and apply methods to predict off-flavor episodes and manage off-flavor compounds; 2)Identify optimal water column conditions for balanced growth of bacteria, phytoplankton, and zooplankton resulting in reduced secondary metabolite formation, and enhanced fish survival and production; 3)Determine influence of chemical and biological factors on channel catfish respiration, growth and produciton, and develop and test management methods to minimize limits on production; and 4)Develop new equipment and technologies to improve profitability of channel catfish farming.

1b.Approach (from AD-416)
Techniques will be developed to use hand-held as well as airborne imaging systems to identify/quantify cyanobacteria in ponds; algal culture will be used to determine possible control measures for harmful algae; laboratory respirometry and small pond production studies will be used to determine impacts of various water quality parameters on growth and production of catfish; the Aquascanner Sonar will be further developed to provide an accurate inventory of mixed-size catfish populations in large commercial ponds; high potential management applications and equipment will be tested in ponds and tanks on the Thad Cochran National Warmwater Aquaculture Center, and in commercial catfish ponds of cooperators.

3.Progress Report
This report documents research under research project, 6402-13320-003-00D, “Optimizing Catfish/Water Quality Interactions to Increase Catfish Production”. During this past year the research has focused on identifying algal toxins, determining dissolved oxygen requirements of catfish eggs and food fish, developing improved pond and hatchery oxygen management techniques and equipment, and completing work on the AquaScanner side scan sonar system. During the year project scientists received one national and one regional technology transfer award for work on oxygen management in channel catfish hatcheries. This project is being re-written as “Improving Production Efficiency in Warm Water Aquaculture through Water Quality Management”.

1. Commercial Potential of Hybrid Blue Catfish Ictalurus furcatus X Channel Catfish Ictalurus punctatus. Hybrid catfish fry have been produced experimentally for nearly five decades. While most studies show them to be superior to channel catfish, limited fry/fingerling availability has precluded commercial production. However, in the last few years experimental reproduction techniques (hormone injection of female channel catfish, followed by hand-stripping and artificial fertilization with blue catfish sperm) have approached commercial potential. This year close to 50 million hybrid catfish eggs have been produced on commercial catfish farms and research in this project has been expanded by the National Program Leader (NPL) to include the evaluation of improved germplasm, such as hybrid catfish, developed by research project 6402-31000-008-00D, in both research and commercial sized ponds. Research ponds have been stocked for a second year with hybrid catfish at 8,000/acre and are being maintained at two different morning dissolved oxygen concentrations while the fish are being fed to satiation. Research results from last year indicate that hybrid catfish have better oxygen tolerance (consume more feed at a low dissolved oxygen (DO) concentration) than channel catfish, and have a significantly higher survival rate as well. This research will prove valuable as further improvements in reproductive techniques increase the availability of fingerlings.

2. Discovery of New Toxin. Toxic algae are a serious industry problem, resulting in millions of dollars in losses annually. The causative algae and associated toxin responsible for over $1.4 million dollar losses has been identified and the structure fully characterized. Characterization includes both mass spectrometry and Nuclear Magnetic Resonance (NMR) analyses. The toxin is produced by certain Euglena species and is a novel compound similar to solenopsin (fire ant venom). ARS has finalized patenting this product.

3. Ultrasound Technology for Bacterial Control. Bacterial diseases are among the major causes of catfish mortality in pond production systems. Available antibiotics are expensive and lack effectiveness when sick fish do not eat. Application of ultrasound technologies to control microbial populations in ponds resulted in dramatic decreases in bacterial abundance and selected mortality of algae in ponds. Laboratory studies demonstrated 60% reduction in bacteria within 3 days of ultrasound exposure. Fish growth was not affected if ultrasound was off during feeding. Control of pathogenic bacteria with ultrasound may provide an effective alternative to medicated feed.

4. Secondary Benefit from Control of Snails. Rams Horn Snails are the intermediate host for the catfish trematode. While it has been determined that they can be controlled with copper sulfate applications, the effect of this algicide on the pond plankton was unknown. Pond studies demonstrated that 3 mg/L copper treatments significantly altered the phytoplankton community to one dominated by green algae (from blue-greens). Use of copper will kill the intermediate host responsible for catfish trematodes and favorably alter algal composition.

5. New Catfish Incubator Design. Catfish eggs have been incubated in essentially the same way for the past century. Egg masses are placed in a screen basket and water is circulated with rotating paddles. An ARS scientist theorized that a different method, one in which the eggs are placed in baskets which are periodically lifted out of the water, could be more efficient. A commercial-scale unit was fabricated and tested at a commercial hatchery during the 2008 spawning season, resulting in a technical note on this new incubator design. While standard troughs are loaded with not more than 18 pounds of eggs and require at least 2 ½ gallons per minute (GPM) of water flow, the new design incubated up to four times that amount on as little as 2 GPM water flow. Work continued at a second hatchery in Mississippi during the 2009 spawning season. Sixteen troughs using the new design were constructed and used (in modules of four troughs operated with one motor), hatching over 30 M eggs. While development of this incubator is still in the preliminary stages, it appears that it will save both space and water compared to existing equipment.

6. Aquascanner SONAR. University of Mississippi - National Center for Physical Acoustics (UM-NCPA) scientists and staff have continued with the field use of the AquaScanner side scan sonar system. The units were used to observe smaller fish in small grow out ponds. While the SONAR consistently over predicted the contents of these small ponds as too much of the extraneous bank clutter (grass, scour holes, aerators, etc) was included as valid targets the predictions did identify which ponds had higher or lower stocking densities relative to each other. This data is being re-investigated to determine if improved signal analysis to discriminate fish from other potential targets will produce better absolute accuracy on pond inventories. Furthermore, in these measurements, the fish can be observed reacting to external stimuli such as feeding and moving toward the aerator at night in the summer when oxygen levels are presumably at their lowest. This work could be useful to new research on using acoustics to either attract or repel fish in a certain direction during seining or feeding to improve production.

7. Additional Uses of Acoustics to Improve Production. Enumerating fish, both in a pond and while being moved during the production process, remains a problem. Work continued on an allied grant on an individual fish-sizer which can provide the size distribution of a sample of captured fish in collaboration with the University of Arkansas at Pine Bluff. After a small sub-sample of fish has been captured, they are acoustically scanned as they return to the pond through a restrictive pipe. In a set of preliminary measurements in fall 2008, the unit predicted a mean and standard deviation in weight of 2.47 and 1.65 lbs, for a fish sample population (100 fish) that had a measured mean and standard deviation in weight of 2.34 and 1.18 lbs. Most of the fish missed by the unit were smaller than 0.75 lbs which would skew the data. More testing is planned for the summer and fall of 2009. The measurements on noise emitted from shrimp during feeding (noted in last year’s report) was extended to freshwater prawns at a commercial farm in Leland, MS. These measurements suggest that passive measurements could be used to rapidly (and inexpensively) identify a mass mortality in a pond so that it could be restocked. A more rigorous measurement might be able to estimate biomass. Similar measurements on catfish fry and fingerlings in harvest tanks are planned as part of the next project.

5.Significant Activities that Support Special Target Populations
Catfish farming is truly a national industry with over 1,100 commercial producers located in 13 states. While there are some large farms, the majority are small family-owned and operated, averaging only 160 water acres. The USDA/NASS Census of Aquaculture conducted in 2000 classified 84% of catfish farms as small businesses, with annual sales of less than $500,000, and 38% (515) with annual revenues of less than $25,000. In spite of recent historically low pond-bank prices, farmers have survived through increased efficiency, producing more fish on fewer acres each year. Last year (2008) the industry produced over 509 M pounds at a wholesale price of 78.0¢/pound, but with increased foreign competition, and higher feed and fuel prices, the future is uncertain. Those dedicated catfish farmers are the primary customers of this research through the availability of innovative technologies, management strategies and equipment to increase their efficiency even more. Research on management of nuisance algae and dissolved oxygen is critical for success of all catfish farms, but will have far greater impact on smaller farms with a generally narrower profit margin. Catfish processors benefit from a more stable fish supply resulting from improved off-flavor management and detection methods. Average consumers also benefit from the increased availability of higher-quality, safer domestic products at a reduced price.

6.Technology Transfer

Number of Active CRADAs1
Number of Other Technology Transfer5

Review Publications
Torrans, E.L. 2008. Production Responses of Channel Catfish to Minimum Daily Dissolved Oxygen Concentrations in Earthen Ponds. North American Journal of Aquaculture 50(4):371-381.

Mischke, C.L., Wise, D.J., Zimba, P.V. 2009. Impact of Copper Sulfate on Plankton in Channel Catfish Nursery Ponds. Journal of the World Aquaculture Society. 40(1):122-128.

Sassenrath, G.F., Heilman, P., Luschei, E., Bennett, G.L., Fitzgerald, G., Klesius, P.H., Tracy, W., Williford, J.R., Zimba, P.V. 2008. TECHNOLOGY, COMPLEXITY AND CHANGE IN AGRICULTURAL PRODUCTION SYSTEMS. Renewable Agriculture and Food System 23(4):285-295

Bucolo, A.P., Sullivan, M.J., Zimba, P.V. 2008. Effects of Nutrient Enrichment on Primary Production and Biomass of Sediment Microalgae in a Subtropical Seagrass Bed. Journal of Phycology 44:874-881.

Smith, J.L., Boyer, G.L., Zimba, P.V. 2008. A review of cyanobacterial odorous and bioactive metabolites: impacts and management alternatives in aquaculture. Aquaculture 280:5-20.

Sthapit, E., Ochs, C., Zimba, P.V. 2008. Spatial and Temporal Variation in Phytoplankton Structure in a Southeastern U.S. Reservoir Determined by HPLC and Light Microscopy. Hydrobiologia 600:215-228.

De La Cruz, A., Rublee, P., Hungerford, J.M., Zimba, P.V., Wilhelm, S., Meriluoto, J.A., Echols, K., Meyer, M.T., Stelma, G., Mandeville, R., Lawton, L., Sivonen, K., Furey, A. 2007. Chapter 20:analytical methods workgroup report. Advances in Experimental Medicine and Biology 619:469-482.

Last Modified: 9/20/2014
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