Largemouth Research Articles

Effects of Astaxanthin on Ovarian Development of Largemouth Bass (Micropterus salmoides)

The purpose of the study was to investigate the effects of astaxanthin on ovarian development of largemouth bass (Micropterus salmoides) female. Five isonitrogenous and isolipidic feeds with varying levels of astaxanthin (0.8, 19, 41, 97, and 200 mg/kg) were grouped as AS0, AS20, AS40, AS100, and AS200, respectively. The results indicated that the gonadosomatic index (GSI) was significantly greater in the AS40 and AS100 than in AS0 and AS200 (p < 0.05). The AS40 and AS100 exhibited a dramatically lower hepatosomatic index (HSI) compared to the other groups (p < 0.05). The content of vitellogenin (VTG) was significantly increased in AS100 compared to the AS0, AS20, and AS200 (p < 0.05). Testosterone (T) levels were significantly lower in the AS200 compared to the other groups (p < 0.05). The AS40, AS100, and AS200 groups exhibited significantly greater follicle‐stimulating hormone (FSH) levels than the AS0 and AS20 group (p < 0.05). The luteinizing hormone (LH) level was significantly higher in AS100 compared to the other groups (p < 0.05). The estradiol (E2) levels were significantly higher in AS40 compared to the AS0 and AS200 groups (p < 0.05). The total antioxidant capacity (T‐AOC) was significantly higher in AS100 than the AS0 and AS20 groups (p < 0.05). The superoxide dismutase (SOD) activity was significantly higher in AS40 compared to the AS0 and AS200 groups (p < 0.05). The malondialdehyde (MDA) level was significantly decreased in AS40 than the other groups (p < 0.05). Transcriptomic analysis of ovarian tissue revealed that differentially expressed genes primarily involved in pathways such as “ovarian steroidogenesis,” “steroid hormone biosynthesis,” and “arachidonic acid metabolism.” The expression of genes involved in ovarian steroidogenesis and arachidonic acid metabolism, such as cytochrome P450 family 2 subfamily J member (cyp2j), insulin‐like growth factor 1 (igf1), phospholipase A2 group (pla2g), FSH receptor (fshr), and acute regulatory protein (star), was significantly upregulated in the AS40 group (p < 0.05). In summary, appropriate amount of astaxanthin supplementation in the diet enhance gonadal development, antioxidant capacity, and sex hormone levels, promote the expression of genes related to gonadal development, and consequently, enhance reproductive performance of largemouth bass.

Construction of Healthy Liver of Largemouth Bass (Micropterus salmoides) in the Short Term by Steroidal Saponins before Heat Season Comes

Construction of Healthy Liver of Largemouth Bass (<i>Micropterus salmoides</i>) in the Short Term by Steroidal Saponins before Heat Season Comes

Quantitative Analysis of Fish Morphology Through Landmark and Outline-based Geometric Morphometrics with Free Software.

Morphology underpins key biological and evolutionary processes that remain elusive. This is in part due to the limitations in robustly and quantitatively analyzing shapes within and between groups in an unbiased and high-throughput manner. Geometric morphometrics (GM) has emerged as a widely employed technique for studying shape variation in biology and evolution. This study presents a comprehensive workflow for conducting geometric morphometric analysis of fish morphology. The step-by-step manual provides detailed instructions for using popular free software, such as the TPS series, MorphoJ, ImageJ, and R, to carry out generalized Procrustes analysis (GPA), principal component analysis (PCA), discriminant function analysis (DFA), canonical variate analysis (CVA), mean shape analysis, and thin plate spline analysis (TPS). The Momocs package in R is specifically utilized for in-depth analysis of fish outlines. In addition, selected functions from the dplyr package are used to assist in the analysis. The full process of fish outline analysis is covered, including extracting outline coordinates, converting and scaling data, defining landmarks, creating data objects, analyzing outline differences, and visualizing results. In conclusion, the current protocol compiles a detailed method for evaluating fish shape variation based on landmarks and outlines. As the field of GM continues to evolve and related software develops rapidly, the limitations associated with morphological analysis of fish are expected to decrease. Interoperable data formats and analytical methods may facilitate the sharing of morphological data and help resolve related scientific problems. The convenience of this protocol allows for fast and effective morphological analysis. Furthermore, this detailed protocol could be adapted to assess image-based differences across a broader range of species or to analyze morphological data of the same species from different origins. Key features • This protocol provides a comprehensive set of commonly used GM-analyzing methods and visualizing skills plus supporting information to help assess the appropriate analysis method • By incorporating both landmarks and outlines, this protocol facilitates a thorough analysis of two-dimensional shape variation in fish, covering a wide range of morphological features • The simplified workflow and detailed procedures make it accessible for non-experienced users to successfully complete the analysis while also providing valuable insights for experienced users Graphical overview Workflow for conducting geometric morphometrics analysis on fish. The steps include image acquisition as data sources, digitization of fish morphology using landmark-based methods, analysis of shape variation characteristics, and visualization of the results in relation to biological interpretation. Largemouth bass (Micropterus salmoides) is used as an example in the schematic representation.

Length-weight relationship and condition factor for five common fish species in a recently constructed reservoir (Tugwi-Mukosi Dam) - Zimbabwe

Tugwi-Mukosi is a recently constructed reservoir in the Masvingo Province of Zimbabwe. The objective of the study was to estimate the length-weight relationship (LWR) and condition factors (K) of five freshwater fish species collected from the dam. Three hundred eighty-seven fish samples were caught by gill nets and sein between January and September 2021. The estimated exponent value b varied between 2.814 and 3.228 among the fish species. The b values indicated that three species (Oreochromis niloticus, Coptodon rendalli and Micropterus salmoides) followed negative allometric growth (b &lt; 3). In contrast, Clarias garipinus showed isometric growth (b = 3), while Oreochromis mossambicus exhibited positive allometric growth (b &gt; 3). More than 94% (R2 &gt; 0.94) of the weights (responses) variations were explained by the models, so the models fit the data well. The K values of all the fish species, except for C. gariepinus, ranged between 1.3 - 2.2; this indicates that these species are doing well in the reservoir. This observation suggests that Tugwi-Mukosi currently provides a favourable habitat for the fish species. The current study's findings will give valuable baseline data for assessing the status of fish populations and conducting ecological surveys for future fish conservation and management.

A Study on Ecological Culture Technology of Chinese Mitten Crab with Largemouth Bass in Net Cages

A Study on Ecological Culture Technology of Chinese Mitten Crab with Largemouth Bass in Net Cages

Establishment and Application of a SYBR Green I Real-Time Quantitative PCR for Detection of Micropterus salmoides Rhabdovirus

Establishment and Application of a SYBR Green I Real-Time Quantitative PCR for Detection of Micropterus salmoides Rhabdovirus

Research on Largemouth Bass Target Recognition and Tracking Utilizing the Optical Flow Approach

Research on Largemouth Bass Target Recognition and Tracking Utilizing the Optical Flow Approach

绿色养殖时代：大口黑鲈的创新与可持续养殖

绿色养殖时代：大口黑鲈的创新与可持续养殖

Can habitat enhancement limit the ecological impacts of predatory fish stocking? An experimental approach

Fish stocking is a ubiquitous management measure in freshwater fisheries but it can induce important ecological impacts on communities and recipient ecosystems. Habitat enhancement might limit the ecological impacts of fish stocking by directly supporting biodiversity and helping to maintain ecosystem functioning. In the present, we used a mesocosm experiment to assess whether habitat enhancement, through the addition of coarse woody habitat (CWH) in the form of thin branches bundled or within an iron cage, can limit the impact of stocking of a predatory fish, juvenile largemouth bass Micropterus nigricans, on prey communities and ecosystem functioning. Results demonstrated that, prior to stocking, there was overall no significant effect of habitat enhancement on zooplankton communities and a strong effect on benthic macroinvertebrate communities that was associated with a decrease in the decomposition rate of organic matter in mesocosms containing caged-CWH. We also found that the stocking of juvenile largemouth bass significantly affected the structure of zooplankton communities while we did not observe significant effects on macroinvertebrate communities and ecosystem functioning. This effect on zooplankton community structure was compensated by habitat enhancement, notably when using caged-CWH. This study showed that habitat enhancement alone may not be sufficient to compensate the potential effects of predatory fish stocking, and that the choice of materials used to enhance habitats is fundamental in driving the efficiency.

