Catfish Industry Research Articles

Growth performance and economic analysis of hybrid Catfish (Channel Catfish Ictalurus punctatus ♀ × Blue Catfish, I. furcatus ♂) and Channel Catfish (I. punctatus) produced in floating In-Pond Raceway System

The In-Pond Raceway System (IPRS) is a promising technology that addresses issues that have troubled the U.S. catfish industry for decades. This case study evaluated hybrid and Channel Catfish growth performance and economic efficiency in two sizes of floating IPRS units using two stocking density approaches. Each IPRS unit was placed into a 0.4 ha pond. In year 1, hybrids were raised in the IPRS and net yields ranged from 12,848 kg/ha to 15,330 kg/ha, with survival from 75%–97%. Individual hybrid Catfish harvest weights ranged from 671 to 825 g (268 days of production) with 90–97% of the fish in the premium size class (0.454–1.82 kg) and had a feed conversion ratio (FCR) of 1.50–1.64. In year 2, Channel Catfish were raised in the IPRS, with net yields from 7,416 to 9,819 kg/ha, and survival from 67% to 94%. The average Channel Catfish weight at harvest ranged from 525 to 861 g (217 days of production) with 79–94% in the premium size class and a FCR range from 1.78 to 2.40. Total investment for each 63 m3 raceway was US$34,570 in year 1, plus an additional US$2,280 for year 2. Total investment for each 45 m3 raceway was US$14,949 in year 1, plus an additional US$2,280 for year 2. Income above variable cost was positive for all four raceways in year 1, though negative for large raceways when fixed costs were included. In year 2, all four raceways had negative incomes above variable costs and net returns. This IPRS study showed better performance and economic results for hybrid over Channel Catfish and further research is needed to assess more efficient management strategies for Channel Catfish and, also, to lower initial investment and production costs.

Technological progress in the US catfish industry

AbstractThe 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.

Production economic relationships in intensive U.S. catfish production systems

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.

Establishment and characterization of a cell line from ictalurid catfish

AbstractThe catfish industry is integral to the economy of the southern United States contributing >70% of the total U. S. finfish production. Intensive catfish production systems are more vulnerable to infectious disease outbreaks resulting in significant economic losses. Viruses are a major concern especially in the hatchery and nursery phases of catfish rearing. These infectious agents require host cell machineries to replicate. The ability to propagate fish viruses in vitro using cell cultures is imperative in advancing virus research and facilitating disease management strategies. Several viruses show host‐ or even tissue‐specificity. Scarcity of host‐specific fish cell lines forces researchers to rely on general cell lines that might not be conducive for the replication of some viruses, thus hindering their isolation, identification, and characterization. The ictalurid cell line (channel catfish ovary [CCO‐ATCC® CRL‐2772]) previously available from cell repository (ATCC) has recently been reported as cross‐contaminated by brown bullhead (BB) cells. Lack of host‐specific cell cultures and contamination issues necessitated initiation of cell cultures from the fin tissues of hybrid catfish (♀ channel catfish × ♂ blue catfish). A combination approach involving tissue explantation and enzymatic digestion methods were used to develop catfish fin cell cultures. These cultures were passaged over 100 times and transitioned into an established cell line. The hybrid catfish fin (HCF) cell line was characterized, growth conditions optimized, species of origin molecularly authenticated, and the susceptibility to fish viruses evaluated. This catfish cell line could serve as an efficient tool for virus studies, antiviral agent screening, and vaccine development benefitting catfish aquaculture.

