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The Borneo earless monitor lizard (Lanthanotus borneensis) is one of the endemic animals of Indonesia. In 2019, the IUCN listed L. borneensis as an 'endangered' species. The declining population of the L. borneensis is a major concern for conservation efforts. One of the efforts to conserve endangered wild animals is to know the gut microbiome profile and the relationship between the host and the bacterial community in the body, which is associated with an influence on health. This research aims to determine the gut microbiome profile of animals with metagenomic analysis using Next-Generation Sequencing (NGS). This research was carried out by providing three feed types: earthworms, shrimp, and fish. Sample feces was collected by cloacal swabs and the DNA was sequenced using the Illumina NGS technique in the V4 16S rRNA region to examine the gut microbiome. The results of the metagenomic analysis showed differences in bacterial abundance in each feed treatment. The L. borneensis treated with earthworms and fish were dominated at the phylum level by Proteobacteria and Bacteriodota, while in shrimp, the phyla were Proteobacteria and Firmicutes. Index Shanon, Simpson, and the rarefaction curve also showed the highest bacterial diversity found in the fish treatment. This study can be used as a reference in designing suitable feed formulations for effective captive breeding for the conservation of L. borneensis [ABSTRACT FROM AUTHOR]

Exploring the seasonal dynamics of different components of biodiversity (alpha, beta, and zeta) and identifying the factors driving these patterns can help to reveal the health conditions and changes of ecosystems across different seasons. Seasonal differences in coastal fish biodiversity components were determined based on data of species abundance, traits, and mitochondrial genes. We then used multiple models to assess the relative importance of environmental and geographic variables in shaping the spatial patterns of different components of diversity. The results showed that the variation patterns of alpha diversity indices among seasons were inconsistent. All beta diversity indices showed significant seasonal variations. The rate of zeta diversity decline was highest in winter, and the compositional turnover showed no significant variations among the other three seasons. In spring, longitude was the most important factor influencing variations in alpha and beta diversity, while sea surface temperature and distance from mainland were important drivers for fish zeta diversity. Distance from mainland, sea surface temperature, and salinity were the most critical factors shaping the spatial pattern of diversity in summer, autumn, and winter, respectively. Our results suggest that environmental and geographic factors play an important role in shaping the patterns of coastal fish diversity. [ABSTRACT FROM AUTHOR]

Lack of sufficient knowledge of biological diversity is the first barrier to promoting scientifically‐based conservation policies in Neotropical regions, where high diversity and limited sampling remains a challenge. We compiled fish occurrences data from the whole Upper Paraguay River basin (UPRB) and evaluated the altitudinal variation in species richness, local contribution to beta diversity (LCBD) and composition. We also evaluate the influence of other environmental variables on species richness. Occurrence of a total of 342 native and five exotic fish species were recorded. Fish species richness was higher in lower portions of the basin, with a clear decrease from 400 m.a.s.l. Richness was negatively correlated with altitude, and positively correlated with net primary productivity and slope. The LCBD presented higher values on floodplain and in headwaters. Intermediate classes presented greater relative importance, as they present greater relative richness in a small relative area in the basin. We observed a partial overlap in species composition along altitude classes. Three species classified in some category of threat according to the conservation status of ichthyofauna in Brazil have a limited spatial extent of occurrence, restricted within the Serra da Bodoquena plateau. The obtained results highlight the unique diversity in the floodplain–plateau continuum, therefore, choosing protected areas must consider altitude gradients in the UPRB. Given the small area of the conservation units in the basin, the important role of higher altitude streams in regional fish species diversity and the several threats in the plateau, we conclude that an increase in conservation effort is needed in the plateau portion of the Upper Paraguay River basin. [ABSTRACT FROM AUTHOR]

The Neotropical region exhibits a remarkable diversity of freshwater fish, with the Upper Grande River in the La Plata basin emerging as a significant yet underexplored hotspot. However, this region is confronted with escalating threats from human activities, such as hydroelectric damming and urbanization, which jeopardize its ichthyofauna. This research conducted a comprehensive inventory of the ichthyofauna in the Upper Grande River, covering diverse environments and sub-basins. Fish sampling at 185 sites revealed over 94 species, indicating a high richness and abundance of migratory fish, as well as the presence of two endangered species. While the study provides valuable insights into fish species richness and distribution, accumulation curves suggest the need for additional sampling efforts. The presence of non-native species, especially in the Aiuruoca and Grande sub-basins, raises conservation concerns. The study underscores the Upper Grande River’s critical role as an area for fish diversity, emphasizing the necessity for ongoing monitoring, conservation efforts, and additional sampling to fully uncover the extent of its ichthyofauna. [ABSTRACT FROM AUTHOR]

Small indigenous fish (SIF) production from wetlands provides nutritious food and supports the livelihood of the fishing community. The present study investigated the fish production trend, SIF diversity, and role of environmental and climatic parameters in Beledanga, a floodplain wetland in lower Ganges, through the sampling and collection of data from the local fishermen cooperative society. The fish catch composition in the wetland shifted after 2019, with the increased Ctenopharyngodon idella (grass carp) contribution from 11% to 17% due to the introduction of in situ seed-raising technology of an HDPE (high-density polyethylene) pen culture system. The fish fingerling stocking has a profound impact on fish production (R2 = 0.60, p = 0.007). During the study period, 19 species of SIF were recorded, with a higher abundance observed in the monsoon season. The naturally occurring SIF contributed 16% of the total fish catch, with the highest catch in 2011 (11,970 kg). Water pH and phosphate content are the two most important environmental parameters that influence SIF. The generalized additive model (GAM) indicated that the optimum annual rainfall for fish production in the wetland was between 750 and 1250 mm. The average annual fish production of 43,017 kg through stocking and SIF support the livelihood and nutritional security of the fishers. As the SIF showed a decreasing trend of production, habitat protection, scientific stocking, and in situ enclosure culture are recommended for sustainable enhancement of fish production and to conserve the SIF diversity. [ABSTRACT FROM AUTHOR]

ABSTRACT Aim Location Taxon Methods Results Main Conclusions Poeciliids are ecologically important, are widely used as pets, and also have value as model organisms. To understand diversity within this family, we study their phylogenetic diversity (PD) at regional and local scales to delimit bioregions and identify patterns of biodiversity.The Americas.Poeciliidae (Actinopterygii: Cyprinodontiformes).We expanded an existing dated phylogeny from 164 to 261 species with distributional data for 1o × 1o latitude × longitude cells (~111 km2) and conducted a cluster analysis (phylo‐jaccard distance) to delineate bioregions. For individual cells, we mapped species richness (SR), phylogenetic diversity (PD), weighted endemism (WE) and phylogenetic endemism (PE). We used randomisation tests to map phylogenetic clustering and over‐representation of short‐branch species by cell. We used categorical analysis of neo‐ and palaeo‐endemism to map neo‐, palaeo‐, mixed and super (mixed) endemism.We delineated six bioregions. Highest regional species density and density of PD occurred on the Isthmus of Panamá (IOP). At the grid‐cell scale, the Grijalva–Usumacinta drainage is a hotspot for SR, PD, PE and WE; the IOP has high PD and PE; the Isthmus of Tehuantepec (IOT) has high PD, WE and moderately high SR; and western Hispaniola has high WE and moderately high SR. The Grijalva–Usumacinta drainage also includes cells of super (mixed) and palaeoendemism, while mixed endemism is widespread in Middle America and the Greater Antilles. Phylogenetic clustering is widespread, whereas over‐representation of short‐branch species is concentrated in the Chihuahuan Desert–Sierra Madre Oriental region and in western Hispaniola, both hotspots of neoendemism.We found widespread diversification of genera intermixed with relict species (mixed endemism). Furthermore, SR and PD were strongly correlated. Centres of endemism include the Chihuahuan Desert–Sierra Madre Oriental, western Hispaniola, the IOT, the IOP and (most of all) the Grijalva–Usumacinta drainage. However, conservation efforts must occur within each bioregion and for each genus. [ABSTRACT FROM AUTHOR]

The impacts of hydropower plants and their reservoirs on floodplains can potentially create new environmental filters and reduce the exchange of organisms and access to habitats. In this study, we aimed to compare the fish assemblage associated with aquatic macrophytes between floodplain lakes under natural conditions and a regulated floodplain lake in the Environmental Protection Area of Rio Pandeiros, Brazil. We tested the hypothesis that in the regulated floodplain lake, there would be a lower richness and a greater of abundance of macrophytes and fish than is natural. We also verified the influence of the seasons, macrophyte bank richness, and biomass on the fish assemblage abundance. The fish assemblages differed between the regulated and natural floodplains due to the higher richness and abundance of fish in the natural floodplains. The presence of non-native and generalist species in the regulated floodplain influenced the dissimilarity between the floodplains. Migratory species have been found only in natural floodplains. Fish abundance was negatively related to macrophyte richness on the regulated lake. There was a lower fish abundance and macrophyte richness in the regulated lake. There was no evidence that macrophyte biomass affected the abundance and richness of fishes. Our results confirm that the Pandeiros small hydroelectric dam affects the fishes' assemblage and the macrophyte community, since the regulated floodplain lake has a lower richness and abundance of fish. The regulated floodplain lake is connected to a reservoir created by a small hydroelectric dam, which will be removed in the coming years. The removal of this dam might change these dynamics, and this must be evaluated when the change is implemented. [ABSTRACT FROM AUTHOR]

The reuse of wastewater for beneficial purposes (e.g. irrigation) can boost water sustainability, but may have positive or negative impacts on the environment. In some drought-prone or over-allocated river basins, wastewater is an important component of stream flows and may buffer river ecosystems from drought. In these locations, wastewater may have a net positive impact on river ecosystems and its capture and reuse would be harmful to these ecosystems. In other locations, wastewater may have a net negative impact if the quality of the wastewater (i.e. concentrations of contaminants and nutrients) is lower than that of the receiving water body. In this study, we quantified the effects of wastewater on fish and macroinvertebrate communities in the Red River, Oklahoma. We investigated two competing hypotheses. First, we hypothesized that if wastewater flows buffer aquatic communities from drought, then measures of biodiversity should be higher at sampling sites near wastewater outfalls than at sites not near wastewater outfalls. Second, we hypothesized that if wastewater outfalls negatively impact water quality or homogenize the flow regime, then measures of biodiversity should be lower at sites near wastewater outfalls. To test these competing hypotheses, we calculated a suite of biodiversity indices at 320 biological sampling sites in the Red River Basin and analyzed for significant differences in communities based on proximity to wastewater outfalls. We found that proximity to upstream wastewater outfalls had significant positive impacts on macroinvertebrate community biodiversity, but we did not find any significant relationships with fish community diversity. Findings from this study provide insight to management decisions on wastewater reuse initiatives in beneficial subbasins while minimizing harmful ecological impacts. [ABSTRACT FROM AUTHOR]

The study was carried out in the rocky bottom habitat of Boğsak Island in Mersin Bay in November, March and July 2022-2023, using visual census method between 0-18 m depth and the survey was conducted along a transect. In the study, the structure of the fish community of the rocky bottom habitat of Boğsak Island was determined and the seasonal availability, abundance, feeding status and distribution of native and non-native fish species were determined. Shannon-Weiner Diversity Index (H') was used to determine species diversity and multidimensional scaling analysis was used to determine the relationship between the data. A total of 29 fish species, including 28 bony fish species belonging to 15 families and 1 cartilaginous Gymnura altavela (Linnaeus, 1758) were identified in the study area. The richest family in terms of species diversity was Sparidae (6), followed by Mullidae (3), Serranidae (3), Tetraodontidae (2), Soleidae (2), Labridae (2) and other families with 1 species each. It was determined that 52% of the fish species found in the study area throughout the year were Atlantic, 37% were Indo-Pacific and 11% were cosmopolitan. It was determined that 41% of the fish species were invertivores, 22% were carnivores (feeding on fish and invertebrates), 18% were omnivores, 11% were planktivores, 4% were herbivores and 4% were piscivores. The most abundant species were Torquigener flavimaculosus in summer, Cheilodipterus novemstriatus in spring and Chromis chromis in fall. Shannon species diversity (H'-2.956), richness (d=4.804) and homogeneity (J=0.800) were highest in the fall, followed by spring and summer. [ABSTRACT FROM AUTHOR]

The south-central coastal waters of Bangladesh are recognized as one of the foremost aquatic biodiversity hotspots despite severe anthropogenic and environmental hazards to natural fishery resources. Therefore, this study was undertaken to examine the current status of fish faunal diversity and evaluate the condition and conservation status of fish in the rivers spanning the south-central coastal region of Bangladesh. During the research period, spanning from July 2021 to February 2022, a total of 105 fish faunal species belonging to 84 genera, 50 families, and 14 orders were documented. The order Perciformes (27.62%) was found to be the most diverse fish group, followed by Cypriniformes and Scombriformes (12.38%), Siluriformes and Clupeiformes (11.43%), Synbranchiformes and Pleuronectiformes (3.81%). According to the International Union for Conservation of Nature (IUCN) Red List classification, 52 species recorded from the studied areas were determined to be of Least Concern, while 11 species were Vulnerable, 14 species were classified as Endangered, and 7 species are recognized as Critically Endangered. In order to assess the species diversity, richness, and evenness of the fish assemblage in the sampling areas, four diversity indices, viz. the Shannon-Wiener index (H), Simpson's dominance index (D), Simpson's index of diversity (1-D), and Margalef's index (d), were applied. Their overall values were 3.39–3.59, 0.05–0.07, 0.95–0.94, and 7.67–8.75, respectively. All of the species were more or less evenly distributed throughout the three sites, with Kalapara having the most even distribution. Several anthropogenic and natural attributes that contribute to decline in fish diversity were recorded using a survey questionnaire which revealed that management and conservation measures should be taken with utmost urgency. [ABSTRACT FROM AUTHOR]

Besides providing key ecosystem services, including improved water quality, coastal protection, and carbon sequestration, seagrasses are highly productive habitat-forming species essential in supporting fish diversity at the global level. In the Mediterranean Sea, seagrasses represent the main component of the sublittoral marine environment hosting a huge number of fish species that use this habitat for reproduction, foraging and/or refuge from predation. However, a complete synthesis of fish species observed in different seagrass habitats is still lacking at the whole Mediterranean basin scale, so hindering a thorough understanding of the main mechanisms involved in determining fish diversity patterns. We performed a systematic review by implementing a semi-automated, threshold-based filtering pipeline that allowed building up a dataset concerning all fish species reported in native Mediterranean seagrasses, including specific functional traits known to be involved with the potential use of seagrasses by fish. These data allowed to carry on a narrative synthesis on fish diversity in seagrass habitats, providing support to several assumptions repeatedly stated in literature but so far sustained mainly by local and fragmented data. Our findings suggested the onset of a general pattern in the occurrence of species, mostly based on life history and driven by body size and feeding habits. We evidenced unexpected knowledge gaps on the role of habitat heterogeneity and fish life stages in determining the presence and the potential use of seagrasses by species. In depth studies are therefore needed to better understand the mechanisms behind the structuring of fish communities, fundamental for the maintenance of marine biodiversity. [ABSTRACT FROM AUTHOR]

ABSTRACT Understanding how low salinity gradients (0‰–5‰) influence fish life cycles is critical for clarifying principles of fish assemblage formation in estuarine ecosystems. This study is intended to provide a foundation for predicting changes in fish populations amidst ongoing surface salinity decreases in the Baltic Sea. In the Neva River Estuary, differences in fish diversity and distribution between fish assemblages in freshwater and oligohaline areas were assessed using beach seine and multi‐mesh gillnet surveys. The use of multiple sampling gears greatly enhanced understanding of fish distribution across salinity gradients. Fish assemblages were analysed depending on the different areas of the estuary, seasons of sampling, salinity and confounding environmental variables such as water temperature and depth. Salinity was the major influencing factor for the surf zone fish assemblages and a season of sampling was the main factor for coastal assemblages of larger fish studied with the gillnets. Fish assemblages in the surf zone exhibited significant but gradual changes in freshwater and marine‐estuarine fish occurrence and abundance along the critical oligohaline barrier ‘δ‐horohalinicum’ (0.5‰–1.9‰). Although freshwater species showed high occurrence and abundance throughout the estuary, their juveniles were less abundant in the oligohaline surf zone with salinity ≥ 2‰, where small‐size marine‐estuarine and euryhaline species predominated. Coastal multi‐mesh gillnet catches showed remarkable similarity between assemblages of larger fish in freshwater and oligohaline areas. Differences in species richness and diversity indices were not pronounced throughout the salinity gradient; the decline in freshwater species was offset by an increase in marine‐estuarine and euryhaline species. [ABSTRACT FROM AUTHOR]

When evaluating the success of a stream restoration, it is pivotal to assess its ecological functionality as a sustainable habitat. In this study, we investigated fish communities across three sites with distinct structural features and environmental conditions in an urban restored stream located near the lower part of a major river. We analyzed the α‐ and β‐diversity of fish communities and estimated the restored stream's contribution to the river's fish diversity. We also examined ecological niche space and niche overlap among fish species using carbon and nitrogen stable isotope analysis. Results revealed that the restored stream increased overall diversity and β‐diversity in the region. Additionally, food web structure analysis showed variation in fish food source diversity among sites and species, resulting in diverse ecological niche areas and forms. The structural heterogeneity of the restored stream influenced fish feeding habits. However, many tolerant and invasive species were observed, with the invasive species Lepomis macrochirus markedly influencing competitive relationships with other fishes through its broad ecological niche area and overlap. These results emphasize the need to prioritize indigenous or non‐native species establishment during stream restoration. Overall, our study highlights the important role of restored streams in increasing catchment fish diversity. Nevertheless, food web‐centric monitoring and management strategies are necessary to effectively sustain local diversity. [ABSTRACT FROM AUTHOR]

Major trade-offs often manifest as axes of diversity in organismal functional systems. Overarching trade-offs may result in high trait integration and restrict the trajectory of diversification to be along a single axis. Here, we explore the diversification of the feeding mechanism in coral reef fishes to establish the role of trade-offs and complexity in a spectacular ecological radiation. We show that the primary axis of variation in the measured musculo-skeletal traits is aligned with a trade-off between mobility and force transmission, spanning species that capture prey with suction and those that bite attached prey. We found weak or no covariation between about half the traits, reflecting deviations from the trade-off axis. The dramatic trophic range found among reef fishes occurs along the primary trade-off axis, with numerous departures that use a mosaic of trait combinations to adapt the feeding mechanism to diverse challenges. We suggest that morphological evolution both along and independent of a major axis of variation is a widespread mechanism of diversification in complex systems where a global trade-off shapes major patterns of diversity. Significant additional diversity emerges as systems use weak integration and complexity to assemble functional units with many trait combinations that meet varying ecological demands. The diversity of coral reef fishes' feeding apparatus aligns with the trade-off between mobility and force transmission, but weak trait covariation and complexity allow jaw traits to evolve independently to adapt to diverse ecological challenges. [ABSTRACT FROM AUTHOR]

Marine biodiversity is increasingly threatened by overfishing and marine pollution. A comprehensive understanding of the biodiversity in the Yellow and Bohai Seas is essential for resource conservation. This study conducted a large-scale survey of fishery resources in the Yellow and Bohai Seas to investigate fish community structure and diversity using eDNA technology. The results showed that 57 and 65 fish species were recorded in spring and summer, respectively, with 46 species identified in both seasons. A total of nine dominant species were identified in spring, mainly belonging to Perciformes, while seven dominant species were identified in summer, primarily from Clupeiformes. In different regions, no significant differences in fish α diversity were observed between spring and summer. However, significant seasonal differences were found in both α and β diversity. At the spatial level, fish species in the Yellow and Bohai Seas occupied similar ecological niches. However, at the temporal level, there are certain differences in the ecological niches of fish communities between seasons. Phylogenetic diversity showed no significant differences at the spatial scale, yet notable seasonal variations were observed at the temporal scale, with spring (661.46) significantly exceeding summer (540.30). The Mantel test indicated that nitrate and salinity were key environmental factors influencing α diversity. RDA analysis revealed that the dominant species in spring were mainly influenced by chlorophyll-a and water temperature, while those in summer were mainly affected by water depth, nitrite, water temperature, and salinity. [ABSTRACT FROM AUTHOR]

The Tumen River, which delineates the border between China, North Korea, and Russia, is a vital river in Northeast Asia. Understanding its current fish diversity holds significant scientific value for aquatic ecological protection. Therefore, traditional and eDNA sampling were conducted from 2022 to 2023. Integrating the historical literature with our field collection results reveals that the Tumen River has a total of 64 native fish species, of which 51 species have been surveyed in the wild. The fish composition is mainly dominated by cold-water species, with a high proportion of these being rare, endangered, and nationally protected. eDNA surveys are crucial complements in boundary rivers where traditional methods are not feasible. The results indicated that α diversity values were highest in the Hunchunhe River, attributed to the favorable natural geographical conditions and effective conservation efforts. Recently, the fish diversity in the Tumen River has been disrupted, primarily reflected in the absence of migratory species such as Oncorhynchus gorbuscha and Pseudaspius hakonensis. The study suggests that establishing nature reserves, preventing and controlling alien species, and strengthening international cooperation are key to protect fish diversity. [ABSTRACT FROM AUTHOR]

Simple Summary: Urbanization has been regarded as a major threat to fish diversity in urban waters. Xinglinwan Reservoir, a lentic brackish ecosystem with a distinct salinity gradient in southeastern China, is experiencing rapid urbanization, and there are no reports on fish diversity here. Environmental DNA metabarcoding (eDNA) has been applied to biodiversity assessments in aquatic ecosystems, but there has been limited work on fish diversity in lentic brackish ecosystems. We assessed the fish diversity and spatial distribution along a salinity gradient in Xinglinwan Reservoir, combining eDNA and the traditional survey method (TSM). This study provides realistic pictures of fish species assemblages in Xinglinwan Reservoir and tests the efficiency of eDNA for assessing fish diversity in lentic brackish ecosystems. Our results contribute to the conservation of fish resources in Xinglinwan Reservoir and advance the application of eDNA in lentic brackish ecosystems. With the decrease in fish diversity, the monitoring of fish has become a current research hotspot. Here, the fish diversity and spatial distribution along a salinity gradient (0.28‰–3.32‰) in Xinglinwan Reservoir, China, were investigated using eDNA and the TSM. With the combination of both methods, 12 species from 6 orders, 9 families, and 11 genera were observed. The invasive species Oreochromis niloticus had the highest relative abundance, accounting for 56.91% in the TSM and 89.80% in eDNA, respectively. eDNA detected 83.33% of the species detected using the TSM, and an additional six species (50.0% of the total species) were detected via only eDNA. Moreover, eDNA supplemented the unavailable abundance data from the TSM. The TSM revealed that the diversity and relative abundance of fish inhabiting seawater and brackish water increased with an increase in salinity, but this was not found using eDNA. Thus, our study highlights that Xinglinwan Reservoir has a low species richness and is suffering from the great harm of ecological invasion. Our findings also show that eDNA could be reliable for providing a comprehensive picture of fish, but discriminating the spatial heterogeneity of fish communities is a challenge for its widespread adoption in lentic brackish systems. [ABSTRACT FROM AUTHOR]

The herbivorous mud skipper, Boleophthalmus pectinirostris and carnivorous eel goby, Odontamblyopus lacepedii are important species in the mudflat ecosystem of the Ariake Sea (Japan). To gain basic knowledge of the ecological and fishery applications of the Ariake tidal flat, an important wetland area, the microbiota of the mudflat and gut contents of B. pectinirostris and O. lacepedii were analysed using 16S rDNA amplicon sequencing. The amplicon sequence variant numbers in the mud and gut of B. pectinirostris and O. lacepedii were 1200, 110, and 140, respectively. The Shannon and Simpson alpha diversity indices of the fish contents were several-fold lower than those of the mud. In mud, Exiguobacteraceae (20%), followed by Anaerolineae (13%), were identified as the predominant bacterial families. In B. pectinirostris gut, Mycoplasmoidaceae (45%) were predominant, followed by Vibrionaceae (28%). In O. lacepedii gut, Desulfovibrionaceae (17%), Brevinemataceae (Spirochaetota) (15%), Vibrionaceae (14%), and Ruminococcaceae (10%) were dominant. These results suggest that, among the wide variety of bacteria in a mud environment, only compatible bacteria can settle in the fish gut. The differences between the two fish species may be due to differences in feeding habitat. The roles of Mycoplasmoidaceae and Brevinemataceae in their hosts are subjects of future research. [ABSTRACT FROM AUTHOR]

Diversity and interspecific synchrony are among the main drivers behind the temporal stability of community abundance. Diversity can increase stability through the portfolio effect, while higher synchrony generally decreases stability. In turn, species interactions and similar responses to environmental variation are considered the main factors underlying the strength of interspecific synchrony, despite the challenges in determining their relative roles. The analysis of the relationship between interspecific synchrony and the trait (or phylogenetic) distance between species can increase the robustness of inferences about these factors.Here, we used pairwise interspecific and community‐wide analyses to investigate, respectively, the drivers of interspecific synchrony and the influence of trait and phylogenetic diversity on the stability of fish communities. For that, we used 18 years of fish abundance data from the Upper Paraná River floodplain.At the interspecific level, we used quantile regressions to test within‐guild relationships between interspecific synchrony and trait and phylogenetic distance between species. At the community level, we tested the relationships between community‐wide synchrony, stability, and (trait and phylogenetic) diversity.We found that interspecific synchrony decreased with trait and phylogenetic distances. In the community‐level analysis, we found that more synchronous fish communities were less stable, but the relationship between diversity and stability was in general weak.At the interspecific level, our study highlights the role of similar responses to environmental variation in driving species' temporal dynamics. At the community level, the strength of the relationships between trait or phylogenetic diversity and community stability depended on the feeding guild. On the other hand, we found strong relationships between synchrony and stability. These results suggest that increased synchrony levels in response to regional environmental changes could decrease the stability of fish communities in this floodplain. [ABSTRACT FROM AUTHOR]

Hatchery production is common in salmonid management for harvest and conservation. Many hatcheries employ integrated broodstock programs, where wild-origin fish are included as broodstock and uni- or bi-directional gene flow between wild and hatchery components of the population is encouraged. Such approaches often assume that opportunistically obtained wild fish meet the genetic goals of minimizing hatchery–wild differentiation and maintaining genetic diversity. This may be incorrect if fine-scale spatial genetic structure exists. Here we investigate the population genetic consequences of such hatchery operations in coho salmon (Oncorhynchus kisutch) in a small river system featuring a large integrated broodstock program. We do so using 11 082 SNPs scored in wild-origin and hatchery-origin fish collected throughout the system. We found no evidence for genetic differentiation between hatchery-origin and wild-origin fish, no evidence of lowered genetic diversity in hatchery-origin fish, and no evidence for genetic differentiation among fish sampled throughout the river system. In addition, we did not detect inbreeding. Collectively, these results are consistent with current practices meeting integrated hatchery program goals of adequately sampling the genetic diversity present in wild-origin fish, although they may slightly reduce the effective population size of the combined population. [ABSTRACT FROM AUTHOR]

The ecological impact of dreissenid mussel (e.g., quagga and zebra) populations and their empty shells on native fauna in large rivers and lakes has been extensively studied. However, there is limited information on their effects in small wadable streams. Although established mussel populations in these systems are uncommon, their shells are found in high densities in benthic environments and may adversely impact stream communities. Shell densities were quantified using quadrats in two wadable streams to assess impacts on native benthic macroinvertebrates and fish. Eight reaches of each river were sampled, four with dreissenids and four without, totaling 16 locations. Macroinvertebrate and fish communities were characterized using diversity and environmental tolerance indices. Shell densities were significantly higher in dreissenid-invaded sites compared to sites with only native bivalves in both rivers. Dense shell beds had degraded biological conditions with fewer sensitive macroinvertebrates, but bed density did not affect overall macroinvertebrate or fish diversity. These findings differ from lake and large river studies, which found a greater impact of dreissenid shell deposition on macroinvertebrate and fish diversity than we observed in small wadable streams. Thus, a different approach to management and restoration may be necessary to maintain a natural community composition in wadable streams. [ABSTRACT FROM AUTHOR]

The trade-off between current and future reproduction remains a central issue for understanding the diversity of fish life-histories along a slow-fast continuum. Fish living in rivers of tropical oceanic islands generally have a fast type life-history, but variations in key reproductive traits can occur in response to spatial changes in selection pressures. Here, we investigated the reproductive strategies of two sympatric amphidromous gobies widely distributed in Caribbean streams, Sicydium plumieri (n = 308) and Sicydium punctatum (n = 383), along a river gradient of Guadeloupe Island. Beyond the new insights provided on the reproductive traits (ovarian organization, gonadal development, length at maturity, and spawning season), the histological observations of testes and ovaries revealed variation in reproductive strategies. Sicydium punctatum showed a time-minimizing strategy, featuring early reproduction, a high spawning frequency, an extended reproductive period, and a broad spawning area along the river course. Sicydium plumieri displayed a size-maximizing strategy, featuring a delayed maturity, lower spawning frequency, and a shorter reproductive period restricted to the upper reaches of rivers. We discuss the advantages provided by these two strategies in response to the spatial changes in predation and disturbance levels along the upstream–downstream continuum, which probably affects the survival rate and mortality risk before the first reproduction. [ABSTRACT FROM AUTHOR]

Environmental DNA (eDNA) metabarcoding has the potential to significantly improve surveys of biodiversity in freshwater systems. However, this methodology is still infrequently used in global hotspots of endemic species, in part because of two major barriers to the success of eDNA metabarcoding: (1) insufficient regional taxonomic representation in public reference sequence databases; and (2) inconsistent species incidence and abundance estimates when compared to conventional surveys.We sampled eDNA and conducted visual surveys in the headwaters of two rivers in the Cape Fold aquatic ecoregion, South Africa. A reference sequence database was generated for the regional diversity of fishes to improve taxonomic classification of endemic species. We also compared the consistency of incidence data and relative abundance estimates of fishes from eDNA metabarcoding sequencing results and visual surveys (snorkel and underwater cameras) at each site sampled.Only 1% of eDNA metabarcoding reads could be classified to fish species without the supplementation of reference sequence databases for local endemic species. Once regional reference sequences were added, a total of nine species were detected and >99% reads classified. A strong positive relationship (Φ = 0.75) was observed between the patterns of detections using eDNA and visual approaches. However, eDNA metabarcoding detected more species than visual methods. In addition, the relative read frequency and abundance observed in visual surveys was significantly correlated (R2 = 0.85–0.88, p < 0.001) in the majority of the small pools surveyed.Incomplete public reference sequence databases hinder the use of eDNA metabarcoding in regions of high endemicity. Local reference sequence libraries can overcome these challenges. When appropriately implemented, eDNA metabarcoding shows promise, producing results consistent or better than the more frequently used and labour‐intensive visual surveys.Efficient survey methods like eDNA metabarcoding are urgently needed to improve aquatic monitoring efforts globally. Understanding how eDNA metabarcoding sequencing results relate to conventional survey methods is a key step in its implementation in ecoregions with high endemicity. [ABSTRACT FROM AUTHOR]

The present study was conducted from April 2016 to March 2017 in a freshwater-dominated coastal wetland of the Indian Sundarban ecoregion to illustrate the fish diversity, and abundance and the predictor variables determining fish assemblage structure in the wetland. A total of 27 fish species belonging to 13 orders, 16 families, and 23 genera with Cyprinidae (18.5%) as the most dominant family were recorded from the wetland. Fish species richness was found to vary noticeably across the season with the highest number of taxa during the monsoon season (25 species). The study revealed that small indigenous fish species (SIFs) were found dominating the overall species richness and abundance which accounted for 70.37% of the total fish diversity. Among SIFs, Mystus gulio dominated (33 − 42%) the total fish abundance followed by Amblypharyngodon mola (12 − 21.7%), Oryzias dancena (11 − 14.9%), Parambassis ranga (6 − 32%), Puntius sophore (5 − 10.8%), and Parambassis lala (3 − 5.9%). Thirteen fish species were found as inhabitants of truly freshwater, eight species of freshwater and brackish water, and six of freshwater, brackish, and marine form. The developed GAM model proved water turbidity to be the best predictor variable determining fish abundance and assemblages in the wetlands. Besides, turbidity, salinity, transparency, and temperature were found to influence the fish assemblages. There was no visible response to water depth, although this has a linear effect on fish abundance. Water temperatures up to about 30.5 °C had a positive effect on fish abundance and the highest fish abundance in the wetland to be found in the range of 29 to 30.5 °C. [ABSTRACT FROM AUTHOR]

The declining population of otter species in Malaysia, including the Asian small‐clawed otter (Aonyx cinereus), smooth‐coated otter (Lutrogale perspicillata) and hairy‐nosed otter (Lutra sumatrana), is primarily attributed to habitat changes. Understanding the ecological aspects of otters, including their diets, is crucial for formulating effective conservation management strategies. To address this knowledge gap, we employed Next Generation Sequencing (NGS) as an alternative approach to enhance our understanding of the species' food chain. Specifically, this study investigated the diets of Asian small‐clawed otters and smooth‐coated otters by analysing an ~130 bp segment of the Cytochrome b (Cytb) gene using Illumina Miniseq platform. The analysis successfully generated 572,311 reads, identifying four families, nine genera and 11 food species consumed by both otter species. Smooth‐coated otters primarily consumed fish (96%) and frogs (4%), whereas Asian small‐clawed otters exclusively fed on fish (100%), with the genus Esomus being the predominant fish genus found in the spraints. The diversity analysis of their diets revealed significant differences between two species (p < 0.05). As a result, DNA metabarcoding provides a reliable method for verifying otter dietary information and can serve as a valuable tool in assessing fish diversity, thus contributing significantly to the management and conservation of otter populations, particularly in Malaysia. [ABSTRACT FROM AUTHOR]

The transition from the Andes to the Amazon lowland hosts a high biodiversity and currently is facing several anthropogenic activities, including hydropower infrastructure projects. Little is known about the geomorphology of the Andean gorges, rivers and the interaction with the fish diversity upstream and downstream of gorges. The Marañón River is a major river that connects the Andes to the Amazon lowland and it carries 40% of the sediment load arriving to Brazil. The Santiago River is the last tributary into the Marañón River before the last gorge (Manseriche). Current plans for hydropower reservoirs include the construction of several dams along the Marañón River, being the largest with a 4,500 MW capacity at the Manseriche Gorge (MG). This study seeks to characterize the baseline processes of the hydrogeomorphology and fish diversity. Results show that the Santiago River is under transitional morphodynamic regime while the Marañón River is a fully developed anabranching river. This study reveals a clear difference in fish species richness and abundance between the upstream and downstream regions of the MG, with some species only found in specific regions. The MG acts as a natural boundary condition for the hydrogeomorphology and fish diversity. If the hydropower dam at MG was built, the reservoir in the upstream reach will produce the Santiago River to disappear and sedimentation to occur, consequently modifying sediment transport boundary conditions for the lower Marañón River. Downstream of the potential dam incision will occur, reducing lateral connectivity, particularly at sites where unique species were found. Plain Language Summary: The Manseriche Gorge located at the transition from the Andes to the Amazon lowland imposes natural boundary conditions for hydrogeomorphology and fish diversity. If a hydropower dam is built at the Manseriche Gorge, several impacts will be observed such as the disappearance of tributary Santiago River, geomorphic and fish diversity alterations between upstream and downstream regions. Key Points: Meandering and anabranching rivers are found along the transition from the Andes to the Amazon lowlandThe Manseriche Gorge acts as a natural boundary condition for hydrogeomorphology and fish diversityIf the Manseriche hydropower dam was built, the Santiago River will disappear, and river connectivity and sediment supply to the Amazon lowland will be impacted [ABSTRACT FROM AUTHOR]

The study of beta diversity and its turnover and nestedness components allows us to understand the mechanisms that structure biotic communities within an ecosystem, which in turn enables the creation of strategies for their conservation and management. This study analyzed the beta diversity of fish assemblages in a coastal lagoon from two diversity facets: taxonomic and functional. Six bimonthly samplings were conducted by dividing the lagoon into three zones (inlet, mixing, and upper). Three trawls were performed at random points within each zone, and the parameters of dissolved oxygen (DO), pH, total dissolved solids (TDS), salinity, temperature, and depth were determined. A total of 1437 fish were captured and identified, and 14 functional traits related to locomotion and feeding were determined. Additionally, the beta diversity and its components for each diversity facet were determined. Differences in physicochemical parameters between climatic seasons and lagoon zones were identified; the external zone showed a higher number of species. However, the mixing zone exhibited greater functional richness, indicating that species with different functional characteristics converged in this area. Functional beta diversity showed higher values than taxonomic beta diversity, demonstrating functional differentiation of fish in the lagoon. In both facets, the turnover component predominantly contributes to beta diversity. The correlation between diversity and physicochemical parameters suggests that an environmental filter determines the presence of certain species and functions within the lagoon. [ABSTRACT FROM AUTHOR]

Abstract Fish diversity, an important indicator of aquatic ecosystem health, is declining due to water pollution, overfishing, climate change, and invasive species. Effective surveying and monitoring are required to protect fish diversity. Here, a high-sensitivity environmental DNA (eDNA) metabarcoding technique was used to investigate fish diversity in the Danjiang River, