Channel Catfish Farming Research Articles

Constituents From Brazilian Propolis Against Edwardsiella ictaluri and Flavobacterium covae, Two Bacteria Affecting Channel Catfish (Ictalurus punctatus).

Edwardsiella ictaluri and Flavobacterium covae are two bacteria species that cause diseases in farm-raised channel catfish (Ictalurus punctatus) that cause heavy economic damage to the aquaculture industry, particularly to the channel catfish farming. In search for environmentally benign antibacterial compounds active against E. ictaluri and F. covae, we investigated the constituents isolated from Brazilian red, brown and green propolis. We have also synthetically modified active constituents to see if lipophilicity plays a role in enhancing antibacterial activities. Vestitol, neovestitol and methylvestitol were found to be the active constituents with minimum inhibitory concentration (MIC) relative to drug control florfenicol (RDCF) values (MIC-RDCF) of 7.6, 7.6 and 7.9 mg/L, respectively, against F. covae. The activity against E. ictaluri was not significant.

Protein extraction pH and cross-linking affect physicochemical and textural properties of protein gels made from channel catfish by-products.

Channel catfish farming is very important aquaculture industry in the southern states of the USA. However, huge amounts of by-products are generated from catfish fillet-processing. The by-products (mostly heads and bone frames) are excellent sources of proteins. Currently, catfish by-product has little value, and is regarded as a 'waste', which if not utilized properly could cause serious environmental pollution. Therefore, to find a way to utilize those by-products is critical for the economy of aquaculture. Protein isolates were extracted from the mixture of catfish by-products (heads and frames) under different alkaline conditions (pH 7.5-11) and made into protein gels. Secondary structures of extracted protein isolates were studied. Microbial transglutaminase (MTGase, 0-4 U g-1 proteins) was incorporated to improve gel structure. Gelling, physicochemical, textural and thermal properties of protein gels treated with/without MTGase were investigated. Protein pattern changes of MTGase-treated protein gels were studied and the microstructure of the protein gels was analyzed. Alpha-helicity of protein isolates made at pH 11 was 21.5% lower than that extracted at pH 8.5. Storage modulus (G') of protein gel decreased with increasing extraction pH (pH > 9) of the corresponding protein isolate. MTGase treatment exhibited significant effects on denaturation temperature and enthalpy of protein gels. Excessive MTGase (>2 U g-1 ) could weaken the gel structure. Protein isolates can be extracted from catfish by-products and made into protein gels, which are a value-added product. © 2021 Society of Chemical Industry.

Research Verification of Single‐ and Multiple‐Batch Production Practices at Two Channel Catfish Farms in Western Alabama

AbstractAquaculture verification programs are designed to demonstrate and test research‐based recommendations on commercial‐scale operations. From 2010 to 2013, three management protocols were followed on two Channel Catfish Ictalurus punctatus farms in western Alabama. They were an owner‐defined multiple‐batch (MB) system, an Alabama Cooperative Extension System (hereafter, “Extension”)‐defined single‐batch (SB) system, and an Extension‐defined MB system. Three ponds on each farm accommodated the three treatment systems. Data were collected for two completed SB cycles per farm and the two continuous MB systems over the 37‐month period on each farm. The data were combined from the two farms by management system, and averages were calculated for the following production parameters: production period, stocking, water quality, harvest, size distribution, survival, and feed conversion ratio (FCR). Enterprise budgets were developed for each management approach and compared. The feed conversion ratio was found to be the most efficient for the Extension‐defined SB (1.91), followed by the Extension‐defined MB system (2.46) and the owner‐defined MB system (2.63). While the owner‐defined MB system had the greater harvest weight, it also had the longest production period, greatest weigh‐back pounds, and least efficient FCR, resulting in a net return above all costs ($334/acre yearly) below that of the Extension‐defined SB ($553/acre yearly) and MB ($393/acre yearly) systems. This converse finding is due to the owner‐defined MB having higher costs for feed, harvest and transport, diesel, and interest on operating costs. The Extension‐defined SB and MB systems recommended feeding 90% of a weekly determined satiation‐feeding amount, resulting in reduced overall feeding, without diminishing fish growth, and a more efficient FCR. The results from this study showed that all three systems were profitable, with the net return from the Extension‐defined SB system being higher than that from the Extension‐ and owner‐defined MB systems ($160 and $219/acre yearly, respectively). Yield verification programs provide detailed production and economic knowledge of farm management system effects.

