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The article explores the impact of prebiotic and probiotic diets on the gut bacterial microbiota and susceptibility to Edwardsiella ictaluri challenge in oxytetracycline-treated channel catfish. The study found that oxytetracycline did not induce dysbiosis in the catfish gut microbiome, contrary to common beliefs about antibiotic effects. The research also investigated the effectiveness of prebiotics and probiotics in aiding gut microbiome recovery and enhancing survival during bacterial challenges. Further research is suggested to understand the observed lack of dysbiosis and to evaluate the effects in pond-cultured fish. [Extracted from the article]

The study in the Journal of Fish Diseases explores the impact of dietary iron fortification on channel catfish juveniles' intestinal microbiome and resistance against Edwardsiella ictaluri. Iron supplementation did not affect the intestinal microbiome but decreased the fish's resistance to the bacteria. The findings suggest that caution should be exercised when supplementing catfish diets with iron, especially during periods of increased risk for bacterial disease. Further research is needed to assess the impact of iron supplementation on larger catfish and market-sized fish. [Extracted from the article]

Salinity is an important environmental factor affecting fish growth and development. To investigate the effects of salinity stress on the growth performance, tissue structures, and expression of genes related to apoptosis and immune response in large‐sized channel catfish (Ictalurus punctatus) juveniles, an 8‐week salinity stress experiment was conducted. Six salinity levels (3, 3.8, 4.7, 5.9, 7.3, and 9 psu) were set according to an equal logarithmic concentration gradient method, along with a control group (0), and growth performance and physicochemical indices were measured. The survival rate of channel catfish in all salinity groups was 100%. Body length, body weight, weight gain rate, and specific growth rate decreased with increasing salinity, with higher salinity levels resulting in more significant reductions in growth performance. At 9 psu, both the specific growth rate (SGR) and weight gain rate (WGR) decreased significantly to 0.61%/day and 40.86%, respectively (p < 0.05). Histological analysis results indicated that with the increase in salinity, the number of intestinal mucosal folds relatively increased, while the number of goblet cells gradually decreased. Hepatocytes became more densely packed, and the hepatic lobule gaps widened. Apoptosis detection results revealed that in the liver, the number of apoptotic cells at 4.7 psu salinity was more than that in the control group and at 9 psu salinity. In the intestine, the number of apoptotic cells at 9 psu salinity was significantly higher than in the other two groups (p < 0.05). Quantitative polymerase chain reaction (qPCR) analysis of the expression patterns of genes related to apoptosis and immunity showed that the expression levels of caspase 3, caspase 8, INF‐I, IL‐1β, and bax genes in the liver and intestinal tissues were higher in the experimental groups than in the control group, while the expression of bcl‐2 decreased with increasing salinity in liver tissue but increased in intestinal tissue. These findings can provide theoretical guidance for the aquaculture of channel catfish in saline‐alkali land. [ABSTRACT FROM AUTHOR]

Previously, dietary humic substances (HSs) or protease complexes (PCs) in fingerling channel catfish Ictalurus punctatus (Rafinesque) have demonstrated potential for health enhancement. Two trials were conducted to elucidate an optimal HS or PC administration plan for growth and health promotion. The first feeding trial was conducted within a recirculating aquaculture system. Catfish fingerlings were fed a commercial control (28% protein) or supplemented diet (control + PC or HS). Diets were administered through four feeding regimens of either HS, or PC‐supplemented diet. After 60 days, continuous feeding of diets with HS or PC contributed to improved feed efficiency and weight gain of the fish. Similarly, catfish growth was enhanced following the application of HS or PC for the final 4 weeks. Serum lysozyme activity was relatively improved in catfish when a PC or HS diets were offered for 60 days. Feeding either of the supplements for the final 4 weeks improved skin lysozyme activity compared to the control group. In the second trial, catfish were fed either the commercial control diet, PC‐supplemented diet, or HS‐supplemented diet in an outdoor production environment for 60 days. Both HS and PC catfish groups had higher survival rates than the control group. Furthermore, growth performance was superior in additive‐fed groups. After HS or PC application, gut microbiota analysis from catfish fecal at two time points revealed significant variation in alpha diversity, community abundance, and beta diversity. However, the association of dietary HS or PC on improved survival, immunity, and gut microbiota modulations presents their importance as functional immunostimulants in catfish aquaculture. [ABSTRACT FROM AUTHOR]

Six 0.1‐ha earthen ponds with 45 kW/ha of aeration capacity were stocked with hybrid catfish (Ictalurus punctatus x I. furcatus) ranging from 15,000 to 90,000 fish ha−1 in 15,000 fish ha−1 increments to analyze the effect of nitrogen loading on ammonia accumulation and fish production. Minimum dissolved oxygen (DO) concentration was maintained above 3.0 mg O2 L−1 to prevent hypoxia‐induced appetite reduction. Stocking density did not impact survival but decreased average fish harvest weight and increased food conversion ratio (FCR). Gross production increased with stocking density and ranged from 7249 to 35,674 kg ha−1. Average total (TAN) and un‐ionized ammonia (NH3) were not different among stocking densities despite greater nitrogen inputs in ponds with higher feeding rates. Nitrite (NO2−) and nitrate (NO3−) concentrations were significantly higher in ponds with higher stocking densities, suggesting that nitrification increased with nitrogen loading. Phytoplankton assimilation of ammonia is the primary ammonia removal process in traditional catfish ponds with modest fish densities and feeding rates. However, in intensively aerated ponds with high feeding rates, nitrification can become an important process for ammonia removal. These data indicate that small earthen hybrid catfish ponds with high aeration capacities can increase catfish production without ammonia accumulating. [ABSTRACT FROM AUTHOR]

Weight loss during feed deprivation is correlated with feed conversion efficiency (FCR) in several fish species, suggesting weight loss could be used to indirectly select for improved feed conversion. Trials were conducted to determine relationships among weight loss and FCR with Delta Select and Delta Control line channel catfish fingerlings. Weight loss was measured for 79 Delta Select line families and 20 Delta Control line families in replicate feed deprivation trials. Weight loss was higher for Delta Controls than Delta Selects. The 10 Delta Select families with the highest weight loss, 10 Delta Select families with the lowest weight loss, and 10 random Delta Control families were used in a feeding trial. Initial weight, final weight, percent weight gain, and percent feed consumption were similar among Delta Select groups but higher than the Delta Control's. Feed conversion and survival were similar for all groups. Fish from the feeding trial were used in a third feed deprivation trial. Family means for weight loss were positively correlated across three feed deprivation trials but not correlated with feed conversion indicating selection for weight‐loss would not improve feed conversion. The faster growth of Delta Select catfish is as a result of increased feed consumption. [ABSTRACT FROM AUTHOR]

Background: Snakehead vesiculovirus (SHVV) has led to huge economic losses in snakehead aquaculture, and its pathogenic mechanisms is still not fully understood. MicroRNAs (miRNAs), as an important class of non-coding RNAs, play a key regulatory role in the process of viral infection. Methods: We examined the effect of SHVV infection on the expression of miR-130c-5p and the effect of overexpression of miR-130c-5p on the proliferation of SHVV. Cotransfection of viral N protein and miR-130c-5p, and the effect of miR-130c-5p on the expression of N protein was detected. Meanwhile, the effect of overexpression of miR-130c-5p on the expression of various immune factors in the case of viral infection were also tested. Results: In this study, SHVV infection significantly upregulated the expression of miR-130c-5p in channel catfish ovary (CCO) cells in a time- and dose-dependent manner. The further research revealed that miR-130c-5p mimic significantly inhibited, while its inhibitors promoted SHVV replication. In addition, miR-130c-5p could directly target the viral mRNA of n gene, and overexpression of miR-130c-5p could significantly decrease, and conversely, downregulation of miR-130c-5p could increase the mRNA and protein expression of the viral n gene. Meanwhile, overexpression of miR-130c-5p also upregulated the expression of immune-related genes, such as nucleotide-oligomerization domain (NOD)-like receptor subfamily C3 (NLRC3), myeloid differentiation factor 88 (MyD88), nuclear factor kappa-B (NF-κB), interleukin-6 (IL-6), interleukin-22 (IL-22), and interleukin-1beta (IL-1β) in host cells. Conclusion: miR-130c-5p was upregulated in the host during SHVV infection, and the upregulated miR-130c-5p directly inhibited viral replication by targeting the n gene of SHVV and promoting viral nucleoprotein degradation. The up-regulated miR-130c-5p also activated the expression of immune-related genes such as NLRC3, MyD88, NF-κB, IL-6, IL-22, and IL-1β, which were involved in the regulation of the signaling pathways including NF-κB, MyD88, Toll-like receptor (TLR), NLR, and janus tyrosine kinase-signal converter and activator of transcription (JAK-STAT), to enhance the host's antiviral immune response, and thus indirectly inhibited the viral proliferation. [ABSTRACT FROM AUTHOR]

