Channel Catfish Research Articles

Air exposure leads to short term reflex impairment, but does not impact blood physiology, in angled channel catfish Ictalurus punctatus

Catch-and-release angling is an oft-practiced conservation tool whereby fish are, either as a result of harvest regulations or conservation ethic on the part of the angler, released after capture. Central to this practice is the assumption that release fish survive after capture, however a large body of work has shown that post-release physiological disturbances and mortality can occur, particularly for fish subjected to long handling times out of the water. It is also known that different species may respond differently to the process of capture and handling, however many popular gamefish have not been studied in this context. To address this, we conducted a study on channel catfish Ictalurus punctatus angled from a lake in southern Illinois, USA. Fifty-eight channel catfish were angled using conventional techniques and either treated as a control or subjected to one of four different combinations of holding (0.5 or 4 h) and air exposure (0 or 5 min) time. Catfish were assessed for Reflex Action Mortality Predictors (RAMP) with blood biopsy providing measures of glucose, lactate, hematocrit, alkaline phosphatase activity, and lactate dehydrogenase activity. Results showed that catfish subjected to long air exposure were more likely to show reflex impairment within 0.5 h of capture, however recovery typically occurred by 4 h. Air exposure had no impact on any blood metric in this study, and no post-capture mortality occurred. These results indicate that channel catfish are relatively robust to catch-and-release, however the presence of short-term impairment leads us to recommend that air exposure times be minimized in order to achieve best outcomes for this species.

Efficacy of crystalline amino acids supplementation in reduction of intact protein level in channel catfish Ictalurus punctatus diets

A 9-week growth trial was performed to assess the role of indispensable (IAA) and dispensable amino acids (DAA) supplementation in diets designed for juvenile (10.6 g) channel catfish (Ictalurus punctatus). The effects on fish growth, feed utilization, proximate, amino acids (AA) composition, and morphometric indicators were followed. Nine iso-lipidic (8 %) experimental diets were formulated with different levels of intact protein (32, 30, 28, 26, and 24 IP) supplemented with IAA (Lysine and Histidine) to restore IAA balance to those stated in NRC (2011). Additionally, DAA (Glutamic acid and Glycine) were added to the 24IP at different rates (2 %, 4 %, 6 %, and 8 %). At the conclusion of the growth trial, however, there was a linear decrease in fish growth as IP was lowered from 32% to 24%. But, based on mean separation; final mean weight (g), thermal growth coefficient (TGC), and feed conversion ratio (FCR) of channel catfish were not significantly different (P > 0.05) among fish groups fed diets containing 32 %, 30 %, 28 % and 26 % IP supplemented with IAA. Fish growth was significantly reduced, while apparent net protein retention (ANPR) and FCR significantly increased as IP was lowered to 24%. While growth and FCR of catfish fed 24IP with DAA (2–6 %) were not significantly different compared to catfish fed 32 % and 30 %IP diets. In conclusion, IAA (lysine and histidine) could be used as a supplement to reduce intact protein from 32 % to 26 % in channel catfish diets with maintaining IAA balance as recommended by NRC (2011). Catfish growth was improved by fortification of the 24IP diet with DAA (2–6 %), so the dietary IP level could be further lowered to 24 % with supplementation of IAA and DAA.

