Search Results (488)

Managing invasive species such as the Chinese sleeper (Perccottus glenii) supports the goals of sustainable development by preserving native biodiversity. This study investigated the population structure, growth, and ecological impact of P. glenii in a small, anthropogenically altered tributary of the Vistula River (central Poland). Electrofishing surveys conducted between 2017 and 2023 assessed sex ratio, age structure, body size, condition (Fulton’s index), and growth parameters, as well as changes in the local fish community. The sex ratio was nearly balanced (♀:♂ = 1.00:0.99), and average standard length and weight were 6.54 cm/9.11 g (females) and 6.36 cm/7.69 g (males). Dominant individuals were from age group of 2+ years. The Fulton condition factor ranged from 2.54 to 2.58, while positive algometric growth was observed for both sexes. The von Bertalanffy growth model parameters (L∞ = 175.37 mm, k = 0.104, t₀ = −1.711) revealed slower growth compared to other Eurasian populations. In the individual months of the study, changes in the sex structure, length, weight, and age of the fish were observed. This seasonality may have resulted from physiological changes (including fish growth and reproductive processes), their migration, and environmental changes, such as food availability and hydrochemical parameters, occurring during this period. Additionally, over the study period, the abundance and density of P. glenii increased significantly, coinciding with a marked decline in native fish species. These findings highlight the adaptability of this invasive fish and emphasise the need for targeted management strategies in degraded freshwater ecosystems. Full article

Oryza sativa L. is the largest food crop in the world. The harmful filamentous green algae Spirogyra in paddy fields poses a serious threat to O. sativa yield. Therefore, biological control for Spirogyra is important for sustainable agricultural development. The native fish species Acrossocheilus yunnanensis can graze on Spirogyra and exhibits strong environmental adaptability, providing a novel approach to the biological control of Spirogyra. Therefore, we designed the O. sativa+Spirogyra+A. yunnanensis co-culture system to study the effects of A. yunnanensis on O. sativa growth and physiological characteristics. The results indicated that Spirogyra stress significantly inhibited O. sativa biomass accumulation, root length and plant height development, reduced photosynthetic efficiency, and increased the contents of oxidative stress markers including malondialdehyde (MDA) and hydrogen peroxide (H₂O₂). Interestingly, grazing of A. yunnanensis on Spirogyra increased the biomass of Oryza sativa by 58.60%, the root–shoot ratio by 78.01%, and the root length and plant height by 49.83% and 25.85%, respectively. Meanwhile, the soil nitrate nitrogen (NO₃⁻-N), ammonium nitrogen (NH₄⁺-N), and available phosphorus (AP) were enhanced, which improved O. sativa nutrient uptake and promoted photosynthetic pigment accumulation. This was manifested by an increase in chlorophyll content, net photosynthetic (Pn), transpiration rate, stomatal conductance (Gs), and intercellular CO₂ concentration (Ci). Grazing of A. yunnanensis on Spirogyra alleviated the oxidative damage to O. sativa induced by Spirogyra, as evidenced by decreased malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) level in both leaves and roots, along with increased protein content. This provides a new strategy for constructing a rice–fish symbiotic system by using indigenous fish species, achieving Spirogyra control and sustainable agricultural development. Full article

Polemonium caeruleum L. (Polemoniaceae) is a perennial flowering plant native to Eurasia and North America, which is used as a fodder, medicinal, and ornamental plant. Many issues related to the taxonomy and origin of this valuable species still remain unclear. The intraspecific genetic variability of P. caeruleum and chromosomal organization of its genome are insufficiently studied. For the first time, we analyzed NGS genomic data of P. caeruleum using ReapeatExplorer2/TAREAN/DANTE Pipelines. In its repeatome, we identified 66.08% of Class I retrotransposons; 0.57% of Class II transposons; 0.42% of ribosomal DNA; and 0.87% of satellite DNA (six high-confident and three low-confident putative satellite DNAs). FISH chromosome mapping of seven tandem DNAs was carried out in two P. caeruleum varieties and two wild populations. Our results demonstrated the effectiveness of using satDNAs Pol_C 46 and Pol_C 33 in combination with 45S rDNA and 5S rDNA for precise chromosome identification. This approach allowed us to study intraspecific chromosomal variability and detect chromosomal rearrangements in the studied accessions of P. caeruleum, which could be related to the speciation process. These novel molecular markers are important for chromosome studies within Polemonium to clarify its taxonomy and phylogeny, and also, they expand the potential of different breeding programs. Full article

