Search

Columnaris disease generates substantial losses of many freshwater fish species; one is the hybrid striped bass. The ubiquitous aquatic bacterium Flavobacterium columnare can be highly effective in biofilm formation on fish skin and gills. Previous research showed a difference between columnaris disease susceptibility of hybrid striped bass (Morone saxatilis × M. chrysops) and white bass (M. chrysops). To understand these differential susceptibilities and possible mucosal relationship, we assessed total bacterial growth and biofilm formation with mucus derived from each moronid parental species: white bass and striped bass (M. saxatilis). Differential susceptibility was confirmed of the other parent species, the striped bass (M. saxatilis). In addition to intraspecies investigations, individual hybrid striped bass mucosal affects were also studied for deferential responses to bacterial growth and biofilm formation. Species- and concentration-dependent differences were detected in the total growth of the bacteria to host mucus. Our data suggest that bass mucus can significantly affect biofilm formation with the F. columnare isolate tested. There appears to be a correlation between the bacteria's response of growth and biofilms and bass species susceptibility. This study provides insight into our understanding of the host-pathogen interaction between F. columnare and moronids.

The Smallmouth Bass (Micropterus dolomieu; SMB) is a widely distributed black bass species, but the southwestern edge of the species range within the Interior Highlands contains some of the most divergent ecotypes. The Neosho subspecies (M. d. velox) inhabits tributaries of the Arkansas River within the Ozark Mountains and a second lineage is reported from drainages of the Ouachita Mountains. We sought to develop a single nucleotide polymorphism (SNP) panel to (1) diagnose hybridization with sympatric Spotted Bass (Micropterus punctulatus; SPB) and non-native Northern SMB (M. d. dolomieu) stocked in the region, and (2) delineate population structure within the ranges of the Neosho and Ouachita SMB lineages. We obtained 76 individual SMB samples from across their range but concentrated within the Interior Highlands (n = 50). We also included 3 SPB to allow for hybrid detection and 3 Shoal Bass (Micropterus cataractae) as an outgroup. Phylogenetic trees constructed with the generated SNP data corroborated the existence of at least three major lineages of SMB (Northern, Neosho, and Ouachita), each containing varying degrees of differentiation among major drainages. Simulation analyses revealed that chosen SNPs had high power (> 0.9) to assign SMB × SPB hybrid categories and similarly high power (> 0.8) for Northern SMB × Interior Highlands SMB hybrids. Clustering methods delineated major inter-basin population structure within the native ranges of Neosho and Ouachita SMB with chosen SNPs. Anticipated uses of the resulting 192-loci SNP panel include conservation planning, fisheries management assessments, and ecological investigations of the Neosho and Ouachita SMB lineages.

Introduction of non-native piscivores has been implicated in the decline of native Chinook Salmon Oncorhynchus tshawytscha via predation during juvenile life stages. However, isolating effects of predation on Chinook Salmon survival is complicated by changes in physical habitat that are often concomitant with non-native piscivore establishment. We performed two field experiments with enclosures deployed in tidal freshwater habitat to quantify effects of non-native Largemouth Bass Micropterus salmoides density and habitat type on the survival and movement behavior of juvenile Chinook Salmon. In experiment one, bass densities were doubled and quadrupled across treatment levels with a baseline value of field-observed densities. In experiment two, three habitat types (dock, submerged aquatic vegetation (SAV), and open water) were tested while bass density was held at the medium (doubled) value. Juvenile Chinook Salmon implanted with passive integrated transponders were released into the enclosures to assess their survival and movement through the treatments over multiple trials. Mark-recapture models indicated that the survival of juvenile Chinook Salmon was reduced in the medium bass density, but not the high-density treatment, when compared to the lowest density value suggesting relationships may be non-linear. The SAV treatment had a well-supported negative effect on juvenile Chinook Salmon survival relative to a dock or open water. Residence time was positively related to bass density. Relationships with a habitat were not consistently different. These results suggest that restoration strategies targeting non-native SAV control could reduce predation on juvenile Chinook Salmon by Largemouth Bass. However, piscivore density manipulation may only be effective over a narrow range of densities.