Positive interactions such as mutualism and facilitation between invasive species can magnify their impact on invaded ecosystems. Yet, few studies have explicitly evaluated symbioses between invasive species that span the terrestrial–aquatic interface. We conducted two experiments to investigate the fitness outcomes (growth and germination) of frugivory and ichthyochory involving invasive channel catfish (Ictalurus punctatus) that consume fruits and pass seeds of invasive Russian olive (Elaeagnus angustifolia). Our results indicate that catfish frugivory of olive fruit provides an energy source that allows the catfish to maintain body mass and seeds passed by catfish were four times more likely to germinate than untreated seeds, suggesting catfish are viable olive seed dispersers. As such, we concluded that the interaction of frugivory of invasive olive fruits by invasive catfish and ichthyochory resulting from passed olive seeds constitute a facultative mutualism spanning the aquatic–terrestrial interface. The impact of the olive–catfish mutualism on the abundance, persistence and spread of both invasive species requires further study. Researchers and managers should consider the potential of positive interactions across ecotones to facilitate invasions [ABSTRACT FROM AUTHOR]

Channel catfish (Ictalurus punctatus) and Nile tilapia (Oreochromis niloticus) are two aquaculture species of great importance. Intensive production is often hindered by poor growth performance and disease mortality. The aim of this study was to evaluate the potential of a commercial fermented yeast product, DVAQUA, on channel catfish and Nile tilapia growth performance metrics and disease resistance. Channel catfish and Nile tilapia were fed practical diets supplemented with 0%, 0.1% or 0.4% of DVAQUA over approximately 2‐month feeding periods in recirculation aquaculture systems. To assess the potential of the postbiotic against common aquaculture pathogens, juvenile catfish were subsequently challenged by immersion with Edwardsiella ictaluri S97‐773 or virulent Aeromonas hydrophila ML09‐119. Nile tilapia juveniles were challenged by injection with Streptococcus iniae ARS‐98‐60. Serum lysozyme activity, blood chemistry and growth metrics were measured at the end of the feeding period, but no differences were observed across the different metrics, except for survival. For the pathogen challenges, there were no differences in endpoint mortality for channel catfish with either pathogen (p >.05). In contrast, Nile tilapia survivability to S. iniae infection increased proportionally to the inclusion of DVAQUA (p =.005). Changes to sera lysozyme activity were also noted in the tilapia trial, with a reduction of activity in the fish fed the 0.4% DVAQUA diet compared to the control diet (p =.031). Expression profiles of proinflammatory genes and antibodies were also found to be modulated in channel catfish fed the postbiotic, indicating some degree of protective response. These results suggest that this postbiotic may be beneficial in protecting Nile tilapia against S. iniae infection by influencing immune parameters and additional research is needed to evaluate the potential of this DVAQUA for improving catfish health and disease control. [ABSTRACT FROM AUTHOR]

Ictalurid herpesvirus 1 (IcHV1) is the most significant viral agent in U.S. catfish aquaculture. Little is known regarding the genetic stability and antigenic variability of IcHV1. Herein, the genetic and antigenic diversity of IcHV1 field isolates was assessed by restriction fragment length polymorphism (RFLP) analysis and serum neutralization assays. RFLP analysis identified two distinct genotypes (IcHV1A and IcHV1B), both discrete from blue catfish alloherpesvirus (BCAHV). Neutralization assays with anti‐IcHV1 monoclonal antibody Mab‐95 indicate shared antigenic determinants for IcHV1A and IcHV1B that are absent from BCAHV, which Mab‐95 did not neutralize. Virulence assessments with representative isolates demonstrate significant differences between isolates within RFLP groups and pooled RFLP group data suggest IcHV1B (pooled survival [mean ± SE]: 58.3% ± 2.6) may be more virulent than IcHV1A (survival: 68.6% ± 2.4). Rechallenges with representative IcHV1A and IcHV1B isolates indicate a cross‐protective effect, with fish surviving initial exposure to IcHV1A or IcHV1B showing robust protection when subsequently re‐exposed to IcHV1A or IcHV1B. This work demonstrated significant differences in virulence between case isolates, identifying two discrete IcHV1 lineages, distinct from BCAHV, with similar virulence in channel and channel × blue catfish hybrids and a cross‐protective effect in catfish surviving exposure to either lineage. [ABSTRACT FROM AUTHOR]

As a notable commercial aquaculture species, channel catfish (Ictalurus punctatus) in US faces challenges including the global market competition and enhanced feed costs. Since fish bone waste is a major source of calcium and hydroxyapatite, re-utilization gives birth to several advanced products in the development of animal feed, fertilizers, and nutrition supplements. Recent research findings introduce fish bone powder (FBP) reinforcement in Fused Deposition Modeling (FDM) of plastic composites. However, FBP so far has not been widely utilized for Direct Ink Writing (DIW) 3D printing of silicone composite. In this paper, catfish bone waste has been recycled and processed with a thermal procedure. FBP reinforced silicone composite structures have been developed and manufactured using low-viscosity DIW 3D printing. Morphological and chemical structures of FBPs were analyzed and compared before and after calcination. The rheological and mechanical characterization have indicated the potential of calcinated FBP in advancing the silicone composites. With 0%–50% weight percentages of FBP, composite samples can be designed to get any specified mechanical response (0.5–1.4 MPa in 50% tension strain and 150–550 N in 30% compression strain). The shape holding, overhang, and dimensional accuracy of FBP reinforced silicone composites in single (DIW) and dual (FDM + DIW) 3D printing processes have been demonstrated and summarized. With appropriate adjustments, this FBP-based 3D printing technology can be applied to byproduct recycling of all the US food-fish species, poultry, and livestock. [ABSTRACT FROM AUTHOR]

Proliferative gill disease (PGD), caused by the myxozoan Henneguya ictaluri, has been the most notorious parasitic gill disease in the US catfish aquaculture industry. In 2019, an unusual gill disease caused by massive burdens of another myxozoan, Henneguya exilis, was described in channel (Ictalurus punctatus) × blue (Ictalurus furcatus) hybrid catfish. Targeted metagenomic sequencing and in situ hybridization (ISH) were used to differentiate these conditions by comparing myxozoan communities involved in lesion development and disease pathogenesis between massive H. exilis infections and PGD cases. Thirty ethanol-fixed gill holobranchs from 7 cases of massive H. exilis infection in hybrid catfish were subjected to targeted amplicon sequencing of the 18S rRNA gene and compared to a targeted metagenomic data set previously generated from clinical PGD case submissions. Furthermore, serial sections of 14 formalin-fixed gill holobranchs (2 per case) were analyzed by RNAscope duplex chromogenic ISH assays targeting 8 different myxozoan species. Targeted metagenomic and ISH data were concordant, indicating myxozoan community compositions significantly differ between PGD and massive branchial henneguyosis. Although PGD cases often consist of mixed species infections, massive branchial henneguyosis consisted of nearly pure H. exilis infections. Still, H. ictaluri was identified by ISH in association with infrequent PGD lesions, suggesting coinfections occur, and some cases of massive branchial henneguyosis may contain concurrent PGD lesions contributing to morbidity. These findings establish a case definition for a putative emerging, myxozoan-induced gill disease of farm-raised catfish with a proposed condition name of massive branchial henneguyosis of catfish (MBHC). [ABSTRACT FROM AUTHOR]