Potential of plant as antiparasite for fish

Parasites are organisms that live on the body of another organism of a different type and larger in size, called the host. In the body of the host, the parasite gets several advantages, among others, as a shelter, obtaining nutrients for its survival, while for the host parasite attack gets several losses, among others, body damage occurs, growth becomes slow, and even death occurs. Various types of parasites can cause disease in various types of cultured freshwater fish, including Lernaea sp., Argulus sp., Ergasilus sp., all of which belong to the crustacean group of parasites. From the trematode worm group, namely Dactylogyrus sp., Gyrodactylus sp. and Diplozoon sp. Ichthyophthirius multifilis, Trichodina sp. and Episthylis belong to the Ciliata class of protozoa. All these types of parasites can reduce crop yields, causing unnecessary losses to farmers. Efforts to control diseases caused by parasites can be done by using inorganic chemical drugs, but this method can pollute the environment and food products. Parasite control using natural ingredients sourced from plants is relatively safer for fish and the environment. Plants contain various types of organic chemical compounds that act as antiparasitic, including tannins, alkaloids, phenols and saponins. The purpose of writing this article is to convey information from various research results regarding the potential of plants that can be used to treat parasites in cultured freshwater fish. Based on the results of the submission of the article, it proves that several types of plants have the potential to treat diseases caused by several types of parasites, including Piper betle L, Leucas lavandulaefolia, Moringa oleifera, Morinda citrifolia, Allium sativum, Galla chinensis, Mucuna pruriens and Carica papaya. The types of parasites that can be controlled with these medicinal plants include Dactylogyrus sp., Trichodina sp., Argulus sp. Myxobolus sp., Lernaea sp., Neobenedenia sp., Ichthyophthirius multifiliis, Gyrodactylus turnbulli and Epistylis sp. which attack the fish Cyprinus carpio L, Oreochromis niloticus, Clarias sp., Carassius auratus, Lates calcarifer, Ictalurus punctatus and Ictaurus punctatus. The application of treatment was carried out through immersion, but neither immersion time nor standard dose was obtained that could be used for all types of fish.

Diet of Ictalurus punctatus (Actinopterygii, Ictaluridae) in a mountain reservoir surrounded by forest land in Japan

Diet of Ictalurus punctatus (Actinopterygii, Ictaluridae) in a mountain reservoir surrounded by forest land in Japan

The Use of Poultry Corn By-Product Meal on the Growth Performance of Channel Catfish, Ictalurus punctatus

In this study, three growth trials were conducted to check the efficacy of poultry corn by-product meal, which was a combination of wet poultry processing waste and corn that was co-dried. It was relatively a new product, and its first growth trial was conducted in a laboratory (aquarium study) to evaluate the substitution of whole corn meal with poultry plus corn by-product meal (PCBM) in practical diets for channel catfish. In this trial (84 days culture period), 7 levels of PCBM (0, 5, 10, 15, 20, 25 and 30%) were evaluated in a practical diet containing 32% protein and 6% lipid. The results indicated that fish fed PCBM20 had the highest FW, WG and WG% among all the treatments, and these values were significantly higher (p < 0.05) than at baseline or with PCBM5 treatment. The second trial (fingerlings to sub-market) was conducted in 12 raceways with 4 levels of PCBM (0, 10, 20 and 30%) and 600 fish (mean initial weight 42.3 ± 5.06 g) in each raceway. After 143 days of culture, the results demonstrated that there were no significant differences (p > 0.05) between the FW, WG and WG% and the survival of the fish. To validate our results again, the third trial (sub-market to market) was conducted in 6 raceways with 2 levels of PCBM (0 and 30%). A total of 600 fish (mean initial weight 136.8 ± 6.3 g) were stocked in each raceway. The results revealed that there were no significant differences (p > 0.05) between the FW, WG and WG% and fish survival after the culture period of 133 days. In all three trials, upon termination, the hepatosomatic index (HIS), the intraperitoneal fat (IPF), and the dress-out (headed and gutted) percentages were measured for trials 2 and 3. The results showed that there were no significant differences (p > 0.05) between all these parameters except for HIS in trial 1 and IPF in trial 2 (p < 0.05). In conclusion, PCBM can be used up to 30% in the diets of channel catfish.

Evaluation of Edwardsiella piscicida basS and basR mutants as vaccine candidates in catfish against edwardsiellosis.

Catfish farming is the largest aquaculture industry in the United States and an important economic driver in several southeastern states. Edwardsiella piscicida is a Gram-negative pathogen associated with significant losses in catfish aquaculture. Several Gram-negative bacteria use the BasS/BasR two-component system (TCS) to adapt to environmental changes and the host immune system. Currently, the role of BasS/BasR system in E.piscicida virulence has not been characterized. In the present study, two mutants were constructed by deleting the basS and basR genes in E.piscicida strain C07-087. Both mutant strains were characterized for virulence and immune protection in catfish hosts. The EpΔbasS and EpΔbasR mutants were more sensitive to acidic environments and produced significantly less biofilm than the wild-type. In vivo studies in channel catfish (Ictalurus punctatus) revealed that both EpΔbasS and EpΔbasR were significantly attenuated compared with the parental wild-type (3.57% and 4.17% vs. 49.16% mortalities). Moreover, there was significant protection, 95.2% and 92.3% relative percent survival (RPS), in channel catfish vaccinated with EpΔbasS and EpΔbasR against E.piscicida infection. Protection in channel catfish was associated with a significantly higher level of antibodies and upregulation of immune-related genes (IgM, IL-8 and CD8-α) in channel catfish vaccinated with EpΔbasS and EpΔbasR strains compared with non-vaccinated fish. Hybrid catfish (channel catfish ♀ × blue catfish ♂) challenges demonstrated long-term protection against subsequent challenges with E.piscicida and E.ictaluri. Our findings demonstrate BasS and BasR contribute to acid tolerance and biofilm formation, which may facilitate E.piscicida survival in harsh environments. Further, our results show that EpΔbasS and EpΔbasR mutants were safe and protective in channel catfish fingerlings, although their virulence and efficacy in hybrid catfish warrant further investigation. These data provide information regarding an important mechanism of E.piscicida virulence, and it suggests EpΔbasS and EpΔbasR strains have potential as vaccines against this emergent catfish pathogen.

Dynamics of bacterial community and antibiotic resistance genes in the aquaculture ponds of channel catfish (Ietalurus Punetaus): An association with the mobile genetic elements and environmental factors

Aquaculture is a vital link between aquatic products and public health, but the effects of potentially hazardous factors in aquaculture have been grossly underestimated. In this study, a total of 15 potentially pathogenic bacteria (PPB) and 39 antibiotic resistant bacteria (ARB) were identified in the aquaculture pond environment based on 16S rRNA genes. And, 89 antibiotic resistance genes (ARGs) subtypes combined with eight mobile genetic elements (MGEs) and nine environmental factors were also investigated. Cyanobacteria and Proteobacteria were observed as the dominant phyla at different culture stages. The total abundances of PPB and ARB showed an increasing trends from juvenile to harvesting culture stage, revealing that they are widely disturbed in aquaculture ponds. Further, intI-1 exhibited the highest abundance among MGEs and sul1 had the highest abundance among ARG subtypes. The OLS regression analysis showed significant positive correlations among abundances of MGEs and ARGs. The RDA demonstrated that the temperature, transparency and Chlorophyll a exhibited significant correlations with different bacterial phylum, and the positive correlation between MGEs (intI-1) and ARGs (ereA and sul1) highlighted their horizontal migration via associated bacterial communities (e.g. Proteobacteria). The co-occurrence patterns indicated that the MGEs (intI-1 and IS613) and the genus Pseudoramibacter, Citrobacter, Mycobacterium, Moraxella, Pseudoalteromonas, Eikenella, Providencia, and Proteus may play a leading role in the distribution of ARGs during the cultivation of channel catfish. Our results provide a systematic understanding of the rational regulation of PPB, as well as the prevention of ecological and health risks associated with ARB and ARGs in aquaculture.

Developmental osteology of Ictalurus punctatus and Noturus gyrinus (Siluriformes: Ictaluridae) with a discussion of siluriform bone homologies