Action Implementation and Performance Assessment with Continuous Improvement and Innovation Process in Sharptooth Catfish (Clarias gariepinus) Small Businesses in South Africa

Continuous Improvement and Innovation (CI&I) is a business management strategy that concentrates thinking and action on the things that makes the real difference. Performance assessment is the most significant step in CI&I, as it analyses and reports on outcomes – it reveals which goals have been achieved and which are still to be achieved. Emerging aquaculture farmers are not searching for handouts; they want to compete on a commercial scale. Aquaculture can only attract investors if it becomes profitable and viable. As part of the research reported here, role-players in sharptooth catfish businesses attended focus group discussions, and were equipped to implement actions and assess their own performance. The performance assessment process was followed to monitor the action that had been taken and to report results. Mechanisms such as action monitoring and support; observation; the formulation of questions and ideas; identifying opportunities; performance assessment; and achievement stacker were applied to assess the achieved outcomes. The study led to the identification of markets and potential customers; signed orders; access to processing plants; the printing of business material (e.g., stickers); training; and the completion of new ponds. Questionnaires were sent out and completed. An experiment with earthworms and tilapia fry used as catfish feed was completed successfully. In conclusion, the outcomes of this study have revealed a need for further research that would assist small businesses in the catfish industry in growing and becoming profitable.

Economic contribution of the U.S. catfish industry

The catfish industry is the largest U.S. aquaculture sector and a major contributor to the rural economies of the Southern states of Alabama, Arkansas, and Mississippi. Economic contributions of this industry to the tristate region were estimated using an input-output modeling approach with the IMPLAN database and software (Impact Analysis for Planning MIG, Inc.). An analysis-by-parts approach was employed as the IMPLAN database does not disaggregate the catfish sector from other livestock industries which have expenditure patterns that differ substantially from those of catfish. All major actors of the catfish industry, i.e. feed mills, hatcheries, foodfish farms, and processing plants, were surveyed to obtain their expenditure patterns and output in terms of sales. Data were obtained from 68 farms (hatcheries and foodfish combined), four feed mills, and eight processing plants in the tristate region. Sales and expenditure values were converted to coefficients employing standard enterprise budgeting techniques and imported to the IMPLAN model for estimating industry contributions during 2019. The direct output from the catfish industry ($1.10 billion) generated a total economic contribution of $1.91 billion. The industry directly employed 4,298 people and created an additional 4,868 jobs in the tristate economy for a total employment effect of 9,166 jobs. Catfish industry spending created an indirect economic effect of $552 million in other secondary sectors that supplied production inputs and services. The induced economic effect generated from household spending amounted to $254 million. Some of the key sectors influenced by the catfish industry were grain farming, banking and financial institutions, truck transportation services, electricity generation, equipment, and machinery manufacturing. The industry also generated $78 million in local, state, and federal taxes. This study provides critical insights for policymakers and others into the contribution of the U.S. farm-raised catfish industry to local and regional economies as well as its diverse-industry interconnections.

Deciphering the Molecular Basis for Attenuation of Flavobacterium columnare Strain Fc1723 Used as Modified Live Vaccine against Columnaris Disease.

Vaccines are widely employed in aquaculture to prevent bacterial infections, but their use by the U.S. catfish industry is very limited. One of the main diseases affecting catfish aquaculture is columnaris disease, caused by the bacterial pathogen Flavobacterium columnare. In 2011, a modified-live vaccine against columnaris disease was developed by selecting mutants that were resistant to rifampin. The previous study has suggested that this vaccine is stable, safe, and effective, but the mechanisms that resulted in attenuation remained uncharacterized. To understand the molecular basis for attenuation, a comparative genomic analysis was conducted to identify specific point mutations. The PacBio RS long-read sequencing platform was used to obtain draft genomes of the mutant attenuated strain (Fc1723) and the parent virulent strain (FcB27). Sequence-based genome comparison identified 16 single nucleotide polymorphisms (SNP) unique to the mutant. Genes that contained mutations were involved in rifampin resistance, gliding motility, DNA transcription, toxin secretion, and extracellular protease synthesis. The results also found that the vaccine strain formed biofilm at a significantly lower rate than the parent strain. These observations suggested that the rifampin-resistant phenotype and the associated attenuation of the vaccine strain result from the altered activity of RNA polymerase (RpoB) and possible disrupted protein secretion systems.

Population parameters, exploitation rate and diet of black-chinned Tilapia, Sarotherodon melanotheron Rüppell, 1852 (Pisces: Cichlidae), from Badagry Creek, Lagos, Nigeria

The black-chinned tilapia (Sarotherodon melanotheron) is a member of the cichlid family, which can be cultured to complement the output from a predominantly catfish aquaculture industry in Nigeria. In order to achieve this objective, it is important to study the bio-ecology of the fish to ascertain the exploitation status and the potential for culture. Fish were collected monthly from February to November 2018 from three sampling sites (Topo, Akarakumo and Ajido) in Badagry Creek, Lagos, Nigeria using gears like cast net, gill nets and traps. The samples were analysed for length-weight relationship, population parameters and feeding preference. The population dynamics of the stock was assessed by the Von Bertalanffy growth model (VBGM) using Electronic Length Frequency Analysis. The parameters of VBGM; asymptomatic length (L∞) and growth coefficient (K) were 20.46 cm and 0.62 year−1, respectively. The growth performance index (Ǿ) was 2.41 and the potential longevity (tmax) was 4.84 years. The total, natural and fishing mortalities were 1.06, 0.68 and 0.38 year−1, respectively. The exploitation rate was estimated as 0.36. The length at first maturity (L50) was 13.79 cm and the length at first capture (Lc) was 12.27 cm. E0.1, E0.5 and Emax are 0.60, 0.38 and 0.70, respectively. The dominant food items in the gut of the fish belong to the algae phylum, Chlorophyta. The study showed that S. melanotheron from Badagry Creek are planktivores and the exploitation rate of the fish is currently close to optimum and should be sustained at this level to prevent overexploitation.

Effect of Federal Inspection on Louisiana Wild-Caught Catfish Industry, Prevalence of Salmonella, and Microbial Characteristics of Raw Wild-Caught Catfish Fillets

The United States is one of the largest catfish producers in the world. Louisiana is the leading producer of wild-caught catfish. Historically, the U.S. Food and Drug Administration inspected all seafood products; however, in 2008, Congress moved the inspection of fish in the order Siluriformes to the U.S. Department of Agriculture (USDA), Food Safety and Inspection Service. Full enforcement of the rule began on 1 September 2017. The present study was conducted to assess the impact of USDA Siluriformes fish regulation on small Louisiana wild-caught catfish processors and to determine the microbiological quality of and Salmonella prevalence in raw fillets. Nine facilities participated in the assessment study. Surveys were conducted before and after full enforcement to identify whether facilities had established prerequisite programs and record keeping associated with sanitation, hazard analysis and critical control point (HACCP) plans, food defense, and product recall. The processors' attitude about the change in regulations also was analyzed. For analysis of the microbiological quality and Salmonella prevalence, catfish samples were collected once per month for 2 years. Samples were evaluated for aerobic bacteria counts (APC), coliforms, Escherichia coli, Staphylococcus aureus, and Salmonella. The preenforcement survey revealed that only one facility had developed a HACCP plan, but it was not implemented. After 1 year of full enforcement, all the facilities developed and implemented a HACCP plan to process fresh catfish, and 78% of the processors reported a reduction in the amount of catfish processed due to limits in hours of operation and loss of fishermen. For microbiological quality, the mean (±SD) APC and counts of E. coli, coliforms, and S. aureus were 5.01 ± 0.70, 0.58 ± 0.89, 2.16 ± 0.77, and 0.73 ± 1.02 log CFU/g, respectively; 5.3% of the samples was confirmed positive for Salmonella. These findings indicate that after USDA enforcement, facilities improved food safety program documentation; however, the processing practices did not change. The microbial quality of the catfish fillets was within the acceptable levels in accordance with the International Commission on Microbiological Specifications for Foods.

Status, Trends, and Prospects of the Channel Catfish Industry in China and the impact of the Covid-19 epidemic

In 1984, the Fisheries Research Institute of Hubei Province first introduced channel catfish from the US to China. Since then, the production of China’s channel catfish has undergone volatile changes. In 2003, as a substitute for Pangasius fillets from Vietnam, the export volume of channel catfish-processed products increased considerably. In recent years, the Chinese channel catfish industry has shifted from dependence on American and European markets to dominance in Chinese markets. It is expected that the continuing impact of the Covid-19 epidemic in China and the development of the global pandemic will significantly affect the channel catfish farming sector in China. This paper outlines China’s channel catfish industry’s development, markets, costs, and benefits and provides some suggestions for its development.

