Freshwater Fish Species Research Articles (Page 1)

The pumpkinseed Lepomis gibbosus is a freshwater fish species native to North America. It has been introduced to Europe, where it is recognized as one of the worst aquatic invaders due to its high adaptability and invasive potential. This study aimed to determine the presence of L. gibbosus in small to medium-sized water bodies, both lotic and lentic, across the Sava River Basin in continental Croatia and identify the environmental variables associated with its occurrence. Lepomis gibbosus was recorded at 22 out of 111 lotic sites and 16 out of 29 lentic sites. The best-fitting Bernoulli generalized linear model on lotic data indicated that L. gibbosus occurrence was significantly and positively associated with the maximum depth of the sampling site and its distance from agricultural areas; the best-fitting lentic model showed that species occurrence was positively correlated with the pH and surface area of the water body. The lotic model was more robust, whereas the lentic model was interpreted with caution due to the smaller sample size. The species' presence in isolated larger ponds, usually more attractive to anglers, indicates that human introduction as a bait fish could be a primary driver of its dispersion. The findings of this study provide a first step in understanding the ecological habitat preferences of L. gibbosus in this region and could serve as a starting point for future research, monitoring and management of this invasive species.

The striped snakehead, Channa striata, is a commercially and ecologically significant freshwater fish species in India. This study provides a comprehensive morphometric and meristic analysis of its population in Nagapur Dam, Parli Vaijnath, Beed District, Maharashtra. A total of 176 specimens were collected from January 2023 to December 2024. Sixteen morphometric characters and five meristic counts were recorded. The population showed a wide size range, with total length (TL) from 15.2 to 55.0 cm and body weight (BW) from 32.5 to 1380.5 g. The length-weight relationship was determined as W = 0.021L³.⁰⁵, indicating positive allometric growth (b > 3). Linear regression analysis revealed highly significant (p < 0.001) relationships between TL and all other morphometric characters, with coefficients of determination (R²) exceeding 0.98 for most parameters, demonstrating strong morphological integration. Meristic counts were stable, with dorsal fin rays (DFR) ranging from 37-45 and pelvic fin rays (PFR) showing 97.7% consistency at 6 rays. The results confirm a healthy, well-adapted population and establish crucial baseline data for the sustainable management and future monitoring of this valuable fishery resource in Nagapur Dam.

Ecological and evolutionary processes generate biodiversity, yet how biodiversity data are organized and shared globally can shape our understanding of these processes. We show that name-bearing type specimens—the primary reference for species identity—of all freshwater and brackish fish species are predominantly housed in Global North museums, disconnected from their countries of origin. This geographical divide creates a ‘knowledge split’ with consequences for biodiversity science, particularly in the Global South, where researchers face barriers in studying native species’ name bearers housed abroad. Meanwhile, Global North collections remain flooded with non-native name bearers. We relate this imbalance to historical and socioeconomic factors, which ultimately restrict access to critical taxonomic reference materials and hinder global species documentation. To address this disparity, we call for international initiatives to promote fairer access to biological knowledge, including specimen repatriation, improved accessibility protocols for researchers in countries where specimens originated and inclusive research partnerships.

Assessing the human health risks from organophosphate esters: exposure assessment via wild freshwater fish consumption.

ABSTRACTAcross many ecto‐ and endothermic organisms, climate change has induced a general shift towards smaller body sizes. Several existing hypotheses (e.g., Temperature Size Rule—TSR, metabolic theory) contribute to our understanding of climate‐driven changes in body size. However, empirical support for climate‐induced reductions in body size is mixed with some species growing larger under warmer temperatures, and underlying mechanisms are under debate. To address these inconsistencies, we used Bayesian hierarchical modeling to determine if mean length‐at‐age (proxy for growth) changed from 1945 to 2020 for age classes of 13 freshwater fish species. Then, we used boosted regression trees (BRTs) to disentangle the impacts of climate change on growth from other environmental factors. Hierarchical modeling revealed that 37% of age classes were decreasing in mean length through time (69% were qualitatively decreasing). BRTs demonstrated that growing degree days and mean annual surface water temperature had varying effects on growth. For cold‐and cool‐water adapted fishes, length‐at‐age usually increased as a function of degree days but decreased as a function of surface temperature. Warm‐water adapted fishes, however, typically decreased in response to both degree days and surface temperature. The direction of change in length‐at‐age as a function of surface temperature corresponded to the direction of change over time for 62% (8/13) of species. Overall, we found widespread decreases in length, including age classes from all thermal guilds and juveniles (contrary to TSR assumptions). Mixed results in prior literature may result from choosing different variables to represent climate warming and/or not considering age‐specific length responses. When specific climate variables and age are considered, climate change effects on body size may be more predictable at large temporal and spatial scales than previously thought. Continued decreases in length for the youngest and oldest fishes could lead to biodiversity loss and diminished ecosystem functions and services.