Coptodon zilli and Micropterus salmoides were introduced into Lake Naivasha in 1929 and 1959 respectively. The reasons for the introduction were to boost the fisheries and for recreational fishing respectively. However, the numbers of the two fish species in the lake have been declining over the years. It is therefore necessary to assess various aspects of their growth such as length-weight relationship, condition factor, sex ratio and length at first maturity to inform management and policy making for enhanced recovery and establishment of their populations. Length-weight relationship, condition factor, sex ratio and length at first maturity of the fish were studied from October 2016 to November 2018. A total of 303 fish samples; 193 C. zilli and 110 M. salmoides were studied. Results showed that C. zilli and M. salmoides had an allometry coefficient value of 2.9 and 3.1 and condition factor (K) value of 1.77 and 1.39 respectively. The sex ratios (male: female) of C. zilli and M. salmoides were 1.1:1 and 1.3: 1 respectively. The shortest total length for mature C. zilli and M. salmoides recorded were 12 cm and 26.5 cm while 21.8 cm and 51 cm were for the longest respectively. The fish growth pattern therefore failed to obey the cube law of b=3 thus exhibiting allometric growth. The two fish species were found to be in good condition with K factor above 1. It can therefore be concluded that the fish are generally in a good condition though the early maturity especially for C. zilli could be a sign of pressure either from environmental factors or human induced. Domination of the species by males, although a common feature in African lakes, is a case for concern since it presents uncertainty on the future of the fisheries. Restocking of Lake Naivasha with the two fish species should be considered and proper fishing practices enforced

Largemouth bass (LMB) were fed diets developed to substitute fishmeal (FM) using a blend of alternative proteins. Diets included a FM control (FMC), two FM-free formulae (FMF), one of which (FFF) was formulated using an algal oil replacing fish oil (FO) and, for comparative purposes, a commercial LMB feed (COM). Fish (densities of 3.11±0.29 kg m-1) were arbitrarily distributed into one of eight tanks configured as a recirculating system (RAS; 28.3±0.76 oC; DO2: 7.7±1.19 mg L-1) and tanks randomly assigned to one of the four treatments (i.e. each treatment was tested in duplicate). Animals were fed 3x daily to apparent satiation and group weighed every 3 weeks for 18 weeks. No differences were observed in feed consumption between groups (P >0.05) but LMB fed the COM diet were heavier (P 0.05). Results from the present study show that, with prudent dietary control, complete replacement of FM/FO in LMB diets is attainable and verifiable, without compromising growth performance or consumer acceptance of the final product.

Diets were manufactured for largemouth bass (LMB) replacing fishmeal (FM) with poultry by-product meal (PBM), soybean meal (SBM), and a hydrolyzed soy meal. Experimental diets included a FM control (FMC), and three FM-free formulations containing equal amounts of PBM and SBM with fish oil (diet F2), Algal meal DHA (F3) or a soy protein concentrate (SPC). A commercial LMB diet was included for reference. Fish (n=20 per group) were randomly dispersed into one of 20 tanks with group weights of ±5%, and densities of 7.39±0.17 kg m-3. Tanks were maintained as a RAS (28.3±0.76 oC, DO2 at 7.7±1.19 mg L-1) and randomly assigned to one of the five diets (n=80 fish per diet). Animals were fed to apparent satiation 3x daily for 12-weeks. Groups were weighed every 3 weeks and feed consumption recorded for calculation of FCRs. At trial end all fish were weighed and measured individually and 3 fish per tank employed for various analyses and comparisons against pre-trial samples. At trial end no differences (P > 0.05) were observed between groups for growth, SGR, or condition. FCR differed between the commercial and F3 diets (P < 0.05). F2 fed fish had higher (P < 0.05) visceral fat than F3 fed fish. Survival was 98-100% across all groups. Results indicate that judicious dietary manipulations may allow elimination of FM from LMB diets without compromising overall performance.

This study was conducted to determine the effects of feeding frequency on the growth, serum biochemical parameters, antioxidant status and hepatic growth hormone (GH), insulin-like growth factor I (IGF-I), lipoprotein lipase (LPL) and hepatic lipase (HL) gene expression levels of juvenile largemouth bass (Micropterus salmoides) reared in an in-pond raceway recirculating culture system (IPRS). Fish (initial body weight 5.0 ± 0.4 g) were hand-fed with a commercial diet under one of three different feeding frequency treatments (2, 3 or 4 meals/day) for 120 days. The results indicated that no significant differences were observed in the final body weight, weight gain and specific growth rate of fish fed different feeding frequencies on 30 days and 60 days (P > 0.05). Fish fed 2 times/day had higher growth than that fed 4 times/day on 90 days but had higher growth than those fed 3 and 4 times/day on 120 days. No significant differences were found in serum alanine aminotransferase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP) activities, total protein (TP), lysozyme and triglyceride (TG) content, hepatic total antioxidant capacity (T-AOC), glutathione peroxidase (GSH-PX) activities and malondialdehyde (MDA) content among fish fed different feeding frequency (P > 0.05). Serum glucose (Glu) content and catalase (CAT) activity decreased, while total cholesterol (TC) content increased with increasing feeding frequency. Fish fed 2 times/day had higher hepatic total superoxide dismutase (T-SOD) than that fed 4 times/day on 60 days, 90 days and 120 days (P