Economic Losses of Catfish to Avian Predation: A Case Report

AbstractAvian predation in catfish aquaculture has been a persistent issue throughout the history of the industry, and as production has expanded predation from piscivorous birds has intensified. Catfish ponds in the Mississippi River delta (in the Mississippi migratory flyway) provide a constant and readily accessible supply of forage for birds. Intensive foraging by fish‐eating birds has led to a specific regulatory policy and numerous on‐farm and regional management efforts. However, in 2016, legal challenges lead to recision of some federal policies and uncertainty as to allowable management, resulting in limitations on bird depredation. Estimating the extent of fish losses to avian predators is difficult, as loss estimates from farms are often confounded with disease‐ and management‐related mortalities. This study details the reported losses to birds that were observed in commercial‐scale catfish ponds at the Thad Cochran National Warmwater Aquaculture Center, Stoneville, Mississippi, during periods of limited bird management. The observed fish losses attributed to birds ranged from 33% to 95% loss in survival and potential yield losses of 4,396 to 8,889 lb/acre, increasing production costs and decreasing net returns. Net economic losses when accounting for negative net returns and lost profits ranged from US$3,518 to $4,060/acre. Losses of this magnitude on commercial fish farms are economically detrimental, especially because catfish farms lack the compensatory economic relief programs that are available in other agriculture sectors. Roost dispersal activities that are organized by federal agencies and avoiding delays in issuing bird depredation permits are vital for mitigating this persistent and growing regulatory problem in the U.S. catfish industry.

Protein extraction from catfish byproducts and physicochemical properties of the protein isolates.

In order to optimize protein recovery from catfish byproducts by alkaline extraction, the effects of different factors, including particle size, mince-to-water ratio, pH, and extraction time were investigated. It was found that a protein recovery of about 30% could be achieved. Increases in pH (pH 10.5, 11, and 11.5) not only improved protein recovery, but also increased protein denaturation evidenced by decreased solubility, decreased α-helix, increased β-sheet, and increased random coil. The color and texture of gels made from protein isolate were greatly affected by the pH values used for protein extraction. For the gels made from fillet mince, and protein isolates extracted at pH 10.5, 11, and 11.5, the "L" values were 78.96, 60.38, 57.74, and 54.39, the breaking forces were 205, 492, 585, and 458 g, and deformation values were 10.59, 8.07, 6.73, and 5.04 mm, respectively. Electrophoresis revealed protein degradation during alkali-aided extraction with MHC, the most predominant band, showing about 50% decrease in comparison with fillet mince. It also demonstrated that gelation not only caused cross-linking, but also autolysis with 53%, 56%, 59%, and 81% decrease in MHC intensity for fillet mince, protein isolates extracted at pH 10.5, 11, and 11.5, respectively. Fillet mince and protein isolates exhibited different storage modulus patterns during temperature sweep, implying different gelation mechanisms. This study proved the protein extracted from catfish byproducts was potential to be utilized as edible food components especially in gel making. PRACTICAL APPLICATION: Catfish byproducts, which account for 70% of total weight and 50% of total protein of catfish, are normally used as animal feed, fertilizer, or even waste. This study demonstrated the potential of the utilization of catfish wastes to develop edible food components. This could reduce the total processing waste being discarded into the environment and nutrient loss, therefore increasing profitability of catfish industry.