Recombinant ATPase of Virulent Aeromonas hydrophila Protects Channel Catfish Against Motile Aeromonas Septicemia.

Channel catfish farming dominates the aquaculture industry in the United States. However, epidemic outbreaks of motile Aeromonas septicemia (MAS), caused by virulent Aeromonas hydrophila (vAh), have become a prominent problem in the catfish industry. Although vaccination is an effective preventive method, there is no vaccine available against MAS. Recombinant proteins could induce protective immunity. Thus, in this work, vAh ATPase protein was expressed, and its protective capability was evaluated in catfish. The purified recombinant ATPase protein was injected into catfish, followed by experimental infection with A. hydrophila strain ML09-119 after 21 days. Results showed catfish immunized with ATPase exhibited 89.16% relative percent survival after challenge with A. hydrophila strain ML09-119. Bacterial concentrations in liver, spleen, and anterior kidney were significantly lower in vaccinated fish compared with the non-vaccinated sham group at 48 h post-infection (p < 0.05). Catfish immunized with ATPase showed a significant (p < 0.05) higher antibody response compared to the non-vaccinated groups. Overall, ATPase recombinant protein has demonstrated potential to stimulate protective immunity in catfish against virulent A. hydrophila infection.

Comparing the kinetics of the hydrolysis of by-product from channel catfish (Ictalurus punctatus) fillet processing by eight proteases

Channel catfish farming is the most important warm water aquaculture in the United States and is very important to the rural economy. This study's objective was to investigate the kinetics of the enzymatic hydrolysis of catfish by-product. Channel catfish (Ictalurus punctatus) by-products (heads and frames) were collected from local catfish processing plant. Papain, ficin, bromelain, neutrase, alcalase, protamex, novo-proD and thermolysin were used for hydrolysis. Proteolytic activities of those proteases were examined at different hydrolysis temperature, proteases cost for reaching certain degree of hydrolysis was predicted. Degree of hydrolysis (DH) of the hydrolysates and hydrolysis kinetics were studied. Emulsifying and foaming property and stability of selected hydrolysates were evaluated. Results indicated that thermolysin had the highest activity (8.2 × 108 Azocoll U/g and 5.6 × 106 Azocasein U/g) at 70 °C. The highest DH of the hydrolysates were observed in 120 min with the concentration of 80 AzU/g for all enzymes. Ficin (80 AzU/g) was the most efficient in hydrolyzing the by-product (DH reaching 71%) in 120 min at 30 °C. The hydrolysis curves fit the Peleg model well with R2 higher than 0.91. This study provides important engineering information for choosing proteases and processing conditions for optimization of efficiency, yield and economy.

Comparative Genomics of Aeromonas hydrophila Secretion Systems and Mutational Analysis of hcp1 and vgrG1 Genes From T6SS.

Virulent Aeromonas hydrophila causes severe motile Aeromonas septicemia in warmwater fishes. In recent years, channel catfish farming in the U.S.A. and carp farming in China have been affected by virulent A. hydrophila, and genome comparisons revealed that these virulent A. hydrophila strains belong to the same clonal group. Bacterial secretion systems are often important virulence factors; in the current study, we investigated whether secretion systems contribute to the virulent phenotype of these strains. Thus, we conducted comparative secretion system analysis using 55 A. hydrophila genomes, including virulent A. hydrophila strains from U.S.A. and China. Interestingly, tight adherence (TaD) system is consistently encoded in all the vAh strains. The majority of U.S.A. isolates do not possess a complete type VI secretion system, but three core elements [tssD (hcp), tssH, and tssI (vgrG)] are encoded. On the other hand, Chinese isolates have a complete type VI secretion system operon. None of the virulent A. hydrophila isolates have a type III secretion system. Deletion of two genes encoding type VI secretion system proteins (hcp1 and vgrG1) from virulent A. hydrophila isolate ML09-119 reduced virulence 2.24-fold in catfish fingerlings compared to the parent strain ML09-119. By determining the distribution of genes encoding secretion systems in A. hydrophila strains, our study clarifies which systems may contribute to core A. hydrophila functions and which may contribute to more specialized adaptations such as virulence. Our study also clarifies the role of type VI secretion system in A. hydrophila virulence.