Abstract The skeleton of Siluriformes is characterized by several autapomorphies, including secondary absence, extreme modification, and purported fusion of several ossifications. Although well documented in adults, information on skeletal development in catfishes is relatively sparse and typically focused on particular regions of the skeleton (e.g., Weberian apparatus). To further our understanding of the siluriform skeleton, I document the development of the entire skeleton in two ictalurid species, Ictalurus punctatus (channel catfish) and Noturus gyrinus (tadpole madtom) from five days pre-hatch to adult. I reexamine the homologies of bones previously hypothesized to represent compound elements in catfishes as well as an additional element only known to occur in some ictalurids. Development of the skeleton is complete in I. punctatus at 22.4 mm SL and almost complete in N. gyrinus (except dorsal- and anal-fin distal radials) at 14.1 mm SL. No signs of ontogenetic fusion were observed in any of the purported compound elements. Previous hypotheses of the homology of these elements and of additional ossifications are reviewed in light of developmental information obtained herein. No dermal parietal component is present at any stage in the so-called parieto-supraoccipital. The bone is the supraoccipital which ossifies from two lateral centers of ossification which later fuse, rather than from a median center. The ‘posttemporo-supracleithrum’ originates from a single center of ossification and represents the supracleithrum. The posttemporal is present in ictalurids and many other catfishes as a canal-bearing bone between the supracleithrum and the pterotic, a bone sometimes identified as the extrascapular. The extrascapular is missing in catfishes. Ictalurids have an additional dermal bone above the posttemporal, which is either an independently ossifying fragment of the posttemporal or a neoformation restricted to some members of this family. The single chondral bone of the pectoral girdle originates from a single center of ossification that represents the coracoid. The scapula is missing in catfishes. Dorsal-fin distal radial 2 is absent in catfishes and the foramen of dorsal-fin spine 2 is formed from modifications to the base of the fin-ray itself. Unlike loricarioid catfishes, the urohyal of ictalurids originates solely as an ossification of the sternohyoideus tendons. The anteriormost infraorbital element ossifies from a single center of ossification around the infraorbital sensory canal and represents the lacrimal. The antorbital is missing in catfishes. Finally, skeletal development of I. punctatus is compared to that available for other otophysans, including the cypriniforms Danio rerio and Enteromius holotaenia and the characiform Salminus brasiliensis.

Genome-wide identification and expression analysis of mitogen-activated protein kinase (MAPK) genes in response to salinity stress in channel catfish (Ictalurus punctatus).

The mitogen-activated protein kinase (MAPK) gene family has been systematically described in several fish species, but less so in channel catfish (Ictalurus punctatus), which is an important global aquaculture species. In this study, 16 MAPK genes were identified in the channel catfish genome and classified into three subfamilies based on phylogenetic analysis, including six extracellular signal regulated kinase (ERK) genes, six p38-MAPK genes and four C-Jun N-terminal kinase (JNK) genes. All MAPK genes were distributed unevenly across 10 chromosomes, of which three (IpMAPK8, IpMAPK12 and IpMAPK14) underwent teleost-specific whole genome duplication during evolution. Gene expression profiles in channel catfish during salinity stress were analysed using transcriptome sequencing and qRT-PCR (quantitative reverse transcription PCR). Results from reads per kilobase million (RPKM) analysis showed IpMAPK13, IpMAPK14a and IpMAPK14b genes were differentially expressed when compared with other genes between treatment and control groups. Furthermore, three of these genes were validated by qRT-PCR, of which IpMAPK14a expression levels were significantly upregulated in treatment groups (high and low salinity) when compared with the control group, with the highest expression levels in the low salinity group (P < 0.05). Therefore, IpMAPK14a may have important response roles to salinity stress in channel catfish.

Improved Growth and High Inheritance of Melanocortin-4 Receptor (mc4r) Mutation in CRISPR/Cas-9 Gene-Edited Channel Catfish, Ictalurus punctatus.

Effects of CRISPR/Cas9 knockout of the melanocortin-4 receptor (mc4r) gene in channel catfish, Ictalurus punctatus, were investigated. Three sgRNAs targeting the channel catfish mc4r gene in conjunction with Cas9 protein were microinjected in embryos and mutation rate, inheritance, and growth were studied. Efficient mutagenesis was achieved as demonstrated by PCR, Surveyor® assay, and DNA sequencing. An overall mutation rate of 33% and 33% homozygosity/bi-allelism was achieved in 2017. Approximately 71% of progeny inherited the mutation. Growth was generally higher in MC4R mutants than controls (CNTRL) at all life stages and in both pond and tank environments. There was a positive relationship between zygosity and growth, with F1 homozygous/bi-allelic mutants reaching market size 30% faster than F1 heterozygotes in earthen ponds (p = 0.022). At the stocker stage (~ 50g), MC4R × MC4R mutants generated in 2019 were 40% larger than the mean of combined CNTRL × CNTRL families (p = 0.005) and 54% larger than F1 MC4R × CNTRL mutants (p = 0.001) indicating mutation may be recessive. With a high mutation rate and inheritance of the mutation as well as improved growth, the use of gene-edited MC4R channel catfish appears to be beneficial for application on commercial farms.

Producing xenogenic channel catfish, Ictalurus punctatus with cryopreserved testes and ovarian tissues of blue catfish, I. furcatus

Xenogenesis has been identified as an innovative hatchery technology for hybrid catfish (channel catfish, Ictalurus punctatus ♀ × blue catfish, I. furcatus ♂) embryo production. The xenogeneic process can be accomplished by transplanting primordial germ cells, spermatogonial stem cells (SSC), or oogonial stem cells (OSC), derived from a donor diploid fish into a sterile recipient, which then enables recipient fish to produce donor-derived gametes. Currently, freshly extracted stem cells are used to create xenogens, which is challenging, especially considering germ cell production is donor size and age specific as well as dependent on seasonal cycles. Thus, having frozen stem cells available in germplasm repositories will help to facilitate xenogenesis technology for hybrid catfish production. This study was conducted to assess the effectiveness of fresh and cryopreserved stem cells for germ cell transplantation to support xenogenesis. At 5 days post hatch (DPH), triploid channel catfish were injected with fresh or cryopreserved SSC or OSC labeled with PKH26 dye. At 45 and 90 DPH, body size (total length and weight) and survival of these recipient fish were evaluated. In addition, colonization of fresh and cryopreserved donor cells was evaluated in recipients using PKH26 dye florescence (for percentage of cell area and cluster area) and PCR from gonadal samples. No significant differences in body size characteristics were detected between the fresh and cryopreserved injection treatments at 45 and 90 DPH. Survival was significantly higher in the control treatment than the SSC and OSC injected treatments at both sampling days. Fluorescent imaging revealed that percentage of SSC cell area, SSC cluster area, OSC cell area, and OSC cluster area did not significantly differ between the fresh and cryopreserved treatments at 45 and 90 DPH. There was a significant increase in cell area and cluster area from 45 to 90 DPH for all treatments. According to PCR analyses, a high proportion of xenogens (at 45 and 90 DPH, respectively) were detected in recipient fish injected with fresh SSC (72.2 and 83.3%), cryopreserved SSC (61.1 and 66.6%), fresh OSC (66.7 and 61.1%), or cryopreserved OSC (61.1 and 61.1%). Taken together, our results show that cryopreserved donor stem cells can recover in recipient gonads and perform as well as their freshly extracted counterparts. Hence, cryopreserved stem cells can be used for future germ cell transplantation to support xenogenesis. These findings will enhance the efficiency of germ cell transplantation in xenogenesis for commercial scale hybrid catfish production.

Pathology and virulence of Edwardsiella tarda, Edwardsiella piscicida, and Edwardsiella anguillarum in channel (Ictalurus punctatus), blue (Ictalurus furcatus), and channel × blue hybrid catfish.

In the mid-2010s, Edwardsiella tarda was reaffiliated into three discrete taxa (E. anguillarum, E. piscicida, and E. tarda), obscuring previous descriptions of E. tarda-induced pathology in fish. To clarify ambiguity regarding the pathology of E. tarda, E. piscicida, and E. anguillarum infections in US farm-raised catfish, channel catfish (Ictalurus punctatus), blue catfish (I. furcatus), and channel × blue catfish hybrids were challenged with comparable doses of each bacterium. The most severe pathology and mortality occurred in fish challenged with E. piscicida, supporting previous reports of increased pathogenicity in commercially important ictalurids, while E. anguillarum and E. tarda warrant only minimal concern. Acute pathologic lesions among bacterial species were predominantly necrotizing and characteristic of gram-negative sepsis but became progressively granulomatous over time. After 100 days, survivors were exposed to the approximate median lethal doses of E. piscicida and E. ictaluri, revealing some cross-protective effects among E. piscicida, E. anguillarum, and E. ictaluri. In contrast, no fish that survived E. tarda challenge demonstrated any protection against E. piscicida or E. ictaluri. This work supports reports of increased susceptibility of channel, blue, and hybrid catfish to E. piscicida, while highlighting potential cross-protective affects among fish associated Edwardsiella spp.

