Location: Warmwater Aquaculture Research Unit
2017 Annual Report
Objectives
The overall objective of this project is to increase profitability of catfish aquaculture by improving farm-level production efficiency. This will be accomplished by developing new production systems and management practices that allow greater control of the culture environment, with the end result that the genetic potential of catfish can be fully expressed. Studies will also be conducted on the use of ultrasound to kill the intermediate host of an important catfish pathogen and reduce bacterial loads in processing plant cold-water washes. Over the next 5 years, we will accomplish the following objectives:
1) Enhance Control of Pond-Based Ecosystems to Maximize Production and Product Quality.
Sub-objective 1.1 Optimize split-pond design for food-sized catfish aquaculture.
Sub-objective 1.2 Maximize catfish production potential of conventional ponds using intensive aeration.
Sub-objective 1.3 Evaluate management practices to reduce the final size variation resulting from variable growth rates in hybrid catfish.
2) Determine the Suitability and Feasibility of Polyculture or Off-season Production of Other Species Using Catfish Culture Infrastructure.
Work on this objective will focus on developing technologies for production of a secondary, non-catfish species, such as tilapia, in split-ponds. Production of secondary filter-feeding species can potentially increase on-farm profits by generating an additional crop at little extra expense and may improve water quality in split-pond systems by feeding on plankton and detritus that are an oxygen-consuming waste product in catfish monocultures.
3) Develop Acoustic Technology and Methodologies to Improve the Production and Profitability of Pond-based Aquaculture in the United States.
Sub-objective 3.1 Develop and test the potential for control of ramshorn snails in ponds using ultrasound.
Sub-objective 3.B. Develop and test the potential for ultrasound to reduce bacteria in the cold-water wash in processing plants.
Work on this objective will be conducted using congressionally mandated funds administered through Specific Cooperative Agreement 58-6402-9-427 (“Development of Active and Passive Acoustic Measurements to Improve Production and Profits of U.S. Aquaculture”) between the ARS Warmwater Aquaculture Research Unit, Stoneville, MS, and the National Center for Physical Acoustics, at the University of Mississippi. Under this Agreement and as part of this Project Plan, novel application of acoustic technology will be tested and developed, including Sub-objective 3.A, developing and testing the potential for control of ramshorn snails (a disease vector in catfish ponds) using ultrasound, and Sub-objective 3.B, reducing bacteria in the cold-water wash in catfish processing systems using acoustic cavitation.
Approach
Four, 7-acre earthen ponds at the National Warmwater Aquaculture Center at Stoneville, Mississippi, will be modified into split-ponds (Sub-objective 1.A). Pump-performance curves will be developed by systematically changing pump operational parameters for four pump types—one pump for each split-pond. High aeration rates will be used to culture hybrid catfish (channel catfish x blue catfish) and measured variables will include fish growth, survival, production, processing yield, feed conversion ratio, dissolved oxygen concentrations, and water quality variables measured biweekly. Relationships among average flow rate (pump type) and fish growth, feed conversion ratio, and selected water quality variables for each year over the 3-year study will be assessed using regression analysis and results will yield different options for farmers using this technology in the industry.
Six, 0.25-acre ponds with 24 horsepower/acre of aeration for hybrid catfish production will be used in this study (Sub-objective 1.B). Dissolved oxygen, temperature and aerator status will be continuously monitored and the aerators controlled using a pond oxygen monitoring and control system already in place. Water quality will be measured biweekly for hybrid catfish production. Response variables will include final fish weight, weight gain, net production, processing yields, survival, feed consumed, feed conversion ratio, aerator usage), and economics Relationships among stocking rate, aerator usage, feed consumed, weight gain, feed conversion ratio, and selected water quality variables will be assessed using regression analysis. This model should allow us to recommend a stocking rate that will allow satiation feeding through the growing season and will be tested on commercial ponds.
Twelve, 1-acre ponds (10-hp of aeration per acre) will be used to produce hybrid catfish at the Delta Branch Experiment Station, Stoneville, MS (Sub-objective 1.C). Production parameters, coefficients of variation in size, and final economics will be compared among treatments using analysis of variance. Pending the results from this study, further studies on hybrid catfish foodfish management practices to reduce growth rate variation, including feeding schedules and practices, will be conducted.
For Sub-objective 2, a 4.5-acre split-pond aquaculture system located at the National Warmwater Aquaculture Center in Stoneville, Mississippi will be modified for to allow for the production of hybrid catfish and Blue Tilapia. Production performance will be measured and a performance average will be taken after three production seasons and a partial budget developed to measure gauges of economic efficiency of this production method as compared to conventional split-pond catfish aquaculture.
Experiments will be conducted on groups of snails using a commercially available sonicator as the acoustic source to destroy snails (Sub-objective 3.A). The potential use of ultrasonic cavitation to reduce bacteria in the cold-water wash in processing plants will be investigated as well in Objective 3.B. A cost-benefit comparison must be made to determine if the proposed design and technique is warranted.
Progress Report
The focus of this in-house research project is to develop a more complete understanding of the impacts of water quality, particularly dissolved oxygen and ammonia, on economics, growth and production of channel and hybrid catfish, and to develop new equipment, production systems and management strategies to utilize that information. The ultimate goal is to reduce the production costs for American fish farmers, making them more competitive in a world economy and providing quality fish to American consumers at a fair price.
A three-year regional research project involving four institutions in three states, Arkansas (University of Arkansas at Pine Bluff), Mississippi (Agriculture Research Service and Mississippi State University) and Alabama (Auburn University) examining production and economics of three intensive production systems (in-pond raceways, split-ponds, and intensively aerated ponds) on commercial farms was completed with the production of an economic analysis of the three systems. Of the three systems, the in-pond raceway had the greatest investment cost/acre, followed by intensively-aerated ponds, and then split ponds. Operating costs (Total Variable Costs) were greatest for the split ponds, followed by intensively-aerated ponds and then in-pond raceways, due primarily to the greater feed costs resulting from greater stocking densities. Total annual fixed costs were greatest in the in-pond raceway systems due to the greater investment cost. Overall, profits (net returns above total cost) were greatest in split ponds, followed by intensively-aerated pond. In-pond raceways showed losses. High breakeven yields indicate that these systems need to be managed intensively to cover the increased investment costs. Results from the investment analysis showed positive Net Present Value and Modified Internal Rate of Returns greater than the opportunity cost of capital, suggesting economic feasibility of intensive-aeration and split-pond systems under conservative market conditions. However, the yields from in-pond raceways (11,225 pound (lb)/acre) were not sufficiently high to cover the associated high fixed costs ($0.44/lb), resulting in higher production costs ($1.32/lb) and economic infeasibility. Intensively-aerated ponds and split ponds are being recommended to farmers who wish to increase production. Which system is chosen is based on a variety of farm-specific goals and conditions.
As part of a second three-year regional project involving four institutions and three states (Mississippi, Arkansas and Alabama), four, 7-acre earthen ponds at the National Warmwater Aquaculture Center at Stoneville, Mississippi, have been modified by Agricultural Research Service scientists in Stoneville, Mississippi, into split-ponds. Four 3.5-acre intensively aerated ponds have also been constructed in Stoneville and are being used as a comparison of production performance and profitability of new systems. Four pumping systems were installed in the split-ponds: a) 6-hp slow-turning paddlewheel, b) a 10-hp fast-turning paddlewheel, c) a 10-hp high-speed screw pump, and d) a 15-hp high-speed turbine. Engineering tests showed wide ranges of tradeoffs among the pump types. The slow-turning paddlewheel was dependable, much more efficient than the other pumps, and had the highest pumping rates (up to 20,000 gallons per minute (gpm)) but was the most expensive system to install. Pumping efficiency for the slow-turning paddlewheel was strongly dependent on rotational speed, with increasing efficiency up to a point (2 rpm) and then decreasing after that. The screw pump was the least expensive system to install (about 5-times less expensive than the slow-turning paddlewheel) but had the lowest pumping rate (up to 9,000 gpm) and the second-lowest pumping efficiency. The axial-flow pump was developed for sewage treatment plants and is very dependable, but was the least efficient pump tested and had the second lowest pumping rate (up to 12,000 gpm). The fast-turning paddlewheel had the second best pumping efficiency and pumping rate (up to 15,000 gpm) but the large-diameter culverts required in the systems made it the second most expensive system to install. Ponds were stocked with hybrid catfish for production studies in spring 2015 and 2016, and harvested in autumn of each year. In both years, ponds with the highest pumping rates (slow- and fast-turning paddlewheels) had higher net fish production (average = 16,158 lb/acre) and the best feed conversion (average = 1.92) and survival (average = 92%). Split ponds with the lowest pumping rates (screw and turbine pumps) had lower production (average = 13,970 lb/acre) and worse feed conversion (average = 2.11) and survival (average = 87%). The intensively aerated ponds had slightly lower net production ranging from 8,499 to 13,777 pounds per acre, survival was 54.5 to 93.1%, and food conversion ratio (FCR) was 1.83 to 1.90.