Bioeconomic Analysis of Flavobacterium columnare Vaccine Pond Trials with Channel Catfish

AbstractWhile Flavobacterium columnare is a well‐known fish pathogen that has been studied for over 100 years, columnaris disease remains poorly controlled and is in need of improved management solutions for U.S. catfish producers. Outside of therapeutants, the disease remains relatively unchallenged in the commercial catfish industry. Attempts to improve the management of this disease have led to the development of a live‐attenuated genetic group 2 F. columnare vaccine (hereafter, “17‐23 vaccine”) administered via immersion to fingerling‐stage Channel Catfish Ictalurus punctatus. The 17‐23 vaccine was confirmed to protect against F. columnare in Channel Catfish fry during previous studies. In the present study, we investigated and compared the efficacy of the 17‐23 vaccine in Channel Catfish fingerlings versus nonvaccinated (control) fingerlings grown to food‐size fish in earthen ponds. Data were collected from the two treatments (n = 5 ponds/treatment) to evaluate impacts on survival, growth, feed conversion, antibody development, and economic benefit. There were no natural outbreaks of columnaris disease observed during the trial and no significant difference in survival of vaccinated versus control fish. Indirect enzyme‐linked immunosorbent assay results determined that the anti‐F. columnare 17‐23 antibody concentrations were significantly higher in vaccinated fish at 4 weeks postvaccination but not at 12 weeks. Vaccinated fish had a significantly higher average weight at harvest (mean ± SE = 357.5 ± 30 g) than control fish (289.3 ± 20 g), and the feed conversion ratio of vaccinated fish (1.35) was significantly better than that of control fish (2.13). Partial budget analysis of changing production from use of nonvaccinated fingerlings to use of 17‐23 vaccinated fingerlings for grow out resulted in a net benefit of US$1,443/ha. Based on these results, the vaccine appears to show potential economic benefit to producers but should be further substantiated under both research and commercial settings.

Hemolysin Co-regulated Family Proteins Hcp1 and Hcp2 Contribute to Edwardsiella ictaluri Pathogenesis.

Edwardsiella ictaluri is a Gram-negative facultative intracellular pathogen causing enteric septicemia of catfish (ESC), a devastating disease resulting in significant economic losses in the U.S. catfish industry. Bacterial secretion systems are involved in many bacteria's virulence, and Type VI Secretion System (T6SS) is a critical apparatus utilized by several pathogenic Gram-negative bacteria. E. ictaluri strain 93–146 genome has a complete T6SS operon with 16 genes, but the roles of these genes are still not explored. In this research, we aimed to understand the roles of two hemolysin co-regulated family proteins, Hcp1 (EvpC) and Hcp2. To achieve this goal, single and double E. ictaluri mutants (EiΔevpC, EiΔhcp2, and EiΔevpCΔhcp2) were generated and characterized. Catfish peritoneal macrophages were able to kill EiΔhcp2 better than EiΔevpC, EiΔevpCΔhcp2, and E. ictaluri wild-type (EiWT). The attachment of EiΔhcp2 and EiΔevpCΔhcp2 to ovary cells significantly decreased compared to EiWT whereas the cell invasion rates of these mutants were the same as that of EiWT. Mutants exposed to normal catfish serum in vitro showed serum resistance. The fish challenges demonstrated that EiΔevpC and EiΔevpCΔhcp2 were attenuated completely and provided excellent protection against EiWT infection in catfish fingerlings. Interestingly, EiΔhcp2 caused higher mortality than that of EiWT in catfish fingerlings, and severe clinical signs were observed. Although fry were more susceptible to vaccination with EiΔevpC and EiΔevpCΔhcp2, their attenuation and protection were significantly higher compared to EiWT and sham groups, respectively. Taken together, our data indicated that evpC (hcp1) is involved in E. ictaluri virulence in catfish while hcp2 is involved in adhesion to epithelial cells and survival inside catfish macrophages.

Virulence and immunogenicity of blue catfish alloherpesvirus in channel, blue and blue×channel hybrid catfish.