To investigate whether incorporation of small peptides into diets could change the growth performance, muscle quality and liver health of the largemouth bass, four diets were designed: SP0⁺ group (positive control group) was formulated according to the nutritional requirement of the largemouth bass. In SP0⁻ group (negative control group), the crude protein level was decreased by 30 g/kg compared with SP0⁺ group; SP20 group was added 20 g/kg small peptides based on the SP0⁻ group, and its crude protein level did not reach that of SP0⁺ group. In SP65 group, 65 g/kg small peptides were added on the basis of SP0⁻ group to obtain same crude protein level as SP0⁺ group. Fish were fed with these four different diets for 9 weeks. Results showed that, compared with the negative control group, the addition of 20 g/kg small peptides had no significant effect on the weight gain rate and feed coefficient of the largemouth bass; adding 65 g/kg small peptides could significantly increase the weight gain rate and reduce the feed coefficient (p

Steam cooking is a popular way of preparing fish and the end temperature plays a key role in the quality of the cooked fish. In this study, the lipid and protein oxidation, and the related changes in volatile compounds and in vitro digestibility of large-mouth bass ( Micropterus salmoides ) steam cooked to a core temperature of 45℃, 55℃, 65℃, 75℃, and 85℃ were investigated. Steaming caused a significant increase in the peroxide value (PV) and the thiobarbituric acid-reactive substances (TBARS) value, accompanied by the decreased proportion of unsaturated fatty acids like oleic acid and linoleic acid, which was related to the lipid oxidation and the increase in volatile aldehydes as indicated by the partial least squares analysis. The protein oxidation can be reflected by the significant decrease of total thiol groups, combined with the aggregation as shown in SDS-PAGE and the increase in particle size at pre-digestive phase. And the aggregation of proteins further caused the decreased digestibility of fish meat at the gastric phase, especially when the core temperature was above 75℃. Furthermore, steaming significantly decreased the aerobic count, and no coliform or generic E. coli was detected in steamed samples. Thus the core temperature of 65-75℃ was recommended for the consideration of food oxidation and microbial safety.

This study is aimed at identifying the effects of dietary fiber on gut health, as well as the association between that understanding and fiber consumption in fish. A total of 300 juvenile largemouth bass (micropterus salmoides, initial average weight: 15.38 ± 0.16g) were randomly divided into three treatment groups (4 replicates per group). Fish were fed with isoproteic and isolipidic diets containing 0% (low fiber, LF), 4% (moderate fiber, MF) and 8% (high fiber, HF) soybean fiber, respectively. The intestine and intestinal content of test fish per treatment group after 56 days of treatment were sampled. The results showed that the anterior intestinal sections had normal histological architecture, and no considerable damage or inflammation was observed in any histological section from all subjects examined. Curiously, fish fed the MF diet had better histological alterations than the other treatments. Meanwhile, the intestinal antioxidant capacity in the MF group was significantly promoted when compared to the other groups, as well as up-regulated expression of antioxidant-related genes including sod, cat and gpx with increasing dietary fiber concentrations. Importantly, the administrations of MF diet remarkably elevated largemouth bass innate immune parameters include intestinal inducible nitric oxide synthase (iNOS) activity, nitric oxide (NO) and total protein content. Similarly, dietary administrations of fiber down-regulated notablely the expression of pro-inflammatory cytokines including IL-8, IL-1β and TNFα, whereas up-regulated tolerogenic cytokine IL-10 and TGF-β1 mRNA levels. In addition, dietary fibers also modulated the community structure of the intestinal microbiota by significantly altering bacterial diversity. Dietary supplemental fibers regulated intestinal microbiota in largemouth bass, characterized by a reduced abundance of Fusobacteria along with increased abundances of Proteobacteria and Firmicutes. Taken together, the present results suggested that moderate fiber supplementation was beneficial to promoting intestinal health status of fish through antioxidant and anti-inflammatory effects, which could be at least partially responsible by the modulation of gut microbial composition.

Due to geologic processes and recent anthropogenic introductions, patterns of genetic and morphological diversity within the Smallmouth Bass (Micropterus dolomieu), which are endemic to the central and eastern United States (USA), are poorly understood. We assessed genetic and morphological differentiation between the widespread Northern Smallmouth Bass (M. d. dolomieu) and the more restricted Neosho Smallmouth Bass (M. d. velox) where their ranges meet in the Central Interior Highlands ecoregion (CIH). Data from 14 microsatellite loci were used to conduct Structure and principal components analyses to evaluate diversity across populations and screen for hybridization with sympatric Spotted Bass (M. punctulatus). We also tested for morphological differences using five morphometric traits and one meristic trait. We found support for three genetic clusters corresponding to previously described taxonomic variation; five clusters largely corresponding to river systems; and nine clusters representing hierarchical population structure within both ranges. We found evidence of a unique genetic cluster in tributaries of the White River within the Northern Smallmouth Bass range and admixture between the subspecies throughout the Neosho range. We also found evidence of morphological differentiation between subspecies; Neosho Smallmouth Bass exhibited larger head length than Northern Smallmouth Bass relative to total length, and there was a significant interaction of subspecies and orbital length, possibly indicating differential growth patterns between subspecies. Our results reveal multiple levels of divergence, suggesting the CIH harbors greater and more complex Smallmouth Bass diversity than previously thought.