The tropical gar (Atractosteus tropicus Gill, 1863) is a prehistoric fish of high nutritional value in southern Mexico and Central America. However, some aspects related to the effects caused by alternative protein sources, such as insect meal, as a substitute for fish meal on the growth and expression of digestive enzyme genes, are still unknown. A total of 225 juveniles of A. tropicus were used and fed five experimental diets, each in triplicate, with different levels of substitution of fishmeal (FM) protein with house cricket meal (HCM) protein. A control diet that contained no HCM (T1-0% HCM) was used, and substitutions ranged from 25 to 100% of FM protein by HCM (T2-25% HCM, T3-50% HCM, T4-75% HCM, and T5-100% HCM) for 45 days. The results of this study indicate that T4-75% HCM showed the best growth indices, such as feed efficiency (EF), feed conversion ratio (FCR), specific growth rate (SGR), as well as higher gene expression of pepsin and trypsin, while chymotrypsin showed higher expression in T3. The higher performance achieved in T4-75% HCM may be due to the fact that, in the early stages, insects are part of the natural diet of A. tropicus. The inclusion of cricket meal as a partial substitute for fish meal is not recommended in quantities greater than T4-75%. Full article

The Doce River basin is the largest river system in southeastern Brazil. Over the last century, the Doce River has been undergoing a serious process of degradation, culminating in a huge environmental disaster due to Fundão tailing dam bursting in Mariana (Minas Gerais) and causing severe damage to biodiversity and local human communities. Near its mouth, the Doce River harbors an extensive lake area, with over ninety lakes on coastal lowlands. These lakes are of fluvial origin and connected to each other and to the main Doce River by small tributary streams. In this area, one of the main sources of impact on the fish fauna is the presence of non-native fish species. We compared richness, taxonomic diversity, beta diversity, species composition and proportion of non-native species in lakes and streams, and related these variables to each other and to environmental variables. We used the indicator species index (IndVal) to identify species associated with each type of environment. We used multivariate analyses to test the influence of stream habitat on the fish fauna in streams and Generalized Linear Models (GLMs) to test the influence of distance to lakes on the proportion of non-native species in streams, and the influence of this proportion on total and native fish richness and diversity. The results showed that some non-native species originating from lentic environments have adapted to the lakes and are spread throughout the internal lake system. In streams, there are proportionally fewer non-native fish and their distribution is more fragmented, as some stretches do not provide the conditions for the establishment of some of these species, making them potential refuges for native ichthyofauna. As the streams move away from the lakes, the proportion of non-native species tends to decrease. In streams, the richness and diversity of native species are affected by the proportion of non-native species, but not in lakes. The native vegetation in the landscape showed no potential for reducing the invasion of non-native species. The depth and width of the streams are directly related to the proportion of non-native species within the streams and are structural characteristics that should be considered in strategies for the conservation of the fish fauna. Full article