The effect of temperature on the mucosal IgM antibody response to DNP-KLH in channel catfish (Ictalurus punctatus)

Bath immersion remains a practical route for immunizing against disease in channel catfish; however research efforts in this area have revealed variable results when activating mucosal Ab responses with different antigens. This is likely due to a number of factors including the individual species, age of the fish, preparation of the immunogens, and differences in the overall dosage and the duration of exposure to vaccines. The current study sought to evaluate the effect of water temperature on the in vivo mucosal adaptive immune response in channel catfish to a protein-hapten antigen, DNP-KLH. Fish were bath immersed at different water temperatures and periodically evaluated over an eighteen week period for the development of serum and mucosal IgM antibodies to DNP-KLH using an indirect enzyme-linked immunosorbent assay. None of the temperature groups produced a serum antibody response; however there were detectable DNP-KLH specific IgM antibodies in the mucus starting at week eight. The extent of the mucosal antibody response and duration differed between the treatments. Our results show that there are intrinsic differences in the capacity to generate in vivo mucosal Ab responses in the skin at different water temperatures and the implications of these findings to channel catfish farming will be discussed.

Characterization of Histopathological and Ultrastructural Changes in Channel Catfish Experimentally Infected with Virulent Aeromonas hydrophila.

A highly virulent clonal population of Aeromonas hydrophila (vAh) has been the cause of recent motile Aeromonas septicemia epizootic in channel catfish (Ictalurus punctatus) farms in the Southeastern United States. The pathology of the disease caused by vAh has not been studied well yet. Thus, our aim was to determine histopathological and ultrastructural changes in channel catfish following vAh challenge. To accomplish this, catfish fingerlings were challenged with vAh (strain ML09-119) by bath. Six fish per each time point were collected at 1, 3, 5, 6, 24, and 48 h for light microscopy, and six fish were collected at 48 h for transmission electron microscopy (TEM). The first pathological lesions were detected in the spleen and stomach at 1 h post-challenge (HPC) while intestine, gills, kidney, and liver lesions were observed at 24 and 48 HPC. Histopathological examination revealed degenerative changes, necrosis, extensive edema, and inflammation in internal organs. The TEM showed severe tissue destruction with multiple bacterial cells secreting outer membrane vesicles, especially in spleen and gills and far number in the stomach. Degenerated bacterial cells were observed in the intestinal lumen and the phagosomes of phagocytic kidney cells. We identified, for the first time, degranulate eosinophilic granular cells, and dendritic cells like (DC-like) cells in the necrotic intestinal epithelium. These findings suggest that vAh rapidly proliferated and spread through the catfish organs following bath challenge.

POTENSI PENGEMBANGAN USAHA BUDIDAYA IKAN PATIN (Pangasius SP) DI DESA TATELU KABUPATEN MINAHASA UTARA

AbstractThe objective of this research was to study the potential business development of Channel catfish farming (Pangasius sp) in Tatelu Village North Minahasa regency. This research was a case study and the data collected was analyzed qualitatively and quantitative. Observation and interview to Tatelu village community were used to gather the primary and secondary data. The results of the research showed that the land, fries, and feed can be used for the potential businnes development of farming channel catfish in Tatelu village of North Minahasa Regency. The problems faced by fish culturist included cost, fish disease, level of community education and market demand. The skill of fish culturist needed to be develop through education , training and socialization about the benefits of fish culture. This was important due to the development of channel catfish farming had positive impact increasing people welfare. This is important because the development of channel catfish farming has a positive impact on improving people's economi Key words : channel catfish, tatelu village, business development

Δ6-fatty acid desaturase and fatty acid elongase mRNA expression, phagocytic activity and weight-to-length relationships in channel catfish (Ictalurus punctatus) fed alternative diets with soy oil and a probiotic.

