Location: Warmwater Aquaculture Research Unit
2024 Annual Report
Objectives
1. Develop improved production strategies for hybrid and channel catfish.
1.1. Expanding temporal harvest of hybrid catfish in intensive production systems.
1.2. Optimization of channel catfish production in intensively aerated single and multiple batch production systems.
1.3. Economic losses associated with warehousing market-sized hybrid catfish in intensive production systems.
1.4. Evaluate effects of longer-term maintenance feeding on body weight, survival, and processing yield of market-size hybrid catfish and determine optimum refeeding duration before harvesting.
2. Develop cost-effective feeds and optimal feeding practices for catfish aquaculture.
2.1. Compare diets containing fish meal, animal by-products, and all plant protein sources for growth and health of channel and hybrid fingerlings.
2.2. Optimize lysine supplementation in diets for channel and hybrid catfish.
2.3. Evaluate feed additives on growth and health of channel and hybrid catfish.
3. Environmental manipulation to improve growth and health of catfish.
3.1. Development of methods to promote natural food sources in catfish nursery ponds.
3.2. Evaluating chemical treatments and treatment strategies to control disease vectors.
3.3. Effects of natural feed supplementation on channel catfish growth and health.
4. Identify economic factors influencing cost-efficiency of catfish aquaculture.
4.1. Evaluate the economics of various traditional and alternative catfish production strategies.
4.2. Economic risk associated with various catfish production technologies.
4.3. Monitoring the adoption of various production enhancing technologies in the U.S. catfish industry.
Approach
We will develop improved production strategies for hybrid and channel catfish by exploring strategies to expand the temporal harvest of hybrid catfish from intensive production systems, optimize channel catfish production in intensively aerated single and multiple batch production systems, quantify economic losses associated with warehousing market-sized hybrid catfish in intensive production systems, and evaluate effects of longer-term maintenance feeding on body weight, survival, and processing yield of market-size hybrid catfish. We will develop cost-effective feeds and optimal feeding practices for catfish aquaculture through the comparison of diets containing fish meal, animal by-products, and all plant protein sources for growth and health of channel and hybrid fingerlings, optimization of lysine supplementation in diets for channel and hybrid catfish, and evaluation of feed additives on growth and health of channel and hybrid catfish. To obtain environments for improved growth and health of catfish, we will develop methods to promote natural food sources in catfish nursery ponds, evaluate chemical treatments and treatment strategies to control disease vectors, and determine the effects of natural feed supplementation on channel catfish growth and health. We will also determine economic risks associated with catfish production technologies and monitor the adoption of various production-enhancing technologies in the U.S. catfish industry.
Progress Report
The United States catfish industry is the largest aquaculture industry in the United States, yielding roughly $437 million in sales in 2023. In the early 2000’s there were about 150,000 water acres in catfish production, with most produced in Mississippi. Acreage in catfish production has drastically declined resulting from high feed and energy costs and an influx of cheap imports devaluing domestically raised catfish. As a result, acreage in catfish production has decreased by about 70%. This economic crisis led to development of technologies and adoption of intensive production systems. While the development of intensive production systems has resulted in increased yields, profitability of various intensive production systems has only been loosely defined.
To ensure the profitability of domestically raised catfish, it is critical to refine feed formulations using alternative feed ingredients and evaluate the utility of feed supplements to improve feed digestibility and fish health. Also, with technology adoption, the cost structure of catfish production strategies has significantly changed. Ensuring profitability now involves refining feed formulations with alternative ingredients to reduce costs, evaluating feed supplements for improved digestibility and fish health, and redefining the cost structures of commercial production strategies. Pond preparation and disease control treatments need optimization, with considerations to lowering environmental impact.
Research related to Objective 1 and 4: Using hybrid catfish in intensive production systems has led to a 3-fold increase in yield and efficiencies. However, hybrid catfish cannot be graded at harvest with traditional grading socks; hybrid catfish must be raised as a single batch and completely harvested at the end of the season. This creates a bottleneck in processing causing harvest delays. Research was conducted to determine the most economical strategy to maintain fish size without losing yield. Fish fed once weekly did lose weight, but target yield could be normalized in fish fed once weekly or not fed at all provided fish were fed daily for 30 d after feed restriction. A second scenario evaluated the economic cost of warehousing overwintered fish. Fish were harvested at the end of the season and yield was compared to fish harvested the following spring. Fish were fed when water temperatures were permissive for feeding. There were no significant differences in production variables other than a slight decrease in returns related to increased feed costs.
