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El'gygytgyn is the only ancient lake in the Arctic that avoided continental-scale glaciations. This lake is located on an arid mountain plateau, far from the main routes of post-glacial freshwater fish dispersal, and it is therefore challenging to consider the local fauna in a historical context. Here we present a study of the ecology and evolutionary history of the local charr complex (genus Salvelinus). We found that the endemic charrs exhibit extreme longevity, contrasting lifestyles and phenotypes. Salvelinus svetovidovi is a relic benthivorous species. The remaining charrs are descendants of Salvelinus taranetzi. Mitochondrial and microsatellite DNA polymorphisms analyzed in them and in charrs from surrounding basins indicate that S. taranetzi invaded the lake from Arctic Chukotka in the late Pleistocene as two distinct, previously diverged lineages. Descendants of both lineages occupied the pelagic food chain. The first lineage has flourished as a monomorphic planktivorous population since colonization. The second represents an example of a recent in-lake adaptive divergence, in which a deepwater piscivore specialist formed a new epilimnetic ecomorph of an impressive size (up to 9.0 kg). We suggest that this diversification was triggered by modern warming in the Arctic, which led to the formation of a productive littoral ecosystem. [ABSTRACT FROM AUTHOR]

Increasing rates of hybridization and introgression in managed populations of freshwater fish are a major threat to the long-term viability of native species. The conservation challenge begins with identifying native gene pools. For brown trout (Salmo trutta Linnaeus, 1758) in the Upper Danube drainage, this task is complicated by the presence of both naturally and anthropogenically induced admixture of highly divergent lineages (Atlantic and Danubian). Herein, a ddRADseq protocol was used to type 377 individuals from 24 populations in the Upper Danube in Austria and Germany, and from reference populations from adjacent drainages and commercial hatcheries. High genetic differentiation at small geographic scales was found among pure Danubian-lineage populations, especially in the Kalkalpen National Park (Austria). In the Upper Danube drainage of Germany, as well as in the Rhine and Elbe drainages, brown trout populations were predominantly of Atlantic-lineage origin – as were those of all commercial hatcheries. Most populations, however, showed various degrees of admixture between Danubian and Atlantic lineages, hypothesized to be the result of both natural and anthropogenic processes. We highlight the conservation value of pure Danubian-lineage populations, and the challenges promoting conservation of naturally admixed populations, while discouraging continued stocking and admixture via management activities. [ABSTRACT FROM AUTHOR]

In biogeography, vicariance and long‐distance dispersal are often characterised as competing scenarios. However, they are related concepts, both relying on collective geological, ecological, and phylogenetic evidence. This is illustrated by freshwater fishes, which may immigrate to islands either when freshwater connections are temporarily present and later severed (vicariance), or by unusual means when ocean gaps are crossed (long‐distance dispersal). Marine barriers have a strong filtering effect on freshwater fishes, limiting immigrants to those most capable of oceanic dispersal. The roles of vicariance and dispersal are debated for freshwater fishes of the Greater Antilles. We review three active hypotheses [Cretaceous vicariance, Greater Antilles–Aves Ridge (GAARlandia), long‐distance dispersal] and propose long‐distance dispersal to be an appropriate model due to limited support for freshwater fish use of landspans. Greater Antillean freshwater fishes have six potential source bioregions (defined from faunal similarity): Northern Gulf of México, Western Gulf of México, Maya Terrane, Chortís Block, Eastern Panamá, and Northern South America. Faunas of the Greater Antilles are composed of taxa immigrating from many of these bioregions, but there is strong compositional disharmony between island and mainland fish faunas (>90% of Antillean species are cyprinodontiforms, compared to <10% in Northern Gulf of México and Northern South America, and ≤50% elsewhere), consistent with a hypothesis of long‐distance dispersal. Ancestral‐area reconstruction analysis indicates there were 16 or 17 immigration events over the last 51 million years, 14 or 15 of these by cyprinodontiforms. Published divergence estimates and evidence available for each immigration event suggests they occurred at different times and by different pathways, possibly with rafts of vegetation discharged from rivers or washed to sea during storms. If so, ocean currents likely provide critical pathways for immigration when flowing from one landmass to another. On the other hand, currents create dispersal barriers when flowing perpendicularly between landmasses. In addition to high salinity tolerance, cyprinodontiforms collectively display a variety of adaptations that could enhance their ability to live with rafts (small body size, viviparity, low metabolism, amphibiousness, diapause, self‐fertilisation). These adaptations likely also helped immigrants establish island populations after arrival and to persist long term thereafter. Cichlids may have used a pseudo bridge (Nicaragua Rise) to reach the Greater Antilles. Gars (Lepisosteidae) may have crossed the Straits of Florida to Cuba, a relatively short crossing that is not a barrier to gene flow for several cyprinodontiform immigrants. Indeed, widespread distributions of Quaternary migrants (Cyprinodon, Gambusia, Kryptolebias), within the Greater Antilles and among neighbouring bioregions, imply that long‐distance dispersal is not necessarily inhibitory for well‐adapted species, even though it appears to be virtually impossible for all other freshwater fishes. [ABSTRACT FROM AUTHOR]

Largemouth bass (Micropterus salmoides, LB) is an important aquaculture and fishing species in the world. LB has been introduced into China since 1983, and its aquaculture production has increased year by year. The total yield of LB in China reached 802,486 tons in 2022, ranking seventh in China's freshwater fish aquaculture. However, the LB is facing threats such as degradation of germplasm resources and disease susceptibility due to limitations in the scale of introduction, coupled with the effects of high-density aquaculture, inbreeding, and species hybridization. This paper summarizes the current status of LB germplasm resources, variety genetic improvement, nutrition and fodder, aquaculture mode and diseases, and circulation and processing. This paper also provides recommendations on how to fully explore and utilize the existing germplasm resources of LB; culture new LB germplasm that combines excellent resistance and growth characteristics through innovations in breeding techniques; reduce the morbidity rate and improve the efficiency of cultured LB through the optimization of fodder formulations and innovation of aquaculture modes; and shift the processing of LB toward standardization, efficient nutrition and safety through the integration of high-tech and large-scale production. This paper provides a reference for the sustainable and healthy development of the LB industry. [ABSTRACT FROM AUTHOR]

Fish populations rely on complex environmental conditions involving physical, chemical, and biological factors. Understanding the factors that control population persistence and productivity is essential for species management. We assessed the distribution and associated habitat features of a species at risk in Canada, Silver Shiner (Notropis photogenis), within Sixteen Mile Creek, a tributary of Lake Ontario. Using random forest models, we quantified a range of ecological factors (n = 25) to estimate habitat associations for sampled populations and life stages (juvenile, adult). A complex set of ecological factors were informative predictors of Silver Shiner distribution, including physical (stream morphology, water velocity, substrate type), and biological (aquatic and riparian vegetation) conditions. Juveniles were less responsive to habitat conditions but exhibited high seasonal variability in occurrence. Adults were most common in stream sections with greater than 0.5 m depth and stream velocity less than 0.6 m/s, and areas without silt substrate. Broadly, the models predicted Silver Shiner distribution with 68–92% accuracy in non-training data. Our findings describe the habitat conditions that Silver Shiner currently occupies in an urban drainage, which may serve as a point of reference for habitat protection and restoration. Further, predictive species distribution models can serve to identify habitat for further monitoring and restoration. [ABSTRACT FROM AUTHOR]

Species of the catfish genus Rineloricaria are common in the Paraíba do Sul River basin, in southeastern Brazil; here we present a revision of the taxonomic diversity and geographic distribution of the species of the genus inhabiting the basin, based on novel morphologic and molecular data. Five species delimitation methods based on cytochrome C oxidase subunit 1 nucleotide sequences yielded comparable molecular operational taxonomic units. The automatic barcode gap discovery, assemble species by automatic partitioning, barcode index number, and Bayesian implementation of the Poisson tree process methods supported the recognition of five evolutionary lineages. These taxonomic units were assigned to the previously described Rineloricaria nigricauda, Rineloricaria steindachneri, Rineloricaria zawadzkii, and Rineloricaria nudipectoris, and an additional undescribed species. R. zawadzkii was further divided into two intraspecific geographically structured lineages using the generalized mixed Yule coalescent delimitation method. A maximum likelihood phylogenetic analysis revealed that the five lineages from the Paraíba do Sul have closer relationships to different species from southern and southeastern Brazil (Ribeira de Iguape, Lagoa dos Patos, Uruguay, Paraguay, and Parana river basins) than to each other. Based on the analysis of lectotypes, recently collected material, and specimens from ichthyological collections, the poorly described R. nigricauda and R. steindachneri are redescribed following current descriptive standards. The undescribed species from the middle and upper Paraíba do Sul River basin is formally described. The description of a new species, along with the description of species boundaries in R. nigricauda and R. steindachneri, contributes to the knowledge of the ichthyofauna of the Paraíba do Sul River basin and adjacent coastal drainages of southeastern Brazil. An identification key for the species of Rineloricaria occurring in the Paraíba do Sul River basin is provided. [ABSTRACT FROM AUTHOR]