A time-course feeding trial was conducted for 120 days on juvenile channel catfish (Ictalurus punctatus) to study the effects of diets differing in oil source (fish oil or soy oil) and supplementation with a commercial probiotic. Relative levels of Δ6-fatty acid desaturase (Δ6-FAD) and fatty acid elongase (FAE) expression were assessed in brain and liver tissues. Both genes showed similar expression levels in all groups studied. Fish weight-to-length relationships were evaluated using polynomial regression analyses, which identified a burst in weight and length in the channel catfish on day 105 of treatment; this increase was related to an increase in gene expression. Mid-intestinal lactic acid bacterium (LAB) count was determined according to morphological and biochemical criteria using API strips. There was no indication that intestinal LAB count was affected by the modified diets. The Cunningham glass adherence method was applied to evaluate phagocytic cell activity in peripheral blood. Reactive oxygen species (ROS) generation was assessed through the respiratory burst activity of spleen macrophages by the NBT reduction test. Probiotic-supplemented diets provided a good substrate for innate immune system function; the phagocytic index was significantly enhanced in fish fed soy oil and the probiotic, and at the end of the experimental period, ROS production increased in fish fed soy oil. The substitution of fish oil by soy oil is recommended for food formulation and will contribute to promoting sustainable aquaculture. Probiotics are also recommended for channel catfish farming as they may act as immunonutrients.

Identification of Two Channel Catfish Stocks, Ictalurus punctatus, Cultivated in Northeast Mexico

AbstractThe channel catfish farming in Mexico began in the 1970s. One of the most important areas of production is its northeastern region. Traditionally, the channel catfish farmers have attempted to preserve their original genetic stock. After more than 30 yr of production, the genetic relationship between stocks has not been assessed. The goal of this study was to evaluate the genetic differentiation between five channel catfish farm populations, using 13 microsatellite markers. A total of 154 fin clip samples were collected from five channel catfish farms in Tamaulipas. We also included 31 individuals of the commercial strain NWAC103. In each population, we calculated parameter of genetic variability: inbreeding coefficient (FIS), pairwise differentiation (FST), and genetic distance (DC). For the inference of populations and individual assignment two Bayesian methods were used. Genetic variability parameters were NA = 9.54–11.08 and AE = 5.40–6.67. Hardy–Weinberg equilibrium deviations were observed for all farm populations examined, and a deficit of heterozygotes was found. Signals of inbreeding were observed, particularly for the ACU (Acuamex) hatchery. Populations EKA (Empresas Karol) and ACU showed higher genetic differentiation values with respect to the commercial strain (FST = 0.107; FST = 0.082, respectively). Moderated genetic differences (FST = 0.067; DC = 0.080) were observed between the EKA and ACU. Clustering analysis revealed a well‐defined group between EKA and TPA (El Tiron Parejo). In the Bayesian analysis three groups were defined. The first group was formed by EKA and TPA, the second group included ACU, LAJ (La Lajilla), and PRO (Prodatec). In the third group was the commercial strain. In the assignment of individuals, EKA and ACU were represented by exclusive genotypes. Identification of two genetic stocks, one located in the EKA and the other in the ACU population, will be relevant for future management of these hatcheries. Additionally, the information from microsatellites and the statistical procedures presented will be important tools for genetic monitoring of these farm populations.

