No description available.

Color and color components are important quality attributes for fresh channel catfish muscle. The objective of the present research was to obtain inside understanding regarding color distribution, color component stability and the pre-slaughter conditions influence on color and color components and other quality attributes. Catfish fillets were rendered to be paler and redder on iced storage; and paler, less red and less yellow by ice-water chilling process. Visual classified “reddish” catfish fillets had higher heme-protein content than “white” fillets and these pigments were derived mainly from hemoglobin. Pre-slaughter live fish chilling in ice water and bleeding at slaughter also slightly affected muscle color and total heme-protein content, but they were not the main factors for the “reddish” color on catfish muscle. Catfish hemoglobin autoxidation rate was similar at room and at refrigeration temperature. Myoglobin gene and hemoglobin beta gene were cloned and expressed in Eschericia coli cells in insoluble form. The myoglobin gene had an open reading frame of 444 nucleotides and translated into 147 amino acids with molecular weight of 16,909 and pI of 9.43. The myoglobin gene in vivo expression in white muscle was not affected by pre-slaughter chilling. Pre-slaughter chilling is a stressor to channel catfish and shortens the pre-rigor time postmortem; thus, it is not recommended in catfish processing.

Thesis(M.S.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references.

Red fillet results in a profit loss for catfish processors and producers alike; however, neither the cause nor the abundance of red fillet has been studied extensively. Therefore, an assessment of red fillet in the catfish industry was conducted along with studies subjecting catfish to poor water quality and inoculation with Aeromonas sobria. Within every catfish harvest, 0.12% of fillets were rejected due to blotchy red coloration. Histology revealed congestion of erythrocytes indicating internal hemorrhaging, and A. sobria was isolated from 63% of all red fillets compared to 28% of acceptable fillets. Acute exposure to poor water quality did not produce red fillet in catfish despite high stress levels and mortality rates (22%). Inoculation with A. sobria did induce red fillet with similar coloration to red fillets obtained from catfish processors.

Virulent Aeromonas hydrophila (vAh) is an important emerging bacterial pathogen causing motile Aeromonas septicemia (MAS) in farmed catfish. Understanding the pathogenicity of the disease is essential for the development of preventive measures. In this study, we aimed to develop a bioluminescent virulent A. hydrophila (BvAh) strain to understand the pathogen-host interactions during infection. To achieve this, a new bioluminescence expression plasmid, pAKgfplux3, was constructed and mobilized to vAh. Catfish were challenged with BvAh using immersion, injection, and adipose fin clip procedures, and bioluminescence signal was tracked in live catfish during infection. We developed a novel BvAh strain for the first time, conducted imaging of BvAh in live fish, detected infection routes and attachment sites of the pathogen, and determined target organs, which provided new insights on the pathogenesis of vAh. MAS progressed better in fish when protection of skin was bypassed. Abraded skin seems to provide a potential portal of entry during vAh infection.

Incidence and prevalence of Edwardsiella piscicida has increased in Mississippi farm-raised catfish in recent years. Edwardsiella piscicida affects mostly market-sized catfish during the final stages of the production cycle resulting in significant economic losses. The objectives of this study were to determine the genetic variability of E. piscicida, assess virulence in channel and hybrid catfish, and evaluate the capacity of a live-attenuated E. ictaluri vaccine to protect channel and hybrid catfish against heterologous E. piscicida isolates. This work identified five discrete E. piscicida lineages, along with group specific associations of several virulence related genes. In general, E. piscicida was shown more virulent in hybrids than channel catfish, in line with previous work. Further, a live-attenuated E. ictaluri vaccine was shown to confer cross-protective immunity in channel and hybrid catfish against E. piscicida.