Using commercial farm data, economic risks associated with six catfish production strategies were evaluated. Stochastic Monte Carlo simulations using established enterprise budgets found fish yield, feed price, and feed conversion ratio contributed to variations in production cost. While multiple-batch (MB) farming of channel catfish was the least risky strategy, both MB and intensively aerated production were stochastically dominant to low-intensity single-batch production. Split ponds and intensively aerated hybrid catfish production showed consistently lower production costs and were stochastically dominant to medium-intensity single-batch production. Multiple-batch and intensively aerated production of channel catfish were more susceptible to price risk, while hybrid catfish production was more susceptible to yield risks. Dominance of split-pond technology on larger farms compared to low-intensity culture on smaller farms suggested yield increasing intensive production practices supersede low-intensity technologies and help achieve economies of scale. However, producers who are risk averse are better off choosing medium intensive multiple-batch production of channel catfish. Study results provide critical information on the relative risk associated with different catfish production strategies under varying economic and market conditions.
Research related to Objective 2: Soy lecithin, a co-product of soy oil extraction, was shown to improve growth at an inclusion rate of 1% in the feed formulation. On-going studies are evaluating the influence of soy-lecithin on intestinal microbiota and resistance against enteric bacterial pathogens affecting channel and hybrid catfish. Pond studies are being conducted evaluating optimal inclusion levels based on laboratory studies to evaluate growth potential and profitability of using soy lecithin as a nutritional supplement. The use of corn-fermented protein (CFP) was also evaluated as an alternative ingredient to replace soybean meal (SBM). Channel catfish were fed diets where SBM was incrementally replaced with CFP. When comparing the nutrient digestibility of these ingredients, SBM had a slightly higher protein digestibility compared to CFP, although phosphorus and lipid availability were twice as available for CFP. The feeding trial conducted in recirculating system showed no differences between whole-body proximate analysis, and protein conversion efficiency. However, weight gain, feed efficiency, intraperitoneal fat and whole-body lipid were significantly affected by dietary treatment, with CFP able to replace up to 40 to 50% of the SBM protein in the diet while providing similar production performance as the SBM control diet. At present, CFP appears to be a promising alternative protein ingredient to replace soybean meal with high protein and phosphorus digestibility.
The gut microflora between faster and slower growing fish within the same pond environment was characterized to possibly identify differences in the intestinal microbiome communities, and screening beneficial probiotic bacteria that could be related to superior growth performance. A total of twenty lactic acid bacteria were recovered from overperforming fish and identified as potential probiotics. These isolates were based on probiotic traits such as proteolysis, lipolysis and inhibition of bacterial pathogens for catfish. Lactococcus lactis MA5 was considered the most promising probiotic candidate based on beneficial nutrient processing, metabolic roles and disease resistance. Further work focuses on developing a commercialized form of MA5 and is being evaluated in laboratory and experimental pond studies.
Research related to Objective 3: Proper pond preparation is critical in maximizing growth of newly stocked catfish fry in nursery ponds. Fertilization regimes were developed to promote desirable zooplankton, serving as a natural food source. Rotenone is a commonly used fish toxicant to remove unwanted fish from nursery ponds before stocking but has been reported to cause significant declines in zooplankton populations. Applying rotenone to partially drained experimental ponds had no effect on water quality, or phytoplankton but caused a temporary decline in zooplankton populations. Neutralization with KMnO4 did not affect any measured variables. Desirable zooplankton numbers for catfish culture reached 100 organisms/L 11–14 d after treatment. When a whole pond was treated with rotenone, desirable zooplankton numbers reached 100 organisms/L 7 d after treatment if neutralized with KMnO4 and about 11 d after treatment without neutralization. Rotenone treatment did not reduce predatory macroinvertebrates, and this should be addressed using additional management strategies.
In the late 1990’s Bolbophorus damnificus was identified as a cause of decreased profitability of commercially raised catfish in the southeastern United States. The life cycle sequentially involves the American White Pelican, aquatic snails, and fish. Control strategies focus on eradicating snail hosts from the culture environment. Previous studies demonstrated multiple low dose treatments of copper are equally as effective as a single high dose treatment. However, in toxicity trials, poor survival was observed in non-treated snails, possibly related to poor vigor of snails collected from catfish production ponds. Copper sensitivity of laboratory-reared Marsh Rams-horn snails, as well as shedding (infected snails) and non-shedding individuals from commercial ponds was evaluated. Survival curves and hazard analysis showed laboratory-reared snails were most resistant to copper, followed by non-shedding pond snails. Shedding snails were most sensitive to copper treatment. When targeting snails in commercial aquaculture ponds, lower copper doses than those reported to kill laboratory-reared snails may be effective.
In addition, the effects of multiple low dose copper treatments on zooplankton, phytoplankton and water quality variables were evaluated. Copper treatments significantly influenced phytoplankton communities, with dose-dependent reductions in Cyanophyta. Charophyta increased in copper-treated ponds compared to controls. Phytoplankton populations persisted throughout the study, even in the highest treatments, and oxygen depletions were not observed. At harvest, there were no differences among treatments in production variables. There were no treatment effects on water quality variables or zooplankton communities. Further, CSP appeared to stabilize microbial communities. Control and 0.5 mg/L treatments had temporary dynamic fluctuations, while 1.0 and 1.5 mg/L treatments were relatively constant. Collectively, data suggests repeated, low dose copper treatments could be a safer alternative to single, high dose copper applications.