Blue catfish alloherpesvirus (BCAHV) is a novel virus isolated from the blue catfish (Ictalurus furcatus). To date, the ultrastructure, virulence and immunogenicity of BCAHV have not been reported. Given the importance of blue catfish in producing channel ♀ (I. punctatus)×♂ blue (I.furcatus) catfish hybrids and the increasing demand for hybrid catfish in the US catfish industry, the susceptibility of blue, channel and hybrid catfish to BCAHV was assessed. Further, the cross-protective potential of BCAHV against Ictalurid herpesvirus 1 (IcHV1) was investigated in channel and hybrid catfish that survive BCAHV exposure. Neutralization assays revealed BCAHV is refractive (neutralization index [NI]=0) to anti-IcHV1 monoclonal antibody Mab 95, compared to IcHV1 (NI=1.8). Exposure of blue catfish fingerling to 1.3×105 TCID50 /L BCAHV produced cumulative mortality of 51.67±0.70% and pathologic changes similar to those of channel catfish virus disease. No mortality was observed in channel or hybrid catfish. Twenty-eight days post-challenge, surviving channel and hybrid catfish were exposed to 9.4×104 TCID50 /L IcHV1 (LC50 dose), resulting in 100% relative per cent survival compared to naïve cohorts. These data provide baseline information for BCAHV and lay the groundwork for future studies. Data also identify BCAHV as a potential vaccine candidate against IcHV1. Based on host range and immunogenicity evaluations, in addition to genome sequence data from previous studies, BCAHV should be given consideration as a new species of Ictalurivirus.

Interspecies transmission of Edwardsiella ictaluri in Brazilian catfish (Pseudoplatystoma corruscans) from exotic invasive fish species.

Infections caused by Edwardsiella ictaluri are one of the biggest problems in the catfish industry in North America and have been reported in fishes around the world. E. ictaluri was detected in juvenile pintado Pseudoplatystoma corruscans-a Brazilian catfish-in a farm in Paraná State, Brazil; diseased animals showed ascites and neurological signs of infection, with more than 50% mortality. Exotic invasive species susceptible to this bacterium have been reported in this area. We assessed the susceptibility of pintado to E. ictaluri with experimental infection via intraperitoneal and immersion methods as well as a cohabitation experiment with Nile tilapia Oreochromis niloticus and African walking catfish Clarias gariepinus, 2 exotic invasive species. All pintados challenged by intraperitoneal and immersion routes and those cohabiting with infected C. gariepinus died within 17 d of the challenge. Mortality of Nile tilapia reached 71.42% after the intraperitoneal and 35.71% in the immersion challenges within 28 d, whereas African walking catfish showed zero mortality. Observed clinical signs were comparable to those in the farm and those described in the literature as enteric septicemia of catfish. With this study, we demonstrated the susceptibility of P. corruscans to E. ictaluri, as well as interspecies transmission of this bacterium.

Proteome analysis of virulent Aeromonas hydrophila reveals the upregulation of iron acquisition systems in the presence of a xenosiderophore.

The Gram-negative bacterium, Aeromonas hydrophila, has been responsible for extensive losses in the catfish industry for over a decade. Due to this impact, there are ongoing efforts to understand the basic mechanisms that contribute to virulent A. hydrophila (vAh) outbreaks. Recent challenge models demonstrated that vAh cultured in the presence of the iron chelating agent deferoxamine mesylate (DFO) were more virulent to channel catfish (Ictalurus punctatus). Interestingly, differential gene expression of select iron acquisition genes was unremarkable between DFO and non-DFO cultures, posing the question: why the increased virulence? The current work sought to evaluate growth characteristics and protein expression of vAh after the addition of DFO. A comparative proteome analysis revealed differentially expressed proteins among tryptic soy broth (TSB) and TSB+DFO treatments. Upregulated proteins identified among the TSB+DFO treatment were enriched for gene ontology groups including iron ion transport, siderophore transport and siderophore uptake transport, all iron acquisition pathways. Protein-protein interactions were also evaluated among the differentially expressed proteins and predicted that many of the upregulated iron acquisition proteins likely form functional physiological networks. The proteome analysis of the vAh reveals valuable information about the basic biological processes likely leading to increased virulence during iron restriction in this organism.

Cathelicidins enhance protection of channel catfish, Ictalurus punctatus, and channel catfish ♀×blue catfish, Ictalurus furcatus ♂ hybrid catfish against Edwarsiella ictaluri infection.

