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United States Department of Agriculture

Agricultural Research Service

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Location: Warmwater Aquaculture Research Unit

2012 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 United States fish farmers, making them more competitive in a world economy and providing quality fish to U.S. consumers at a fair price. We have completed testing of the see-saw incubator at a collaborating commercial catfish hatchery. We believe this incubator is ready for commercial application and technology transfer efforts have begun. Preliminary studies have begun examining the effect of DO concentration during egg incubation on the so-called “triple-tail” deformity of channel catfish; work was also begun on the DO requirements of channel catfish fry. A third 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 U.S. Patent and Trademark Office. The u-tube has been scaled up and installed in an 8-acre pond at National Warmwater Aquaculture Center (NWAC). The new aerator will be evaluated in this commercial-scale setting. If this test goes well, expansion to on-farm trials will begin as early as next year. 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. 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 2012 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 lbs (6.8 kg) per trough. ARS 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 gallon per minute (gpm) 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 M egg 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. Intensive production of hybrid catfish. ARS researchers at Stoneville, Mississippi, have completed three 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 dissolved oxygen (DO) 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.

3. Improved catfish feed conversion through pond oxygen management. Dissolved oxygen (DO) 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 channel catfish have been lacking. ARS researchers at Stoneville, Mississippi, are concluding a ten-year research program examining the impact of pond DO 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.

4. 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 dissolved oxygen (DO) conditions in commercial ponds. ARS 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. At a 20-ft sparger water depth preliminary testing indicates that the PTA has a standard oxygen transfer rate (SOTR) and standard aeration efficiency (SAE) slightly less and approximately equal to a 10-hp paddle-wheel aerator, respectively. With an increase in sparger water depth and/or the use of pure oxygen, SOTR and SAE will likely exceed that of paddle-wheel aerators. Fewer moving parts and improved efficiency would reduce the costs associated with repair and maintenance, and lower power (electricity) consumption, respectively. Two commercial-scale PTAs have been installed in an 8-acre catfish production pond for onsite field testing, and field trials on commercial farms are expected to begin in FY 2013. This invention has a patent application currently pending with the U.S. Patent and Trademark Office.

5. Triple-tail deformity in channel catfish. Channel catfish occasionally will be found with abnormal caudal fin structures. These deformities vary in size and appearance but generally occur as an extra fin protruding from the lateral surface of the caudal peduncle. The phrase “triple-tail” is often used to describe fish with these fin irregularities. Observations from previous hatching seasons suggests that low dissolved oxygen (DO) concentrations during incubation can result in premature hatching and this may cause the triple-tail defect. A study was conducted by ARS researchers in Stoneville, Mississippi, to determine if premature hatching resulting from low-DO concentration during incubation contributes to the incidence of triple-tail deformities. Those fry that were forced to hatch prematurely from low DO concentrations had significantly higher occurrences of triple-tails than those hatched naturally. Poor incubation conditions (namely low DO concentration) may be the leading factor in the development of the triple-tail abnormality and could be improved by the addition of oxygen or better incubation practices. Recommendations have been made to the industry which could correct this problem.

6. Dissolved oxygen (DO) requirements of channel catfish fry. There is interest in growing fry to a larger size (1.5” total length) in the hatchery before stocking in commercial earthen ponds as a means of minimizing the variability in fry survival in ponds. ARS researchers in Stoneville, Mississippi, measured the effect of DO concentration on growth of juvenile (2-8, 10-16, 15-21, and 53-54 days post-swim-up) channel catfish fry. Dissolved oxygen concentrations were maintained at 90% saturation (high oxygen) or 50% saturation (low oxygen) in replicate aquaria. Catfish fry up to 15-21 days post swim-up (approximately 0.75” long) do not require DO concentrations higher than 50% air saturation. However, it does appear that the older and larger fish require a higher DO concentration for maximum growth than their younger and smaller counterparts. Farmers rearing catfish fry to a larger size before release to ponds should progressively increase the DO concentration up to 70% air saturation as the fish grow.

7. Use of sound to move fish in advance of seine nets. Collaborators at the University of Mississippi working at Stoneville, Mississippi, facilities learned that short bursts of intermittent, low frequency noise near 100Hz, provided a dramatic startle response in catfish and rapid fish movement each time the sound came on. The work was done in small concrete raceways. Investigation of the use of these sounds in larger outdoor ponds has been hampered by the difficulty in observing fish reactions to stimuli. Other means of evaluating the noise’s effectives on fish motion are being pursued in the summer of 2012 including using screens to block fish once they move to one side of a longer raceway or simply performing direct assessment on ponds already slated for harvesting. If successful, the technique may reduce the number of passes required to seine ponds reducing labor and other harvesting costs.

8. Use of ultrasound to kill ram’s horns snails. Collaborators at the University of Mississippi working at Stoneville, Mississippi, facilities repeated preliminary tests of ultrasound on snails to better determine efficacy at snail control. Repeated tests on snails with control groups resulted in approximately 35% of the snails exposed being killed immediately after exposure. Continued observations indicated 42% more dying after a few days compared to 9% of the control group suggesting some mortal wounding which may allow for shorter exposure times. If successful this technique may allow for a mechanical rather than chemical means of controlling the parasite.

Review Publications
Torrans, E.L., Ott, B.D. 2012. Effects of DO concentration in growout performance of blue catfish with comparison to channel catfish. North American Journal of Aquaculture. 74(2):273-282.

Chatakondi, N.G., Torrans, E.L. 2012. The effect of calcium hardness on hatching success of channel catfish x blue catfish hybrid catfish eggs. North American Journal of Aquaculture. 74(3):306-309.

Last Modified: 08/15/2017
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