Space use and residency patterns of largemouth bass relative to a freshwater protected area

Space use and residency patterns of largemouth bass relative to a freshwater protected area

Largemouth bass galectin, MsGal-9: Mediating various functions as a pattern recognition receptor and a potential damage-associated molecular pattern

Galectins are lectins that bind to β-galactose and are widely expressed in immune system tissues, playing pivotal roles in innate immunity through their conserved carbohydrate-recognition domains (CRDs). In this present investigation, a tandem-repeat galectin was discovered in the largemouth bass, Micropterus salmoides (designated as MsGal-9). The open reading frame of MsGal-9 encodes two CRDs, each containing two consensus motifs that are essential for ligand binding. MsGal-9 is expressed in various tissues of the largemouth bass, with particularly high expression levels in the liver and spleen. The full-length form of MsGal-9, as well as the N-terminal (MsGal-9-N) and C-terminal (MsGal-9-C) CRDs, were individually recombined. Their ability for nonself recognition was studied. The three recombinant proteins were able to bind to glucan (GLU), peptidoglycan (PGN), and lipopolysaccharide (LPS), with MsGal-9 displaying the highest binding activity. Furthermore, rMsGal-9-N exhibited higher binding activity towards GLU in comparison to rMsGal-9-C. Further investigations revealed that the full-length rMsGal-9 could significantly bind to Gram-positive bacteria, Gram-negative bacteria, and fungi, while rMsGal-9-C specifically bound to Escherichia coli. However, rMsGal-9-N did not exhibit significant binding activity towards any microbes. These findings indicate that MsGal-9 requires both CRDs to cooperate in order to fulfill its nonself recognition function. All three recombinant proteins demonstrated agglutination activity towards various microbes, with MsGal-9 and MsGal-9-N displaying a similar broad binding spectrum, while MsGal-9-C agglutinated three types of bacteria. Moreover, both MsGal-9 and MsGal-9-N were capable of coagulating largemouth bass red blood cells, whereas MsGal-9-C lacked this ability. However, MsGal-9-C played a significant role in enhancing the encapsulation of leukocytes in comparison to MsGal-9-N. All three proteins acted as potential damage-associated molecular patterns (DAMPs), inducing apoptosis in leukocytes.

Importance of quantifying the number of viral reads in metagenomic sequencing of environmental samples from the Huanan Seafood Market.

In March 2023, the Chinese CDC publicly released raw metagenomic sequencing data for environmental samples collected in early 2020 from the Huanan Seafood Market. Prior to that data release, some scientists had suggested that these samples could be informative for establishing if animals such as raccoon dogs had been infected with severe acute respiratory syndrome virus 2 (SARS-CoV-2). However, no one had analyzed how much SARS-CoV-2 was actually present in the metagenomic sequencing data. After the raw data became available, I fully analyzed the abundance of both viral and animal genetic material in the samples. That analysis, which was published in Virus Evolution, found that the SARS-CoV-2 content of most samples was very low and that the abundance of SARS-CoV-2 was most strongly associated with animals such as largemouth bass that are not plausible candidates for having been infected. Based on these results, I concluded that the metagenomic content of the samples was not informative for determining if any non-human animals in the market had been infected with SARS-CoV-2. One of the authors of an earlier study of these samples, Florence Débarre, recently submitted a response to my paper. Here, I reply in turn to explain why it is important to quantify the abundance of viral material before drawing conclusions from metagenomic sequencing. I also report new analyses of other animal coronaviruses in the samples and show that material from some other animal coronaviruses is much more abundant than SARS-CoV-2 in samples collected on the date when most wildlife stall sampling was performed. I further show that material from some of these animal coronaviruses is associated with the animals they probably infect but that no such association exists for SARS-CoV-2. Overall, these new analyses further emphasize the importance of quantifying the actual amount of viral material in metagenomic samples and underscore why the environmental samples from the Huanan Seafood Market are not informative for determining if any non-human animals were infected with SARS-CoV-2.

Accumulation and health implications of arsenic, mercury, and selenium in selected freshwater fish species in the uMgeni River, South Africa

ABSTRACT Metal pollution threatens freshwater ecosystems and consequently the well-being of human communities consuming fish. The study evaluated the concentration of arsenic (As), mercury (Hg) and selenium (Se) in six fish species in the uMgeni River, and the edibility thereof. Water, sediment and fish were sampled during low and high flow seasons in the Inanda and Nagle dams. Metals were below detection level in the water column whereas notable concentrations were observed in sediment. Arsenic and Se concentrations were within the guidelines for all species, whereas Hg exhibited concentrations exceeding the guidelines except for Clarias gariepinus, Micropterus salmoides, and Cyprinus carpio. For non-carcinogenic risks, the THQs > 1 was observed for As and Hg for all species except C. carpio whereas Se showed THQs < 1 for all species. These findings suggest that consuming fish from the uMgeni River could result in As and Hg related non-carcinogenic health hazards.

Artificial infection pathway of largemouth bass LMBV and identification of resistant and susceptible individuals

Identifying disease-resistant and disease-susceptible materials in largemouth bass can provide fundamental analytical information for disease-resistant breeding research on this species. To date, no stable and effective artificial infection pathway has been established against largemouth bass virus (LMBV) in largemouth bass. In this study, using the pathogen at a concentration of 1.60 × 105 TCID50/mL, largemouth bass juveniles were infected using three different methods: muscle injection, feeding, and immersion. A comprehensive comparative study was conducted on parameters such as disease progression, viral load, pathological changes, and electron microscopy. The results revealed that the injection group experienced rapid mortality, with all individuals dying within 6 days after the infection. The feeding group showed minimal mortality, with an overall mortality rate of 28.57%. The immersion group reached its peak mortality on the 9th day after infection, with an accumulated mortality rate of 63.24%. Viral gene quantification results showed that while in the injection group muscles had the highest viral load followed by the liver and spleen, the other infection methods led to the highest viral loads in the liver and spleen. Tissue pathology and electron microscopy observations revealed that the liver and spleen exhibited the most significant pathological changes and were the easiest organs to detect viral particles, indicating that the liver and spleen are the primary target organs of LMBV in largemouth bass. In conclusion, this study suggests that immersing largemouth bass in LMBV at a concentration of 1.99 × 103 c/mL (diluted 80 times) closely mimics the natural infection rate, allowing for a clear differentiation between causes of death and survival, making it an almost non-invasive artificial infection method that closely resembles natural infection conditions. These findings can provide crucial support for the accurate identification of disease-resistant and disease-susceptible materials in largemouth bass and the breeding of disease-resistant varieties.

Orange-spotted grouper IFNh response to NNV or MSRV and its potential antiviral activities

Type I interferon (IFN) plays a crucial role in the antiviral immune response. Nervous necrosis virus (NNV) and Micropterus salmoides rhabdovirus (MSRV) are the most important viruses in cultured larvae and juveniles, causing great economic losses to fish farming. To better understand the antiviral activities and immunoregulatory role of IFN from orange-spotted grouper (Epinephelus coioides), EcIFNh was cloned from NNV infected sample. EcIFNh has an open reading frame (ORF) of 552 bp and encodes a polypeptide of 183 amino acids. Phylogenetic tree analysis showed that EcIFNh was clustered into the IFNh branch. The tissue distribution analysis revealed that EcIFNh was highly expressed in the liver and brain of healthy orange-spotted grouper. The mRNA levels of EcIFNh were significantly upregulated after poly (I:C) stimulation and NNV or MSRV infection. Furthermore, the promoter of EcIFNh was characterized and significantly activated by EcMDA5, EcMAVS, EcSTING, EcIRF3, and EcIRF7 in the luciferase activity assays. We found that EcIFNh overexpression resisted the replication of NNV and MSRV, while EcIFNh silencing facilitated NNV replication in GB cells. In addition, EcIFNh recombinant protein (rEcIFNh) enhanced the immune response by inducing the expression of ISGs in vivo and in vitro, suggesting the potential application of rEcIFNh for anti-NNV and anti-MSRV. Taken together, our research may offer the foundation for virus-IFN system interaction in orange-spotted grouper.

Fish assemblages along a bathymetric gradient in the northern Aegean Sea: An ecomorphological approach

Morphological studies of fish assemblages are a crucial aspect of ecology, as they can provide insight into functional roles and changes beyond taxonomically oriented approaches. In addition, depth is an important factor that impacts the structure of fish assemblages. In the present study, samples of 115 demersal actinopterygian species were collected during a bottom-trawl survey conducted in the northern Aegean Sea, in the summer of 2020. The samples were collected by 65 hauls across depths ranging from 0 to 650 m. The samples were photographed, and the images were analyzed through geometric morphometric methods, by defining 27 landmarks and semilandmarks on each photo. Principal Components were estimated to construct morphospaces and between group Principal Component Analysis was used to distribute the mean body shape of each assemblage along morphological axes. Ecological, taxonomic and morphological diversity indices were then computed for each haul, and the potential effects of depth on these indices were tested with Generalized Additive models. All indices were significantly affected by depth, except for species richness, on which the effect was marginally insignificant. Concerning the morphological diversity indices, morphological disparity indices, estimated with 2 different methods, as well as the ecomorphological diversity found to increase with depth, whereas morphological richness fluctuated. Next, Generalized Linear Models were employed to examine the variations in the morphological traits of the mean shape of each formed assemblage. The results indicated that assemblages distinguished into two groups, one inhabiting the continental shelf (<200 m), and the other the upper-medium slope (>200 m). Specifically, with increasing depth, fish converge towards an elongated body, with larger mouth and eyes, but smaller pectoral fin. The findings of this study, contribute to better understanding of the impact of depth on the ecological and morphological structure of demersal assemblages, and highlight the importance of morphological diversity indices as a complement to conventional approaches.

Type II interferons (IFN-γ and IFN-γrel) activate downstream genes through various potential receptor combinations to exert antiviral functions in spotted sea bass (Lateolabrax maculatus)

Type II interferons (IFNs) exert antiviral functions by binding to receptors and activating downstream signaling pathways. However, our understanding of the antiviral functions and the receptor complex model of type II IFNs in teleost fish remains limited. In this study, we determined the functions of type II IFNs (LmIFN-γ and LmIFN-γrel) in Lateolabrax maculatus and assessed their antiviral ability mediated by their combination with different cytokine receptor family B members (LmCRFB6, LmCRFB13, and LmCRFB17). After infection with largemouth bass ulcer syndrome virus (LBUSV), the expression levels of LmIFNs and LmCRFBs increased significantly in vitro and in vivo. Incubation or injection with LmIFNs-His activated the expressions of LmISG15, LmMx, and LmIRF1. LmIFN-γ and LmIFN-γrel both bound to the extracellular domains of the three CRFBs via Pull-down. Furthermore, LmIFN-γ combined with LmCRFB6, LmCRFB6+LmCRFB13, and LmCRFB6+LmCRFB13+LmCRFB17 and LmIFN-γrel combined with all combinations containing LmCRFB17 induced the transcription of downstream genes and reduced the number of LBUSV copies. Therefore, type II IFNs (LmIFN-γ and LmIFN-γrel) contribute to enhanced antiviral immunity in L. maculatus and that ligand-receptor combinations effectively suppress virus replication. These findings provide a reference for future studies of the signal transduction mechanism of type II IFNs in teleost fish.

Evaluation of shoreline rotenone application to control Largemouth Bass recruitment in small impoundments

AbstractObjectiveReducing Largemouth Bass Micropterus salmoides recruitment and therefore population density could benefit recreational fisheries in small impoundments by improving individual growth rates and increasing the average size and condition of Largemouth Bass. To achieve these effects, methods of controlling Largemouth Bass recruitment should avoid reducing the productivity of their primary prey species, the Bluegill Lepomis macrochirus.MethodsWe tested this hypothesis by evaluating the effects of shoreline rotenone application on the density of Bluegill and the density, growth, and survival of age‐0 and age‐1 Largemouth Bass in 15 Alabama small impoundments.ResultAfter treatment, Largemouth Bass age‐0 densities declined and mean age‐1 length increased, whereas Bluegill populations were not significantly reduced.ConclusionOur study indicates that shoreline rotenone application may be a valuable method for reducing Largemouth Bass recruitment and increasing the growth of age‐1 Largemouth Bass in small impoundments. However, further research is needed to understand the effects of treatment on nontarget fishes and to better assess the effects of factors such as impoundment surface area and treatment frequency and duration on the ultimate utility of the approach.

Effects of replacing fishmeal with different proportions of mixed protein source in the diet of largemouth bass (Micropterus salmoides)

Fishmeal is an important protein source for largemouth bass (Micropterus salmoides). However, the production of fishmeal is decreasing each year and the price of fishmeal is rising. Therefore, it is necessary to find new high-quality and suitable protein sources. This study used a mixed animal protein source (chicken meal:blood meal:shrimp meal:brewer's yeast = 50:12.5:25:12.5) to replace fishmeal. Using a 48 % fishmeal group as the control, five diets with different fishmeal levels (FM48, FM44, FM40, FM36, FM32) were established to determine the effects on largemouth bass growth performance, liver health and intestinal health. There were no significant differences in the percentage weight gain, specific growth rate, feed conversion rate, and condition factor of largemouth bass, but the hepatosomatic and viscerosomatic indexes were significantly decreased when the dietary fishmeal level was reduced to 40 %. The content of taurine, glycine, and histidine was significantly reduced in the muscle of largemouth bass fed the FM32 diet compared with those fed the FM48 and FM44 diets. Mixed protein feed reduced the total bile acid content and increased the low-density lipoprotein cholesterol content in the plasma of largemouth bass. The replacement of fishmeal with the mixed protein source inhibited the expression of tnf-α and caspase 3 and enhanced the expression of apoa1 in the liver, as well as enhancing the protein expression of FXR and SREBP and inhibiting the protein expression of P-PPARA in the liver. The intestinal pparα expression was suppressed when dietary fishmeal was replaced. When dietary fishmeal decreased, the mucosal folds height and muscle layer thickness also decreased. In conclusion, partial replacement of fishmeal with the mixed protein source did not affect the growth performance, while lipid metabolism and intestinal health were negatively affected when dietary fishmeal levels were below 36 %.

Mercury and selenium in three fish species from a dam 20 months after a mine-tailing spill in the SE Gulf of California ecoregion, Mexico

During January 2013, a mining spill occurred in the Santa Maria mining region, releasing around 300,000 m3 of tailings on Los Remedios river, which was transported through the San Lorenzo river and finally to El Comedero (EC) dam. Twenty months later, we examined the concentrations of Hg and Se in the muscle, liver, gills, and guts of three fish species (Cyprinus carpio, Oreochromis aureus, Micropterus salmoides) captured in the EC dam to assess the performance of the cleaning operations. A high Se concentration in the liver of all species (carp, 1.2 ± 0.4; tilapia, 3.9 ± 2.1; bass, 3.5 ± 1.1 µg g−1 ww) was consistently observed, while this behavior was only found in the blue tilapia for Hg (0.15 ± 0.11 µg g−1 ww). Tilapia (benthic-detritivorous) exhibited the highest Se concentrations compared to the carp (omnivore) and the largemouth bass (piscivore). In contrast, the largemouth bass had the highest Hg levels in the muscle compared with the other fishes. Such differences could be related to the different metabolism and feeding habits among species. Compared to a tilapia study carried out three months after the mine spill during a mortality event, a decrease was evident in the liver for Se and Hg by 7.2 and 4.7 times, respectively. This reveals that cleaning operations were more efficient for Se and less for Hg, and that a prolonged period was required for the partial recovery of the element levels in fish from sites impacted by mining. Considering the Mexican consumption scenarios for each fish species, it could be concluded that there will be no non-cancer risk by exposure to Hg or Se.