Profiles of plasma estradiol and testosterone concentrations, cathepsin D, L, and B activities, and quantitative and qualitative protein content were developed and evaluated in four commercial strains of channel catfish, Gold Kist (2), Thompson and NWAC-103 for one year (age 2 to age 3). Great variation between individuals of the same strain precluded the identification of any significant, strain-specific differences for the variables under investigation. When variables from fish of all strains were collectively evaluated over time, both estradiol and testosterone concentrations significantly increased in July and then later from February to April. The increase in hormone concentration was accompanied by oocyte growth and increases in proteolytic activity of cathepsins D, L, and B, supporting the role of estradiol in regulating vitellogenesis. Vitellogenin was enzymatically broken down into smaller protein units by cathepsins L, D, and B that were separately predominant at different stages of oocyte development. During oocyte development, there were sequential relationships among hormone concentration, cathepsin activity, protein content, and predominant oocyte proteins. This observation was associated with high levels of activity of cathepsin L in February, suggesting an important role in protein degradation during that time, while high activity of cathepsin B occurred, stimulating during November to January. Cathepsin B is more important in oogenesis or early vitellogenesis, and cathepsin L assumes a principal role during middle vitellogenesis. Twenty hours subsequent to the injection of fish with either carp pituitary hormone or luteinizing hormone releasing hormone, increases in the concentration of plasma estradiol and testosterone, activities of cathepsins L, D, and B, egg size, and egg protein content occurred, stimulating the process of oocyte maturation. The percentages of spawning obtained were 18.8% of LHRH injected fish, 12.4% of CPE injected fish, 9.4% of fish not injected, and 0% of saline injected fish. Injection of females with LHRH can potentially serve as a tool to increase spawning success in appropriate commercial settings, particularly for improving three year old catfish spawning success early in the spawning season. Low estradiol levels in all three-year-old fish suggest that insufficient stimulation of vitellogenin production by estradiol may underlie the lack of vitellogenin incorporation into developing oocytes. In the present study, the measurement of the activities of the cathepsins and their relationships to other parameters were evaluated for the first time. This is also the first study to report plasma estradiol and testosterone concentrations, protein content, and egg size in 2 to 3-year old channel catfish. All of the parameters collectively evaluated may serve to assist in the selection of the best 2- year old channel catfish female broodstock, and to determine the optimal timing of treatments of hormone injection to increase reproductive performance.

Proliferative gill disease (PGD) caused by the myxozoan parasite Henneguya ictaluri is one of the most devastating parasitic infections in channel catfish aquaculture. Currently, there is no effective treatment for H. ictaluri and the unpredictable outbreaks can result in 100% mortality. Management strategies have been developed to prevent losses in newly stocked fingerlings by evaluating the PGD status of a pond prior to stocking, which is difficult since resident fish may not show clinical signs even when actinospore levels are lethal to naive fish. Current diagnostic methods are limited to the identification of an active infection and methods of predicting potential outbreaks have several limitations. The PGD status of a pond to be stocked can be determined using sentinel fish exposures which are labor intensive and require a source of parasite free fish. These limitations necessitated the development of more rapid and efficient means of determining actinospore concentrations to determine the risk of losing fish prior to stocking. The development of a quantitative real-time polymerase chain reaction (QPCR) assay provided a more rapid, sensitive and quantitative method of diagnosing active infections and also provides a means to predict potential PD outbreaks and determine the PGD status of a pond prior to stocking. Another approach in the control of this parasite is the identification of a less susceptible culturable species or to identify traits that could be targeted in a selective breeding program. Challenge studies have shown that the closely related blue catfish (Ictalurus furcatus) does not exhibit as severe an inflammatory response to H. ictaluri and mortalities are significantly lower than in channel catfish. Comparisons of PGD severity and H. ictaluri infection in channel catfish, blue catfish and channel x blue catfish backcross hybrids by gross examination, histopathology and the newly developed H. ictaluri real-time PCR (QPCR) assay supported previous research suggesting the life cycle of the parasite can not be completed as efficiently through the blue catfish host. This dissertation describes the development and validation of a QPCR assay to detect H. ictaluri in both fish tissues and environmental samples and the application of this assay in both research and production settings.

The overall purpose of this study is to estimate how the rise in grain prices (especially corn prices) induced by ethanol production impacts U.S. catfish industry. Using monthly data from January 1996 to December 2007, an ARDL model and bounds testing procedure were used. The existence of cointegration between the feed price and its regressors and between the farm price and its regressors was found. Results show that the short- and long-run feed price elasticity with respect to corn prices were 0.224 and 0.075, respectively. It was found that energy is more important to catfish feed production than to farm level catfish production, and is more important to processor level production than to farm level production. Results further showed that catfish farmers will lose net returns because the estimated farm price elasticity with respect to feed prices was smaller than the necessary change that would keep net returns the same. The overall purpose of this study is to estimate how the rise in grain prices (especially corn prices) induced by ethanol production impacts catfish feed prices and catfish prices at the farm level. Using monthly data from January 1996 to December 2007, an ARDL model and bounds testing procedure were used to test the existence of cointegration between the variables of interest. The existence of cointegration between the feed price and its regressors and between the farm prices and its regressors was found. Estimation results show that the short- and long-run feed price elasticity with respect to corn prices were 0.224 and 0.075, respectively. Feed and farm price elasticities with respect to energy prices were highlighted. The results show that energy is more important to catfish feed production than to catfish production at the farm level, and energy is more important to catfish production at the processor level than to production at the farm level.