A two-year study has been completed with hybrid catfish at stocking rates ranging from 6,000/acre to 36,000/acre. With an aeration capacity of 24 horsepower/acre, dissolved oxygen could be controlled at optimum levels (a minimum of 3 mg/L). First year production was 31,393 pounds per acre at the highest stocking rate and 6,379 at the lowest. Food conversion ratio averaged 1.85 overall. Aeration costs (based on an electric rate of $0.15/kW), averaged $0.13/pound produced, and was slightly higher at lower stocking/production rates. No water quality parameters reached critical levels. Ammonia, previously presumed to become critical at extremely high feeding rates did not. While mechanisms are still being studied it appears that volatization of ammonia at high aeration rates and nitrification by bacteria at high feeding rates limited the ammonia concentrations at high density/aeration rates/feeding rates. It does appear that potential production rates in conventional earthen ponds are higher than previously believed. This is one study in a larger effort to increase production efficiency of catfish through intensification.
Numerous pond studies have demonstrated that dissolved oxygen concentrations below 3 mg/L in the morning result in lower feed intake, growth, and production in Channel, Blue, and hybrid Catfish. A laboratory project has begun to understand the physiological mechanisms that impact appetite/feed intake in Channel Catfish during periods of low dissolved oxygen (acute hypoxia). Several neuropeptides (brain proteins) are suspected to be involved in the control of appetite in catfish. This project has four components; development of the analytical techniques needed to measure neuropeptides and their gene expression; a broad sampling of neuropeptide(s) gene expression during hypoxia; measuring specific neuropeptide gene expression during varying durations of hypoxia; and determining the function of selected neuropeptides. We have developed a laboratory water handling system that allows us to control dissolved oxygen concentrations in tanks so we can perform the necessary experiments on groups of catfish. Additionally, we have developed analytical methods to measure gene expression of the neuropeptides of interest. Initial results have shown that only certain regions of the brain are involved in the response to hypoxia. We are currently collecting tissue and measuring blood parameters during varying durations of hypoxia. Besides providing a greater basic understanding of the responses of fish to environmental stressors, these studies may lead to a more efficient selection of fish based on the individual gene expression of critical neuropeptides rather than mass selection from long-term pond production studies.
Split ponds use screens to prevent the movement of fish between the two sections. The screens themselves restrict the water flow reducing efficiency to some extent, and collection of grass clippings, weeds and other debris on the screens restrict it further. Significant labor is required to clean the screens. Scientists at the University of Mississippi in Oxford, Mississippi, began studying the possible use of acoustic stimuli as deterrents to fish movement between the sections in split ponds. A hardware system was assembled to generate sounds in a pond and simultaneously record the sound levels at multiple locations within the pond. The system was used in a split pond at the National Warmwater Aquaculture Center, using sounds previously determined to elicit a flight response in catfish. The experiments were conducted with no fish in the pond in order to avoid possibly harming the fish. Analysis of this data began in order to determine how the desired sounds propagate within split ponds, specifically from one side of the pond to the other. Acoustic equipment will be developed to repel fish from the two channels used for water movement without affecting fish behavior in the production section.
Accomplishments
1. Development of circulation equipment for use in split-pond aquaculture systems. Pump performance and fish production tests have been performed by Agricultural Research Service scientists in Stoneville, Mississippi, on four different pumping systems in four commercial-scale split ponds. In summary, the selection for a pumping system in a commercial environment requires a compromise among pumping efficiency, initial investment cost, reliability and fish production. Long-term studies which define the relationship between water flow rate and fish production in split-ponds have been completed. This information has helped to identify the pumping system most appropriate for split-pond aquaculture and recommendations are being adopted by the industry. Most farmers are now using one of the pumping systems evaluated by Agricultural Research Service scientists.
2. Limits to intensive production of catfish in ponds. It has been assumed that at very high fish stocking and feeding rates ammonia would become limiting. Recent studies by Agriculture Research Service scientists in Stoneville, Mississippi, using catfish stocking rates up to 36,000/acre now question that assumption. Data indicates that at high aeration rates, high feeding rates do not result in high ammonia concentrations. Farmers are advised that intensive production limits may be determined by aeration capacity and general economic considerations, but issues with ammonia concentrations should not factor in.
Review Publications
Mischke, C.C., Torrans, E.L., Brown, T.W., Tucker, C.S., Wise, D. 2017. Reducing size variation in hybrid catfish culture through graded partial harvest. North American Journal of Aquaculture. 79:84-89.
Tucker, C.S., Mischke, C.C., Brown, T.W., Torrans, E.L. 2016. Water quality and plankton communities in hybrid catfish (female channel catfish, Ictalurus punctatus x male blue catfish, I. furcatus) ponds after partial fish harvest. Journal of the World Aquaculture Society. 48:46-56.