ABSTRACT 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. [ABSTRACT FROM AUTHOR]

This study looked at the prevalence, abundance, and mean intensity of the parasite Ligictaluridus floridanus (Monogenoidea: Dactylogyridae) in channel catfish (Ictalurus punctatus), hybrid catfish (I. punctatus x I. furcatus), and the striped catfish (Pangasianodon hypophthalmus), an exotic, nonlocal species. The channel catfish was the most susceptible to L. floridanus infection, followed by the hybrid catfish with a 100 % prevalence. The striped catfish was the least susceptible, and although the parasite was detected once, this species does not seem susceptible to long-term infection. [ABSTRACT FROM AUTHOR]

The aim of the present study was to evaluate propofol as an anesthetic and its effects on physiology and histology in Ictalurus punctatus. To determine the ideal concentration, juvenile of I. punctatus (96.60 ± 27.70 g) were used, submitted to different concentrations of the anesthetic: 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, and 6.0 mg L−1. The concentration evaluated as ideal was 2.5 mg L−1. To evaluate the physiological and histological effects of propofol exposure, juvenile of I. punctatus (99.71 ± 26.38 g) were sampled immediately (T0) and 30 min after anesthesia (T30) with 2.5 mg L−1, had blood, liver, and gill samples collected. The exposure of the animals to propofol in both treatments (T0 and T30) caused increases in plasma glucose and lactate levels (p < 0.05) but prevented an increase in cortisol (p > 0.05). The histological study showed mild to moderate changes in the gills (congestion in the lamellar vessels and central vein and epithelial elevation) and moderate and severe changes in the liver (congestion and degeneration). This study concludes that the concentration of 2.5 mg L−1 of propofol provides safe anesthesia for I. punctatus and prevents increased plasma cortisol levels. [ABSTRACT FROM AUTHOR]

Objective: In West Alabama, catfish Ictalurus spp. producers routinely face the challenge of fish that exceed market size (aka "Big Fish") in their commercial ponds. These fish are skilled at evading seine nets during harvest and can increase in size significantly before subsequent harvests occur. This is problematic for catfish producers because processing plants prefer catfish within the 0.45–1.81‐kg range and farmers are paid a premium price for catfish of this size. Due to their larger size and growth potential, hybrid catfish (female Channel Catfish Ictalurus punctatus × male Blue Catfish I. furcatus) can become a more significant issue than Channel Catfish if they evade harvest. The objective of this study was to describe and quantify the age structure and growth rate of hybrid catfish that evade capture and remain in commercial ponds following harvest and grow beyond acceptable market size as defined by catfish processing plants (i.e., Big Fish). Methods: Hybrid catfish were collected from 12 recently harvested commercial ponds in West Alabama from December 2021 to August 2022 using an electroshocking boat. Total length (mm), body weight (kg), and sex of collected fish were recorded, and lapilli otoliths were removed to estimate fish age and determine total length and total body weight at estimated ages. Result: In this study, 1005 hybrid catfish were collected with the successful age estimation for 1001 catfish, ranging from 1 to 11 years. Results of this study indicate that hybrid catfish exceeded the premium size threshold in 2.72 years ± 8 months. Additionally, from age 2 to age 3, the average hybrid catfish gained 2.90 kg, growing from 0.40 to 3.30 kg. Growth rate was significantly affected by sex; males overall were predicted to weigh more than females based on the weight‐at‐age model. Conclusion: Hybrid catfish should be completely harvested from commercial ponds following 1 year of harvest to receive the premium price per kilogram of live fish. If a complete harvest is unsuccessful, farmers can receive a discounted price per kilogram of leftover hybrid catfish based on current market trends. Impact StatementCollecting age and growth statistics on leftover hybrid catfish allowed researchers to estimate at what age these catfish should be harvested based on the premium size category set by catfish processing plants. Researchers were also able to estimate hybrid catfish growth and that the average hybrid catfish will exceed the premium size category by age 3 and grow into a "Big Fish" by age 4. [ABSTRACT FROM AUTHOR]

The Delta Select channel catfish strain (DS) was developed by selection for increased growth and carcass yield. Progeny from DS and the Delta Control (DC) strain (a randomly bred strain from the same base population as DS) were compared in three trials. Trial 1: unvaccinated ~1‐year‐old fingerlings from each strain reared communally in 0.4‐ha ponds. Trial 2: vaccinated ~ 1‐year‐old fingerlings from each strain grown in separate replicated 0.4‐ha ponds and fish in about half the ponds were given an ESC vaccine‐booster at 13 months post‐hatch. Trial 3: same procedures as Trial 2, except fish were raised in replicate 0.04‐ha ponds with no vaccine‐booster. In Trial 1 DS were larger at stocking, larger at harvest, and had higher carcass yield than DC; in Trial 2 DS were larger at harvest, had better survival and higher production/ha than DC. Vaccine‐booster had no effect on fish growth or survival. DS and DC were not different for any traits in Trial 3. Although outcome varied among trials, the overall results indicated a vaccine booster did not affect growth or survival, DS strain fingerlings grew faster than DC fingerling, and DS had higher carcass yield than DC strain fish when reared communally. [ABSTRACT FROM AUTHOR]

The catfish industry is the largest sector of U.S. aquaculture production. Given its role in food production, the catfish immune response to industry-relevant pathogens has been extensively studied and has provided crucial information on innate and adaptive immune function during disease progression. To further examine the channel catfish immune system, we performed single-cell RNA sequencing on nuclei isolated from whole spleens, a major lymphoid organ in teleost fish. Libraries were prepared using the 10X Genomics Chromium X with the Next GEM Single Cell 3' reagents and sequenced on an Illumina sequencer. Each demultiplexed sample was aligned to the Coco_2.0 channel catfish reference assembly, filtered, and counted to generate feature-barcode matrices. From whole spleen samples, outputs were analyzed both individually and as an integrated dataset. The three splenic transcriptome libraries generated an average of 278,717,872 reads from a mean 8,157 cells. The integrated data included 19,613 cells, counts for 20,121 genes, with a median 665 genes/cell. Cluster analysis of all cells identified 17 clusters which were classified as erythroid, hematopoietic stem cells, B cells, T cells, myeloid cells, and endothelial cells. Subcluster analysis was carried out on the immune cell populations. Here, distinct subclusters such as immature B cells, mature B cells, plasma cells, γδ T cells, dendritic cells, and macrophages were further identified. Differential gene expression analyses allowed for the identification of the most highly expressed genes for each cluster and subcluster. This dataset is a rich cellular gene expression resource for investigation of the channel catfish and teleost splenic immunome. [ABSTRACT FROM AUTHOR]

Ferritin, transferrin, and transferrin receptors I and II play a vital role in iron metabolism, health, and indication of iron deficiency anaemia in fish. To evaluate the use of high‐iron diets to prevent or reverse channel catfish (Ictalurus punctatus) anaemia of unknown causes, we investigated the expression of these iron‐regulatory genes and proteins in channel catfish fed plant‐based diets. Catfish fingerlings were fed five diets supplemented with 0 (basal), 125, and 250 mg/kg of either inorganic iron or organic iron for 2 weeks. Ferritin, transferrin, and transferrin receptor I and II mRNA and protein expression levels in fish tissues (liver, intestine, trunk kidney, and head kidney) and plasma were determined. Transferrin (iron transporter) and TfR (I and II) genes were generally highly expressed in fish fed the basal diet compared to those fed the iron‐supplemented diets. In contrast, ferritin (iron storage) genes were more expressed in the trunk kidney of fish fed the iron‐supplemented diets than in those fed the basal diet. Our results demonstrate that supplementing channel catfish plant‐based diets with iron from either organic or inorganic iron sources affected the expression of the iron‐regulatory genes and increased body iron status in the fish. [ABSTRACT FROM AUTHOR]