Francisella orientalis is a highly virulent, emerging bacterium that causes mass mortalities in tilapia. This pathogen also affects numerous other warm-water fish species, including three-line grunt, hybrid striped bass and various ornamental fish. This study sheds light on two new species of fish that are susceptible to F. orientalis. Asian seabass and largemouth bass showed variable levels of susceptibility in a bacterial challenge experiment. After intraperitoneally injected with a dose of 106 CFU/fish, a total of 64.28% and 21.42% mortalities were obtained in Asian seabass and largemouth bass, respectively. Meanwhile, Nile tilapia showed acute mortality of 100%. All fish showed typical lesions of francisellosis, including multifocal granulomas in the spleen and head kidney. Immunohistochemical analysis revealed strong positive signals inside the granulomas of all fish. The bacterial recovery in solid media from infected fish was highest in Nile tilapia (85.71%), followed by Asian seabass (35.71%) and largemouth bass (21.42%). PCR results tested 100% positive for Nile tilapia, and 78.57% and 21.42% for Asian seabass and largemouth bass, respectively. In conclusion, Asian seabass and largemouth bass are susceptible to this pathogen, which warrants new management strategies when employing predation polyculture systems of these species with tilapia.

This study examined the effects on conformation and oxidation of myofibrillar protein in largemouth bass by different thawing methods. The conventional thawing, microwave thawing, microwave (MVT) or ultrasound combined with vacuum thawing, microwave or far-infrared thawing (FMT) combined with magnetic nanoparticles were used in this experiment. The physicochemical changes were analyzed by differential scanning calorimetry and dynamic rheology. The protein structure changes were measured by Raman, intrinsic fluorescence, and second-derivative ultraviolet spectrometry. The degree of protein aggregation was evaluated by surface hydrophobicity, particle size, and zeta-potential measurements. Total sulfhydryl content, protein carbonyl content, Ca2+ -ATPase activity, and SDS-PAGE were used to analyze the degree of protein oxidation. Results showed that MVT and FMT samples had better thermal stability, more stable protein conformation, and a lower degree of protein oxidation. Thus, these two methods would be beneficial to sustain the quality of thawed fillets. PRACTICAL APPLICATIONS: In the market circulation, largemouth bass (Micropterus salmoides) need to be frozen. The thawing methods can directly affect the quality of frozen fish, thus causing the changes in the conformation of the myofibrillar protein in fish, and also affecting the degree of protein oxidation. The results showed that the microwave combined with vacuum and the magnetic nanoparticles combined with far-infrared thawing had less effect on myofibrillar protein of fish and were a better thawing method.

Striped Bass, Morone saxatilis (Walbaum, 1792), is an anadromous fish species that supports fisheries throughout North America and is native to the North American Atlantic Coast. Due to long coastal migrations that span multiple jurisdictions, a detailed understanding of population genomics is required to untangle demographic patterns, understand local adaptation, and characterize population movements. This study used 1,256 single nucleotide polymorphism (SNP) loci to investigate genetic structure of 477 Striped Bass sampled from 15 locations spanning the North American Atlantic coast from the Gulf of St. Lawrence, Canada, to the Cape Fear River, United States. We found striking differences in neutral divergence among Canadian sites, which were isolated from each other and US populations, compared with US populations that were much less isolated. Our SNP dataset was able to assign 99% of Striped Bass back to six reporting groups, a 39% improvement over previous genetic markers. Using this method, we found (a) evidence of admixture within Saint John River, indicating that migrants from the United States and from Shubenacadie River occasionally spawn in the Saint John River; (b) Striped Bass collected in the Mira River, Cape Breton, Canada, were found to be of both Miramichi River and US origin; (c) juveniles in the newly restored Kennebec River population had small and nonsignificant differences from the Hudson River; and (d) tributaries within the Chesapeake Bay showed a mixture of homogeny and small differences among each other. This study introduces new hypotheses about the dynamic zoogeography of Striped Bass at its northern range and has important implications for the local and international management of this species.