Studies on the Indian catfish Clarias magur reveal Insulin‐Like Growth Factor II to be the major type and its upregulation in high‐growth performing fish

Expression of three growth-associated genes, IGF-I, IGF-II and IGF acid-labile subunit (IGFALS), was compared between highest and lowest growth performing families of Clarias magur being genetically selected for growth. Only IGF-II and IGFALS showed 3.50- and 2.10-fold differential expression, respectively, in RNASeq data of five pooled tissues, brain, liver, muscle, kidney and gonads. Relative expression profiling in brain, liver and muscle by qPCR showed 3.4-fold and 2.8-fold upregulation of IGF-II in muscle and liver, respectively, in higher performing family compared with the lower ones, while IGF-I was invariant and also the less expressed gene in all tissues. IGFALS expression was found to vary in accordance with IGF-II. Genotyping of one non-synonymous SNP (valine to isoleucine) identified in IGFALS revealed a significantly higher frequency of the isoleucine genotype in the high-performing group. Present study shows that in magur, IGF-Is significantly expressed not only in the liver but also in the muscle. Unlike other teleosts like cyprinids and cichlids where IGF-I has been reported to be the major component in the somatotropic axis, IGF-II is seen to be the major type in catfish, as also reported in Channel catfish, and is upregulated in high-growth individuals.

Transcriptome Analysis Reveals Key Gene Expression Changes in Blue Catfish Sperm in Response to Cryopreservation.

The hybrids of female channel catfish (Ictalurus punctatus) and male blue catfish (I. furcatus) account for >50% of US catfish production due to superior growth, feed conversion, and disease resistance compared to both parental species. However, these hybrids can rarely be naturally spawned. Sperm collection is a lethal procedure, and sperm samples are now cryopreserved for fertilization needs. Previous studies showed that variation in sperm quality causes variable embryo hatch rates, which is the limiting factor in hybrid catfish breeding. Biomarkers as indicators for sperm quality and reproductive success are currently lacking. To address this, we investigated expression changes caused by cryopreservation using transcriptome profiles of fresh and cryopreserved sperm. Sperm quality measurements revealed that cryopreservation significantly increased oxidative stress levels and DNA fragmentation, and reduced sperm kinematic parameters. The present RNA-seq study identified 849 upregulated genes after cryopreservation, including members of all five complexes in the mitochondrial electron transport chain, suggesting a boost in oxidative phosphorylation activities, which often lead to excessive production of reactive oxygen species (ROS) associated with cell death. Interestingly, functional enrichment analyses revealed compensatory changes in gene expression after cryopreservation to offset detrimental effects of ultra-cold storage: MnSOD was induced to control ROS production; chaperones and ubiquitin ligases were upregulated to correct misfolded proteins or direct them to degradation; negative regulators of apoptosis, amide biosynthesis, and cilium-related functions were also enriched. Our study provides insight into underlying molecular mechanisms of sperm cryoinjury and lays a foundation to further explore molecular biomarkers on cryo-survival and gamete quality.

Chromosome-level assembly and annotation of the blue catfish Ictalurus furcatus, an aquaculture species for hybrid catfish reproduction, epigenetics, and heterosis studies.