Vibrio cholerae is the etiological agent of cholera in humans. The bacterium is frequently detected in aquatic products worldwide. However, the current literature on the genome evolution of V. cholerae of aquatic animal origins is limited. Here, we firstly characterized the growth and genome features of V. cholerae isolates with different resistance phenotypes from three species of common freshwater fish. The results revealed that the non-O1/O139 V. cholerae isolates (n = 4) were halophilic and grew optimally at 2% NaCl and pH 8.0. Their draft genome sequences were 3.89 Mb–4.15 Mb with an average GC content of 47.35–47.63%. Approximately 3366–3561 genes were predicted to encode proteins, but 14.9–17.3% of them were of an unknown function. A number of strain-specific genes (n = 221–311) were found in the four V. cholerae isolates, 3 of which belonged to none of any of the known sequence types (STs). Several putative mobile genetic elements (MGEs) existed in the V. cholerae isolates, including genomic islands (n = 4–9), prophages (n = 0–3), integrons (n = 1–1), and insertion sequences (n = 0–3). Notably, CRISPR-Cas system arrays (n = 2–10) were found in the V. cholerae genomes, whereby the potential immunity defense system could be active. Comparative genomic analyses also revealed many putative virulence-associated genes (n = 106–122) and antibiotic resistance-related genes (n = 6–9). Overall, the results of this study demonstrate the bacterial broader-spectrum growth traits and fill prior gaps in the genomes of V. cholerae originating from freshwater fish. [ABSTRACT FROM AUTHOR]

Freshwater fish are threatened globally and in addition, knowledge of their diversity is incomplete and species richness is underestimated. Within the ichthyofauna of the Cape Fold Ecoregion of South Africa, many undescribed lineages exist and for most of these, information is limited regarding their ecology, distribution and threats. The Tradouw redfin Pseudobarbus sp. 'burchelli Tradouw' is a novel and range-restricted lineage within the Breede River redfin Pseudobarbus burchelli. Annual monitoring conducted between 2012 and 2016 investigated spatial and temporal trends in the distribution and population dynamics of this taxon. Results indicated that it is highly fragmented within its distribution range, likely a result of the combined pressures of invasive fish and poor land use practices. Short-term monitoring results indicated that invasive fish are established in most of the catchment and that the relative abundance of redfins remained constant only in the limited section of river where alien fish were absent. Poor land use practices such as water over-abstraction and surface water pollution, are pervasive threats, but the extent to which these affect the redfins requires further investigation. The long-term survival of this taxon remains uncertain, and short-term and long-term conservation and management options are explored. [ABSTRACT FROM AUTHOR]

The European mudminnow (Umbra krameri Walbaum, 1792) is a freshwater fish species with scattered distribution in the Danube and Dniester drainages, being the only native member of the Umbridae family in Europe. It inhabits irrigation canals, slow flowing and stagnant waters with dense vegetation, such as small ditches, oxbows and backwaters. In Croatia, it was first mentioned in 1897 in the Drava River drainage, and later on was recorded in the Mura River and in several localities of the Sava watershed. We studied 212 localities and recorded the presence of the species in 26 of them in the Drava, Sava and Mura river systems in Croatia. We present the first comprehensive data on the distribution and habitat preferences of Umbra krameri in Croatia, including historical data and recent data collected in the last six years. Our results show that U. krameri is an abundant and prevalent species in several localities in the Drava River system. Field data shows the suitability of secondary habitats for U. krameri, such as artificial canals with intensive organic load and pollution from anthropogenic sources, as well as the Sava River system being the southern border of the distribution of this species. [ABSTRACT FROM AUTHOR]

River restoration programmes with the goal of conserving and rehabilitating inland fishes have a multi‐decadal history, but evaluation and synthesis of past restoration actions have been limited by a lack of monitoring and reporting. Given that calls for both monitoring and systematic reviews of restoration have increased, we were interested in the influence that restoration has had on improving conditions for riverine fishes resulting from long‐standing and increasingly prominent stressors. Our objectives were to (1) identify which stressors were targeted in river restoration efforts, (2) determine the proportion of published studies that articulate restoration goals and develop comparative monitoring designs for assessing the effects of restoration on fishes, and (3) conduct a meta‐analysis to synthesise fish responses to restoration projects.We assessed restoration effectiveness for increasing fish density and richness from peer‐reviewed papers published over the past decade using a global systematic review and meta‐analysis.We found that restoration actions addressed major stressors primarily by improving in‐stream habitat (37%), increasing in‐stream longitudinal connectivity (26%) and increasing lateral floodplain connections (9%). Although 81% of studies had comparative monitoring designs (i.e., before/after and control/impact) and stated restoration goals, only 40% of those studies reported sufficient data to be included in the meta‐analysis. Projects which increased in‐stream connectivity had the largest positive effect size on fish density and richness compared to in‐stream habitat improvements and increasing floodplain connections. Time since restoration and restoration size (i.e., geographical footprint) were not strong predictors of fish response effect sizes.Restoration effectiveness was highly variable among project types. Authors of studies included in the meta‐analysis often identified spatial or temporal scale of monitoring, overriding catchment conditions, and recolonisation potential as sources of variability and effectiveness in restoration outcomes. Systematic reporting of these and other covariates may help guide processes in restoration evaluation and provide valuable research insights. Despite increased emphasis on monitoring, incomplete data reporting limited the number of studies that could be included for quantitative meta‐analysis. Persistent emphasis on setting specific criteria (e.g., measurable outcomes of fish response) for restoration goals, project monitoring, data reporting, information sharing and collaborative projects is likely to continue to improve understanding of restoration effectiveness transferable to future endeavours.Our results can be used to support river restoration practitioners with evidence‐based information to evaluate the cost–benefit ratio of competing restoration priorities, and inform restoration planning and implementation for riverine fish. [ABSTRACT FROM AUTHOR]

Phylogeography bears an important part in ecology and evolution. However, current phylogeographic studies are largely constrained by limited numbers of individual samples. Using an environmental DNA (eDNA) assay for phylogeographic analyses, this study provides detailed information regarding the history of Siberian stone loach Barbatula toni, a primary freshwater fish across the whole range of Hokkaido, Japan. Based on an eDNA metabarcoding on 293 river water samples, we detected eDNA from B. toni in 189 rivers. A total of 51 samples, representing the entire island, were then selected from the B. toni eDNA‐positive sample set for the subsequent analyses. To elucidate the phylogeographic structure of B. toni, newly developed eDNA metabarcoding primers (Barba‐cytb‐F/R) were applied to these samples, specifically targeting their haplotypic variation in cytochrome b. After a bioinformatic processing to mitigate haplotypic false positives, a total of 50 eDNA haplotypes were identified. Two regionally restricted, genetically distinct lineages of the species were revealed as a result of phylogeographic analyses on the haplotypes and tissue‐derived DNA from B. toni. According to a molecular clock analysis, they have been genetically isolated for at least 1.5 million years, suggesting their ancient origin and colonisation of Hokkaido, presumably in the glacial periods. These results demonstrate how freshwater fishes can alter their distributions over evolutionary timescales and how eDNA assay can deepen our understanding of phylogeography. [ABSTRACT FROM AUTHOR]