The freshwater fish diversity of Ujani Reservoir, Pune District, Maharashtra, India, was assessed from April 2021–March 2023. A total of 56 freshwater fish species belonging to 39 genera and 18 families were documented. Comparative analysis with previous literature suggests a historical record of approximately 60 species in the reservoir. Of the 56 species recorded, 41 are endemic to the Oriental zoogeographical realm, while eight are endemic to the Krishna River system. Notably, two species, Parambassis lala, native to the Ganga, and Brahmaputra river basins, and Nandus nandus the Gangetic Leaffish, were recorded for the first time in Ujani Reservoir. The ichthyofauna of the reservoir faces significant threats from invasive alien species, industrial, and agricultural pollution, expanding human settlements, and overfishing. Given the presence of eight endemic and six threatened species, conservation measures are imperative to mitigate anthropogenic pressures, and preserve biodiversity. This study provides an updated account of fish diversity and distribution in Ujani Reservoir, serving as a crucial baseline for future conservation, and management initiatives.

The International Union for Conservation of Nature (IUCN) Green Status of Species (GSS), introduced in 2021, is a global standard of measurement used to assess the level to which a species has recovered (i.e., is viable and providing its ecological function across its entire range). It is also used to evaluate how a species has responded to past conservation actions and the expected conservation gains and recovery potential it would receive in the short- and long-term future. Preliminary application of the GSS method has relied on expert knowledge from individuals or small groups of specialists. However, more accurate and reliable results are likely to be produced by formally eliciting individual judgments from a diverse range of experts, followed by discussion, reevaluation, and synthesis of these judgments. We developed a method in which 2 structured expert elicitation workshops are used to conduct GSS assessments and applied this method to 8 Australian freshwater fish species from the Murray-Darling Basin. We integrated the investigate, discuss, evaluate, aggregate protocol into the GSS methods; experts assessed the species' IUCN Green Score (percent recovery) in the current state and for 5 other scenarios in the past and future with and without conservation. Four GSS conservation impact metrics were calculated based on the averages of expert judgments. Experts forecasted that impact in the short-term would be minimal (i.e., conservation gain metric=zero or low) for 5 of the 8 species because targeted and maintained conservation actions are often lacking. In contrast, experts indicated long-term recovery potential would be considerably higher if implementation of appropriate recovery activities could be sustained (all 8 species had medium or high recovery potential). We concluded that the GSS is well suited to a modified workshop approach because it aims to reduce biases associated with expert judgments and encourages valuable knowledge sharing among experts.

Simple SummaryAntibiotics are commonly used in aquaculture to prevent disease, but their residues can remain in pond water and affect the environment. In this study, we measured sulfonamide and fluoroquinolone antibiotics in 40 aquaculture ponds around Wuxi, China, during two key farming stages: the summer grow-out period (August) and the autumn harvest (October). Using sensitive LC–MS/MS analysis, we found that antibiotics were widespread. Enrofloxacin, a fluoroquinolone, was dominant in August, occurring in over half the ponds at concentrations up to 2.36 µg/L. By October, sulfonamides such as sulfamethoxazole and sulfadiazine became more common, with one pond showing sulfadiazine levels above 4 µg/L. Statistical analyses confirmed a clear seasonal shift in antibiotic patterns and revealed that multiple sulfonamides were often used together in autumn. These results highlight two key issues: (1) different antibiotics dominate at different farming stages, and (2) combined use of drugs increases potential risks of antimicrobial resistance and ecological harm. To address these concerns, we recommend stricter monitoring and regulation, better farm management to reduce reliance on antibiotics, and promotion of alternative disease-control strategies. This study provides valuable baseline data for improving the sustainable and safe use of antibiotics in aquaculture.Antibiotic use in aquaculture has become widespread to sustain production and control bacterial diseases, but it poses significant ecological and human health risks due to residue accumulation and resistance development. This study investigated the occurrence, dominance, and combined use of sulfonamide and fluoroquinolone antibiotics in freshwater fish aquaculture ponds around Wuxi, China. Here, the term aquaculture refers specifically to the controlled farming of freshwater fish species such as carp and crucian carp in managed pond systems. A total of 80 water samples (collected exclusively from pond waters) were obtained from 40 ponds during the high intensity rearing and harvest stage of fish. Residues of enrofloxacin and sulfonamide antibiotics were analyzed using a validated LC–MS/MS method with detection limits in the low nanogram-per-liter range. Results revealed that antibiotics were ubiquitous in pond waters, with enrofloxacin emerging as the dominant compound in August, reaching concentrations of up to 2.36 µg/L. By October, sulfonamides, particularly sulfamethoxazole and sulfadiazine, became more prevalent, with a maximum sulfadiazine concentration exceeding 4 µg/L. Multivariate analyses demonstrated a clear seasonal shift in antibiotic profiles, while correlation analyses indicated limited combined use in summer but notable co-occurrence of sulfonamides in autumn. These findings underscore that antibiotic application patterns in aquaculture are strongly linked to production stages, with potential consequences for environmental safety, resistance development, and food security. Effective monitoring, stricter regulation, and alternative disease management strategies are urgently required to mitigate risks and promote sustainable aquaculture practices.

In the present work, we aimed to extract and identify microplastics (MPs) in two different species of fish, namely, Rohu fish (Labeo rohita) and Freshwater Shark (Wallago attu), inhabiting the Tanguar Haor (wetland) that is a part of the Surma River, Bangladesh. Three different parts, namely, the stomach, intestine, and dorsal muscle of the corresponding fish samples, were digested with a 10% KOH solution. We conducted a qualitative assessment using FTIR, UV-visible, and SEM/EDS measurements to confirm the presence of MPs. The study identified various types of MPs, including Polypropylene (PP), Polyethylene (PE), Polyvinylchloride (PVC), Polyamide (PA), Polyethylene terephthalate (PET), and Polymethyl methacrylate (PMMA), in three different parts of the respective fish samples. Among the different portions of fish, the intestine contained the most diverse range of MPs, with six different types identified. In comparison, five types of MPs were found in the stomach, and only three types were observed in the dorsal muscle. The mean diameter of the identified MPs determined by SEM analysis revealed the smallest mean diameter of 570nm in the dorsal muscle portion of the L. rohita and the largest mean diameter of 889nm in the intestine part of W. attu, respectively. Thus, the outcome of this investigation sheds light on the possible presence of MPs in freshwater wetland ecosystems.

Background:Empirical evidence to support an association between biodiversity and childhood asthma remains limited, and the contributions of specific taxonomic groups have been poorly understood. This nationwide, retrospective cohort study aimed to evaluate the associations between a wide range of biodiversity indices during pre-, peri-, and post-natal periods and childhood persistent asthma.Methods:We included child-mother dyads between January 2005 and January 2017 from the Japan Medical Data Center database. Species richness, net relatedness index (genetic diversity), and land-use types were defined based on the municipalities in which the children resided during each exposure period. The primary outcome was persistent asthma in children aged 4–5 years. Modified Poisson regression models were used to evaluate the association between the biodiversity indices and childhood persistent asthma. Results were adjusted for confounders and predictors of asthma, including infant sex, cesarean section delivery, parental history of asthma, particulate matter ≤2.5 µm in aerodynamic diameter, nitrogen dioxide, population density, metropolitan area status, municipality-level area deprivation index, and prefectural-level smoking prevalence.Results:A total of 109,233 child-mother dyads were included; 34.7% of the children had persistent asthma at 4–5 years of age. Greater species and genetic diversity of freshwater fish, along with stagnant water areas, were consistently associated with a 2–5% lower risk of childhood asthma.Conclusions:Biodiversity during early life was heterogeneously associated with childhood asthma. These findings suggest that conserving freshwater fish species and their habitats may contribute to asthma prevention in children.