The reported requirements of largemouth bass (LMB, which is native to North America) for dietary protein and lipids varied substantially among previous studies, and this fish fed current formulated diets exhibit poor growth performance and pale liver syndrome. Because amino acids and lipids are known to affect hepatic metabolism and function in mammals, it is imperative to understand the impacts of these dietary macronutrients on the growth and liver morphology of LMB. In this study, we designed six isocaloric diets to determine the effects of different dietary crude protein (CP; 40%, 45%, and 50%; dry matter basis) and lipid levels (7.5% and 10%; dry matter basis) on fat and glycogen deposits, as well as hepatosis in LMB. There were four tanks (12 fish per tank, an average initial weight of 18.4 g/fish) per dietary treatment group and the trial lasted for 8 weeks. Fish were fed to apparent satiation three times daily. Results indicated that LMB fed the 45% or 50% CP diet grew faster (P

A 12-week feeding trial was conducted to evaluate the effects of replacing fish meal by chicken haemoglobin powder in largemouth bass diets. Four isonitrogenous (48%) and isolipidic (12%) diets were formulated to replace 0% (control), 9.80%, 19.61% and 29.41% of fish meal with chicken haemoglobin powder. Each diet was fed to triplicate groups of fish (initial weight: 49.50 ± 0.07 g) twice daily. The fish specific growth rate was significantly reduced when diet replacement level was up to 19.61%, which may be related to the feed intake and apparent digestibility coefficient of protein and amino acids. Meanwhile, the feed efficiency ratio and protein efficiency ratio were not significantly decreased until the replacement level up to 29.41%. The activity of CCP was significantly reduced when 19.61% of fish meal was replaced. Meanwhile, the activity of lysozyme and serum protein content was significantly altered in fish fed with the diets up to 29.41% replacement. Additionally, the red blood cell count and haemoglobin content was significantly decreased when the replacement level was up to 19.61%. In overall, the diet with 9.80% of chicken haemoglobin powder was more suitable for largemouth bass.

Protein accretion in some fish species is affected by dietary lipids, starch and their interactions, but this aspect of nutrition is largely unknown in largemouth bass (LMB). Therefore, we designed six experimental diets with three starch levels (5%, 10%, and 15%; dry matter basis) and two lipid levels (10% and 12.5%; dry matter basis) to evaluate the effects of dietary starch and lipid levels on the protein retention, growth, feed utilization, and liver histology of LMB. There were three tanks (18 fish per tank, ~ 4.85 g per fish) per dietary treatment group and the trial lasted for 8 weeks. Fish were fed to apparent satiation twice daily. Results indicated that increasing the dietary starch level from 5 to 15% reduced (P

BACKGROUND Irradiation can cause lipid oxidation of fish. This study aimed to examine the effect of radiation (method, dose and dose rate) on the acid value (AV), peroxide value (PV), thiobarbituric acid reactive substances (TBARS) content and fatty acid profile of fresh and freeze-dried largemouth bass flesh. RESULTS AV, PV and TBARS presented a dose-dependent increase in fish meat for both cobalt-60 (60 Co) and electron beam (EB) irradiation. With a 6 kGy dose of radiation, all measured indices in the 60 Co group were significantly higher than those in the EB group (P

Aquafeeds for carnivorous species face a nutritional–technological conundrum: containing sufficient starch to meet specific manufacturing requirements for binding, extrusion and expansion, but ideally containing as little starch as possible owing to their limited ability to utilise carbohydrates. The present study evaluated the effects of dietary starch with different amylose to amylopectin ratios and resistant starch contents on growth performance, hepatic glycogen accumulation and glucose metabolism of an important cultured carnivorous finfish, largemouth bass (Micropterus salmoides). A common starch source (α-cassava starch (CS)) was tested as is or after being enzymatically de-branched at three different inclusion levels in diets for largemouth bass. Results showed that the increased dietary starch levels compromised performance and high dietaryα-CS content led to obvious liver damage. However, the growth performances of fish fed the diets with de-branched starch (DS) were improved, and no manifest liver damages were observed even at the higher inclusion level. The increasing dietary starch contents significantly increased hepatic glycogen accumulation, but not when DS was used. High dietary starch content, without regard to starch sources, had no effect on the expression of glucose metabolism-related genes, except for down-regulation of insulin receptor expression. However, the use of dietary DS promoted the expression of genes involved in the insulin pathway and glycolysis. In conclusion, this study showed that the use of starch sources with a high amylose to amylopectin ratio and resistant starch in the feed for cultured carnivorous finfish could alleviate the hepatic glycogen deposition through regulating the insulin pathway and glycolysis.