Commercial culture of channel catfish (Ictalurus punctatus) occurs in earthen ponds that are characterized by diel swings in dissolved oxygen concentration that can fall to severe levels of hypoxia, which can suppress appetite and lead to suboptimal growth. Given the significance of the hypothalamus in regulating these processes in other fishes, an investigation into the hypothalamus transcriptome was conducted to identify specific genes and expression patterns responding to hypoxia. Channel catfish in normoxic water were compared with catfish subjected to 12 h of hypoxia (20% oxygen saturation; 1.8 mg O2/L; 27°C) followed by 12 h of recovery in normoxia to mimic 24 h in a catfish aquaculture pond. Fish were sampled at 0-, 6-, 12-, 18-, and 24-h timepoints, with the 6- and 12-h samplings occurring during hypoxia. A total of 190 genes were differentially expressed during the experiment, with most occurring during hypoxia and returning to baseline values within 6 h of normoxia. Differentially expressed genes were sorted by function into Gene Ontology biological processes and revealed that most were categorized as "response to hypoxia," "sprouting angiogenesis," and "cellular response to xenobiotic stimulus." The patterns of gene expression reported here suggest that transcriptome responses to hypoxia are broad and quickly reversibly with the onset of normoxia. Although no genes commonly reported to modulate appetite were found to be differentially expressed in this experiment, several candidates were identified for future studies investigating the interplay between hypoxia and appetite in channel catfish, including adm, igfbp1a, igfbp7, and stc2b. NEW & NOTEWORTHY: Channel catfish are an economically important species that experience diel episodic periods of hypoxia that can reduce appetite. This is the first study to investigate their transcriptome from the hypothalamus in a simulated 24-h span in a commercial catfish pond, with 12 h of hypoxia and 12 h of normoxia. The research revealed functional groups of genes relating to hypoxia, angiogenesis, and glycolysis as well as individual target genes possibly involved in appetite regulation. Listen to this article's corresponding podcast at https://apspublicationspodcast.podbean.com/e/channel-catfish-transcriptomic-response-to-hypoxia/. [ABSTRACT FROM AUTHOR]

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Abstract Weight loss during feed deprivation is correlated with feed conversion efficiency (FCR) in several fish species, suggesting weight loss could be used to indirectly select for improved feed conversion. Trials were conducted to determine relationships among weight loss and FCR with Delta Select and Delta Control line channel catfish fingerlings. Weight loss was measured for 79 Delta Select line families and 20 Delta Control line families in replicate feed deprivation trials. Weight loss was higher for Delta Controls than Delta Selects. The 10 Delta Select families with the highest weight loss, 10 Delta Select families with the lowest weight loss, and 10 random Delta Control families were used in a feeding trial. Initial weight, final weight, percent weight gain, and percent feed consumption were similar among Delta Select groups but higher than the Delta Control's. Feed conversion and survival were similar for all groups. Fish from the feeding trial were used in a third feed deprivation trial. Family means for weight loss were positively correlated across three feed deprivation trials but not correlated with feed conversion indicating selection for weight‐loss would not improve feed conversion. The faster growth of Delta Select catfish is as a result of increased feed consumption.

This experiment was aimed to screen the key factors regulating pigment cells and elucidate the potential mechanism of yellowing body color in the channel catfish. Three-channel catfish with all-black body color (NS group) and three channel catfish with yellow body color (YS group) were taken for transcript sequencing analysis using Illumina sequencing technology. The results showed that a total of 2368 significant differentially expressed genes (DEGs) were screened. Compared with the transcription expression genes in the NS group, there were 1003 up-regulated genes and 1365 down-regulated genes in the YS group. Seven DEGs related to pigment regulation were selected for qRT-PCR analysis, and the results confirmed that the transcriptome analysis was reliable. Furthermore, the DEGs were subjected to Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis, and the results showed that most of the DEGs were involved in immune response, endocytosis, cell adhesion molecules, etc. Furthermore, analysis of Melanogenesis and Wnt signaling pathways and other pathways with links to pigment regulation obtained by KEGG enrichment revealed that genes that promote melanogenesis, such as etb, plc, and camk2 were significantly down-regulated. Nevertheless, genes that inhibit melanogenesis (nf-κb, tnf-α, ifn) and genes that promote yellow pigmentation (xdh) were significantly up-regulated. In summary, it is hypothesized that oxidative stress is an important factor contributing to the yellowing of the body color of channel catfish, thus causing the expression of genes related to melanogenesis (etb, plc, camk2), yellow pigmentation (xdh), and immune-antioxidant responses (nf-κb, tnf-α, ifn).

High-carbohydrate diet (HCD) usually leads to metabolic disorders and damages liver health in aquatic animals. Curcumin has been shown to improve antioxidant, hypoglycemic, and hypolipidemic effects. However, whether curcumin helps to ameliorate HCD-induced liver damage in fish remains unknown. Here, we formulated four diets: normal-carbohydrate diet (CON), high-starch diets (HSD), 0.02 % and 0.04 % curcumin added to HSD (HSC0.02 % and HSC0.04 %) to investigate the effects of curcumin on the liver health of channel catfish (Ictalurus punctatus). The results showed that HSC0.02 % or HSC0.04 % treatments had no effect on growth performance and HSC0.02 % treatment showed the best hypoglycemic and hypolipidemic effects compared to the HSD group. Dietary curcumin activated Keap1/Nrf2 to increase hepatic antioxidant capacity (T-AOC, SOD and GSH-PX) and inhibit apoptosis pathway (Bax, Bcl2, Caspase 3 and Caspase 9) (P

The North American monsoon season in the southwestern United States can produce heavy precipitation that results in high-flow events. Fish kills can occur when these monsoonal freshets derive from runoff flowing over recently burned catchments, but less is known concerning monsoon-induced fish kills occurring in unburned riverscapes. Here we report on a fish kill unrelated to wildfire that occurred following a monsoonal spate in the San Juan River, Navajo Nation, Utah, USA, that was observed in July 2021. During this event, discharge increased from 18.75 m³/s (662 ft³/s) to 171 m³/s (6040 ft³/s) between 20:30 and 22:30 on 24 July. At the peak of the high flow, numerous fish sought refuge in the low-velocity waters amid the flooded vegetation on an island where we were camped. Many of these fish were lethargic and gulping for air, although some were active and appeared to be surface-feeding. By the morning of 25 July, waters had receded, leaving behind numerous dead fish. We inventoried all the dead large-bodied (i.e., total length ≥ 100 mm) fish we could find along a 72-m search path on the eastern side of the island, where we located 14 Channel Catfish (Ictalurus punctatus), 5 Bluehead Suckers (Pantosteus discobolus'), 4 Colorado Pikeminnow (Ptychocheilus lucius), 3 Flannelmouth Suckers (Catostomus latipinnis), and 1 Razorback Sucker (Xyrauchen texanus). We also observed dead small-bodied (i.e., total length < 100 mm) fish and aquatic macroinvertebrates on the island that were too numerous to count, including Channel Catfish, Fathead Minnow (Pimephales promelas), Red Shiners (Cyprinella lutrensis), Speckled Dace (Rhinichthys osculus), Virile Crayfish (Faxonius virilis), and hellgrammites (Corydalidae). We dissected stomachs from the dead Colorado Pikeminnow and Channel Catfish and found that all Colorado Pikeminnow stomachs were empty, while Virile Crayfish (50% of individuals), amorphous detritus (33%), and Speckled Dace (25%) were the most common diet categories found in Channel Catfish. Lastly, this event resulted in notable downstream movement of Flannelmouth Suckers as revealed from passive integrated transponder and radio-tagging data, with some fish moving downstream as much as 186 river km in only 3 days following the flow pulse. Although we do not know the cause of the fish kill, we suspect that either runoff of anthropogenic chemical pollutants or a hypoxic blackwater event was responsible. Identifying the cause, frequency, and extent of monsoon fish kills in the San Juan River has important conservation implications since these events result in the mortality of imperiled fishes. [ABSTRACT FROM AUTHOR]