Chronic effects of a monogenean Ligictaluridus floridanus (Ancyrocephalidae) infection on channel catfish (Ictalurus punctatus) growth performance

In aquaculture, acute infections may result in fish mortality, but in many cases the chronic effects of infections are not readily detected, and may result in a decrease in fish growth.Ligictaluridus floridanusis a gill monogenean parasite prevalent on channel catfish (Ictalurus punctatus)farms in Northeastern Mexico. In order to assess and evaluate the impact of the chronic infection with this monogenean, 400 six-month-old catfish fingerlings from a hatchery, with a fork length of 10–15 cm were used in this study. Catfish naturally infected withL. floridanus(parasite abundance was 18) were divided in two groups of 200 fish. One group was treated with formalin, and infection was eliminated during a week, while the other group was not treated, and was used as a control. In total, 111 fish of each group were selected, placed into aquaria, and observed for 12 weeks. Indicators of growth such as fork length, mean weight, condition index, specific growth rate, feed conversion index and feed consumed were assessed. Significant differences (P&lt; 0.05) between the treated group and control were found in the mean weight (127.85 g and 107.63 g) and specific growth rate (1.79 and 1.58), respectively. No significant differences were found in the other growth indicators assessed. We proved that growth performance of channel catfish is affected by infection withL. floridanus, which influence the farm economy. This is the first report on the effect ofL. floridanuson the growth performance of channel catfish.

Excess Runoff Contribution to Daily Discharge Frequency of Channel Catfish Farms in Alabama

Abstract Aquaculture facilities producing more than 45,454 kg/yr and discharging 30 d or more annually, excluding excess runoff, are designated concentrated aquatic animal production facilities by the United States Environmental Protection Agency (USEPA), and they require National Pollutant Discharge Elimination System permits. Three individual ponds and three of four channel catfish farms in Alabama discharged 30 d or more annually. USEPA did not define excess runoff or explain how to adjust for it. There is normally at least 7.6 cm storage depth in ponds when rainfall begins. Runoff that causes overflow should be considered excess runoff. The year in Alabama can be divided into three soil moisture epochs. The 24‐h rainfall amounts necessary to cause ponds to overflow under normal conditions for each epoch were estimated by water budgeting. For watershed ponds, daily rainfall greater than amounts given below could cause excess runoff: Period Blackland Prairie region (cm) Other regions (cm) December to April 2 3.3 May to August 3.8 5.8 September to November 5.6 7.5 Daily rainfall above 7.5 cm could cause overflow during any soil moisture epoch from embankment ponds in all regions. Ponds discharged for 2–5 d after some rainfall events, and discharge for up to 4 d after an excess rainfall day should be excess runoff.

Effects of Channel Catfish Farming on Water Quality and Flow in an Alabama Stream1

Big Prairie Creek, Hale County, Alabama, receives overflow and draining effluent from about 5,000 ha of channel catfish, Ictalurus punctatus, ponds. Tributary streams receiving effluent directly from ponds were higher in concentrations of suspended solids, turbidity, nutrients, and biochemical oxygen demand than Big Prairie Creek, and these variables increased from upstream to downstream stations in Big Prairie Creek. Nevertheless, water quality in Big Prairie Creek was good at the last downstream station, and concentrations of variables did not exceed water quality criteria required by the stream classification system. Six reference streams in the same eco-region as Big Prairie Creek, but without channel catfish farms on their watersheds, had concentrations of most water quality variables similar to those found in the downstream reaches of Big Prairie Creek. Findings suggest that channel catfish farming has not had a great impact on water quality in Big Prairie Creek. Although catfish farms occupy 7.5% of the area of the Big Prairie Creek watershed, stream flow has not decreased as a result of impoundment of runoff by ponds. Use of best management practices (BMPs) to reduce the volume and improve the quality of pond overflow and draining effluents should be adequate to prevent negative downstream water quality impacts in catfish farming areas of Alabama. 1 This work was previously printed as an unrefereed Special Report of the Alabama Agricultural Experiment Station to the Alabama Catfish Producers, Montgomery, Alabama, who funded the effort.