Hyperpigmented melanistic skin lesions (HPMLs) of smallmouth bassMicropterus dolomieuare observed in the Potomac and Susquehanna rivers, Chesapeake Bay watershed, USA. Routine, nonlethal population surveys were conducted at 8 sites on the mainstem Susquehanna River and 9 on the Juniata River, a tributary of the Susquehanna River, between 2012 and 2018, and the prevalence of HPMLs was documented. A total of 4078 smallmouth bass were collected from the mainstem Susquehanna River and 6478 from the Juniata River. Lesions were primarily seen in bass greater than 200 mm, and prevalence in the Susquehanna River (8%) was higher (p < 0.001) than in the Juniata River (2%). As part of ongoing fish health monitoring projects, smallmouth bass were collected at additional sites, primarily tributaries of the Susquehanna (n = 758) and Potomac (n = 545) rivers between 2013 and 2018. Prevalence in the Susquehanna River (13%) was higher (p < 0.001) than the Potomac (3%). Microscopically, HPMLs were characterized by an increased number of melanocytes in the epidermis or within the dermis and epidermis. RNAseq analyses of normal and melanistic skin identified 3 unique sequences in HPMLs. Two were unidentified and the third was a viral helicase (E1). Transcript abundance in 16 normal skin samples and 16 HPMLs showed upregulation of genes associated with melanogenesis and cell proliferation in HPMLs. The E1 transcript was detected in 12 of the 16 melanistic areas but in no samples from normal skin. Further research will be necessary to identify the putative new virus and determine its role in melanocyte proliferation.

Fish behavior types can predict angling vulnerability, providing insights about how recreational fishing may lead to artificial trait selection. Most vulnerability studies have focused on species with active foraging strategies, and the impact of environmental conditions on vulnerability has not been quantified. The objective of this study was to determine the influences of behavior types and habitat on angling vulnerability of largemouth bass (Micropterus salmoides (Lacepède, 1802)) — a sit-and-wait predator. Behavior assays quantified individual activity and boldness, then experimental angling took place in ponds with two habitat treatments: (1) structured habitat with artificial structures present and (2) open habitat with no structures added. Two anglers determined which individual largemouth bass were vulnerable to capture across the two contexts. In contrast with previous studies involving active foragers, behavior types of largemouth bass did not influence capture, regardless of habitat type. The number of captures also did not differ between structured and open habitat. However, anglers captured fish with different behavioral phenotypes, revealing additional complexity for factors that may affect behavioral selection. Findings suggest that angling may not be selecting for specific activity or boldness phenotypes of largemouth bass, even across habitat types, but that anglers may influence selection.

A triazole hydrophilic interaction chromatography mass spectrometry (HILIC-MS) method was developed for lipidomics studying the largemouth bass (Micropterus salmoides). The effect of feeds, especially the frozen trash fish and artificially formulated feed, on the phospholipid composition was evaluated. The results showed that the phospholipids could be well separated in the order of phosphatidylcholine, phosphatidylethanolamine, and phosphatidylinositol and phosphatidylserine. Under negative-ion mode, all the phospholipids were ionized by deprotonating as [M-H]− or adducting as [M + HCOO]−. The mass spectrum for each phospholipid class was inspected and a total of 34 phospholipid molecular species (PMS) was identified. Each PMS was extracted by its ion chromatography and quantified using a linear regression model. The calibration curves were linear ranging from 2.00 to 200 μg mL−1 (R2 0.9988–0.9991) with the limit of detection (LOD) and limit of quantitation (LOQ) of 0.15–0.52 μg mL−1 and 0.80–1.80 μg mL−1, respectively. The results indicated that the HILIC-MS method was efficient and reliable in lipidomics analyzing largemouth bass. After orthogonal partial least squares discriminant analysis (OPLS-DA), the major contributors to the difference of largemouth bass samples with different feeds were revealed as PE 760.8, PC 842.8, etc. and validated by permutation test with the intercepts of R2 = (0.0, 0.876) and Q2 = (0.0, − 1.21).

Micropterus Salmoides rhabdovirus (MSRV), as a common aquatic animal virus, can cause lethal and epidemic diseases in the cultivation of largemouth bass. In this study, we reported a kind of immersion single-walled carbon nanotubes-loaded subunit vaccine which composited by glycoprotein (G) of MSRV, and evaluated its protective effect on largemouth bass. The results showed that a stronger immune response including serum antibody levels, enzyme activities (superoxide dismutase, acid phosphatase, alkaline phosphatase and total antioxidant capacity), complement C3 content and immune-related genes (IgM, TGF-β, IL-1β, IL-8, TNF-α, CD4) expression can be induced obviously with single-walled carbon nanotubes-glycoprotein (SWCNTs-G) groups compared with G groups when largemouth bass were vaccinated. After bath immunization with G or SWCNTs-G for 28 days, fish were challenged with a lethal dose of MSRV. The survival rates for control group (PBS), SWCNTs group (40 mg L−1), pure G protein groups (40 mg L−1) and three SWCNTs-G groups (5 mg L−1, 10 mg L−1 and 40 mg L−1) were 0%, 0%, 39.5%, 36.7%, 43.6%and 70.1%, respectively. Importantly, with the assistance of SWCNTs, the immune protective rate of the SWCNTs-G group (40 mg L−1) increased by approximately 30.6%. This study suggested that SWCNTs-G is a promising immersion subunit vaccine candidate against the death caused by MSRV.