Aim: Biotic interchanges between Africa, India, and Eurasia are central to explaining the present‐day distribution and diversity of freshwater organisms across these landmasses. Synbranchiformes is a diverse and species‐rich clade of freshwater acanthomorph fishes found on all southern continents except Antarctica, and include eel‐ and perch‐like, air‐breathing and non‐air‐breathing fishes. Lacking a comprehensive and resolved phylogeny of the entire clade, contemporary interpretations of synbranchiform biogeography invoke scenarios as disparate as Gondwanan vicariance and pan‐global rafting to explain their modern‐day distribution. Here, we study their biogeographic history of continental dispersal events and test whether these are associated with increases in lineage diversification. Location: Asia, India, Africa freshwater habitats. Taxon: Synbranchiformes (gouramis, snakeheads, swamp eels, and relatives). Methods: We used nearly 1000 ultra‐conserved elements (UCEs) and Sanger‐sequenced genes to infer a phylogeny with representatives of all major synbranchiform lineages and nearly two‐thirds of its known species diversity. Incorporating fossil calibrations, we inferred a time‐calibrated phylogeny to which we apply Bayesian methods of ancestral area reconstruction and test for diversification rate shifts. Results: Analyses of UCE data provide a resolved phylogeny for major synbranchiform lineages. Divergence times support a most recent common ancestor of the entire clade approximately 79.2 million years ago. We infer significant increases in lineage diversification in both the spiny eels (Mastacembelidae) and the genus Betta (Osphronemidae). Main Conclusions: Our results reject the hypothesis of Gondwanan vicariance explaining synbranchiform biogeography. Instead, our analyses reconstruct a southeast Asian origin of the entire clade and independent dispersal events to other continents by snakeheads, anabantids, and spiny eels, with no signal of elevated lineage diversification occurring after these invasions. Higher lineage diversification rates in spiny eels pre‐date their arrival to Africa, while the high diversification rates observed in Betta were initiated prior to the flooding of insular Sundaland in southeast Asia. [ABSTRACT FROM AUTHOR]

Aim: Environmental change affects metacommunity structure both directly—via abiotic factors and dispersal that affect species occurrence—and indirectly—via complex interactions among co‐occurring species. We examined how the three main metacommunity factors—environmental conditions, spatial processes and species associations—affect metacommunity structure and whether responses are predictable in real‐world systems by using novel methods to disentangle the drivers. Location: Eastern Asia, northern Europe and central North America. Time period: Contemporary. Major taxa studied: Freshwater fish. Methods: We used a dataset of freshwater fish species occurrences in temperate lakes in three countries in different biogeographic regions. We analysed co‐occurrence patterns by using a joint species distribution model. Results: We demonstrated that environmental processes are the main drivers of species' distribution and diversity, suggesting that future climate change (anthropogenic alteration of abiotic factors) will heavily influence the structure of metacommunities. We also showed that spatial processes and species interactions mediated the influence of environmental processes, especially at the lake level. Main conclusions: Our results indicate that ongoing changes in metacommunity structure are modulated not only by the direct impacts of shifting abiotic factors but also by indirect effects of species interactions. Our global analysis indicates that even under the current high rate of environmental change, an identifiable set of underlying processes can be used to predict impacts of this change on metacommunity structure. [ABSTRACT FROM AUTHOR]

Triclosan (TCS), an antimicrobial drug, is known to occupy different compartments in aquatic ecosystems. The present study focused to evaluate the reproductive toxicity of triclosan, at environmentally relevant (0.009 and 9 μg L−1) and sublethal (176.7 μg L−1) concentrations for 90 days in the pre-spawning phase of the fish, Anabas testudineus. The reproductive biomarkers, namely, gonadal steroidogenic enzymes, expression of aromatic genes, levels of serum gonadotropins, sex hormones, and histology of gonads were analyzed. The weight of the animal, brain weights along with gonadosomatic index decreased while mucus deposition increased significantly at all concentrations of triclosan as the primary defensive mechanism to prevent the entry of toxicants. Triclosan disrupted gonadal steroidogenesis as evidenced by a reduction in the activities of gonadal steroidogenic enzymes. The expressions of cyp19a1a and cyp19a1b genes were up-regulated in the brain of both sexes and testis, while down-regulated in the ovary indicating estrogenic effects of the compound. The endocrine-disrupting effects of triclosan were confirmed. The current results suggest that chronic exposure to triclosan altered reproductive endpoints thereby impairing normal reproductive functions in fish. [ABSTRACT FROM AUTHOR]

The approach of combining cost‐effective nanopore sequencing and emerging environmental DNA (eDNA) metabarcoding could prove to be a promising tool for biodiversity documentation, especially in Malaysia. Given the substantial funding constraints in recent years, especially in relation to the country's biodiversity, many researchers have been limited to conduct restricted research without extended monitoring periods, potentially hindering comprehensive surveys and could compromise the conservation efforts. Therefore, the present study aimed to evaluate the application of eDNA metabarcoding on freshwater fish using short reads generated through nanopore sequencing. This assessment focused on species detection in three selected rivers within the Endau Rompin Landscape in Malaysia. Additionally, the study compared levels of species detection between eDNA metabarcoding and conventional sampling methods, examined the effectiveness of primer choice, and applied both metabarcoding and shotgun sequencing to the eDNA approach. We successfully identified a total of 22 and 71 species with an identification threshold of >97% and >90%, respectively, through the MinION platform. The eDNA metabarcoding approach detected over 13% more freshwater fish species than when the conventional method was used. Notably, the distinction in freshwater fish detection between eDNA primers for 12S rRNA and cytochrome oxidase I was insignificant. The cost for eDNA metabarcoding proved to be more effective compared to conventional sampling with cost reduction at 33.4%. With favourable cost‐effectiveness and increased species detection, eDNA metabarcoding could complement existing methods, enhance holistic diversity documentation for targeted habitats and facilitate effective conservation planning. [ABSTRACT FROM AUTHOR]

The extraction of lipids by the Folch method from the muscles of all the fish studied led to statistically significant differences in the values of δ15N. At the same time, lipid extraction led to a statistically significant increase in δ13C in pike and roach, and to a statistically insignificant decrease in δ13C in perch and bream. Thus, lipid extraction cannot serve as a universal method of sample preparation for the analysis of the isotopic composition of carbon (13C/12C) and nitrogen (15N/14N) in fish muscles. The differences between the δ13C values in the samples before and after lipid extraction were statistically investigated by different models. It is shown that mathematical correction method models can be used, but the results are depending on the fish types. [ABSTRACT FROM AUTHOR]

The coexistence of sexual and asexual lineages is rarely documented in vertebrates. Various ecological and evolutionary mechanisms have been proposed to explain their stable coexistence. Gibel carp (Carassius gibelio), a highly invasive freshwater fish in Europe, is one such example of a sexual and asexual vertebrate, combining gynogenesis (sperm-dependent parthenogenesis) and sexual reproduction. In this study, we focused on vigour-related traits in gynogenetic and sexual forms of gibel carp coexisting in the same habitat, to reveal whether there is a link between parasite load and vigour-related traits reflecting the potential advantage of one reproductive form over another, which may eventually facilitate the obligatory coexistence of sperm-dependent gynogenetic females with sexual males. Using physiological parameters (indexes of somatic condition, energetic condition, and reproductive performance; glucose levels; and erythrocytes-related variables), diploid sexual males, diploid sexual females, and triploid gynogenetic females were found to be differentiated from one another. However, based on immune variables representing innate immunity, specific immunity, and index of immunocompetence, mostly sexual males were found to be weakly differentiated from both groups of females. We revealed different patterns of interactions between parasite abundance and immune variables between sexual and gynogenetic forms. Using parasite assemblage composition, different relationships between parasite assemblage and immunity or physiology in sexual males and sexual females were evidenced, potentially related to male reproduction biology. In contrast, gynogenetic females exhibited the advantage that parasite assemblage composition did not affect their immunity or physiology. Our study suggests that reproduction mode-associated costs of physiology and immunity may facilitate the coexistence of the asexual-sexual complex. We highlight that multiple ecological processes and evolutionary mechanisms contribute to the coexistence of asexual and sexual gibel carp. [ABSTRACT FROM AUTHOR]

Objective To understand the detection of four prohibited veterinary drugs of fresh and live freshwater fish sold in Guangzhou by analyzing the test data from risk monitoring and supervision sampling, so as to provide reference basis for food safety supervision. Methods Through the Guangzhou Food Safety Risk Monitoring system and the Food Safety Supervision and Inspection Public Information report of Guangzhou Market Administration, the test results of fresh water fish samples col-lected from supermarkets, markets, and online e-commerce in Guangzhou from 2017 to 2021 were obtained. The detection of nitrofuran drugs, chloramphenicol, sodium pentachloro phenate, and malachite green drugs were analyzed. Results The total detection rate of banned veterinary drugs in risk monitoring samples was 35.3% (84/238), and that in supervised sampling samples was 3.10% (118/3 806). The banned veterinary drugs with high detection rates of the two data sources were different. The risk monitoring rates of chloramphenicol and sodium pentachloro phenate were 17.23% (41/238) and 17.23% (41/238), respectively, and that of malachite green was 2.18% (83/3 806). The drug detection rate of the samples collected by risk monitoring in the network e-commerce link was Al.50% (19/40), which was the highest among all sampling links. The results of the two data sources showed that the detection rate of banned veterinary drugs in the wholesale market was high: 47.37% (18/38) and 4.13% (5/121), respectively. Conclusion The results of data analysis from the two sources complement each other and jointly reveal the problem of banned veterinary drug residues in fresh freshwater fish sold in Guangzhou from 2017 to 2021. It is suggested that the relevant departments pay more attention to the illegal use of chloramphenicol, sodium pentachloro phenate, and malachite green drugs. [ABSTRACT FROM AUTHOR]

Selenium-based feed supplement is essential for increasing the performance of aquatic organisms. This study aims to analyze and evaluate various data on selenium supplementation in freshwater fish feed by meta-analysis with mixed-model. The study used secondary data from the literature database. Total 27 references containing 125 treatments were analized. Using linear and quadratic regression equations, selenium supplementation in freshwater fish feed resulted in a significantly increased final body weight, weight gain, feed intake, and protein efficiency ratio (P <.05). Then, the GPx activity enzyme in the liver and the increased high-density lipoprotein (HDL) content in the blood of fish exhibited a favorable trend with significantly higher value (P <.05) compared to control fish. However, selenium supplementation could significantly reduce total protein, globulin, low-density lipoprotein (LDL) and cholesterol levels (P <.05). This study concluded that organic selenium supplementation in the range of 0.95 to 6.8 mg/kg feed could improve freshwater fish's performance. [ABSTRACT FROM AUTHOR]

The current study uses meta-analysis to quantitatively synthesize the effectiveness of Bacillus as a potential probiotic in aquaculture. Studies were selected based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines using Web of Science and Google Scholar. Hedges' g effect size was used to quantify differences in final weight, specific growth r ate (SGR), survival rate (SR) and feed conversion ratio (FCR) of fish treated with Bacillus compared to the control. In addition, heterogeneity, moderator effect and publication bias were estimated. All analyses were conducted using metafor package in the program R. Significantly higher final weight, SGR, SR and significantly lower FCR were detected in the overall analysis and all the subgroup analysis for fish, crustaceans, freshwater and marine fish compared to control. A significant level of heterogeneity was identified across the studies, and species was identified as a significant moderator influencing the magnitude of the effect of Bacillus spp. [ABSTRACT FROM AUTHOR]

This study aims to determine the prevalence of Cryptosporidium and Eimeria spp. oocysts in fish specimens in the river Kura. It was conducted during the 2021-2022 at two sites: Mingachevir reservoir in central Azerbaijan and in Neftchala district where the river finally enters the Caspian Sea through a delta of the Kura River estuary. The diagnosis of oocysts was performed microscopically. Fine smears from the intestine epithelial layers stained by Ziehl-Neelsen for Cryptosporidium oocysts. To identify Eimeria oocysts, each fish’s faecal material and intestinal scrapings were examined directly under a light microscope in wet samples on glass slides with a coverslip. Results revealed a prevalence of Cryptosporidium and Eimeria species infections in fish hosts from both territories Rutilus caspicus, Alburnus filippi, Abramis brama orientalis and Carassius gibelio. Of 170 investigated fish specimens, 8.8% (15/170) were infected with Cryptosporidium species oocysts. Eimeria species oocysts were identified in 20.6% (35/170). The presence of Cryptosporidium and Eimeria infections in fish specimens are natural infections. However, their presence in fish species may be attributed to the age of the fish species and water pollution. This is the first report regarding the prevalence of Cryptosporidium oocysts in fish species in Azerbaijan. [ABSTRACT FROM AUTHOR]

The present study aimed to determine the antibiotic resistance, underlying mechanisms, antibiotic residues, and virulence genes involved in 32 multi-drug-resistant Klebsiella pneumoniae isolates from freshwater fishes in Andhra Pradesh, India. Antibiogram studies revealed that all isolates were multi-drug-resistant, harbored tetA (96.8%), tetC (59.3%), tetD (71.9%), nfsA (59.3%), nfsB (53.1%), sul2 (68.7%), qnrC (43.7%), qnrD (50%), blaSHV (75%), blaTEM (68.7%), and blaCTX-M (93.7%) genes. Multiple antibiotic resistance index was calculated as 0.54. Sixteen isolates were confirmed to be hyper-virulent and harbored magA and rmpA genes. In total, 46.9, 31.2, and 21.9% of the isolates were categorized as strong, moderate, or weak biofilm formers, respectively. All isolates possessed an active efflux pump and harbored acrA, acrB, acrAB, and tolC genes in 94% of the isolates, followed by mdtK (56.2%). Porins such as ompK35 and ompK36 were detected in 59.3 and 62.5% of the isolates, respectively. Virulence genes fimH-1, mrkD, and entB were present in 84.3, 81.2, 87.5% of the isolates, respectively. These findings imply a potential threat that multi-drug-resistant bacterial pathogens could transmit to surrounding environments and humans through contaminated water and the aquaculture food chain. [ABSTRACT FROM AUTHOR]

Green terror cichlid (Aequidens rivulatus) is a popular tropical freshwater ornamental fish. In 2021, an unknown disease was observed in cultured A. rivulatus in Tianjin, China, with a cumulative mortality rate of 25% within 7 days of onset. The main clinical signs were scale loss, skin ulceration, and slight bleeding. Histopathological observation revealed obvious damage to the liver, spleen, and kidney of diseased fish. In addition, abundant granulomas were observed in the spleen and head kidney of the diseased fish. To define the potential pathogens from A. rivulatus, bacteria were isolated from the visceral tissue of diseased fish with conventional methods. An artificial infection experiment was carried out to prove the pathogenicity of the isolated bacteria. The strains HG-2021-1 and HG-2021-3 were isolated from diseased fish and identified as being responsible for the disease. They were identified as Streptococcus iniae based on physiological and biochemical tests, lctO gene detection, and 16S rRNA gene sequence analysis. According to the result of multilocus sequence typing (MLST), HG-2021-1 and HG-2021-3 belong to different genotypes of S. iniae. Furthermore, they were found to contain the virulence genes pgmA, scpI, cpsD, and pdi, and the median lethal dose (LD50) for A. rivulatus was 1.8 × 106 Colony-Forming Units (CFU)/mL and 6.6 × 106 CFU/mL, respectively. To our knowledge, this is the first report of fish coinfected by two genotypes of S. iniae. [ABSTRACT FROM AUTHOR]

This article proposes a mechanism that triggers first maturation and spawning in coral reef (bony) fish, which allows for predicting their length at first maturity. Thus, mean lengths at first maturity (Lm) and the corresponding maximum lengths (Lmax) in 207 populations of 131 species of coral reef fish were assembled and used to test the hypotheses that (a) there is, in coral reef fish, a single value of a size-related parameter acting as a trigger for their maturation and eventual spawning, and (b) that this single value is statistically the same as that published previously for other bony fish. The results, based on the assembled Lm and Lmax data and on estimates of the parameter D, which link the length of fish with the relative surface of their gills, covered 44 families and Lmax values ranging from 1.8 to 181.6 cm and confirmed that the threshold in (a) exists. Also, we assessed (in b) that this threshold value, i.e., LmaxD/LmD = 1.35 (±0.02), is not statistically different from similar estimates for other groups of teleosts, notably semelparous salmonids, cichlids, sturgeons and Chinese and Turkish freshwater and marine fish. One implication is that given ocean warming and deoxygenation, coral reef fish will not only be smaller than they currently are, but also mature and spawn at smaller sizes, and thus produce fewer, smaller eggs. [ABSTRACT FROM AUTHOR]

Augmenting depleted genetic diversity can improve the fitness and evolutionary potential of wildlife populations, but developing effective management approaches requires genetically monitored test cases. One such case is the small, isolated and inbred Cotter River population of an endangered Australian freshwater fish, the Macquarie perch Macquaria australasica, which over 3 years (2017–2019) received 71 translocated migrants from a closely related, genetically more diverse population. We used genetic monitoring to test whether immigrants bred, interbred with local fish and augmented population genetic diversity. We also investigated whether levels of river flow affected recruitment, inbreeding depression and juvenile dispersal. Fish length was used to estimate the age, birth year cohort and growth of 524 individuals born between 2016 and 2020 under variable flow conditions. DArT genome‐wide genotypes were used to assess individual ancestry, heterozygosity, short‐term effective population size and identify parent‐offspring and full‐sibling families. Of 442 individuals born after translocations commenced, only two (0.45%) were of mixed ancestry; these were half‐sibs with one translocated parent in common. Numbers of breeders and genetic diversity for five birth year cohorts of the Cotter River fish were low, especially in low‐flow years. Additionally, individuals born in the year of lowest flow evidently suffered from inbreeding depression for juvenile growth. The year of highest flow was associated with the largest number of breeders, lowest inbreeding in the offspring and greatest juvenile dispersal distances. Genetic diversity decreased in the upstream direction, flagging restricted access of breeders to the most upstream breeding sites, exacerbated by low river flow. Our results suggest that the effectiveness of translocations could be increased by focussing on upstream sites and moving more individuals per year; using riverine sources should be considered. Our results indicate that river flow sufficient to facilitate fish movement through the system would increase the number of breeders, promote individuals' growth, reduce inbreeding depression and promote genetic rescue. [ABSTRACT FROM AUTHOR]

This study aims to isolate the freshwater fish–derived potential probiotics and evaluate their beneficial effects on the growth, immune response, and disease resistance of juvenile zebrafish (Danio rerio). Herein, three strains (Leuconostoc mesenteroides GL-5, Weissella hellenica GJ-1, and Pediococcus claussenii GJ-3) were identified with antagonistic activity against fish pathogens, high tolerance to 0.1% bile salt, and good hydrophobicity. As the model, zebrafish (15 days post-fertilization, dpf) were fed with a basal diet (control) supplemented with GL-5, GJ-1, GJ-3, heat-killed Leuconostoc mesenteroides GL-5*, and commercial probiotics (positive control) at a concentration of 1 × 107 CFU/mL for 4 weeks. Compared with the GL-5* (36.35 ± 2.03 mg fish−1) and control (37.31 ± 1.91 mg fish−1) groups, the GL-5 (58.15 ± 2.58 mg fish−1), GJ-1 (69.55 ± 3.85 mg fish−1), GJ-3 (62.90 ± 2.99 mg fish−1), and commercial probiotic (62.03 ± 2.68 mg fish−1) treatment were found to significantly promote the growth of zebrafish. Compared to the control group challenged by immersion with 1 × 107 CFU/mL Aeromonas hydrophila, the GJ-3 and positive groups showed the highest transcript levels of IL-1β and TNF-α at 8 h post-challenge (P < 0.05). The survival rates (80%) of the GJ-3 and commercial probiotic–fed groups were significantly higher than that of the control group (50%) at 32 h post-challenge (P < 0.05). Therefore, Pediococcus claussenii GJ-3 can be considered a potential probiotic for reducing the use of antibiotics and preventing bacterial diseases in fish. [ABSTRACT FROM AUTHOR]

Otocinclus cocama, a uniquely colored species of the loricariid catfish genus Otocinclus described solely from the type locality in the lower Ucayali River in northern Peru, is reported occurring in the Tigre River, a tributary to the Marañón River that drains a different section of the Andean Mountain range in the western Amazon. Both populations differ in the number of dark bars spanning the flanks of the body, and we investigated whether these morphotypes constitute distinct species. The body shapes of populations from the Tigre and Ucayali rivers were compared using geometric morphometrics. Although principal component analysis detected a broad overlap between populations, multivariate analysis of variance and linear driscriminat analysis revealed a subtle differentiation between the populations of the two hydrographic basins. Average body shape of the Ucayali River population tend to be slightly higher than that of the Tigre River, with the caudal peduncle stretched vertically in the Ucayali population. Multivariate regression of shape and centroid size revealed an allometric effect of 10.7% (p < 0.001), suggesting that the variation between Tigre and Ucayali populations was purely shape variation. Molecular data of coI, cytb, nd2, and 16S mitochondrial genes indicated a nucleotide diversity range from 0.001 to 0.003, and haplotypic diversity range from 0.600 ± 0.11 to 0.79 ± 0.07. The median‐joining haplotype network for the concatenated matrix exhibited two divergent haplogroups related to the geographic area and separated by <10 mutational steps. The molecular species delimitation methods based on distance (automatic barcode gap discovery and assemble species by automatic partitioning) recovered two molecular lineages evolving independently, being one of the lineages formed by individuals from both populations. Tree‐based methods (generalized mixed Yule coalescent and Bayesian implementation of the Poisson tree process) recovered similar topologies and supported single lineage recognition. Methods of molecular delimitation of species disclosed the high similarity between the two populations of Otocinclus cocama, further supported by the presence of old haplotypes common to both groups which could indicate that the populations still maintain gene flow. Although the morphological data reveal a subtle variation between both river basins, the molecular data suggest a weak population structuration based on hydrographic areas, but not different species lineages, therefore Otocinclus cocama is composed of a single lineage with two distinct morphotypes. [ABSTRACT FROM AUTHOR]

A taxonomic revision of Sturisoma is presented. Individuals including both type and non‐type specimens of all valid species were examined. Sturisoma was found to comprise 10 valid species: Sturisoma barbatum, Sturisoma brevirostre, Sturisoma graffini, Sturisoma guentheri, Sturisoma lyra, Sturisoma monopelte, Sturisoma nigrirostrum, Sturisoma reisi, Sturisoma rostratum, and Sturisoma tenuirostre. Furthermore, four new species are described: Sturisoma ghazziae, new species, from the Araguaia River, belonging to the Tocantins‐Araguaia basin, Central Brazil; Sturisoma careirensia, new species, from the middle Amazon basin, Brazil; Sturisoma rapppydanielae, new species, from the Purus River, Amazon basin, Brazil; and Sturisoma defranciscoi, new species, from the Putumayo and Solimões rivers, upper Amazon basin, Colombia, and Brazil. Sturisoma robustum is confirmed as synonym of S. barbatum, species registered along the Paraguay/Parana/La Plata River basin in Argentina, Brazil, and Paraguay. New records were found for S. nigrirostrum as present in the upper Amazon basin, in the Yavari River, Brazil, in addition to its already known locality, the Ucayali River, Peru. The distribution of the type species of the genus S. rostratum is limited to the lower portion of the Amazon basin in the Araguaia, Maranhão, Mearim, Tapajós, and Tocantins rivers and its affluents, Brazil, in contrast to the assumed widespread distribution across the main basins of South America, as previously proposed for the species; the Mearim River is a new record for the species. Updated diagnoses and descriptions are offered for species of Sturisoma, in addition to distribution maps and an identification key for the species. [ABSTRACT FROM AUTHOR]

Recent studies have linked ecosystem warming to decreased mean body size in aquatic ectotherms but have often relied on experimental approaches. This study explores how climate change modifies adult body sizes in natural communities for five culturally, commercially, and recreationally important freshwater fish species that vary in thermal preferences (lake trout (Salvelinus namaycush), lake whitefish (Coregonus clupeaformis), walleye (Sander vitreus), yellow perch (Perca flavescens), and smallmouth bass (Micropterus dolomieu)). Using data for >170 000 sampling records from >600 lakes spanning the entire province of Ontario, Canada, we employ a spatial analysis technique based on Integrated Nested Laplace Approximation to detect body size changes due to warming lake conditions. With warming conditions, cold-adapted species (lake whitefish) decreased in adult body size, while cool- and warm-adapted species (walleye and smallmouth bass) increased in adult body size. Our study, like others recently conducted in marine and freshwater systems, demonstrates that the responses of fish body sizes to warming are not a unidirectional shift and may be linked to the habitat and thermal preferences of individual fish species. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) have attracted global concern because of their harmful effects on marine biota; their toxic properties can negatively impact aquatic ecosystems. Fish is an essential source of protein for humans, playing a crucial role in daily food intake. Until recently, MPs were addressed primarily as environmental pollutants, but they are now increasingly recognized as contaminants in the food supply. The present review has comprehended the current knowledge of MP contamination in freshwater and marine fishes of Asia, including 112 peer‐reviewed sources from 2016 to 2023. The review recorded 422 Asian fishes (345 marine and 77 freshwater) to be contaminated with MPs. Clarias gariepinus and Selaroides leptolepi have shown maximum MP contamination in the freshwater and marine environments of Asia, respectively. Omnivorous and carnivorous fishes exhibited higher susceptibility to ingesting MPs. Benthopelagic, demersal, and reef‐associated habitats were identified as more prone to MP accumulation. In both freshwater and marine environments, China has the highest number of contaminated species among all the countries. Pollution indices indicated high MP contamination in both freshwater and marine environments. A prevalence of fibers was recorded in all fishes. Black‐ and blue‐colored MPs of <500 µm–1 mm size were found dominantly. Polyethylene terephthalate and polyethylene were recorded as the prevalent plastic polymers in freshwater and marine fish, respectively. Overall, the review served as a comprehensive understanding of MP concentrations and variations between species, between feeding habits, and between geographic locations, which can be pivotal for addressing pressing environmental challenges, protecting human health, and fostering global sustainability efforts in the face of escalating plastic pollution. Environ Toxicol Chem 2024;43:671–685. © 2024 SETAC. [ABSTRACT FROM AUTHOR]

Rocio is a small genus of Neotropical freshwater fishes that is distributed in Atlantic drainages of northern Middle America. Two species of Rocio, R. spinosissima and R. octofasciata, exhibit sympatry in the Río Dulce basin in eastern Guatemala. Rocio spinosissima is endemic to the Río Dulce basin, while R. octofasciata has a larger geographic range that includes this area. Our goal was to explore the ecological and morphological variation shown by these two closely related species and determine their differences. A combination of field work, analysis of museum specimens, and ecological niche modelling helped to better understand the differences in habitat and environmental characteristics, along with the body shape variation. Local‐scale environmental data suggest that both species inhabit lentic environments, with R. spinosissima using narrower and low canopy‐covered habitats and R. octofasciata inhabiting areas with a larger range of environmental characteristics. Ecological Niche Models indicated that land cover, soil, precipitation, and temperature largely define the distribution of both species. Body shape differs between species, with R. spinosissima exhibiting a rounder and deeper body while R. octofasciata is more elongated. Specimens of R. octofasciata across its distribution also show variation in head shape, mouth position, fin, and caudal peduncle characteristics, possibly as a response to trophic strategies that reduce competition. Similarities in their environments and morphologies allow us to identify broadly overlapping niches in the two species of Rocio, while the fine scale differences documented between species will have conservation implications for the endemic R. spinosissima. [ABSTRACT FROM AUTHOR]

Connectivity is a foundational concept in ecology and conservation and was the organising theme for the 2022 Annual Meeting of the Southeastern Fishes Council, a professional organisation dedicated to the study and conservation of freshwater fishes native to the southeast region of the United States (US). We introduce a Special Contribution of five papers selected from presentations at that meeting that illustrate perspectives on connections created by fish migration and dispersal, evolved life histories and habitat affinities and interspecific facilitation. Although focused on streams of the southeast US, each of these topics is broadly relevant to freshwater fish conservation, particularly with respect to causes and consequences of migratory fish depletion, population fragmentation and species declines. Many other connections relevant to the ecology and conservation of freshwater fishes remain relatively unexplored but could substantively advance conservation. We highlight the potential that species evolutionary histories, that is connections through time, reconstructed using species distributions and phylogenies may improve predictions of species responses to environmental change. Identifying species interdependencies, including undiscovered interactions that support survival or reproduction, could provide insights into how species losses may cascade as aquatic communities unravel. Finally, efforts to elucidate diverse connections between people and freshwater biodiversity, particularly where fisheries are historic and streams mostly go unnoticed, may prove essential to building public support for conservation measures. A research agenda anchored on 'biodiversity connections' has the potential to advance ecological understanding and public engagement, elements essential to conserving freshwater fishes. [ABSTRACT FROM AUTHOR]

Metacommunity theory seeks to explain how local and regional processes contribute to the organisation of biological communities. Recent conceptual frameworks of this theory indicate that the dynamics of populations and communities are jointly established by dispersal, species responses to environmental conditions and biotic interactions dependent on species density. Here, we use hierarchical joint species distribution modelling to verify the effects of environmental factors (at multiple spatial scales), drainage network configuration, spatial autocorrelation and interspecific interactions on the structure of fish assemblages in terra‐firme streams in the Eastern Brazilian Amazon. Thirty streams were sampled in two field surveys, and 89 species were collected in total. Our results confirm the effects of limited dispersal, environmental conditions (at multiple scales) and the configuration of the drainage network on the dynamics of these assemblages. Furthermore, our results suggest that interspecific interactions are less relevant for the structuring of fish metacommunities in small Amazonian headwater streams. Abiotic factors like drainage networks and environmental heterogeneity were better predictors of species distributions than co‐occurrence patterns with potential competitors or predators. [ABSTRACT FROM AUTHOR]

In three water‐supply reservoirs in the catchment area of the Odra River (Czech Republic), a special fish stock was monitored for control of health to estimate the mutagenic effect of chemicals. The results contribute to obtaining initial information about the morphology of erythrocyte abnormalities classified in 21 categories in 16 fish species in reservoirs with abundant salmonids (the Morávka Reservoir) or with the prevalence of cyprinids (the Kružberk and Šance Reservoirs), not directly exposed to the adverse environmental effects such as industrial, urban, agricultural and intensive farming activities. The different intensities and prevalence of nuclear abnormalities (NA) and cytoplasmic abnormalities (CA) in fish from the same reservoir habitat show that to be able to obtain an objective view of the genotoxic risk of chemicals, it is necessary to respect the different requirements of the fish for the exploitation of the food available in the biotope and to subject all representatives of piscivorous, omnivorous and benthophagous fishes in the reservoir to cytogenetic analysis. The occurrence of certain categories of erythrocyte abnormalities in diseased fish draws attention to the need to know the state of health of the fish and to employ this knowledge to exclude parasitological, viral and other infectious agents. These results are the first report of the frequencies of erythrocyte abnormalities in native fish. They should serve to check which of the categories examined could be of use in assessing the genotoxic risk in other stagnant and running aquatic ecosystems affected by anthropogenic activities. [ABSTRACT FROM AUTHOR]

The high intraspecific variability of the morphological characters of Acanthocephala can complicate their taxonomic classification. To solve this problem, molecular markers are used. Here, we present the identification and determination of genetic variability of four species of the Acanthocephala genera Pomphorhynchus, Acanthocephalus and Dentitruncus, obligate endoparasites of freshwater fishes. The DNA sequences of the three markers that evolve at different rates (18S rDNA, COI and ITS) were analysed. To put the genetic position of the Croatian Acanthocephala specimens in a broader context, the COI and ITS sequences of the other European specimens from the NCBI GenBank were used. Genetic structuring at the local level was minor or not visible at all, but in the context of European phylogeographic structuring, the Croatian P. laevis showed a clear grouping to the geographical subcluster Ponto-Caspian Balkans. Only two P. laevis Danubian haplotypes, which were not analysed morphologically, were assigned to the Ponto-Caspian Danube subclade together with the recently identified P. bosniacus from Austria. The haplotypes of P. tereticollis from Croatia were clustered within the two main European clades. In connection with the phylogeographic distribution of Acanthocephala and their hosts, we hypothesised possible phylogeographic patterns. [ABSTRACT FROM AUTHOR]

Aeromonas spp. are the opportunistic pathogens that infect both aquatic and terrestrial homeotherms. They were commonly present in aquatic environments, including effluent, tap water, marine, river, and lake, where they are often isolated from aquatic animals, including fish, molluscs, and crustaceans. The Aeromonas infections can cause sepsis, ulcer, and other symptoms, resulting in the death of massive aquatic animals. Therefore, the prevention and control of Aeromonas is of great significance for the healthy development of aquaculture. In this study, we used modern molecular methods to enhance disease control of Aeromonas isolates from freshwater fish in Hebei Province. A total of 130 Aeromonas spp. isolates were isolated from freshwater fish farms in Hengshui, Handan, and Shijiazhuang and all 130 Aeromonas spp. isolates were sequenced for species identification. Of the 130 Aeromonas spp. isolates, 104 isolates were successfully sequenced, and BLAST analysis showed that Aeromonas veronii was predominant in freshwater fish farms in Hebei Province. In addition, 26 antibiotic resistance profiles were obtained from 102 fully cultured isolates among the 104 Aeromonas spp. isolates whose species was primarily identified, and 44 multidrug-resistant bacteria among the 102 isolates were identified using an antibiotic susceptibility test. Using the Multilocus Sequence Typing (MLST) method, 33 out of 44 multidrug-resistant isolates with 14 non-Aeromonas reference strains were selected for phylogenetic and MLST analysis, and all 33 multidrug-resistant isolates were A. veronii. A total of 30 new Sequence Types (STs) were obtained by comparing concatenated sequences (gyrB-groL-gltA-metG-ppsA-recA) on PubMLST website. Furthermore, recombination event analysis detected using RDP5 and ClonalFrameML software 42 and 49 recombination events, respectively, and 22 recombination events were validated by four or more algorithms. Since mutation and recombination events increase clonal diversity and single housekeeping gene sequence alignments are limited for identifying species, we propose the use of multiple concatenated sequence loci to increase discriminatory power. In addition, we propose that the MLST method is an appropriate technique to study and develop the resistance mechanisms of multidrug-resistant Aeromonas and to identify Aeromonas systematically in complex samples obtained from the environment. [ABSTRACT FROM AUTHOR]

This study presents results of extracting hydrolyzed collagen peptide from fresh‐water fish scale and using it to prepare a nanoemulsion based on Sacha inchi (Plukenetia volubilis L.) seed oil and collagen peptide. The sacha inchi seed oil is extracted from the seeds of Sacha Inchi (abbreviated as sachi) plant and contains approximate 45 % triple omega 3–6‐9 (ω‐3, ω‐6, ω‐9) content. Pseudo‐ternary phase diagrams of three components: aqueous collagen solution, sachi seed oil, and surfactant/co‐surfactant (Smix) have been constructed. The parameters including the composition of Smix, sachi seed oil, and aqueous collagen solution have been selected to optimize the technology factors for the emulsion process. A quadratic regression equation was chosen, and experimental planning following the Box‐Behnken model using response surface methodology was used to optimize the preparation conditions for the nanoemulsion. The average droplet size of the emulsion systems is the object function for optimization. The Smix is a mixture of surfactant (Tween80) and propylene glycol (PG) with different ratios of Tween80/PG of 1/1, 2/1, 3/1, and 4/1, corresponding to the formation of four emulsion systems, code 1, 2, 3, 4, respectively. The optimal parameters for each emulsion system are different, however, the aqueous collagen solution contains a higher proportion in emulsions. Under the optimal conditions, the predicted values of the objective function of emulsions code 1–code 4 ranged from 95.62 to 185.14 nm, increasing together with the Tween80 ratio in Smix. The experiment values of the objective function of emulsions code 1–code 4 prepared under the optimal conditions are 104.22, 133.70, 159.27, and 207.87 nm, respectively. These values are close to the predicted values, suggesting that the suitability of the experiment and theory. Additionally, the stability of the nanoemulsion prepared under the optimal conditions is also evaluated. A stable nanoemulsion is potentially for loading nutraceuticals and vitamins for applications in personal health care and medicinal fields. [ABSTRACT FROM AUTHOR]

Simple Summary: Anthropogenic pollution poses a major threat to aquatic ecosystems, which can lead to their degradation. The accumulation and toxicity of metals and trace elements in fish leads to physiological and chemical changes in the fish body. In this study, we investigated the effects of bioaccumulation of metals and trace elements on freshwater fish fatty acid profiles at two different sites before and after the discharge of untreated municipal wastewater in two fish species with different diet habits. Although the concentrations of toxic elements were below the maximum levels proposed by the EU and the Republic of Serbia, this study showed statistically significant correlations between the presence of certain elements and the fatty acid (FA) profile in fish muscle. Lower concentrations of polyunsaturated FA in fish sampled after the discharge of untreated municipal wastewater were detected. In this study, the concentrations of metals and trace elements (As, Cd, Co, Cr, Cu, Hg, Ni, Pb and Zn) were determined in the muscle tissue of adult roach and white bream at two different sites in the Belgrade section of the Danube. Twenty-six fatty acids, consisting of nine saturated FA (SFAs), seven monosaturated FA (MUFAs) and ten polysaturated FA (PUFAs), were identified. The analysis of the concentration of metals and trace elements of the roach and white bream showed species-specific differences in their bioaccumulation. Four of all elements analyzed (As, Hg, Ni and Pb) correlated significantly with the changes in FA profiles in fish from both sampling sites, with the exception of Cu, which correlated with the FA profile at the site before, and Zn, whose concentration influenced the FA profile at the site after wastewater discharges. The lower PUFA content in the fish from a site under higher environment pressure could indicate that the fish are stressed. The results suggest that changes in lipid composition may be one of the protective mechanisms of cells to cope with anthropogenic stressors. [ABSTRACT FROM AUTHOR]

Candidia barbata is a primary freshwater fish distributed in the western portion of Taiwan Island, but this species has also been found in southern and eastern Taiwan. Previous studies have documented that human-intervention populations of freshwater fishes exist not only in eastern Taiwan but also widely. To investigate the native population genetic diversity and structure and evaluate the sources of human-intervention populations of C. barbata, the sequences from the mitochondrial DNA cytochrome b gene and d-loop region were analyzed. These results indicated that (1) the native populations were distributed in northern, northwestern, western and southwestern Taiwan; (2) the human-intervention populations originated from multiple sources, including native populations and aquarium stocks; (3) most aquarium stocks originated from the northwestern and western populations; (4) the geological history of Taiwan Island shaped the native distribution range and population genetic structure; (5) the effective size of the populations declined greatly; and (6) the native populations could be assorted into three distinct management significant units (α − γ). Finally, the human-mediated dispersal of freshwater species in Taiwan was more severe than expected and should be evaluated and monitored carefully. [ABSTRACT FROM AUTHOR]

Invasion of non-native fishes threatens freshwater biodiversity worldwide. Yet, detailed estimates of population demography for invasive species, such as population size and body size, are rarely integrated in evaluating aquatic community responses. Our study capitalised on detailed brook trout population demographic data collected for a replicated whole lake ecosystem experiment involving experimental harvesting of exotic brook trout in nine mountain lakes. We applied environmental DNA (eDNA) metabarcoding and morphological taxonomy to examine the response of crustacean zooplankton and macroinvertebrate communities to gradients in brook trout effective density and lake elevation. Density-dependent effects of brook trout on crustacean zooplankton and macroinvertebrate communities were detected even decades after their first introductions (between 1926 & 1980). However, they were moderated by environmental factors such as elevation, lake maximum depth and dissolved organic carbon. Elevation was important in structuring crustacean zooplankton and macroinvertebrate community composition. While there were differences in explanatory variables when describing communities characterized by eDNA metabarcoding and morphological taxonomy, the principal environmental factors that structured the communities were similar. Our paper highlights persisting density-dependent impacts of exotic trout on invertebrate communities even decades after first introduction, and it considers the conservation implications for lake restoration. [ABSTRACT FROM AUTHOR]

Habitat fragmentation is among the main threats to freshwater fish biodiversity, with expected effects including genetic impacts due to disturbance of migration and declining population size. Major concern falls on highly exploited species such as Prochilodus magdalenae, a migratory characiform fish endemic to the Magdalena River basin supporting much of the Colombian artisanal fishery, whose migration route was interrupted by the Ituango hydroelectric project in the Cauca River. To determine the potential effects of fragmentation, this study evaluated the population genetics of this species on both geographical (upstream and downstream of the dam) and temporal (before and after the construction) scales by using 11 species-specific microsatellite markers. Contrary to expectation, genetic diversity and structure remained relatively stable. This study provided no evidence of genetic impacts on P. magdalenae associated with fragmentation over the short term (4–10 years, 5–12 generations) despite persisting threats, genetic evidence of bottleneck, and a high degree of inbreeding, showing the ability of this species to withstand disturbance of its habitat. [ABSTRACT FROM AUTHOR]

