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United States Department of Agriculture

Agricultural Research Service

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Location: Warmwater Aquaculture Research Unit

2013 Annual Report

1a. Objectives (from AD-416):
1. Develop and test novel equipment and strategies to increase gas exchange and the efficiency of fish production while minimizing equipment and energy costs. 2. Develop acoustic technology and methodologies to improve the production and profitability of aquaculture in the United States. 3. Determine effectiveness of new germplasm and novel aeration technologies on commercial scales.

1b. Approach (from AD-416):
We have made great strides in understanding the relationships between dissolved oxygen, feed consumption, feed conversion, growth, production and susceptibility to disease, and we will continue to learn more about the impacts of oxygen on fish health, development, growth, and production economics. However, we have learned enough to shift our focus to applications – development, testing and tech transfer of new equipment and techniques to improve oxygen management efficiency in both hatchery and pond systems. We havealso learned a good deal on the use of active SONAR systems to observe and quantify food sized and larger fish in the acoustically complex environment of commercial ponds. We will continue to improve our understanding of this field but will expand it to include other acoustic applications. Acoustic sounds, both from catfish and man-made sources, will be introduced into ponds to determine if the fish can be made to respond in a predictable, desirable manner to improve seining. One of the main objectives of CRIS 6402-31000-008-00D (Catfish Genetics, Breeding, and Physiology) is to “Initiate development of channel catfish and blue catfish germplasm with improved growth, yield, and esc resistance for eventual transfer to commercial producers”. This CRIS has been tasked with developing a procedure that will be used for future on-farm testing and preliminary commercial evaluation of new lines before full-scale release to the industry. Once in place, this model could also be used for assessment of new aeration or pond monitoring equipment, chemical treatments, vaccines, and algal control methods.

3. Progress Report:
The focus of this research project is to develop a more complete understanding of the impacts of water quality, particularly dissolved oxygen (DO), on growth and production of catfish, and to develop new equipment or management strategies to utilize that information. The goal is to reduce the production costs for U.S. fish farmers, making them more competitive in a world economy and providing quality fish to U.S. consumers at a fair price. ARS scientists at Stoneville, MS, have completed development and testing of the see-saw incubator at a collaborating commercial catfish hatchery. This incubator is ready for commercial application and technology transfer efforts have been largely completed. A fourth year of research on DO requirements of hybrid catfish in ponds was completed and indicates that hybrid catfish consume more feed at lower DO concentrations than channel catfish, and should convert feed better in commercial ponds due to reduced mortality resulting from a shorter production cycle. Two studies are underway with hybrid catfish examining relative growth rates over a range of sizes and the comparative effects of fish density and DO concentration on growth and production. Work on development of the U-tube aerator has progressed. An air-lift type system was tested and was determined to be a more efficient means of moving water with the u-tube than other mechanical systems. A patent application for this device is now pending with the US Patent and Trademark Office. The u-tube has been scaled up and installed in an 8-acre pond at National Warmwater Aquaculture Center (NWAC) and the first year of testing under commercial fish densities has been completed. The new aerator will be evaluated in this commercial-scale setting for one additional year before expansion to planned on-farm trials. Other aquaculture engineering projects are underway and show promise. The water supply system at a commercial hatchery was redesigned to include a counter-current heat exchanger to reduce the cost of heating water. Early results indicate a possible savings of up to $500 per day or $22,500 per season in propane. Work has also begun on determining the most economical design for water-moving equipment for use in split-pond production systems. Thus, existing slow-rotating paddlewheels (SRP) are currently being evaluated for performance and reliability at NWAC. A selection program is underway in the Catfish Genetics Research Unit on several line of blue catfish, use for producing hybrid channel X blue catfish. Protocols have been developed and put in place for the periodic release of blue catfish to the industry. Work progressed on the use of sound to move fish in advance of seine nets to improve harvesting. Other means of evaluating the noise’s effectives on fish motion are being pursued in the summer of 2013 with one possibility being direct assessment on ponds slated for harvesting. Work continued on the use of a commercially available sonicator (a high amplitude acoustic source) to eliminate the Ram’s Horn snail, an intermediate host to trematodes that infect catfish. If successful, the use of chemical controls would be reduced or perhaps eliminated.