Purpose. Modern fisheries of Ukraine faces many challenges, among which the adaptation to climate changes as well as the development of recreational fishery and international fishing tourism can be highlighted. The main purpose of the adaptation can be formulated as an improvement of fishery activities due to an increase in average annual temperatures and prolongation of the active growth period of aquatic organisms. Moreover, in the majority of developed countries all around the world, there is a tendency of the transition from perception of fish as a food product to the perception of fish as an object of recreational services. This makes possible to exploit fish stocks more effectively and sparingly, with only a little harm for fish. As a new object of aquaculture that has high adaptive potential to increases in average annual temperatures and takes an important place in recreational fishing across the world, we can consider the largemouth bass (Micropterus salmoides). This fish species, which is native to freshwaters of North America, is currently reared in aquaculture in more than 50 countries, mainly for recreational and sport fishing. The development of methodologies for largemouth bass aquaculture in Ukraine could contribute to more effective fisheries management and to development of recreational fishing services. This in turn would result in income growth to local and general budgets and would contribute to more effective investment raising. Findings. The article contains brief information on the outlooks of reproduction and cultivation of the largemouth bass in Ukrainian aquaculture, ecological and fisheries characteristics of this species with the description of its natural habitats, feeding, growing potential of different age groups, and breeding process in its natural range. Moreover, this review mentions attempts of largemouth bass introduction to Ukrainian water bodies occurred in XІХ-ХХ centuries, and possible reasons of its total and partial failures. Furthermore, this article assesses the potential impact of the largemouth bass on local ichthyofauna and aquaculture conditions, and considers the measures aimed on the prevention of uncontrolled spread of this species during cultivation. Practical value. Information provided in this review can be further used for development of the methodology of largemouth bass aquaculture in Ukraine as well as for popularization of this species for recreational fishing and the development of international fishing tourism.

Ciguatoxins (CTXs), produced by toxic benthic dinoflagellates, can bioaccumulate in marine organisms at higher trophic levels. The current study evaluated the uptake and depuration kinetics of some of the most potent CTXs, Pacific CTX-1, -2, and -3 (P-CTX-1, -2, and -3), in orange-spotted grouper (Epinephelus coioides) exposed to 1 ng P-CTXs g-1 fish daily. Over a 30 d exposure, P-CTX-1, -2, and -3 were consistently detected in various tissues of exposed fish, and the concentrations of the total P-CTXs in tissues generally ranked following the order of liver, intestine, gill, skin, brain, and muscle. Relatively higher uptake rates of P-CTX-1 in the groupers were observed compared with those of P-CTX-2 and -3. The depuration rate constants of P-CTX-1, -2, and -3 in different tissues were (0.996-16.5) × 10-2, (1.51-16.1) × 10-2, and (0.557-10.6) × 10-2 d-1, respectively. The accumulation efficiencies of P-CTX-1, -2, and -3 in whole groupers were 6.13%, 2.61%, and 1.15%, respectively. The increasing proportion of P-CTX-1 and the decreasing proportion of P-CTX-2 and -3 over the exposure phase suggest a likely biotransformation of P-CTX-2 and -3 to P-CTX-1, leading to higher levels of P-CTX-1 in fish and possibly a higher risk of CTXs in long-term exposed fish.

Climate-related changes in fish communities can present new challenges for fishery managers who must address declines in cool- and cold-water sportfish while dealing with increased abundance of warm-water sportfish. We used largemouth bass (Micropterus salmoides) in Wisconsin lakes as model populations to determine whether angler harvest provides a realistic method for reducing abundance of a popular warm-water sportfish that has become more prevalent and has prompted management concerns around the globe. Model results indicate largemouth bass will be resilient to increased fishing mortality. Furthermore, high rates of voluntary catch-and-release occurring in most largemouth bass fisheries likely preclude fishing mortality rates required to reduce bass abundance at meaningful levels (≥25% reductions). Increasing fishing mortality in these scenarios may require more “stimulus” than merely providing anglers with greater harvest opportunities via less stringent harvest regulations. Angler harvest could result in populations dominated by small fish, a scenario that may be undesirable to anglers, but could provide ecological benefits in certain situations.