Objective: Catch‐and‐release angling is an oft‐practiced conservation tool involving the release of captured game fish either due to harvest regulations or conservation ethic on the part of the angler. Central to this practice is the assumption that released fish survive; however, a large body of work has shown that postrelease mortality can occur, especially if fish are injured during the capture process. In this study, we examined hooking location, bleeding, injury rates, and postcapture physiology in Channel Catfish Ictalurus punctatus, a popular game fish species. Methods: A total of 83 Channel Catfish were angled from a lake in southern Illinois using conventional rod‐and‐reel techniques with one of four hook types (J‐hook, shiner, circle, and octopus). Captured fish were then assessed for hooking depth, bleeding, and injury. Subsequently, a subset of 40 fish were additionally held for 4 h in submerged totes before being tested for reflex responsiveness and undergoing a blood biopsy for glucose and lactate levels. Result: Circle and octopus hooks reduced hooking depth in Channel Catfish compared with J‐hooks and tended to reduce postcapture bleeding as well. Postholding physiological results showed no effect of hook type on blood lactate or glucose levels, and reflex impairment was very rare (only a single fish was impaired for any reflexes 4 h postcapture). Conclusion: Overall, the results of this study suggest that the use of circle hooks reduce the likelihood of deep hooking and injury in Channel Catfish, though Channel Catfish, at least in the short term, were physiologically resilient to the effects of capture. Impact statementUse of circle hooks rather than J‐hooks is an effective method to reduce hooking depth and injury in Channel Catfish. [ABSTRACT FROM AUTHOR]

Objective: The Delta Select line of Channel Catfish Ictalurus punctatus was established in 2006 and has undergone five generations of genetic selection, specifically targeting increased growth rate and carcass yield, and was released to U.S. catfish farmers in 2020. While improvements in growth rate and carcass yield have been confirmed, performance for other important production traits has yet to be evaluated. Infectious disease, particularly bacterial infections caused by Edwardsiella spp., cause significant economic losses to catfish producers in the southeastern United States. Given the economic consequences of these bacterial pathogens, experimental infectivity trials were conducted comparing susceptibility to Edwardsiella spp. between the Delta Select line and a randomly bred line of Channel Catfish originating from the same base population (Delta Control line). Methods: Twenty‐six full‐sib families from each line were used in infectivity trials consisting of a high and a low dose of E. ictaluri (immersion challenge: high dose = 1.6 × 107 CFU/mL, low dose = 8.0 × 106 CFU/mL) and E. piscicida (intracoelomic challenge: high dose = 6.3 × 105 CFU/fish, low dose = 1.9 × 105 CFU/fish). Result: The high challenge dose resulted in the highest mortality for both pathogens (p < 0.001), regardless of selection line. There was no significant difference in cumulative percent mortality between the Delta Select and Delta Control lines following the E. ictaluri challenge at either dose (p = 0.55). Delta Selects had reduced mortality (p < 0.001) in response to E. piscicida challenge compared with the Delta Controls, regardless of dose. Conclusion: These results indicate that selection for increased growth rate and carcass yield in the Delta Select Channel Catfish line did not negatively impact resistance to E. ictaluri while potentially improving resistance to E. piscicida. Impact statementSelection for increased growth and carcass yield in the Delta Select line of Channel Catfish has not impacted susceptibility to Edwardsiella ictaluri and appears to have reduced susceptibility to Edwardsiella piscicida. [ABSTRACT FROM AUTHOR]

Over the course of an approximately 11-month period, an outdoor, freshwater, mixed species, recirculating, display system at a public aquarium experienced intermittent mortalities of channel catfish (Ictalurus punctatus) and blue catfish (I. furcatus). Catfish acutely presented for abnormal buoyancy, coelomic distention, and protein-rich coelomic effusion. Gross lesions typically involved massive coelomic distension with protein-rich effusion, generalized edema, and gastric hemorrhage and edema. Microscopically, primary lesions included renal tubular necrosis, gastric edema with mucosal hemorrhages, and generalized edema. Aerobic culture and virus isolation could not recover a consistent infectious agent. Intracoelomic injection of coelomic effusion and aspirated retrobulbar fluid from a catfish into naïve zebrafish (bioassay) produced peracute mortality in 3 of 4 fish and nervous signs in the fourth compared with 2 saline-injected control zebrafish that had - no mortality or clinical signs. Kidney tissue and coelomic effusion were submitted for gas chromatography tandem mass spectrometry by multiple reaction monitoring against laboratory standards, which detected the presence of multiple pyrethroid toxins, including bioallethrin, bifenthrin, trans-permethrin, phenothrin, and deltamethrin. Detection of multiple pyrethroids presumably reflects multiple exposures with several products. As such, the contributions of each pyrethroid toward clinical presentation, lesion development, and disease pathogenesis cannot be determined, but they are suspected to have collectively resulted in disrupted osmoregulation and fluid overload due to renal injury. Pesticide-induced toxicoses involving aquarium fish are rarely reported with this being the first description of pyrethroid-induced lesions and mortality in public aquarium-held fish. [ABSTRACT FROM AUTHOR]

Xenogenesis has been recognized as a prospective method for producing channel catfish, Ictalurus punctatus ♀ × blue catfish, I. furcatus ♂ hybrids. The xenogenesis procedure can be achieved by transplanting undifferentiated stem cells derived from a donor fish into a sterile recipient. Xenogenesis for hybrid catfish embryo production has been accomplished using triploid channel catfish as a surrogate. However, having a surrogate species with a shorter maturation period, like white catfish (Ameiurus catus), would result in reduced feed costs, labor costs, and smaller body size requirements, making it a more suitable species for commercial applications where space is limited, and as a model species. Hence, the present study was conducted to assess the effectiveness of triploid white catfish as a surrogate species to transplant blue catfish stem cells (BSCs) and channel catfish stem cells (CSCs). Triploid white catfish fry were injected with either BSCs or CSCs labeled with PKH 26 fluorescence dye from 0 to 12 days post hatch (DPH). No significant differences in weight and length of fry were detected among BSCs and CSCs injection times (0 to 12 DPH) when fry were sampled at 45 and 90 DPH (P > 0.05). The highest survival was reported when fry were injected between 4.0 to 5.5 DPH (≥ 81.2%). At 45 and 90 DPH, cell and cluster area increased for recipients injected from 0 to 5.2 DPH, and the highest cluster area values were reported between 4.0 to 5.2 DPH. Thereafter, fluorescent cell and cluster area in the host declined with no further decrease after 10 DPH. At 45 DPH, the highest percentage of xenogens were detected when fry were injected with BSCs between 4.0 to 5.0 and CSCs between 3.0 to 5.0 DPH. At 90 DPH, the highest number of xenogens were detected from 4.0 to 6.0 DPH when injected with either BSCs or CSCs. The current study demonstrated the suitability of white catfish as a surrogate species when BSCs and CSCs were transplanted into triploid white catfish between 4.0 to 6.0 DPH (27.4 ± 0.4°C). Overall, these findings allow enhanced efficiency of commercializing xenogenic catfish carrying gametes of either blue catfish or channel catfish. [ABSTRACT FROM AUTHOR]

Channel catfish (Ictalurus punctatus) are a food fish extensively reared in aquaculture facilities throughout the world and are also among the most abundant wild catfish species in North America, making them a popular target of anglers. Furthermore, channel catfish are important members of aquatic ecosystems; for example, they serve as a glochidial host for the endangered winged mapleleaf mussel (Quadrula fragosa), making them critical for conserving this species through hatchery‐based restoration efforts. During a routine health inspection, a novel aquareovirus was isolated from channel catfish used in mussel propagation efforts at a fish hatchery in Wisconsin. This virus was isolated on brown bullhead cells (ATCC CCL‐59) and identified through metagenomic sequencing as a novel member of the family Spinareoviridae, genus Aquareovirus. The virus genome consists of 11 segments, as is typical of the aquareoviruses, with phylogenetic relationships based on RNA‐dependent RNA polymerase and major outer capsid protein amino acid sequences showing it to be most closely related to golden shiner virus (aquareovirus C) and aquareovirus C/American grass carp reovirus (aquareovirus G) respectively. The potential of the new virus, which we name genictpun virus 1 (GNIPV‐1), to cause disease in channel catfish or other species remains unknown. [ABSTRACT FROM AUTHOR]

