Research Project: Improving Efficiency in Catfish Aquaculture

Location: Warmwater Aquaculture Research Unit

2023 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
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 feed being fed overwinter resulting in slightly decreased returns related to increased feed costs. The United States catfish industry has evolved by modifying and adopting many production practices involving different degrees of economic risk. Using commercial farm data, this study quantified the economic risks associated with six catfish production strategies based on variables such as species (channel catfish or hybrid catfish); management practices (single-batch and multiple batch); or variables such as stocking rate, aeration rate, in either traditional open ponds or split ponds. 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. With increasing costs and periodic scarcity of feed ingredients, reducing feed costs by formulating diets with alternative ingredients and developing more efficient feeding practices has become an industry priority. Studies were conducted in experimental ponds where hybrid catfish were fed to apparent satiation or fed 80% of the daily feed ration to determine if feed conversion ratios (FCR) could be improved. Feed-restricted fish treatment had significantly lower yield but unexpectedly did not improve feed efficiencies or survival. Without an improvement in feed conversion, feed restriction is not considered a viable management option, and fish should be fed to satiation. Two fermented corn proteins (FCP48, FCP56) were evaluated as replacements for cottonseed and soybean meal. The initial study aimed to replace cottonseed meal at 50% and 100% on an isonitrogenous basis using FCP48. The results indicated cottonseed meal could be fully replaced with FCP48 without negatively affecting production performance of channel catfish fingerlings. However, an intestinal microbiota assessment revealed a higher relative abundance of lactic acid bacteria in fish fed the control diet compared to those fed diets with 50% and 100% inclusion of FCP48. Nevertheless, despite the dietary-induced shift in microbiota, there was no significant impact on fish survival when challenged with Edwardsiella ictaluri. A later study investigated using fermented corn protein, FCP56, to replace the protein from soybean meal at varying levels. Protein digestibility of FCP56 was significantly lower than soybean meal. However, despite the slightly lower protein digestibility, FCP56 contains 5% more crude protein in its nutritional profile which compensates for this decreased digestibility. Also, the phosphorus digestibility of FCP56 was twice the value of conventional soybean meal, indicating a reduced need for supplemental phytase and dicalcium phosphate. A growth performance study conducted in aquaria using channel catfish fingerlings indicated FCP56 could optimally replace 50% of soybean meal in the diets. Muscle was collected to determine carotenoid levels, along with inflammatory gene expression and anti-inflammatory markers in the distal intestine. Also, the transient digesta was collected for bacterial sequencing to assess the intestinal microbiota. Bacterial challenge was performed on the remaining fish to assess whether inclusion in catfish feeds would affect their susceptibility to infection. A graded response to survival was observed as the inclusion of FCP56 increased in the diet. This improvement in disease resistance could be related to the yeast fraction derived from FCP56, which may have enhanced immune function leading to increased disease resistance. Both alternative ingredients presented promising results and can be potentially included in catfish diets. A field trial is currently being conducted to validate inclusion rates before using this information to manufacture commercial diets. The catfish industry has adopted iron supplementation as a standard practice to address idiopathic catfish anemia, claiming improvements in erythropoiesis and preventing mortality caused by this disease. Studies were conducted to assess potential adverse effects related to this practice. Fish were fed a graded level of iron (0-1500 ppm) resulting in a positive linear response in blood hematocrit. No differences in weight gain, feed conversion, protein conversion efficiency or survivability were found. At the end of the trial, fish were challenged with E. ictaluri to assess disease resistance. Fish supplemented with higher levels of iron had lower survival compared to controls. This observation was confirmed in a second study where high iron diets reduced survival by 44%. Catfish anemia is a condition in large fish which can be amended with high iron diets. Based on these results, supplementing iron sulphate in catfish diets should only be used in response to anemia. Iron-fortified diets should not be used in the nursery phase of production where bacterial infections are most problematic. Avian piscivores cause direct economic losses to the aquaculture industry through predation, as well as indirect losses through transmission of digenetic trematodes. Bolbophorus damnificus is a trematode parasite associated with significant losses in catfish aquaculture. Two snail species, marsh rams-horn snail and ghost rams-horn snail are common in commercial catfish ponds and known to transmit B. damnificus. Previous work related to this project evaluated copper sulfate (CuSO4) toxicity on marsh rams-horn snails; however, data were lacking for ghost rams-horn snails. Ram’s horn snails and Marsh ram’s horn snails were exposed to graded concentrations of Cu ranging from 0.1 to 3.4 mg/L CuSO4. Copper toxicity was comparable between both snail species for all exposure rates, and a single high dose treatment of about 0.75 mg/L CuSO4 killed over 95 % of snails in the laboratory and in ponds within 24 hours. Multiple weekly low-dose concentrations ranging from 0.4 to 1.5 mg/L CuSO4 were evaluated on eggs, juveniles, and adult snails as a potentially safer treatment regime for commercial ponds. Four doses of 0.4 mg/L CuSO4 killed all adult and juvenile snails and levels as low as 0.19 mg/L CuSO4 interfered with embryo development and prevented eggs from hatching. In support of this work, a mechanized granular copper sulfate applicator was developed allowing for precise and even application of copper sulfate around the pond margins in a single pass. The delivery system has been validated in experimental pond trials where multiple low-dose Cu applications did not significantly affect algal blooms or fish production. Commercial pond trials using these protocols are being conducted. Rotenone application has been reported to cause significant declines in zooplankton populations, with cladocerans and copepods being the most susceptible and possibly taking months to recover. Because copepods and cladocerans are a preferred natural food source for fry, rotenone applications could have significant effects on nursery pond production. Experimental ponds were treated with rotenone to reflect industry practices to assess effects on water quality, phytoplankton, zooplankton, and aquatic macroinvertebrates during May and June. Applying rotenone resulted in an initial decline in zooplankton numbers, but populations recovered 7 to 14 days after application depending on the treatment regime. Data indicates rotenone can be used in fry production without decreasing natural food sources, provided rotenone has been neutralized and ponds are stocked two weeks after treatment.

Accomplishments

Review Publications
Engle, C., Hanson, T., Kumar, G. 2022. Economic history of U.S. catfish farming: Lessons for growth and development of aquaculture. Aquaculture Economics & Management. 26(1):1-35. https://doi.org/10.1080/13657305.2021.1896606.
Hedge, S., Kumar, G., Engle, C., Hanson, T., Roy, L., Van Senten, J., Johnson, J., Avery, J., Aarattuthodiyil, S., Dahi, S. 2022. Economic contribution of the U.S. catfish industry. Aquaculture Economics & Management. 26(4):384-413. https://doi.org/10.1080/13657305.2021.2008050.
Hedge, S., Kumar, G., Engle, C., Hanson, T., Roy, L., Van Senten, J., Johnson, J., Avery, J., Aarattuthodiyil, S., Dahi, S. 2022. Technological progress in the US catfish industry. Journal of the World Aquaculture Society. 53(2):67-383. https://doi.org/10.1111/jwas.12877.
Sun, L., Engle, C., Kumar, G., Van Senten, J. 2022. Retail market trends for seafood in the United States. Journal of the World Aquaculture Society. 54(3):603-624. https://doi.org/10.1111/jwas.12919.
Sun, L., Engle, C., Kumar, G., Van Senten, J. 2022. Trends for U.S. catfish and swai products in retail markets. Aquaculture Economics & Management. https://doi.org/10.1080/13657305.2022.2147250.