Suja Aarattuthodi

During the summer of 2023, a spontaneous disease outbreak occurred in intensively stocked hybrid catfish (♀ channel catfish, Ictalurus punctatus × ♂ blue catfish, I. furcatus) in earthen ponds on a commercial aquaculture farm in South Texas. The farmer reported 50 to 80 dead fish per pond daily for a month. The fish were market size (1.0 ± 0.3 kg on average), resulting in substantial economic losses. Fifteen moribund fish were submitted for laboratory examination. Grossly, the fish showed distended abdomens, erythematous fins, and inflamed vents. Autopsy demonstrated visceral congestion, distended gastrointestinal tracts, and serosanguineous peritoneal effusion. Bacterial cultures from the internal organs revealed homogeneous bacterial growth after incubation. Presumptive biochemical characterization of the isolated bacteria identified Plesiomonas shigelloides. Further molecular confirmation was achieved by species-specific PCR amplification and 16S-rRNA sequencing. Juvenile catfish were experimentally challenged with the recovered isolates to fulfill Koch’s postulates. Moreover, an antibiogram was performed to evaluate the susceptibility of the isolates to a panel of FDA-approved antimicrobials. P. shigelloides isolates were pathogenic to channel catfish and alarmingly multidrug-resistant. We report here, for the first time, P. shigelloides infection in Texas commercial catfish aquaculture, emphasizing its significance as an emerging enteric pathogen that is difficult to treat with FDA-approved antimicrobials.

Cryopreservation is a transformative technology that allows for the long-term storage of biological materials by cooling them to extremely low temperatures at which metabolic and biochemical processes are effectively slowed or halted. Cryopreservation utilizes various techniques to minimize ice crystal formation and cellular damage during freezing and thawing processes. This technology has broad applications in the fields of medicine, agriculture, and conservation, spanning across stem cell research, reproductive and regenerative medicine, organ transplantation, and cell-based therapies, each with significant economic implications. While current techniques and their associated costs present certain challenges, ongoing research advancements related to cryoprotectants, cooling methods, and automation promise to enhance efficiency and accessibility, potentially broadening the technology’s impact across various sectors. This review focuses on the applications of cryopreservation, research advancements, and economic implications, emphasizing the importance of continued research to overcome the current limitations.

Edwardsiella piscicida septicemia is a significant threat to aquaculture, causing substantial production and economic losses. The causative bacterium E. piscicida infects multiple fish species of aquaculture relevance. This study investigated the pathogenicity of catfish-derived E. piscicida in largemouth bass (Micropterus salmoides) fingerlings. The experimental infection of largemouth bass using genotypically distinct E. piscicida isolates resulted in significant fish mortality independent of the isolate genotypes. A specific correlation between discrete E. piscicida genotypes and fish mortalities was not identified. The histopathological assessment of tissues from infected fish revealed inflammatory lesions characteristic of bacterial septicemia. This study provides insights into the pathogenesis of heterologous E. piscicida isolates in largemouth bass fingerlings, which could be crucial in developing effective pathogen-targeted management strategies to combat a deadly disease.

Multiple‐batch production is the most common farming strategy for raising channel catfish. Increased adoption of intensified alternative production practices has changed the cost structure of many catfish production practices including multiple‐batch systems. Production efficiency in multiple‐batch production can be enhanced by providing optimal stocking recommendations for fingerlings and carryover fish. Twelve 0.4‐ha ponds were understocked with 20,782 channel catfish fingerlings (mean weight = 30 g/fish) at three different carryover biomass rates (3440; 4580; and 5702 kg/ha). Fish were fed once daily to apparent satiation with a 28% protein floating feed, and ponds were aerated with a 7.4‐kW electric paddlewheel aerator. Gross, net, daily net yields, sub‐marketable yields (<0.54 kg), growth (g/day), and survival were statistically similar among the three treatments, but yield of marketable fish yield (fish ≥0.54 kg) increased significantly with increased carryover biomass. The cost of production was reduced while net returns increased with increased carryover biomass. The lowest carryover biomass treatment (3440 kg/ha) had negative cash flow and net returns when sub‐marketable fish were not assigned value. However, all three carryover biomass treatments attained positive annual net cash flows and net returns when sub‐marketable fish were valued as revenue, the two higher carryover biomass treatments (4580 and 5702 kg/ha) outperformed the low carryover biomass treatment (3440 kg/ha). This study indicates channel catfish carryover biomass rates should be between 4580 and 5702 kg/ha to improve cost efficiency in intensively aerated, multiple‐batch production systems.

Channel catfish virus (CCV) poses a significant threat to catfish culture. Lack of effective vaccines and antiviral treatments necessitates effective disinfection strategies to mitigate its spread. In vitro trials indicated the virus to be inactivated at high temperatures, but was infectious at 40°C. This study evaluated the efficacy of a commercial disinfectant against CCV using both in vitro and in vivo approaches. In vitro experiments assessed the virucidal activity of the disinfectant against CCV in channel catfish ovary (CCO) cells, while in vivo trials evaluated its effectiveness in reducing viral transmission and mortality among channel and hybrid catfish fingerlings. Results indicated that the disinfectant was effective in inactivating the virus at the tested concentrations and improved the survival of fish exposed to the virus. This study provides critical insights into selecting appropriate disinfection protocols to enhance biosecurity in catfish hatchery settings and to mitigate CCV transmission.