4. Accomplishments
1. Development of the see-saw catfish egg incubator. Traditional paddle-type catfish egg incubators have served the industry well for nearly a century but require a high water exchange rate and lose efficiency at egg loading rates above 15 pounds (lbs) (6.8 kilograms) per trough. Agricultural Research Service researchers at Stoneville, Mississippi, in collaboration with industry partners in Watson, Arkansas, and Glen Allan, Mississippi, have developed a new incubator (the see-saw) which can incubate more eggs using less water and labor. In a direct comparison at a similar egg-loading rate (26 lbs per trough), the see-saw produced 2.3 times as many viable swim-up fry as the traditional incubator. Additional studies indicate that 45 lbs of eggs/trough can be hatched in the see-saw using only 1 gpm per minute of water with no negative impact on hatch rate, saving considerable labor, space, ground water, and energy for pumps and heaters. In commercial field trials thus far over 150 male eggs have been hatched. Field trials have now been completed, and technology transfer plans now underway are expected to result in rapid adoption by the catfish industry as well as by public-sector hatcheries which are typically space-limited.

2. Work on water circulation equipment for use in split-pond aquaculture systems. A first generation prototype slow-rotating paddlewheel was evaluated for pumping performance and the results were highly impressive. Recommendations were made to improve efficiency and reliability with a modified design. Pumping performance tests using a standard paddle-wheel aerator are being performed. Catfish farmers are experienced at general repairs and maintenance which makes this device a good candidate to circulate water in split-ponds. In addition, parts availability is great as compared to the elaborate specialized fabrication of slow-rotating paddlewheels.

3. Development of an improved aerator for the catfish industry. Paddlewheel aerators have been used for aeration in aquaculture for over 30 years. They transfer a lot of oxygen to the water but also move a large volume of water which dilutes the aeration effort over the entire pond volume. Thus, a great deal of equipment and a large amount of power is required to prevent low DO (dissolved oxygen) conditions in commercial ponds. Agricultural Research Service researchers at Stoneville, Mississippi, have developed a new aerator, the Power Tube Airlift (PTA) which can concentrate DO into a small zone of water in a pond using less energy than traditional methods. This invention has a patent application currently pending with the U.S. Patent and Trademark Office. Two commercial-scale PTA's were installed in an 8-acre catfish production pond for onsite field testing. Total weight of food fish harvested in November 2012 was 46,100 lb (5,987 lb/acre), average individual weight at harvest was 3.1 lb, survival was 91.2%, and Feed Conversion Ratio (FCR) was 2.2 in 175 culture days. This preliminary evaluation in a commercial-size catfish pond allowed us to begin to define loading limits for the 2nd generation PTAs and to initiate a study in 2013 at higher than normal stocking densities.

4. Intensive production of hybrid catfish. Agricultural Research Service researchers at Stoneville, Mississippi, have completed four years of research on the intensive production of channel catfish female X blue catfish male hybrids (hybrid catfish) using 0.25-acre ponds at the National Warmwater Aquaculture Center in Stoneville and 1-acre ponds under contract at the Delta Western Research Center in Indianola, Mississippi. Research has demonstrated that hybrid catfish can tolerate a slightly lower DO (dissolved oxygen) concentration in the morning than do channel catfish. They also have a greater tolerance to common diseases affecting catfish, resulting in a greater feed intake through spring and fall when diseases are more common. Due to an overall greater feed intake, food fish production only requires two growing seasons, one season for fingerling production and one season (or more typically part of one season) to grow the fingerlings out to food fish. It appears that with an adequate DO concentration (a minimum of 2.5 mg/L in the morning) fish density has little effect on growth rates at least up to stocking rates of 11,000 fish per acre. Continued adoption of hybrid catfish by the industry is expected to result in increased profits (reduced production costs) due to faster growth (reduced production cycle), increased survival, and reduced food conversion ratios.

5. Development of a heat exchanger for use in a commercial catfish hatchery. At a local commercial catfish hatchery, a counter-current heat exchanger system was installed and reduced the non-renewable energy use by approximately 50%. This is equivalent to an estimated energy savings (operating cost) of $790 per day or $35,550 per season (45 days). Modifications to the original design should improve efficiency even more next hatching season.

6. Development of protocols for the release of new line of catfish. One of the missions of the Catfish Genetics Research Unit, in Stoneville, MS, is to develop and release improved lines of catfish to the industry. We have developed and initiated protocols for the release of blue catfish to the industry and anticipate release(s) later this year. The availability of blue catfish is essential for the expansion of the hybrid catfish industry.