This study quantified the Habitat Connectivity Index (DCI) of cascade dams in the mainstream of the Dongjiang River, revealing the non-linear relationship between dam passability (p) and connectivity restoration. Results showed that DCI increased slowly when p < 0.6 (with the magnitude of increase not exceeding 10.41), whereas an exponential response emerged when p > 0.8 (specifically, DCI rose by 16.53 as p increased from 0.8 to 0.9). Time-series analysis indicated that the number of dams increased from 3 to 16 between 1970 and 2020, which plunged the natural-state DCI (set at 100) to 9.01 (representing a 90.99% decrease); notably, 78.14% of the total connectivity loss occurred during the 2000–2010 period. Spatial heterogeneity analysis demonstrated that enhancing the passability of Jiantan Dam increased DCI by 4.68 (under the baseline condition of p = 0.8), whereas the same intervention on Sulei Dam only led to a 0.58 increase in DCI. This finding highlights the importance of key nodes for connectivity restoration and provides a scientific basis for prioritizing the enhancement of connectivity at such nodes in subsequent ecological governance. A 2024 fish community survey found that 84.2% of the recorded species were native (64 out of 76), while only 18.8% of the total individuals (617 individuals) were migratory; the dominant species were identified as generalist residents, including Oreochromis zillii, Cirrhinus molitorella, and Hemiculter leucisculus. This study identifies 0.8 as a critical threshold for connectivity restoration and provides a spatial decision-making framework for prioritizing the restoration of key dams. Full article

The diversity and distribution of fish in the water bodies of the Black Irtysh basin was studied in connection with six abiotic environmental parameters (surface flow velocity, width and depth of rivers, connection with the main river, and bottom and maximum temperature). The current species diversity of fish consists of 29 native and 11 alien species. The diversity of right and left tributaries varies greatly as a result of differences in abiotic parameters. The presence of a hydrological connection of reservoirs by itself does not guarantee the distribution of species throughout the basin. Rare indigenous Siberian Taimen Hucho taimen and Markakol Lenok Brachymystax savinovi were regularly found in the right tributaries of the Irtysh River and Lake Markakol, respectively. New fish species to the Kazakh section of the Black Irtysh River have been discovered: Tibetan stone loach Triplophysa stolickai, Severtsov’s loach Triplophysa sewerzowi and alien fish species as asp Leuciscus aspius, Chinese false gudgeon Abbottina rivularis, sunbleak Leucaspius delinetaus, and Misgurnus sp. Full article

Eelgrass (Zostera marina) is a native perennial marine angiosperm found in shallow bays and estuaries. Eelgrass beds are considered essential fish habitats and provide an important food source for marine organisms and waterfowl. This study examines changes in extent of the eelgrass beds in the southern portion of the Little Narragansett Bay Estuary, Rhode Island/Connecticut, USA, between 2019 and 2022. The primary dataset used to delineate eelgrass beds was side-scan sonar coupled with underwater video imagery. Previous studies showed a decline in the extent of eelgrass here between 2012 and 2016. Our results show an increase in eelgrass coverage from 0.52 km² in 2019 to 0.75 km² in 2022. This increase in the extent of eelgrass occurred against the trends of declining eelgrass coverage both globally and regionally. Full article

The Danube in Croatia serves as an important transport route but also favors the spread of invasive species, especially in the floodplain areas. Many of them originate from the Ponto-Caspian region and influence European ecosystems with their migrations. One of these species, Limnomysis benedeni, a mysid shrimp, thrives in shallow waters and plays a crucial role as a food source for fish. L. benedeni was first recorded in Croatia in 2004 in Lake Sakadaš (Kopački Rit). Prior to the study on aquatic macroinvertebrates in Kopački Rit Nature Park, conducted from July 2020 to July 2023, there had been no documented records in recent years. Sampling was carried out seasonally for macroinvertebrates and monthly for environmental parameters at 15 sites within the park or in the immediate vicinity. Samples were collected according to standard AQEM methodology. A total of 21 macroinvertebrate groups (407 taxa), out of which the most diverse were Diptera with 20 families, were identified in this study, including nine allochthonous species in addition to L. benedeni. The most abundant populations of L. benedeni were found in the Danube, the Petreš channel, and Vemeljski Dunavac channel, which supply the floodplain with water from the Danube. Most individuals were collected in summer and spring, with the highest density being 741 individuals per square meter. Environmental parameters such as water level, type of habitats, pH values, chemical oxygen demand, and phosphorus content, were statistically significant for the distribution of species. The dominant microhabitat for L. benedeni in Kopački Rit was argyllal in combination with coarse particulate organic matter and wood debris, and the composition of these microhabitats remained consistent throughout the seasons. L. benedeni was the only crustacean species to establish a stable population in the floodplain area, excluding Asellus aquaticus (water louse), a cosmopolitan species. The ongoing influence of L. benedeni on the native community still remains to be determined. Full article

Freshwater ecosystems are a significant entity that govern the livelihood of people and are an important source of food, employment, and recreation. However, climate change is impacting freshwater ecosystems by altering their natural habitats. The purpose of this review is to highlight the vulnerability of freshwater fish to climate change. Climate change is invariably affecting natural ecosystems everywhere and in every part of the world, but these threats are more severe in Pakistan. Freshwater fish are important biotic drivers of freshwater ecosystems. Unfortunately, uncertain climate changes and anthropogenic activities have led to a decline in the diversity of these fishes. Rising temperatures, melting glaciers, changes in seasonal patterns, disturbances in the natural flow of rivers, pollution, and invasive species are major threats to native freshwater fish fauna, leading to a decline in fish diversity and population. Tor putitora, Glyptothorax kashmirensis, and Triplophysa kashmirensis are some of the species that are critically endangered in Pakistan due to these factors. In recent decades, insufficient attention has been paid to the freshwater ecosystem. This review of threats to the endemic fish species in this region is presented so that the government and policymakers can use this information as part of their management and conservation policy, thus safeguarding Pakistan’s fish industry. Environmental DNA (eDNA) biomonitoring is a new technique for assessing biodiversity and species distribution and can be useful for conserving biodiversity in this region. Another purpose of this review is to introduce this new conservation strategy to Pakistan. Full article

This study assessed the impact of untreated wastewater discharge in the Danube River on four native fish species: barbel (Barbus barbus), vimba bream (Vimba vimba), perch (Perca fluviatilis), and white bream (Blicca bjoerkna). Biomarkers of exposure and effect were evaluated, including metal and metalloid bioaccumulation in gills, liver, and gonads, DNA damage (comet assay), chromosomal abnormalities (micronucleus assay), liver enzyme activities (ALT, AST), and erythrocyte maturation. White bream showed the highest genotoxic damage (TI% = 22.57), particularly in liver tissue, indicating high sensitivity to pollution. Perch had elevated DNA damage in blood (TI% = 22.69) and strong biomarker responses, likely due to its predatory behavior. Barbel displayed notable DNA damage in gills (TI% = 30.67) and liver (TI% = 20.35), aligning with sediment exposure due to its benthic habits. Vimba bream had the lowest responses, possibly reflecting reduced exposure or resilience. Element accumulation varied across tissues and species, with perch showing the highest overall levels. Hepatic enzyme activities (highest values: ALT = 105.69 in barbel; AST = 91.25 in white bream) and changes in erythrocyte profiles supported evidence of physiological stress. Integrated Biomarker Response (IBR) analysis identified white bream as the most sensitive species, followed by perch and barbel. These results emphasize the value of multi-species biomonitoring and the importance of species-specific traits in freshwater ecotoxicology. Full article

Major human impacts on New Zealand’s ecology began about 800 years ago with immigration firstly from Polynesia, then Europe starting a few centuries later. The humans cleared habitat, hunted species to extinction, and introduced biota, including plants, birds, fish, invertebrates, and mammals. Over the last 70 years, government-funded campaigns have been waged against some of the introduced mammals that became considered harmful to native biota. These campaigns spread poisonous food baits from aircraft to kill and suppress target animals (mainly brushtail possums (Trichosurus vulpecula) and rats (Rattus spp.)) over large areas. Increased intensity, frequency, and scale of poisoning are being trialled under a new conservation strategy (Predator Free 2050) to eradicate several mammalian species. The present study investigates the opportunity for a paradigm shift in conservation, emphasizing the rationales for transitioning from spreading of pesticides to a more targeted approach. NZ’s poison- and predator-focused ecological management has been criticized internationally as cruel and unnecessary, while independent NZ ecologists have called for, and outlined, a new system of conservation management based on ecological knowledge, which embraces all threats to native biota. A central tenet of proposed new methods is the engagement of all relevant stakeholders. Efficient management tools include remote monitoring, and smart, self-resetting kill traps for targeted small mammal control. Ecology-driven, commercially sound, targeted, monitored, relatively humane management can be implemented to protect the remnants of NZ’s natural heritage. Full article

In the native açaí groves of Lago do Maicá, in western Pará, harvesting is still performed using traditional techniques such as the peconha, which is a rope device tied to the feet that helps with climbing açaí palms. The absence of affordable and locally adaptable technologies compromises the safety of extractivists and limits the strengthening of the açaí value chain, affecting the development of a forest-based bioeconomy. This study focused on the Quilombo of Murumuru to understand the profile of local extractivists and identify which technologies could be more easily adopted in floodplain environments. After ethics approval, fieldwork involved participatory activities including knowledge-sharing meetings, transect walks, community discussions, and structured interviews. The results indicated that most collectors identify themselves primarily as açaí extractivists. Some rely exclusively on this activity for income, while others complement it with fishing or agro-extractivism. Reports of occupational risks were frequent, especially due to falls and contact with venomous animals. There was also a clear lack of technical assistance and limited access to context-sensitive technologies. The study highlights the need for institutional partnerships that support income diversification, value traditional knowledge, and improve working conditions. Strengthening the native açaí value chain in floodplain regions is essential for reducing socioeconomic vulnerability and advancing a regenerative, community-centered bioeconomy in the Amazon. Full article

Freshwater ecosystems are increasingly stressed by drought and anthropogenic inputs that can increase specific conductivity (SPC) and pH; however, little is known about how harsher conditions affect fish. We evaluated how fish growth and diet composition changed along a natural gradient in SPC and pH in Wyoming, USA using Northern plains killifish (Fundulus kansae) and Fathead minnows (Pimephales promelas). We surveyed 201 sites where we measured water chemistry, sampled fish, and assessed invertebrate prey availability from May to September 2024. Northern plains killifish and/or Fathead minnows inhabited 12 sites, which were the focus of our study. We measured otoliths to assess growth and stomach contents to estimate dietary selectivity. Growth decreased at higher SPC (486–23,500 µS/cm) for Fathead minnows and pH (7.2–9.0) for both species, suggesting an energy trade-off with osmoregulation. Dietary analyses revealed variable selection for Chironomidae larvae, while other taxa such as Gammaridae and Coleoptera were avoided at higher SPC and pH. Despite the extreme conditions, these fish maintained some dietary preference, highlighting behavioral plasticity. Our findings suggest that while these species can tolerate harsh environments, sublethal effects on growth and diet may limit long-term fitness. This research offers a framework for assessing the viability of fish populations inhabiting ecosystems with increasing salinity and pH that can inform conservation and management strategies under future environmental change. Full article

In the early 1900s, eastern mosquitofish (Gambusia holbrooki) and western mosquitofish (Gambusia affinis) were deliberately and globally introduced for the biological control of mosquito larvae. Subsequently, both species developed a reputation for causing impacts on native small-bodied fish, amphibian larvae, and other aquatic species. This led to both species being considered some of the world’s worst invasive species. Due to morphological similarities, organizations worldwide often consider these species jointly when discussing their introduction and impacts. Recent studies suggest these species differ in fundamental ways, which could affect invasion success. Our goal was to compare eastern and western mosquitofish behavior and invasion success. Replicate populations were collected from the U.S. states of Florida (eastern mosquitofish) and Louisiana (western mosquitofish) to assess variation in aggression, boldness, and sociability. Mesocosm trials were used to compare invasion success between species following introduction to an ecosystem occupied by another small-bodied poeciliid. Eastern mosquitofish caused more damage to similar-sized heterospecifics and western mosquitofish exhibited greater boldness. No differences were found in sociability between the two species. In mesocosms, impacts were observed for both mosquitofish species but were greatest for heterospecifics with eastern mosquitofish. This suggests that two invasive species, even with similar life history and morphology, can differ in traits related to invasion success and ecological impacts. It is important to correctly identify mosquitofish species when evaluating their invasion. Full article