Economics is the study of the allocation of scarce resources to meet human wants and needs and has a critical role to play in addressing challenges related to environmental sustainability, community resilience, and food security. In the context of aquaculture, the key to such a discussion is understanding the linkages of aquaculture farming businesses with other economic sectors and how policy decisions that affect aquaculture result in economic ripples throughout local, regional, and national economies. The only previous national estimates of the economic contributions of U.S. aquaculture are nearly 30 years old. The current study was based on comprehensive data from detailed farm‐level surveys (that captured 77% of the total value of U.S. aquaculture) supplemented by information from publications on the remaining aquaculture sectors. The economic contributions measured in this study were limited to those at the farm level and do not include subsequent impacts that occur as farmed products move through processing, distribution, food service, and retail sectors in the U.S. economy. Results showed that U.S. aquaculture farms contributed $4 billion annually and supported more than 22,000 jobs each year. Labor income and value‐added contributions were $1 billion and $3 billion, respectively. Analysis of the linkages of U.S. aquaculture production activities with other economic sectors showed that nearly all (96%) economic sectors were supported to some degree by U.S. aquaculture farms. Foodfish farms generated the greatest contributions, followed by mollusk farms. Freshwater aquaculture farms contributed twice that of the contributions of marine aquaculture because of the greater size of the freshwater aquaculture sector. Growth of both freshwater and marine sectors would increase overall contributions to the economy. Constraints to growth of aquaculture include regulatory barriers that have restricted existing sectors from meeting current demand for their products. The lack of an adequate regulatory framework for offshore marine aquaculture has constrained its growth and development, especially with respect to the rest of the world. Streamlined regulations implemented in a more timely and efficient manner could result in substantially greater economic contributions from existing U.S. aquaculture farms. The total economic impact of U.S. aquaculture production is likely three to four times greater than the farm‐level impacts estimated in this study as a result of impacts that occur as aquaculture products move downstream through various marketing channels. Additional research is needed to measure the impacts of U.S. aquaculture products in the processing, distribution, food service, supermarket, and restaurant levels of the marketing chain to fully capture the total economic contributions from U.S. aquaculture.

The U.S. catfish industry has adopted several production practices which embody varying degrees of economic risk. Employing commercial farm data, this study quantified the economic risks associated with six catfish food fish production strategies. Stochastic Monte Carlo simulations employing established enterprise budgets found fish yield, feed price, and feed conversion ratio contributing highly to variations in the cost of production. While multiple-batch (MB) farming of channel catfish was the least risky strategy, both MB and intensively aerated production were stochastically dominant (second-order) to low-intensity single-batch production. Split-pond and intensively aerated hybrid catfish production demonstrated consistently lower production costs and were stochastically dominant (second-order) to medium-intensity single-batch production. Multiple-batch and intensively aerated production of channel catfish were more susceptible to price (market) risk while hybrid catfish production was more susceptible to yield (production) risks. First order stochastic dominance of split-pond technology on larger farms as compared to low-intensity culture on smaller farms suggested that yield increasing intensive production practices supersede low-intensity technologies and help achieve economies of scale. Study results provide critical information on the relative risk associated with different catfish production strategies under varying economic and market conditions.

The U.S. catfish industry is evolving by adopting intensive farming practices such as intensively aerated ponds and split-pond systems. The functional relationship between fish yield and key production inputs in these intensive systems was analyzed based on commercial catfish production data from 143 pond observations (2010−2018). A Cobb-Douglas production function was employed for the intensively aerated ponds and a modified translog production function was used to define the production relationships in split ponds. Results indicated that the size of fingerlings at stocking, stocking density, aeration rate, feeding rate, survival, and harvest size of the fish were statistically significant variables influencing fish production in intensively aerated ponds. Initial fingerling stocking biomass (interaction of stocking size and stocking density), feed conversion ratio (FCR), feeding rate, and pond size were the most important variables influencing production in split-pond systems. Feed fed, as well as stocking biomass, were the significant variables found in both models. Both production functions indicated further scope for improvement in the use of inputs to increase production, especially in feed management.

The US catfish industry has undergone significant technological advancements in an attempt to achieve cost efficiencies. This study monitored the progress of the adoption of alternative and complementary technologies in the US catfish industry. A 2019–2020 multi‐state in‐person survey in Alabama, Arkansas, and Mississippi (n = 68), revealed increased adoption of intensively aerated ponds (6,315 ha) and split ponds (1,176 ha). The adoption of alternative, more intensive, production practices has been accompanied by increased adoption of complementary technologies of fixed‐paddlewheel aeration, automated oxygen monitors, and hybrid catfish. As a result, the average aeration rate in the tristate region has increased to 7.8 kW/ha with 97% of catfish farms adopting automated oxygen monitors. About 53% of the water surface area in the tristate region was used for hybrid catfish production. Fingerling producers have also adopted a feed‐based, oral vaccine against Enteric Septicemia of Catfish, with 83% of the fingerling farms and 73% of the fingerling production area vaccinated against ESC in 2020. Increased adoption of productivity‐enhancing technologies in the US catfish industry explains the 59% increase in foodfish productivity from 2010 to 2019. Monitoring the progress of adoption of productivity‐enhancing technologies will guide researchers and Extension personnel involved in the refinement and dissemination of these technologies.