The present study aims to provide an inventory of eight freshwater fish species that represent 6 families obtained from Lake Nasser and the River Nile using DNA barcoding, using analysis of cytochrome oxidase subunit I (COI) gene sequences. Fish samples were identified morphologically as Ctenopharyngodon idella, Oreochromis niloticus, Bagrus bajad, Sarotherodon galilaeus, Auchenoglanis occidentalis, Lates niloticus, Sardinella tawilis, and Coptodon zillii. COI gene was successfully amplified for using PCR, showing a readable fragment length of ~ 700 base pairs (bp). The obtained sequences were compared to GenBank and the Barcode of Life Data System (BOLD). The GenBank and BOLD resulted in a total of 6 fish samples finding their best hits with similarity scores ranging from 99.29 to 100%. The average AT content (53.12%) was higher than the average GC content (46.88%) in the studied fish species. The minimum genetic Kimura 2-parameter (K2P) distance between species was 0.089 and the maximum distance was 0.313. According to phylogenetic tree analysis, the majority of fish species were grouped into monophyletic units. The current study confirms that DNA barcoding is a useful method to identify the vast majority of fish species in Lake Nasser and the River Nile. However, the morphological identification remains crucial.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-20830-z.

Among temperate regions of the world, freshwater fish species richness is highest in the Central Highlands of eastern North America. Historical biogeographic and phylogeographic researchers have investigated mechanisms driving this exceptional diversity, yet the role of major climatic events, like Pleistocene glaciation, is incompletely characterized. In this study, we analyze genomic DNA sequence data sampled from populations of the widely distributed Gilt Darter, Percina evides (Jordan & Copeland 1877), to reconstruct pre-glacial drainage patterns and assess the impact of Pleistocene glaciation on generating the high species diversity of eastern North American freshwater fishes. Phylogenomics, population genomic analyses, and evaluation of morphology delimit five species currently classified as P. evides. These species likely diverged via allopatric speciation among the disjunct regions of the Central Highlands driven by the onset of Pleistocene glaciation. Divergence times among newly delimited species of the Gilt Darter complex are congruent with the onset of glaciation, periods of river incision and aggradation, and river network rearrangement. The discovery of new species in the Percina evides complex and reconstruction of the timing of their diversification provide insight into the role that Pleistocene glaciation and glacial refugia contributed to the remarkable temperate freshwater biodiversity hotspot of the Central Highlands.

Columnaris disease is a highly contagious infection that affects nearly all freshwater fish species worldwide. Grass carp, one of the most economically significant freshwater fish species in China, is particularly susceptible to the disease, leading to large-scale mortality. Flavobacterium columnare and F. covae are the primary pathogens causing columnaris disease in Chinese grass carp aquaculture. Herein, we compare mortality rates, replication rates of typical columnaris symptoms, histopathological changes, and bacterial content in the tissues of grass carp following infection using four challenge models. The mortality rate in grass carp challenged via intraperitoneal injection was 86.7%. All fish infected via intramuscular and intradermal injections died, while immersion resulted in lower mortality. Gill corrosion rates were 67%, 53%, and 87%, respectively, in the intramuscular injection, intradermal injection, and immersion groups. Correspondingly, skin ulceration rates were 75%, 91%, and 63%. However, surface symptoms in the intraperitoneal injection group were milder. Histopathological analysis revealed similar lesions in grass carp subjected to immersion, intramuscular, and intradermal infection, which differed from carp infected via intraperitoneal injection. The trends in bacterial loads in the gills and skin were similar, although the absolute bacterial content varied between tissues. Bacterial loads in the immersion and intraperitoneal injection groups were lower than those in the other groups. Based on these findings, we determined that the optimal model for simulating columnaris disease in grass carp is the intradermal injection of F. covae in 10–12 cm fish. The infection model generated via intradermal injection resembles natural F. covae infection and can serve as a good tool for evaluating the protective effect of anti-F. covae infection vaccines in grass carp.

Otophysans, known for their enhanced hearing enabled by the complex Weberian apparatus, comprise two-thirds of extant freshwater fish species. Previously, they were thought to have originated in fresh water before the breakup of Pangea, implying a nearly 80-million-year gap between the origin and oldest known fossil. However, the discovery of a Late Cretaceous freshwater otophysan challenges this view. Integrating fossil, morphological, and genomic data, we estimate a younger crown group origin of ~154 million years ago. Notably, ancestral range and habitat reconstructions indicate marine origins for the otophysan crown groups, with at least two transitions to fresh water. Functional simulations of the Weberian ossicles of this fossil suggest that the distinctive hearing capabilities of otophysans evolved in conjunction with fusion of hearing ossicle parts and freshwater adaptations.

Ecotoxicological assessment of pesticide mixtures: effects of imidacloprid and propiconazole on Danio rerio and Astyanax lacustris.

Linseed oil injection into the yolk reserve strongly modulates lipid gene expression and fatty acid composition in juvenile Nile tilapia.

Aeromonas veronii, a prevalent Gram-negative bacterium in aquaculture, poses significant health risks to economically important freshwater fish species such as largemouth bass (Micropterus salmoides). This study investigates the role of pyroptosis, a highly inflammatory programmed cell death, in the immune response of largemouth bass to A. veronii infection. We characterised key pyroptosis-associated proteins, MsGSDMEa and MsGSDMEb, which harbour two conserved Gasdermin domains and are crucial in mediating pyroptosis. Following A. veronii infection, largemouth bass exhibited a robust upregulation of inflammatory cytokines (IL-1β, IL-8, TNF-α) and increased lactate dehydrogenase (LDH) activity in serum, indicating extensive cellular damage and inflammation. Quantitative real-time PCR analysis revealed a significant upregulation of pyroptosis-related genes, including NLRP3, ASC, and caspases (Caspase-1/-3/-7), in both spleen tissue and GF-1 cell line post-infection. Western blot analysis confirmed the cleavage of GSDME, a critical step in pyroptosis execution. These findings underscore the role of pyroptosis in the immune response of largemouth bass to A. veronii infection and suggest that modulating pyroptosis could be a potential strategy for disease management in freshwater fish species.

Aeromonas hydrophila is an opportunistic pathogen that is highly important for freshwater fish. In the present study, two freshwater fish species Nile tilapia (Oreochromis niloticus) and Mullet (Mugil cephalus) collected from various fish farms in Kafrelsheikh Governorate, Egypt. The fish samples were examined to determine Aeromonas hydrophila presence (A. hydrophila). In addition, a treatment trial was conducted involving four groups of Nile tilapia fish, which treated with florfenicol (FFC) and oxytetracycline (OTC) based on the antimicrobial susceptibility test results. According to the findings, 12 (20%) A. hydrophila strains were isolated from a total of 60 collected fish samples (30 of Nile tilapia and Mullet with percentages of 30% and 10%, respectively). Based on species-specific 16 S rRNA genes, six (6) isolates were identified as A. hydrophila and carried aerolysin (aerA) and hemolysin (hylA) virulence genes, with percentages of 83.3% and 50%, respectively. Whereas, the antimicrobial resistance gene results were blaTEM with percent (100%) and aadA1 (83.3%). Histopathological changes were significantly reduced in all assessed organs (liver, spleen, kidney, and gills) in the FFC group compared to the OTC-treated group. The prevalence of virulent and multidrug-resistant A. hydrophila in aquaculture poses significant risks to fish health, economic productivity, and public health.

Poly- and perfluoroalkyl substances (PFAS) in marine and freshwater fish muscle tissue from Shandong Province and implications for human exposure.

Decision-making and public health: How the prevalence of Contracaecum spp. larvae in market-size tilapia may influence fish sample-size to be inspected prior marketing