Objective: Age estimation methods have not been validated for many species. Thus, we focused this age estimation study on four species from central Texas: the Guadalupe Bass Micropterus treculii, Channel Catfish Ictalurus punctatus, Gray Redhorse Moxostoma congestum, and Redbreast Sunfish Lepomis auritus. Our objectives for each species were to (1) investigate whether increments form annually in otoliths, fin rays, or spines; (2) determine the seasonal timing of zone deposition in each calcified structure; and (3) compare age estimates between otoliths and fin rays or spines. Methods: Fish were sampled from central Texas waters and injected with oxytetracycline (OTC) quarterly in 2021. In July 2022, otoliths and fin rays or spines were collected to determine whether the increments formed annually and to estimate age. Result: On average, two readers identified the correct number of annuli after the OTC mark in at least 95% of Gray Redhorse, Guadalupe Bass, and Redbreast Sunfish otoliths but in only 69% of Channel Catfish otoliths. However, the more experienced reader identified the correct number of annuli in at least 95% of otoliths from age‐2–4 Channel Catfish. Compared to otoliths, the correct number of annuli after the OTC mark was identified in a smaller percentage of fin rays or spines (47–62%). The probability of identifying the correct number of annuli after the OTC mark differed between the two readers for all spines and fin rays. Age difference plots revealed that age estimates based on fin rays or spines were either overestimated or underestimated compared to otolith‐based ages for all species. Conclusion: We consider annual increment formation in otoliths to be validated for all age‐classes of Gray Redhorse, Guadalupe Bass, and Redbreast Sunfish examined and for ages 2–4 of Channel Catfish. Differences in correctness between readers were most likely due to differences in age estimation experience. Given the level of error observed in our study, caution is advised if using age estimates from unvalidated structures and species. Impact statementWe validated annual increment formation in otoliths from Guadalupe Bass, Gray Redhorse, and Redbreast Sunfish but not in otoliths from Channel Catfish. Annual increment formation was not validated for fin rays or spines from any species examined. [ABSTRACT FROM AUTHOR]

Starch is a common source of carbohydrates in aqua feed. High-starch diet can cause hepatic injury and lipid accumulation in fish. Mangiferin (MGF) can regulate lipid metabolism and protect the liver, but there is limited research on its effects in fish. In the present study, we investigated whether MGF could ameliorate high-starch-induced hepatic damage and lipid accumulation in channel catfish. The channel catfish (Ictalurus punctatus) were fed one of four experimental diets for eight weeks: a control diet (NCD), a high-starch diet (HCD), an HCD supplemented with 100 mg/kg MGF (100 MGF), and an HCD supplemented with 500 mg/kg MGF (500 MGF). The results demonstrated that the weight gain rate (WGR) (p = 0.031), specific growth rate (SGR) (p = 0.039), and feed conversion efficiency (FCE) (p = 0.040) of the 500 MGF group were significantly higher than those of the NCD group. MGF supplementation alleviated liver damage and improved antioxidant capacity (T-AOC) compared to those of the HCD group (p = 0.000). In addition, dietary MGF significantly reduced plasma glucose (GLU) (p = 0.000), triglyceride (TG) (p= 0.001), and low-density lipoprotein cholesterol (LDL) (p = 0.000) levels. It is noteworthy that MGF significantly reduced the plasma total cholesterol (TC) levels (p = 0.000) and liver TC levels (p = 0.005) of channel catfish. Dietary MGF improves cholesterol homeostasis by decreasing the expression of genes that are involved in cholesterol synthesis and transport (hmgcr, sqle, srebf2, sp1, and ldlr) and increasing the expression of genes that are involved in cholesterol catabolism (cyp7a1). Among them, the largest fold decrease in squalene epoxidase (sqle) expression levels was observed in the 100 MGF or 500 MGF groups compared with the HCD group, with a significant decrease of 3.64-fold or 2.20-fold (p = 0.008). And the 100 MGF or 500 MGF group had significantly decreased (by 1.67-fold or 1.94-fold) Sqle protein levels compared to those of the HCD group (p = 0.000). In primary channel catfish hepatocytes, MGF significantly down-regulated the expression of sqle (p = 0.030) and reduced cholesterol levels (p = 0.000). In NCTC 1469 cells, MGF significantly down-regulated the expression of sqle (p = 0.000) and reduced cholesterol levels (p = 0.024). In conclusion, MGF effectively inhibits sqle expression and reduces cholesterol accumulation. The current study shows how MGF supplementation regulates the metabolism and accumulation of cholesterol in channel catfish, providing a theoretical basis for the use of MGF as a dietary supplement in aquaculture. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate cinnamaldehyde (CN) and clove oil (CO) effectiveness in inhibiting growth and killing spoilage and total aerobic bacteria when overlaid with catfish fillet stored at 4 °C. A 1.00 mL concentration of CO inhibited growth by 2.90, 1.96, and 1.96 cm, respectively, for S. baltica, A. hydrophilia, and total bacteria. Similarly, treatment with 1.00 mL of CN resulted in ZIB of 2.17, 2.10, and 1.10 cm, respectively, for S. baltica, A. hydrophilia, and total bacteria from catfish exudates. Total bacteria from catfish exudates treated with 0.50 mL CN for 40 min, resulted in a 6.84 log decrease, and treatment with 1.00 mL resulted in a 5.66 log decrease at 40 min. Total bacteria exudates treated with 0.50 mL CO resulted in a 9.69 log reduction at 40 min. Total bacteria treated with 1.00 mL CO resulted in a 7.69 log decrease at 7 days, while untreated pads overlaid with catfish resulted in ≥9.00 CFU/mL. However, treated absorbent pads with catfish at 7 days, using 0.50 mL and 1.00 mL CN, had a bacterial recovery of 5.53 and 1.88 log CFU/mL, respectively. Furthermore, CO at 0.50 mL and 1.00 mL reduced the bacteria count to 5.21 and 1.53 log CFU/mL, respectively, at day 7. [ABSTRACT FROM AUTHOR]

Channel catfish (Ictalurus punctatus) and blue catfish (Ictalurus furcatus) are two economically important freshwater aquaculture species in the United States, with channel catfish contributing to nearly half of the country's aquaculture production. While differences in economic traits such as growth rate and disease resistance have been noted, the extent of transcriptomic variance across various tissues between these species remains largely unexplored. The hybridization of female channel catfish with male blue catfish has led to the development of superior hybrid catfish breeds that exhibit enhanced growth rates and improved disease resistance, which dominate more than half of the total US catfish production. While hybrid catfish have significant growth advantages in earthen ponds, channel catfish were reported to grow faster in tank culture environments. In this study, we confirmed channel fish's superiority in growth over blue catfish in 60-L tanks at 10.8 months of age (30.3 g and 11.6 g in this study, respectively; p < 0.001). In addition, we conducted RNA sequencing experiments and established transcriptomic resources for the heart, liver, intestine, mucus, and muscle of both species. The number of expressed genes varied across tissues, ranging from 5,036 in the muscle to over 20,000 in the mucus. Gene Ontology analysis has revealed the functional specificity of differentially expressed genes within their respective tissues, with significant pathway enrichment in metabolic pathways, immune activity, and stress responses. Noteworthy tissue-specific marker genes, including lrrc10, fabp2, myog, pth1a, hspa9, cyp21a2, agt, and ngtb, have been identified. This transcriptome resource is poised to support future investigations into the molecular mechanisms underlying environment-dependent heterosis and advance genetic breeding efforts of hybrid catfish. [ABSTRACT FROM AUTHOR]

The antibiotic oxytetracycline (OTC) is a fluorochrome marker, and fluorescence microscopy is used to view OTC marks in fishes' calcified structures. However, OTC marks have been observed in calcified structures using standard light microscopy for multiple species. Therefore, we conducted an experiment to investigate potential factors (i.e., season, total length of fish, growth rate, and sex) influencing the observation of OTC in calcified structures (otoliths and fin rays or spines) from channel catfish Ictalurus punctatus, gray redhorse Moxostoma congestum, Guadalupe bass Mircopterus treculii, and redbreast sunfish Lepomis auritus viewed using standard light and fluorescence microscopy. OTC stains were not observed in any otoliths under standard light; however, OTC marks were commonly observed in I. punctatus spines using standard light microscopy (56.2%). Ninety‐nine percent of otoliths and 88.9% of spines and fin rays had a visible fluorescent OTC mark when viewed using fluorescence microscopy. There was a negative relationship between the observed OTC mark and total length of fish for each season, but fish injected in the summer had the most structures with an observed OTC mark under either light condition. Understanding how OTC marking is affected by biological processes and environmental conditions will assist in future studies that rely on chemical marking of calcified structures by increasing efficacy of OTC marking and interpretation of marks. [ABSTRACT FROM AUTHOR]