Flathead catfish stocks in the Pascagoula River were decimated by the passage of Hurricane Katrina. Age-0 fish survived the storm, producing a strong 2005 year-class. Reproduction by the remaining adults and/or downstream movement from tributaries produced an additional strong cohort in 2006. The strong 2005 year-class resulted in the capture of a high proportion of two-year-old fish in 2007. In 2008, a high proportion of two- and three-year-old fish were captured, illustrating the high rate of survival of the 2005 year-class, and the presence of a strong 2006 year-class. The flathead catfish population of the Pascagoula River was dominated by immature fish that should begin to reproduce in 2009, and most of these fish should reach sexual maturity by 2011. Density estimates are low when compared to other populations, indicating that a management option of a minimum length limit of 610 mm could prove useful in protecting these future spawners.

Despite the growing use of hybrid catfish (Ictalurus furcatus × I. punctatus) in aquaculture, few studies have investigated the comparative effects of temperature on physiological performance with other cultured catfish. Therefore, growth, metabolism, and blood-oxygen affinity of blue (I. furcatus), channel (I. punctatus), and hybrid catfish were compared at moderate (23°C) and high (33°C) water temperatures. Channel catfish had the greatest growth and were in better condition compared to blue and hybrid catfish. Hybrid catfish standard metabolic rates did not differ from blue or channel catfish, while hybrid catfish had higher maximum metabolic rates, larger metabolic scopes, and better swimming performance than blue and channel catfish. Blue and hybrid catfish had a higher affinity to bind oxygen than channel catfish, with hybrid catfish generally having larger Bohr effects than blue and channel catfish. These results indicate hybrid catfish likely achieve superior performance due to larger metabolic scopes and Bohr effects.

US catfish producers, seeking to reduce production costs, adopted technologies and production systems with the potential to increase the catfish pond productivity. Catfish pond intensification was accompanied by increased operating risk due to increased reliance on operating inputs. Split ponds were one adopted production system. The US catfish industry has adopted four split-pond variants differentiated by water circulation mechanism. Variants include the slow-rotating paddlewheel, the modified paddlewheel aerator, the screw pump, and the axial-flow turbine pump. Initial investment ranged from $54,400/4-ha ponds to $71,150/4-ha pond. Mean annual gross fish yield ranged from 12,876 kg/ha to 16,984 kg/ha. Net returns were positive for all designs under current economic conditions. The modified paddlewheel aerator and slow-rotating paddlewheel designs show the most promise for adoption. US catfish producers use multiple production strategies of varying intensity level, species produced, and pond design. Commercial farm data were used to quantify the economic risk of six commonly used catfish production strategies. Second order stochastic dominance (SOSD) was exhibited by multiple-batch and intensively aerated production of channel catfish over low intensity culture of channel catfish. Higher intensity hybrid catfish production strategies exhibited SOSD over medium intensity culture of hybrid catfish. Variations in fish yield, feed price, and feed conversion ratio were the primary contributors to variations in production cost. Hybrid catfish production strategies were dominated by yield (production) risk and channel catfish production strategies were dominated by price (market) risk. Off-flavor has been a persistent problem in the US catfish industry and contributes to economic risk. The cost of off-flavor was quantified at the farm level. A survey of catfish producers carried out in 2022 (n=54) revealed that farms representing 85% of the foodfish production area followed management practices for curbing off-flavor. The average annual off-flavor prevalence and the associated processing plant sample rejection rate was 27%. Off-flavor caused harvest delays averaged 23 days. Copper sulfate and diuron were used for managing off-flavor with diuron being the most popular choice used on 78% of the surveyed area. Direct annual cost associated with off-flavor management on catfish farms amounted to $39.9 million ($2,325/ha or $0.272/kg) in 2022.

Thesis (Ph.D.)--Mississippi State University. Department of Agricultural and Biological Engineering. / Title from title screen. Includes bibliographical references.

Thesis (M.S.)--Mississippi State University. Department of Wildlife and Fisheries. / Title from title screen. Includes bibliographical references.

Thesis (M.S.)--Mississippi State University. Department of Agricultural Economics. / Title from title screen. Includes bibliographical references.

Edwardsiella ictaluri causes enteric septicemia of catfish (ESC), a devastating disease in the channel catfish industry. Our research group has developed several E. ictaluri live attenuated vaccine (LAV) candidates (EiΔevpB, EiΔevpBΔfur, EiΔevpBΔhfq, EiΔevpBΔfurΔhfq), which were able to stimulate an immune response in vaccinated channel catfish and reduce ESC. However, innate, and adaptive immune responses in the lymphoid tissues of channel catfish to these LAVs are not known well. The overall goal of the project is to determine the role of adaptive and innate immune responses in catfish after vaccination with LAVs. Analysis of innate and adaptive immune-related gene expressions showed that the LAVs induced expression of adaptive immune-related genes in lymphoid tissues with less inflammation compared to wild type control. Also, the LAVs induced the expression of IgM in the sera of catfish.