BackgroundThe blue catfish is of great value in aquaculture and recreational fisheries. The F1 hybrids of female channel catfish (Ictalurus punctatus) × male blue catfish (Ictalurusfurcatus) have been the primary driver of US catfish production in recent years because of superior growth, survival, and carcass yield. The channel–blue hybrid also provides an excellent model to investigate molecular mechanisms of environment-dependent heterosis. However, transcriptome and methylome studies suffered from low alignment rates to the channel catfish genome due to divergence, and the genome resources for blue catfish are not publicly available.ResultsThe blue catfish genome assembly is 841.86 Mbp in length with excellent continuity (8.6 Mbp contig N50, 28.2 Mbp scaffold N50) and completeness (98.6% Eukaryota and 97.0% Actinopterygii BUSCO). A total of 30,971 protein-coding genes were predicted, of which 21,781 were supported by RNA sequencing evidence. Phylogenomic analyses revealed that it diverged from channel catfish approximately 9 million years ago with 15.7 million fixed nucleotide differences. The within-species single-nucleotide polymorphism (SNP) density is 0.32% between the most aquaculturally important blue catfish strains (D&B and Rio Grande). Gene family analysis discovered significant expansion of immune-related families in the blue catfish lineage, which may contribute to disease resistance in blue catfish.ConclusionsWe reported the first high-quality, chromosome-level assembly of the blue catfish genome, which provides the necessary genomic tool kit for transcriptome and methylome analysis, SNP discovery and marker-assisted selection, gene editing and genome engineering, and reproductive enhancement of the blue catfish and hybrid catfish.

Potential vulnerability of black bullheads to multiple predators in small impoundments: implications for biological control

Overabundant species can alter a fish community and negatively influence recreationally important species. Introducing new or more predators into a system to control such nuisance fish has been met with limited success and may involve some risk. Understanding to what degree consumption of nuisance species occurs by existing predators and whether an existing predator community is physically capable of consuming the nuisance species can help to determine whether biological control may be possible without new introductions of predators. The objectives of this study were to: (1) document consumption of black bullheads Ameiurus melas by three predators; and (2) determine the relative vulnerability and potential ingestion of bullheads by these predators. We used gastric lavage monthly from May through September to collect stomach contents of channel catfish Ictalurus punctatus, largemouth bass Micropterus salmoides, and walleye Sander vitreus in four reservoirs to calculate the percent occurrence of black bullheads in predator stomachs. We also collected various sizes of juvenile black bullheads to measure body width and depth, with and without the pectoral and dorsal spines extended, respectively. This information was coupled with measured gape widths from the predators to calculate relative vulnerability curves and probabilities of ingestion based on predator size. Black bullheads were rarely consumed by the three predators, and stomach contents generally contained a single black bullhead when consumption did occur. Relative vulnerability based on body depth was similar for all three predators. Potential ingestion was similar among all three predators but was higher for channel catfish compared to the other two predators when black bullhead depths were measured with the dorsal spines extended. This study provides new information about the potential for biological control of black bullheads by an existing predator community.

MRI of the live fish brain at 3 Tesla: Feasibility, technique and interspecies anatomic variations.

Advances in aquatic animal medicine and continued growth of the fish hobbyist and aquaculture communities have led to a developing interest in antemortem diagnostic imaging of aquatic species. The aims of this prospective, pilot study were to determine whether advanced neuroimaging can be safely achieved in live fish using clinically available equipment, to optimize imaging parameters, and to develop a comparative MRI atlas of a few fish species of economic or research value. Two each of channel catfish (Ictalurus punctatus), koi (Cyprinus rubrofuscus), and grass carp (Ctenopharyngodon idella) of at least 30 cm in length were individually anesthetized for 3 Tesla (3T) magnetic resonance imaging (MRI) of the brain. All fish achieved an adequate anesthetic level for prolonged immobilization during imaging. Diagnostic quality images were obtained for all subjects; however, the spatial resolution was maximized with larger fish. Imaging protocols were optimized for standard neuroimaging sequences. Additionally, inversion times for fluid-attenuation inversion recovery (FLAIR) sequences were adapted to the naturally high protein content of fish pericerebral fluid. Following imaging, the fish successfully recovered from anesthesia, were humanely euthanized, and were immediately processed to assess brain histopathology. Necropsy confirmed the sex and health status of each fish. A limited comparative MRI atlas was created of the brains of these species for clinical reference. Findings from the current study supported the use of 3T MRI as an adjunct diagnostic test for fish with suspected neurologic disease and provided a limited anatomic atlas of the teleost brain for use as a reference.

Genome-Wide Identification, Characterisation and Phylogenetic Analysis of 52 Striped Catfish (Pangasianodon hypophthalmus) ATP-Binding Cassette (ABC) Transporter Genes.