Cathelicidins are a class of antimicrobial peptides (AMPs) known to possess rapid and direct antimicrobial activities against a variety of microorganisms. Recently identified cathelicidins derived from alligator and sea snake were found to be more effective in inhibiting microbial growth than other AMPs previously characterized. The ability of these two cathelicidins along with the peptides, cecropin and pleurocidin, to protect channel catfish (Ictalurus punctatus, Rafinesque) and hybrid catfish (I. punctatus ♀×blue catfish, Ictalurus furcatus, Valenciennes ♂) against Edwardsiella ictaluri, one of the most prevalent pathogens affecting commercial catfish industry, was investigated. Cathelicidin-injected fish (50 µgml-1 fish-1 ) that were simultaneously challenged with E. ictaluri through bath immersion at a concentration of ~1×106 CFU/ml had increased survival rates compared with other peptide treatments and the infected control. Bacterial numbers were also reduced in the liver and kidney of channel catfish and hybrid catfish in the cathelicidin treatments 24hr post-infection. After 8days of challenge, serum was collected to determine immune-related parameters such as bactericidal activity, lysozyme, serum protein, albumin and globulin. These immune-related parameters were significantly elevated in fish injected with the two cathelicidins as compared to other peptide treatments. These results indicate that cathelicidins derived from alligator and sea snake can stimulate immunity and enhance the resistance to E. ictaluri infection in channel catfish and hybrid catfish.

Economics of U.S. catfish farming practices: Profitability, economies of size, and liquidity

AbstractEvolution of the U.S, catfish industry, forged by dynamic market forces, has resulted in the development of an array of farming practices. This comparative economic study was developed with data from 325 ponds on 38 commercial catfish farms (Alabama, Arkansas, and Mississippi) and provides concurrent estimates of the cost of production, profitability, and indicators of farm liquidity for the most common catfish growout strategies. Detailed enterprise budgets were developed for nine different catfish production strategies and analyzed on three different farm scales (32, 124, and 592 ha). Profitability differed across catfish farming practices. The split‐pond system using hybrid catfish was the least‐cost production strategy ($1.97/kg), followed by the multiple‐batch system employing channel catfish with increased aeration rates and intensively aerated ponds using hybrid catfish. Long‐term profitability of catfish farming practices increased with increases in farm size. Although seven of the nine production strategies discussed here were profitable in the long‐run on medium (124‐ha) and large (592‐ha) catfish farms, only split and intensively aerated ponds (hybrid catfish and multiple‐batch production with channel catfish with increased aeration rates) were profitable in the long‐run on small farms (32‐ha). Low‐intensity strategies involving channel catfish in single‐ or multiple‐batch systems were not profitable on any scale. High‐yielding strategies resulted in an increased cash flow coverage ratio and decreased debt‐servicing ratios, indicating lower liquidity risk. Economies of scale were evident throughout the analysis but stemmed from two different effects: (a) intensification of production in individual ponds; and (b) larger farm size. Changes in cost structures and economic conditions have changed the degree of profitability of farming practices. A number of previously profitable practices are no longer profitable. Newer, split pond, and intensively aerated farming practices were profitable but require greater attention to cost efficiencies.

The deterioration of weakly vertical linkages in tra catfish industry in An Giang Province, Vietnam

This study analyzes the vertical linkage effectiveness between fish farmers and processing companies on the mutual beneficial relationship, knowledge transfer, quality standards, embedded services, and payment before the United State (US) Department of Commerce has decided to impose new rates of antidumping taxes on tra (Pangasius) fish fillets imported from Vietnam. After conducting the first survey of 70 fish farmers and five in-depth interviews with directors of processing enterprises, representatives of provincial authority, and experts in the field during March and April of 2012 in An Giang province, Vietnam, we found that the mutual beneficial relationship was the most influent factor to vertical linkage effectiveness. However, after new rates of antidumping duties were imposed, we conducted the second survey of 17 in-depth interviews with 12 fish farmers, four local officers and one expert during April and June of 2013 in An Giang province, and recognized that almost all vertical linkages with processing companies to export to the US market have been deteriorated and dispersed.