Catfish pectoral spines are an anti-predator defense mechanism. They can be bound or locked, making the fish harder to swallow, or used to produce distress calls by rubbing ridges on the dorsal process against a channel in the wall of the pectoral girdle. Growth of the pectoral spine and girdle were examined in relation to fish size within and across species that occur throughout central and eastern Virginia. These included blue catfish (Ictalurus furcatus), channel catfish (Ictalurus punctatus), white catfish (Ameiurus catus), brown bullheads (Ameiurus nebulosus), yellow bullheads (Ameiurus natalis), flathead catfish (Pylodictis olivaris), margined madtom (Noturus insignis), and tadpole madtom (Noturus gyrinus).Pectoral spines and girdles grow as catfish increase in size. In larger species spine length and weight increase nonlinearly with fish size, suggesting that maintaining spine dimensions becomes less important in bigger individuals less likely to suffer predation. The incidence of spine breakage also increases in larger fish. In smaller species spine length increases linearly in our samples (brown and yellow bullheads and margined and tadpole madtoms). In all species spine width increases linearly with total length. The spine base (dorsal process width and depth and dorsal-ventral length) grows linearly with total length in most species. However, measurements of the spine base increase nonlinearly in white catfishes, and dorsal process width increases nonlinearly in wild channel catfish although the increase was linear in cultured channel catfish.Girdle depth increased linearly with total length in all species except for wild channel catfish, and the ratio of coracoid to cleithrum depth varied among species. Pectoral girdle weight increased linearly with fish weight in blue catfish, cultured channel catfish, brown bullheads, and margined and tadpole madtoms. However, girdle weight, a major component of the body, increased nonlinearly in wild channel, white, yellow bullheads, and flathead catfishes. Cultured channel catfish had smaller pectoral spines and girdles than wild channels, a likely epigenetic response to predators. Catfish spines were identified to species, allowing determination of catfishes eaten by bald eagles (Haliaeetus leucocephalus) using spines collected near their nests. Bald eagles ate blue catfish (60%), channel catfish (27%), white catfish (9%), brown bullheads (4%) and yellow bullheads (0.5%). Madtom and flathead catfish were not consumed. Mean sizes captured were: Blue catfish (366 mm, 414 g), channel catfish (417 mm, 618 g), white catfish (320 mm, 591 g), brown bullheads (278 mm, 277 g) and yellow bullhead (203 mm, 192 g).

Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1979. / Bibliography: leaves 91-97. / Microfiche. / xii, 97 leaves ill. (some col.) 29 cm

Thesis (M.S.)--Auburn University, 2008. / Abstract. Vita. Includes bibliographical references.

Diseases caused by Edwardsiella spp. are responsible for significant losses in wild and cultured fishes around the world. Historically, Edwardsiella tarda has been considered the most phenotypically and genotypically heterogeneous member of the genus. Investigations into intraspecific variability of E. tarda demonstrated isolates previously classified as E. tarda actually represent three genetically distinct yet phenotypically ambiguous groups, leading to the adoption of E. piscicida and E. anguillarum as discrete taxa. Current genomic investigations have demonstrated significant differences between these organisms. To this end, real-time quantitative PCR assays were developed to quickly and accurately detect the pathogens in pond water, fish tissue and broth culture. Additionally, whole genome sequencing was performed for representative isolates of each Edwardsiella spp. Furthermore, forty-seven Edwardsiella isolates, representing all five taxa, from different hosts and a wide temporal and geographic range were analyzed using commercial microbial identification kits, repetitive sequence-mediated polymerase chain reaction, fatty acid methyl ester analysis, antimicrobial resistance profiles, in addition to 16S, gyrB, sodB and plasmid sequencing. This analysis demonstrated key differences in gene sequences and plasmid profiles among these important bacterial pathogens and further supported contemporary taxonomic classifications. Additionally, a real-time multiplex PCR was developed to accurately discriminate between all Edwardsiella spp. affecting fish; namely E. ictaluri, E. piscicida, E. tarda and E. anguillarum. Moreover, recent publications suggest E. piscicida is more commonly associated with disease outbreaks in Mississippi catfish aquaculture than E. tarda or E. anguillarum. To this end, several different challenge models were evaluated. Comparative virulence was assessed, along with histopathological lesions and posterior kidney clearance rates in channel catfish (Ictalurus punctatus). Diagnostic case submissions suggest E. piscicida is more commonly associated with disease outbreaks in blue catfish (Ictalurus furcatus) x channel catfish hybrids compared to channel catfish. This led to investigations into the relative pathogenicity of E. piscicida in hybrid and channel catfish, which demonstrated a significantly lower median lethal dose (LD50) for E. piscicida in hybrid catfish; an important finding given the increased production of hybrid catfish in U.S. farm-raised catfish in the southeastern United States.