Identification of archeological fish remains requires the use of comparative reference materials, generally in the form of disarticulated fish skeletons. Photographic or illustrative atlases provide an additional resource for the analysis of fish remains. Photographic resources exist for many marine species and for specific geographic regions, whereas freshwater European species have not been covered in great detail. Here, we present a photographic atlas for the bones of freshwater and migratory fish commonly recovered from archeological sites in Central Europe, alongside a discussion of the difficulties and considerations for the analysis of freshwater fish remains. The atlas also highlights the morphological similarity of many species and the interpretive limits of freshwater fish assemblages. The atlas aims to act as an accessible and user‐friendly resource, which can be used for basic identification purposes when access to physical collections is not possible, to supplement pre‐existing collections, or for training purposes. This paper acts as a platform from which the full atlas can be downloaded. [ABSTRACT FROM AUTHOR]

The small indigenous fish (SIF), having length of about 25 cm is locally available in the small water resources viz. wetlands, canals, streams etc. and affordable to the poor people also. These are important food item as animal protein, vitamins and minerals sources in the diet of human beings. The objective of this review is to investigate the availability and importance of SIF in nutritional security and income generation of the community. Published and unpublished sources were used to obtain appropriate data. This study interprets actual availability of different species of SIFs, capture and culture resources, consumption pattern and marketing channels etc. A literature review was conducted to highlight the research attempt made to enhance the socio-economic condition of rural sector and as a result it offers important guidelines to popularize SIFs for nutritional security. In India a total of 765 native freshwater fish species documented, out of which about 450 are categorized as small indigenous fish species. The maximum diversity of the SIF's has been recorded from the North East region followed by Western Ghat and Central India. Review indicates an ardent need of focused research efforts towards the development and conservation of these fishes before they become extinct. [ABSTRACT FROM AUTHOR]

Red tilapia (Oreochromis sp.) is a highly produced aquaculture fish among freshwater species. Coloration is an important factor in determining consumer preferences. Therefore, an 8-week experiment was conducted to enhance the growth performance and body coloration through the inclusion of torch ginger in the feed of red tilapia. Five experimental feeds were prepared from commercial feed (crude protein: 34%, crude lipid: 5%) containing torch ginger powder at 2.5, 5.0, 7.5, and 10% (T1, T2, T3, & T4) inclusion levels while feeding without torch ginger act as a control (T0). Red tilapia (Initial body weight: 0.4±0.1g; Initial total length: 4.0±0.1cm) were distributed at stocking number 20 fish/tank into fiberglass tanks with a capacity of 80 L and triplicates for each treatment. The fish were fed with experimental feeds until satiation. The growth of fish was significantly higher (P<0.05) when the fish fed with T1, T2, and T3 compared to control treatment T0. Moreover, the feed intake was significantly increased (P<0.05) when the torch ginger powder was added to the experimental feeds. In addition, the FCR was significantly better (P<0.05) when the fish fed on T1, T2, and T3 compared to T0. The inclusion of torch ginger powder in the feed did not significantly affect (P<0.05) the body protein and lipids of the experimental fish. The increment of redness was significantly higher (P<0.05) when the fish fed with T1, T2, T3, and T4 compared to T0. However, it showed a declining trend of redness when the inclusion of torch ginger increased to 5.0% and above. Thus, the present study suggested that the inclusion of torch ginger powder improved the performance and enhanced the body coloration of juvenile red tilapia. However, a further increase of torch ginger powder by more than 2.5% did not help in the enhancement of the body coloration. [ABSTRACT FROM AUTHOR]

Ecosystems that are coupled by reciprocal flows of energy and nutrient subsidies can be viewed as a single "meta‐ecosystem." Despite these connections, the reciprocal flow of subsidies is greatly asymmetrical and seasonally pulsed. Here, we synthesize existing literature on stream–riparian meta‐ecosystems to quantify global patterns of the amount of subsidy consumption by organisms, known as "allochthony." These resource flows are important since they can comprise a large portion of consumer diets, but can be disrupted by human modification of streams and riparian zones. Despite asymmetrical subsidy flows, we found stream and riparian consumer allochthony to be equivalent. Although both fish and stream invertebrates rely on seasonally pulsed allochthonous resources, we find allochthony varies seasonally only for fish, being nearly three times greater during the summer and fall than during the winter and spring. We also find that consumer allochthony varies with feeding traits for aquatic invertebrates, fish, and terrestrial arthropods, but not for terrestrial vertebrates. Finally, we find that allochthony varies by climate for aquatic invertebrates, being nearly twice as great in arid climates than in tropical climates, but not for fish. These findings are critical to understanding the consequences of global change, as ecosystem connections are being increasingly disrupted. [ABSTRACT FROM AUTHOR]

Bitterling fishes evolve an idiosyncratic symbiosis with freshwater mussels, in which they are obligated to spawn in the gills of mussels for reproduction. In recent years, freshwater mussel populations have been drastically diminishing, due to accelerating anthropogenic impacts, which can be large threats to the risk of bitterling's extinction cascade (i.e. 'coextinction'). The host mussel size may be an important factor driving the adaptation and evolution of bitterling's reproductive phenotypes. Here we examined the host size preference and morphological adaptation of female bitterling to the host size from 17 localities at the Han River in Korea. Using our developed molecular‐based species identification for bitterling's eggs/larvae inside the mussels, we further determined the spawning patterns of seven bitterling species. Mean length of spawned mussels (N = 453) was significantly larger than that of unspawned mussels (N = 1814), suggesting that bitterling prefers to use larger hosts as a spawning ground. Spawning probability was clearly greater as mussel size increases. Results of our reciprocal transplant experiments do provide some evidence supporting the 'bitterling's larger host preference' hypothesis. Interspecific competition appeared to be intense as two fish species often spawned eggs in the same mussel individuals simultaneously. Longer ovipositor and more elongated egg may evolve in females of Tanakia signifer in response to larger host environments. The observed bitterling's spawning preference for large‐sized mussels may evolve perhaps because of the fitness advantage in relation to the offspring survival. Our findings further inform on the development of effective conservation and management strategy for the endangered bitterling fishes. [ABSTRACT FROM AUTHOR]

Freshwater fishes exhibit a wide range of auditory adaptations and capabilities, which are assumed to help them navigate their environment, avoid predators, and find potential mates. Yet, we know very little about how freshwater environments sound to fish, or how fish with different auditory adaptations respond to different soundscapes. We first compiled data on fish hearing acuity and adaptations and provided a portrait of how anthropogenic sounds compare to natural sounds in different freshwater soundscapes. We then conducted a sound‐enrichment field experiment at Lake Saint Pierre, a large fluvial lake in Canada, to evaluate the effect of motorboat sound exposure on the fish community by looking at the extent to which changes in species abundances were linked to auditory adaptations. Data compilation showed that the hearing acuity of most species overlaps with a wide range of ambient and anthropogenic underwater sounds while the field experiment showed that species with more specialized auditory structures were captured less often in sound‐enriched traps, indicating avoidance behavior. Our findings highlight the importance of considering species' sensorial adaptations when evaluating the community‐scale effects of anthropogenic sounds on the fish community, especially at low levels of anthropogenic activity. [ABSTRACT FROM AUTHOR]

The skin of fish contains a diverse microbiota that has symbiotic functions with the host, facilitating pathogen exclusion, immune system priming, and nutrient degradation. The composition of fish skin microbiomes varies across species and in response to a variety of stressors, however, there has been no systematic analysis across these studies to evaluate how these factors shape fish skin microbiomes. Here, we examined 1922 fish skin microbiomes from 36 studies that included 98 species and nine rearing conditions to investigate associations between fish skin microbiome, fish species, and water physiochemical factors. Proteobacteria, particularly the class Gammaproteobacteria, were present in all marine and freshwater fish skin microbiomes. Acinetobacter, Aeromonas, Ralstonia, Sphingomonas and Flavobacterium were the most abundant genera within freshwater fish skin microbiomes, and Alteromonas, Photobacterium, Pseudoalteromonas, Psychrobacter and Vibrio were the most abundant in saltwater fish. Our results show that different culturing (rearing) environments have a small but significant effect on the skin bacterial community compositions. Water temperature, pH, dissolved oxygen concentration, and salinity significantly correlated with differences in beta-diversity but not necessarily alpha-diversity. To improve study comparability on fish skin microbiomes, we provide recommendations for approaches to the analyses of sequencing data and improve study reproducibility. [ABSTRACT FROM AUTHOR]