The Pangasianodon hypophthalmus (striped or tra catfish) is a Pangasiidae family member famous for its high unsaturated fatty acid content flesh. This riverine catfish can breathe in the air unlike the channel catfish. One of the most well-known ecotoxicological protein superfamily, the ATP-binding cassette (ABC) transporters, has been characterised in channel catfish through a genome-wide approach. Therefore, it is interesting to unearth these proteins within the striped catfish genome for a comprehensive comparison across all catfishes available. A total of 52 ABC transporters were discovered from the striped catfish genome. The motif analysis has unconcealed various unshared characteristics of some catfishes. The phylogenetic analysis has evidenced its effectiveness in the successful annotations of these transporter proteins. Duplicated genes such as ABCA1, ABCB3, ABCB6, ABCC5, ABCD3, ABCE1, ABCF2 as well as ABCG2 were uncovered within the striped and channel catfish genomes. This entire set of ABC transporters yields precious genomic data for future ecotoxicological, biochemical and physiological research in striped catfish.

Ghost Fishing by Abandoned Trotlines in a Simulated and Actual Reservoir

AbstractGhost fishing is described as the continuation of fishing by abandoned fishing gear. The freshwater trotline, a passive gear that is routinely found abandoned, has never been evaluated for its ability to ghost fish. We tested the effectiveness of top‐water set trotlines to ghost fish in (1) a simulated reservoir (i.e., hatchery ponds) and (2) an actual reservoir. In our simulated reservoir, we exposed Channel Catfish Ictalurus punctatus to baited and bare (unbaited) hooks of two hook styles (circle and “J”) during the winter and summer seasons. We found that in the simulated reservoir, catch rates of baited hooks (mean = 18.4 fish per 24 hooks, standard error [SE] = 2.13) did not differ significantly from bare hooks (mean = 15.3 fish per 24 hooks, SE = 1.77), circle hooks were 1.5 times more effective at catching fish than “J” hooks (χ2 = 4.19, df = 1, P = 0.041), and fish were retained longer in the winter (mean = 12.7 d, SE = 0.66) compared to the summer (mean = 2.8 d, SE = 0.21). We used the actual reservoir portion to examine the long‐term fishability and the overall longevity of the trotline gear during the same seasons. Catch was highest during the first week and decreased with time. Trotlines caught mostly fish (81.6%), and most catch (&gt;68%) occurred after the initial bait was lost. Winter‐set trotlines captured more organisms (11.6 per 25‐hook trotline; SE = 2.05) than summer‐set trotlines (5.2; SE = 0.99). Trotline longevity was assessed by counting the fishable hooks through time. Longevity differed between seasons (P = 0.0039), and winter‐set trotlines lasted longer (50% hook loss at 52 d, 95% confidence interval [CI] = [49, 77]) than summer‐set trotlines (32 d, 95% CI = [24, 36]). This study confirms that abandoned freshwater trotlines do ghost fish and will continue for months after they are initially set.

Informative priors assess tradeoffs between mark–recapture and telemetry-based fish movement in a large river system

Telemetry and mark–recapture provide movement information, but each approach comes with tradeoffs, potentially producing conflicting understandings of fish movement patterns. Using a Bayesian framework that allows exchanging priors from either method may help assess these inconsistencies. We evaluated channel catfish Ictalurus punctatus movements in the Red River of the North and Lake Winnipeg system, which impacts harvest management across different jurisdictions and affects different ecosystems (e.g., lotic and lentic). Channel catfish were tagged with T-bar tags or acoustic transmitters. The resulting movement data were modeled using a Bayesian multi-state Cormack–Jolly–Seber model to estimate survival, movement, and recapture probabilities. Model estimates with uninformative priors showed a greater tendency of downstream movement from the Red River into Lake Winnipeg for the T-bar tags. In contrast, the telemetry method showed fish predominantly stay in the river. However, exchanging increasingly stronger prior information from the alternative method's model revealed that telemetry movement estimates were less sensitive than the T-bar model to informative priors. Using priors from both methods provided a transparent means to assessing tagging approach tradeoffs quantitatively.