The hybrid between the female channel catfish (Ictalurus punctatus) and the male blue catfish (I. furcatus) is the best genetic type currently available for commercial catfish farming due to their superior traits. However, further genetic improvements can be achieved by selecting parents with increased combining abilities. Twenty female channel catfish and twelve male blue catfish were crossed in a partial factorial mating design, resulting in forty hybrid families. These families were evaluated for early growth in three different rearing systems, including ponds and aquaria. The early growth performance of hybrid catfish was significantly (p < 0.05) affected by the additive gene action of the female parent and the male parent. There were genotype–environment or genotype–age interactions affecting the combining abilities, both the amount and the type of genetic variation. Dam GCA was significant in all environments/ages; however, sire GCA was variable, and SCA was not significant. These findings suggest that reciprocal recurrent selection for growth could potentially improve the performance of F1 hybrid catfish. [ABSTRACT FROM AUTHOR]

Simple Summary: Sulfamethoxazole is a commonly used antimicrobial drug in aquaculture. In order to understand its effect on the liver transcriptome of channel catfish, we orally administered a certain proportion of sulfamethoxazole into the fish and analyzed the changes in the transcriptome to determine the effect of the drug on the fish. By studying changes in the transcriptome, we found that the drug acted on drug metabolizing functions in the liver. Stimulated fish try to ensure the normal expression of their physiological functions by accelerating the operation of various metabolisms. The detoxification process is facilitated by promoting glucuronidation in the fish liver; while lipid metabolism is increased, the antioxidant pathway is affected, and the glucose xenobiotic pathway is enhanced in order to maintain energy homeostasis and to ensure a normal energy supply for metabolism. Other cellular metabolisms are also carried out to repair damaged normal organisms. This study provides a reference for understanding drug metabolism in channel catfish and provides a warning about the use of the drug. Sulfamethoxazole is a widely used antimicrobial drug used to treat bacterial diseases in aquaculture. To understand the gene expression in channel catfish liver after treatment with sulfamethoxazole, in this study, the treatment group received sulfamethoxazole (100 mg/kg bw), which was administered orally once, and samples were taken at 5 h, 12 h, and 6 d after the administration of sulfamethoxazole, while the control group was orally administered sterile water. To further identify potentially significant genes, a transcriptome analysis using RNA-seq was carried out. More than 50 million high-quality reads were found. After filtering and quality analysis, these reads were identified as 54,169,682, 51,313,865, 51,608,845, and 49,333,491. After counting 23,707 of these transcripts for gene expression, it was discovered that 14,732 of them had genes with differential expression. Moreover, we found that the annotation with the most GO variation was "cellular process" (1616 genes), "metabolic process" (1268 genes), "binding" (1889 genes), and "catalytic activity" (1129 genes). KEGG pathways showed that the "metabolic pathway" was the pathway that was significantly enriched in both experimental groups when comparing the experimental groups: 5 h and 12 h (128 genes); 5 h and 6 d (332 genes); and 12 h and 6 d (348 genes). Also, UDP- glucuronosyltransferase (ugt), which is associated with glucuronidation, and UDP-glucuronosyltransferase 2C1-like (ugt2a1) showed significant upregulation. Carboxylesterase 5A-like (ces3), which promotes fatty acyl and cholesteryl ester metabolism, and the glutathione transferase family were upregulated in the expression of sulfamethoxazole metabolism in the liver, which significantly affected the metabolic effects of the drug. Meanwhile, dypd, uck2b, and rrm2, which are related to nucleotide synthesis and metabolism, were upregulated. Our study extends the knowledge of gene expression in drug metabolism in channel catfish and further provides insight into the molecular mechanism of sulfamethoxazole metabolism. [ABSTRACT FROM AUTHOR]

Russian olive (Elaeagnus angustifolia) is an invasive, fruit‐bearing riparian tree that dominates riparian zones of the San Juan River in the southwestern United States. Previous research in this river suggests olive fruit is common in diets of invasive channel catfish (Ictalurus punctatus), but its energetic importance is unknown (i.e. critical for catfish fitness vs. incidental consumption). We assessed Russian olive consumption in channel catfish diets bimonthly for 1 year, hypothesizing that olive consumption would be greatest during periods of high olive availability and low benthic aquatic invertebrate availability. We found that catfish consumed olive fruit throughout the year and that olive comprised up to 44% of total stomach contents by mass, with peaks in spring and fall. Regression models revealed the presence and mass of olive fruit in catfish stomachs were positively associated with catfish total length, with a significant interaction between water temperature and river discharge. Catfish were more likely to consume olive fruit during higher flows, regardless of temperature and at low discharge with higher temperature. Contrary to our hypothesis, neither olive nor benthic invertebrate availability were associated with olive presence in channel catfish diets. Nutrition analysis indicated that olive alone was a low‐quality diet item but has the potential to provide a reliable energy source. We used seasonal data to estimate the energetic contribution of olive fruit to catfish populations using a bioenergetic model, which estimated that olive fruit accounted for 35.6% of energy (Joules) consumed by catfish populations and satisfied 38% of their metabolic demand. Our results suggest that Russian olive fruit is a significant subsidy to channel catfish in the San Juan River. However, more research is needed to determine the indirect effects of this interaction on native fishes and ecosystem function. [ABSTRACT FROM AUTHOR]

Enteric septicemia of catfish (ESC), caused by the gram‐negative enteric bacteria Edwardsiella ictaluri, is a significant threat to catfish aquaculture in the southeastern United States. Antibiotic intervention can reduce mortality; however, antibiotic use results in an imbalance, or dysbiosis, of the gut microbiota, which may increase susceptibility of otherwise healthy fish to enteric infections. Herein, recovery of the intestinal microbiota and survivability of channel catfish in response to ESC challenge was evaluated following a 10‐day course of florfenicol and subsequent probiotic or prebiotic supplementation. Following completion of florfenicol therapy, fish were transitioned to a basal diet or diets supplemented with a probiotic or prebiotic for the remainder of the study. Digesta was collected on Days 0, 4, 8 and 12, beginning on the first day after cessation of antibiotic treatment, and gut microbiota was characterized by Illumina sequencing of the 16S rRNA gene (V4 region). Remaining fish were challenged with E. ictaluri and monitored for 32 days post‐challenge. Florfenicol administration resulted in dysbiosis characterized by inflated microbial diversity, which began to recover in terms of diversity and composition 4 days after cessation of florfenicol administration. Fish fed the probiotic diet had higher survival in response to ESC challenge than the prebiotic (p =.019) and negative control (p =.029) groups. [ABSTRACT FROM AUTHOR]

Objective: Documenting the movement of Channel Catfish Ictalurus punctatus through telemetry, where a transmitter tag is surgically implanted in the fish, can provide valuable insight into the species' spatial ecology and habitat use. However, since fish in the order Siluriformes can expel foreign objects such as tags from their body cavity, the utility of telemetry technology may be limited for Channel Catfish. This study aimed to determine (1) how quickly Channel Catfish reject tags that were surgically implanted into the body cavity, (2) if surgical implantation of transmitter tags causes mortality, and (3) what surgical method is best to minimize tag rejection and/or mortality. Methods: Three surgical trials were conducted on Channel Catfish (n = 24) using two tag implantation methods: a nontethered method, in which the tag was freely implanted into the body cavity, and a tethered method, where the tag was attached to the pectoral girdle. Fish were observed in the lab for 30 days for trials 1 and 2 and 225 days for trial 3 following tag implantation. Result: No complete tag rejections occurred during any of the three experimental trials. However, all five tethered fish experienced mortality during trial 3 (58-221 days postsurgery). Necropsies indicated that the tethered tagging method led to septicaemia infections and internal lacerations from the tether, which were not observed in the nontethered fish. Tags in the nontethered fish were in the process of being absorbed into the intestinal tract, which over time might have led to tag rejection. Conclusion: While rejection is possibly the end point of the nontethered tagging method, our results suggest it is nevertheless the better tagging method for Channel Catfish given higher survival. [ABSTRACT FROM AUTHOR]