Whole farm analysis of the introduction of CB hybrid (channel catfish, ictalurus punctatus, female X blue catfish, I. furcatus, male) on farm structure and profitability

We use linear programming (IP) to model three sizes of catfish farms: an average size farm of 60 ha (150 acre), a small farm of 20 ha (50 acre), and large farm of 160 ha (400 acres). The objective is to use an investigative model to determine how the introduction of CB hybrid affects the structure and profitability of channel catfish farms. The introduction of the CB hybrid on a channel catfish farm increases net farm income. Fingerling production and sale are the CB hybrid activities observed on all size farms when farmers are free to choose the most profitable farm activity in the absence of market constraints. If production of food‐size fish is forced into solution, net income is reduced. When the average size farm places a market constraint, which approximates 75 % of its acreage being operated, the production of food‐size CB hybrids, and net returns decrease, but total net cash income remains above that of a similar channel catfish farm. All model results show mat CB hybrid production comparatively generates higher levels of income, but requires higher levels of capital. Sensitivity analyses show that net farm cash income is higher for CB hybrid than channel catfish with a larger and more capital‐intensive farm. The risks associated with the introduction of CB hybrid on a channel catfish farm vary based on the activity combination. The introduction of 20 and 60 % of CB hybrid on a channel catfish farm results in less income variation than when channel catfish alone are produced.

The Sock‐Saver: A Small Trailer for Providing Liquid Oxygen to Remote Sites on Commercial Channel Catfish Farms

AbstractA small, single‐axle trailer was designed and built to hold three 50‐gal liquid oxygen Dewar flask tanks. The unit is small enough to be moved around a commercial channel catfish Ictalurus punctatus farm with a pickup truck or small tractor. It is being used successfully to provide supplemental oxygen at remote on‐farm locations to channel catfish that are being held in a sock (net cage or live car) at high density before sale. The total materials cost of the complete sock‐saver with trailer, Dewar tanks, pressure/flow regulators, and diffusers was $8,333.16. It is simple to operate, durable, and virtually maintenance free. Because no electrical or mechanical power source is required, it can be set up anywhere. The small “footprint” of the trailer does not interfere with the other equipment normally used when loading fish from a sock. Individual flow regulators allow use of one, several, or all eight diffusers as needed. The diffusers and hoses are self‐weighted and tangle‐free and do not interfere with the normal process of crowding the fish in the sock and dipping them up in the loading basket. The unit can increase dissolved oxygen in a sock by as much as 0.9 mg/L.

Defining loading limits of static ponds for catfish aquaculture

Commercial channel catfish farming has emerged as the most important aquaculture industry in the United States. During the last two decades, industry growth has occurred by expansion in the number and area of facilities and through production intensification. Evidence suggests that catfish farming has apparently reached the limits of the production system as currently configured. The success of commercial catfish culture can be attributed in part to low production costs resulting from the inherent waste assimilation capacity of aquaculture ponds, although operating within this capacity is complex and associated with several poorly defined limitations and hidden costs. Loading limits for pond aquaculture are based on the waste assimilation capacity of ponds and tolerance limits of the cultured species. The important design and operational considerations affecting loading limits include temperature effects, oxygen requirements, fish water quality tolerance limits, organic matter decomposition, and nutrient removal. Engineering solutions for extending the loading limits of pond aquaculture must account for the highly dynamic and complex nature of the pond ecosystem, particularly processes related to phytoplankton and microbial dynamics. Characteristics of hypertrophic ponds amenable to engineering solutions include excessive phytoplankton biomass, dominance of phytoplankton communities by cyanobacteria, intense diurnal stratification, chronic undersaturation of dissolved oxygen at the sediment–water interface, and limitations of current aeration technology. Improvements in the profitability of catfish pond aquaculture requires broad-scale implementation of a production paradigm based on measures of performance efficiency.

Channel Catfish Farming in Ponds: Lessons from a Maturing Industry

In the southeastern United States, the commercial culture of channel catfish Ictalurus punctatus has developed into a mature and sustainable industry. This article explores the catfish industry as a case study for the development of a sustainable pond aquaculture industry. The prerequisite knowledge base to support catfish industry development was largely in place by 1960. The industry developed from multiple centers, but became firmly rooted in northwest Mississippi by the mid-1960s. The industry expanded and became progressively more vertically integrated, a process that was completed by the mid-1970s. During the 1980s, industry output expanded at a rate nearly three times greater than the increase in pond area, indicating significant intensification of production, related to the widespread adoption of paddlewheel aeration. Factors that contributed to the success of the channel catfish industry include the characteristics of channel catfish, physical and edaphic factors, personal attributes of farmers, regional socio-economics, marketing and product promotion, and research and extension. Many of the important technical challenges to production of catfish in ponds are related to an inadequate level of control over production at the current level of system intensity. These problems are manifest in diseases and environmental impacts. The unique and complementary roles of catfish producers, research scientists, and organizations or institutions in developing solutions to industry challenges are discussed. Catfish production in ponds as currently practiced is sustainable, but further increases in profitability and solutions to challenges faced by catfish producers will require a greater emphasis on efficiency rather than yield.

Feasibility of Retention Structures, Settling Basins, and Best Management Practices in Effluent Regulation for Alabama Channel Catfish Farming

The United States Environmental Protection Agency has initiated rule making for aquaculture effluents. The contents of the rule will not be finalized until June 2004, but effluent containment in retention structures, effluent treatment in settling basins, and best management practices have been components of rules for other animal production facilities. The main aquaculture activity in Alabama is pond culture of channel catfish (Ictalurus punctatus). Fish are harvested with seines, and it is not necessary to drain ponds more than once in 5 to 10 years. Thus, effluents result mainly from storm overflow in winter and early spring. Catfish ponds in Alabama cannot be operated without effluent. A retention structure of enormous size would be necessary to retain storm overflow without discharge. Treatment of storm overflow by sedimentation also is not feasible. Settling basins with enough volume to provide a hydraulic retention time of 8 h would often be larger than production areas. Most catfish farms in Alabama are built to property lines or streams, and there would seldom be enough space available for settling basins to treat draining effluent. The best approach to effluent management in Alabama catfish farming appears to be the development and implementation of best management practices (BMPS) to reduce the volume and improve the quality of effluents. Considerable research has been conducted on water quality in catfish production ponds, and there is a large database to use in forming BMPs. Several categories of BMPs are provided for consideration as follows: BMPs to reduce effluent volume; BMPs to minimize suspended solids through erosion control; BMPs to improve pond water and effluent quality; BMPs for use of therapeutic agents and other chemicals; BMPs for siting and construction of new ponds or farms. Suggestions on how a formal system of BMPs could be prepared for Alabama catfish farming are given.

Epizootics in farm‐raised channel catfish, Ictalurus punctatus (Rafinesque), caused by the enteric redmouth bacterium Yersinia ruckeri

AbstractIn the winters of 1995 and 1996, unusual disease outbreaks occurred on two separate channel catfish farms in Arkansas, USA. Affected fish exhibited extraordinary haemorrhaged rings around the eyes and raised haemorrhaged areas overlying the frontal foramens. Other signs included abnormal swimming, lethargy, loss of equilibrium, and exophthalmia. Bacterial isolates from the moribund fish were identified as Yersinia ruckeri by biochemical tests, no lysis by the Hafnia‐specific bacteriophage 1672, and Y. ruckeri‐specific growth patterns on Shotts‐Waltman media. Fingerling catfish injected intraperitoneally with the bacterial isolate at 7.8 × 106 bacteria fish−1 developed lesions characteristic of the epizootics at 13, 18, and 22 °C and a biochemically identical isolate was recovered. Fingerling rainbow trout injected with the channel catfish isolate at 1 × 105 bacteria fish−1 and held at 20 °C developed signs typical of enteric redmouth by 4 days post‐inoculation and were moribund by 5 days post‐inoculation. Some differences of clinical signs occurred between experimentally infected rainbow trout and channel catfish. Clinical and biochemical similarities between infections of Y. ruckeri and many warmwater pathogens in affected catfish may lead to incorrect diagnosis of ERM infections.