7. Improved catfish feed conversion through pond oxygen management. Dissolved oxygen is assumed to be the most critical water quality parameter in warmwater aquaculture but controlled studies of the impact of this diurnally-fluctuating parameter on hybrid catfish have been lacking. Agricultural Research Service researchers at Stoneville, Mississippi, are concluding an 11-year research program examining the impact of pond DO (dissolved oxygen) concentrations on blue, channel, and blue X channel catfish growth, production, food consumption and food conversion. These studies were made possible by the use of a computer-controlled pond oxygen monitoring system which could initiate aeration at precise DO set-points and continuously record DO, temperature and aerator usage. Results with all three species show that higher DO concentrations than previously thought (best performance at minimum daily DO concentrations of 2.5-3.0 mg/L) are required for optimum food intake and growth, and this improved growth will significantly shorten the production cycle (currently three to five years) down to two years from egg to food fish. While food conversion is not directly impacted by DO except at extremely low DO concentrations, a shorter production cycle reduces fish losses to all causes, significantly improving food conversion. Feed is the greatest single cost in catfish production. Increased growth resulting from improved DO management can reduce food conversion ratios from an estimated industry-wide 2.5-3.0:1 to 2.0:1, reducing production costs by $0.10-0.20/lb, greatly improving the profitability of catfish farming. Technology transfer efforts have been on-going and commercial farm managers have begun to implement the findings, increasing both the available per-acre aeration and the minimum DO concentrations. Farm-wide fish production rates averaging 12,000 lbs/acre have been seen, with individual ponds producing nearly 20,000 lbs/acre using recommended oxygen management practices.

8. Causes of variation in hybrid catfish growth rates. Hybrid catfish grow rapidly but not uniformly. It is not unusual in a pond harvest to have some individual fish weighing over five pounds while others are less than a pound. This is undesirable and some processors pay a discounted price for larger fish. A study using individually-marked hybrid catfish is underway which is examining the growth rates of a size range of fish during the growing season. Preliminary results indicate that growth of smaller fish is not depressed but the exponential growth curve of the fish results in the larger fish becoming progressively larger through the growing season. Stocking graded fingerlings may be more important than scientist at Catfish Genetics Research Unit, in Stoneville, MS, previously thought. Several other management practices being examined could have a major impact on this problem.

9. Work progressed on the use of sound to move fish in advance of seine nets to improve harvesting. Using sounds previously found to be annoying to fish, direct assessments were made on ponds during seining. Numerous ponds at Delta Western, in Indianola, MS, were seined with and without the use of sound emissions. The results indicated that the use of sound did not statistically increase the number of fish. While the literature provides numerous examples of using sound to alter fish behavior and movement, those examples were not moving fish toward some other perceived danger. It is presumed that being captured in the net was more of perceived threat than the annoying sound.

10. Use of ultrasound to kill ram’s horns snails. Experiments were conducted at the University of Mississippi to investigate the observation that exposure to high amplitude ultrasound may mortally wound a significant percentage of snails and to determine the optimum duration of exposure. Results from the tests run on snails collected in the summer of 2012 are very promising, with one experiment indicating a mortality as high as 85% one week after exposure, compared to 30% of the non-exposed snails. Continued experimentation is planned throughout the summer of 2013.

Review Publications
Brown, T.W., Tucker, C.S. 2013. Pumping performance of a slow-rotating paddlewheel for split-pond aquaculture systems. North American Journal of Aquaculture. 75:153-158.

Torrans, E.L., Ott, B.D., Jones, R., Jones, R. 2013. Channel catfish hatchery production efficiency using a vertical-lift incubator the see-saw at various egg loading densities. North American Journal of Aquaculture. 75(2):235-243.

Brown, T.W., Boyd, C.E., Chappell, J.A. 2012. Approximate water and chemical budgets for an experimental in-pond raceway system. Journal of the World Aquaculture Society. 43:526-537.

Goodwiller, B.T., Chambers, J.P. 2012. The potential use of ultrasound to control the trematode bolbophorus confusus by eliminating the ram's horn snail planorbella trivolvis in commercial aquaculture settings. North American Journal of Aquaculture. 74(4):485-488.

Kroger, R., Tucker, C.S. 2012. Biological productivity in small impoundments. In: Small Impoundment Management in North America, American Fisheries Society. p. 83-112.

Last Modified: 05/22/2017
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