Infection with Edwardsiella ictaluri, a causative agent of enteric septicemia of catfish, threatens profitable catfish production through inventory losses. We previously demonstrated that trans-cinnamaldehyde (TC) enhances the survival of catfish following E. ictaluri infection. The present study was conducted to investigate catfish immune responses to TC feeding and E. ictaluri infection. The expression of 13 proinflammatory, innate, and adaptive immune-related genes was evaluated over time in two sets of experiments using real-time polymerase chain reaction (PCR). In the first experiment, catfish were fed a basal diet with or without TC supplementation, while in the second they were fed a TC-supplemented or normal diet followed by infection with E. ictaluri. The catfish group infected with E. ictaluri and fed a TC-diet showed significant changes in the expression of innate and adaptive immune-related genes compared to control group. At 21 and 28 days post-infection, recovered fish showed significant increases in the expression of IgM in the anterior kidney and spleen. These results suggest that the supplemental dietary intake of TC can improve the immune status of catfish via engaging innate and adaptive immune responses and the production of memory cells in immunocompetent tissues. Together, this study provides an important foundation for the potential application of TC as an antimicrobial alternative in aquaculture. [ABSTRACT FROM AUTHOR]

The culture of African catfish, Clarias gariepinus, is constrained by the high mortality of fry, occasioning a shortage of high-quality seeds for stocking by farmers. Asia, a continent with many success stories for aquaculture, leads in farmed production of some catfishes, a diverse group of 37 different families. Globally, the culture of catfishes ranks fifth in global farmed finfish production. Globally, Vietnam leads in the production and export of farmed striped catfish, Pangasianodon hypophthalmus, with 1,400,000 tonnes produced annually from about 7,000 hectares. Similarly, China farmed the non-native Channel catfish, Ictalurus punctatus, into the major crop, with a current annual production of 250,000 tonnes. On the contrary, C. gariepinus, the main farmed catfish species in Africa, records low annual yields, with 240,000 tonnes for the whole continent. This paper explores the factors behind the high production of P. hypophthalmus and I. punctatus in Vietnam and China, respectively, and draws lessons for C. gariepinus farmers in Africa. Specifically, the use of differentiated hatchery and nursery husbandry practices was critical in boosting seed production, quantity, availability, and distribution for expanding the culture of P. hypophthalmus in Vietnam. Improvement of fish species through well-designed genetic improvement programs helped China substantially increase production of I. punctatus. For both species, intensive fish production, as well as the adoption and implementation of suitable policies, increased seed production from hatcheries in both countries. These are discussed as some of the factors that spurred catfish production in the two Asian countries. We argue that if these are adopted by farmers in Africa, they could help improve the production of farmed C. gariepinus on the continent for food and nutrition security as well as generation of livelihood for local communities. [ABSTRACT FROM AUTHOR]

The global threat posed by non-native species to biodiversity and freshwater ecosystems necessitates understanding their ecological impacts. The invasive North American channel catfish Ictalurus punctatus (Rafinesque, 1818) is such a case, having been shown to not only have considerable impacts to native biodiversity, but also to expand its range. Several decades ago, I. punctatus was introduced to Lake Kasumigaura, Japan. This study investigates the seasonal dynamics of I. punctatus' trophic niche over three consecutive years. Stable isotopes analyses of carbon (δ13C) and nitrogen (δ15N) were utilized to assess isotopic niche variation and feeding habitat. Results demonstrate ontogenetic variations in I. punctatus' trophic position and feeding habitat, influenced by both season and year. Ictalurus punctatus exhibited a wider isotopic niche and greater interindividual dispersion during spring and summer compared to autumn and winter. While the occupied isotopic niche space remained stable across years, significant seasonal differences were observed in 2 out of 3 years. These seasonal differences underscore the high trophic plasticity of I. punctatus, facilitating its ability to exploit a diverse spectrum of resources. This research advances our understanding of this species' trophic traits and invasiveness, emphasizing the significance of considering seasonal variations in the ecological impacts of invasive fish species. [ABSTRACT FROM AUTHOR]

Due to the non-degradable and persistent nature of metal ions in the environment, they are released into water bodies, where they accumulate in fish. In order to assess pollution in fish, the enzyme, glucose 6-phosphate dehydrogenase (G6PD), has been employed as a biomarker due to sensitivity to various ions. This study investigates the kinetic properties of the G6PD enzyme in yellow catfish (Pelteobagrus fulvidraco), and analyzes the effects of these metal ions on the G6PD enzyme activity in the ovarian cell line (CCO) of channel catfish (Ictalurus punctatus). IC50 values and inhibition types of G6PD were determined in the metal ions Cu2+, Al3+, Zn2+, and Cd2+. While, the inhibition types of Cu2+ and Al3+ were the competitive inhibition, Zn2+ and Cd2+ were the linear mixed noncompetitive and linear mixed competitive, respectively. In vitro experiments revealed an inverse correlation between G6PD activity and metal ion concentration, mRNA levels and enzyme activity of G6PD increased at the lower metal ion concentration and decreased at the higher concentration. Our findings suggest that metal ions pose a significant threat to G6PD activity even at low concentrations, potentially playing a crucial role in the toxicity mechanism of metal ion pollution. This information contributes to the development of a biomonitoring tool for assessing metal ion contamination in aquatic species. [ABSTRACT FROM AUTHOR]

Fatty acids from fish are of great interest for human consumption, and the channel catfish (Ictalurus punctatus) is one of the most important aquaculture species in Mexico and perhaps in other countries with similar resource endowments. Channel catfish occupy a trophic level that theoretically and potentially allows the retention and de novo biosynthesis of long-chain fatty acids (FAs), essential for human nutrition and health. Here, we present an overview of the main features of FAs, their reported average levels and extreme values in channel catfish assessments, and their correlations. The importance of FAs for human consumption and some implications for future research are discussed. [ABSTRACT FROM AUTHOR]

This article presents a case study on epizootic ulcerative syndrome (EUS) caused by Aphanomyces invadans in eastern mosquitofish in South Carolina. The study documents the discovery of A. invadans in a small stream and provides information on fish collections, diagnostic studies, and follow-up surveys. The identification of A. invadans was based on clinical signs and DNA sequencing. The outbreak of A. invadans seemed to be limited to the eastern mosquitofish in a specific area, and the study highlights the need for further research to understand the underlying causes of these outbreaks in wild fish populations. [Extracted from the article]

To prevent catfish idiopathic anaemia, diets fortified with iron have been adopted as a regular practice on commercial catfish farms to promote erythropoiesis. However, the effects of prolonged exposure of excess dietary iron on production performance and disease resistance for hybrid catfish (Ictalurus punctatus × I. furcatus) remains unknown. Four experimental diets were supplemented with ferrous monosulphate to provide 0, 500, 1000, and 1500 mg of iron per kg of diet. Groups of 16 hybrid catfish juveniles (~22.4 g) were stocked in each of 20, 110‐L aquaria (n = 5), and experimental diets were offered to the fish to apparent satiation for 12 weeks. At the end of the study, production performance, survival, condition indices, as well as protein and iron retention were unaffected by the dietary treatments. Blood haematocrit and the iron concentration in the whole‐body presented a linear increase with the increasing the dietary iron. The remaining fish from the feeding trial was challenged with Edwardsiella ictaluri. Mortality was mainly observed for the dietary groups treated with iron supplemented diets. The results for this study suggest that iron supplementation beyond the required levels does affect the blood production, and it may increase their susceptibility to E. ictaluri infection. [ABSTRACT FROM AUTHOR]