Accomplishments
1. Control of disease vectors in catfish production systems. In the late 1990s, Bolbophorus damnificus was identified as a cause of decreased profitability in commercially raised catfish in the southeastern United States. The life cycle of this parasite involves the American White Pelican, aquatic snails, and fish. Control strategies by ARS researchers in Stoneville, Mississippi, have focused on eradicating snail hosts from the culture environment. Previous studies demonstrated that four weekly low-dose treatments of copper are as effective as a single high-dose treatment, thereby increasing treatment safety while maintaining effectiveness. However, in a commercial setting, applying multiple treatments across large farms is logistically difficult. To address this issue, researchers at Mississippi State University developed a mechanized system for delivering granular copper sulfate,allowing for the precise application of a targeted dose along pond margins in a single pass. This innovation not only increased the safety margins of copper sulfate treatments but also dramatically facilitated treatment application. A second iteration of the delivery system is currently being evaluated in a commercial setting.
2. Risk and return of catfish production strategies. Over the past 15 years, technological development and adoption have dramatically transformed the landscape of domestic catfish aquaculture, resulting in a three-fold increase in yield and the conservation of land and water resources. While this research has led to improved production by ARS researchers at Stoneville, Mississippi, its effects on economic risk have not been thoroughly addressed. Researchers at Mississippi State University conducted an economic analysis of various production strategies, and analyzed economic risk factors across catfish operations in Mississippi, Arkansas, and Alabama. This study found that more intensive single-batch hybrid catfish farming strategies—such as split ponds, intensively aerated ponds, and modified multiple-batch systems with channel catfish and increased aeration rates—were the most profitable and least risky in terms of liquidity. In contrast, low-intensity single- and multiple-batch systems employing channel catfish were found to be infeasible in the long run from an investment perspective. This information is being utilized by catfish farmers to make better investment and management decisions to ensure profitability.
3. Risk and returns of split pond production systems. Split ponds have proven their potential to increase the productivity of earthen catfish ponds, various pumping systems have been used in commercial settings. Researchers at Mississippi State University evaluated four commercial-scale design variants of split-pond systems (slow-rotating paddlewheel, modified-paddlewheel aerator, screw pump, and axial-flow pump) primarily differentiated by the mechanism of water circulation between the fish-confinement and the waste-treatment sections. This study investigated the production, economic, and investment feasibility of these four split-pond designs under controlled conditions over multiple years. The additional investment capital required for converting a traditional open pond to any of the four split-pond designs ranged from $54,400 to $71,150 per 4-ha pond. The cost of production of the four split-pond designs ranged from $2.02/kg to $2.37/kg and was less than the 3-year average fish price. Higher breakeven yields are required to cover total costs, indicating increased financial risk associated with these intensive-production systems. Net present value (NPV) was highest for the modified-paddlewheel aerator design ($223,893/4-ha pond) and lowest for the screw-pump design ($74,621/4-ha pond). The economic and investment feasibilities of the four split-pond designs were sensitive to the prices of fish and feed. All four designs were economically feasible under current economic conditions with the modified-paddlewheel design showing greater economic potential for adoption.
Review Publications
Gerhart, B.J., Mischke, C.C., Llen, P.J. 2023. Growth, condition factor, and survival of juvenile channel (Ictalurus punctatus), blue (I. furcatus), and hybrid ( I. punctatus x I. furcatus) catfish at moderate and high temperatures. Journal of the World Aquaculture Society. 55:302-311. https://doi.org/10.1111/jwas.13038.
Ghosh, K., Hanson, T., Robinson, D., Bugg, W., Chatakondi, N., Kumar, G., Jeffers, C.D., Dunham, R.A. 2022. Economic Effect of Hybrid Catfish (Channel Catfish ¿ × Blue Catfish ¿) Growth Variability on Traditional and Intensive Production Systems. North American Journal of Aquaculture. 84(1):25-41. https://doi.org/10.1002/naaq.10211.
Asche, F., Garlock, T., Camp, E., Guiillen, J., Kumar, G., Llorente, I., Shamshak, G. 2022. Market opportunities for U.S. aquaculture producers: The case of Branzino. Marine Resource Economics. 37(2):221-233. https://doi.org/10.1086/718437.
Hegde, S., Kumar, G., Engle, C., Avery, J., Johnson, J., Aarattuthodiyil, S., Van Senten, J. 2022. Production economic relationships in intensive U.S. catfish production systems. Aquaculture Economics & Management. 26(3):314-331. https://doi.org/10.1080/13657305.2022.2038720.