The study was carried out to evaluate the pharmacokinetic disposition of enrofloxacin (ENF) with a single dose of 20 mg/kg after oral administration in largemouth bass (Micropterus salmoides) at 28°C. The concentrations of ENF and of its metabolite ciprofloxacin (CIP) in plasma, liver, and muscle plus skin in natural proportions were determined using HPLC. The concentration-time data for ENF in plasma were best described by a two-compartment open model. After oral administration, the maximum ENF concentration (Cmax ) of 10.99 μg/ml was obtained at 0.60 hr. The absorption half-life (T1/2Ka ) of ENF was calculated to be 0.07 hr whereas the elimination half-life (T1/2β ) of the drug was 90.79 hr. The estimates of area under the plasma concentration-time curve (AUC) and apparent volume of distribution (Vd/F) were 1,185.73 μg hr/ml and 2.21 L/kg, respectively. ENF residues were slowly depleted from the liver and muscle plus skin of largemouth bass with the T1/2β of 124.73 and 115.14 hr, respectively. Very low levels of ciprofloxacin were detected in the plasma and tissues. A withdrawal time of 24 days was necessary to ensure that the residues of ENF + CIP in muscle plus skin were less than the maximal residue limit (MRL) of 100 μg/kg established by the European Union.

During recent decades, survey studies have documented the widespread presence of oocytes in the testes of male Smallmouth Bass Micropterus dolomieu collected from surface waters throughout the United States. There are few published reports of testicular oocytes (TO) in Smallmouth Bass before the 1990s, so it is difficult to know how long this has been occurring. Consequently, this study was conducted to evaluate the prevalence and severity of TO occurrence in whole fish specimens from two archival collections-the Smithsonian Institution's National Museum of Natural History in Suitland, Maryland, and Cornell University's Museum of Vertebrates in Ithaca, New York. Gonads were excised from 167 preserved male Smallmouth Bass that were originally collected between 1875 and 2004, and routine histologic sections were prepared and examined. The severity of TO was determined using a semiquantitative scoring system. Overall, 52.1% of male Smallmouth Bass were found to have TO. Affected fish had been collected in 11 of the 18 represented states, and TO were found in specimens harvested during decades as early as the 1880s and 1900s. Unfortunately, the small number of samples acquired at the earliest time periods precluded analyses of prevalence and severity trends over time. The results of this study demonstrated that the phenomenon of TO in male Smallmouth Bass is at least a century old and confirmed the widespread nature of this finding throughout the species' historic range. Further research efforts should focus on determining the baseline prevalence of TO in laboratory-reared male Smallmouth Bass that have not been exposed to endocrine active substances or the effects of experimental estrogen exposure on such fish.

Invasive species and climate change are leading threats to freshwater ecosystems. In the Columbia River Basin (CRB), nonnative fishes are a critical consideration in salmon recovery, yet managers lament a lack of distribution information. Combining a species distribution model (SDM) with environmental DNA (eDNA), we locate range boundary regions of nonnative smallmouth bass (Micropterus dolomieu) and evaluate its overlap with native salmonids. A combination of thermal, hydrological, and geomorphic variables predict that smallmouth bass is distributed across ∼18 000 river kilometres and overlaps with 3%–62% of rearing habitat of salmonids (species-dependent) in the CRB. Under a moderate climate change scenario, smallmouth bass is predicted to expand its range by two-thirds (totaling ∼30 000 river kilometres) by 2080. Basin-wide models were sufficiently accurate to identify upstream invasion extents to within 15 km of the eDNA-based boundary, and including eDNA data improved model performance at critical range boundary regions without sacrificing broadscale model performance. Our study highlights how eDNA approaches can supplement large geospatial data sets to result in more accurate SDM predictions, guiding nonnative species management.

Widespread invasion of Round Goby (Neogobius melanostomus) throughout the Great Lakes has raised concerns regarding increased egg predation on fish species. To better understand nest predation, we examined nesting habitat selected by three upper St. Lawrence River Centrarchid species and the predator assemblage at nests during the 2011 and 2012 egg incubation and larval periods. Following removal of guarding males by angling, 5-min observations were used to identify and enumerate predators at rock bass (Ambloplites rupestris; n = 81), pumpkinseed (Lepomis gibbosus; n = 80), and smallmouth bass (Micropterus dolomieu; n = 40) nests. Differences in nesting habitat among centrarchids corresponded with differences in nest predator assemblages along a gradient defined primarily by depth and substrate. Pumpkinseed nests in shallow depths with soft substrate were visited principally by minnow spp., but few round goby. Smallmouth bass nests at greater depth with hard substrates were frequented nearly exclusively by round goby, while rock bass nests at intermediate depth with a mix of hard and soft substrates were visited by round goby and yellow perch (Perca flavescens). Rock bass nests had a higher predator burden than pumpkinseed nests in 2011, but no differences were observed among centrarchid species in 2012. Round goby were a major component of the predators at rock bass and smallmouth bass nests. However, predation burden imposed by yellow perch was higher than round goby at rock bass nests. We conclude nesting habitat selection influences native and non-native egg predator assemblages, but whether round goby predation is additive or compensatory remains unclear.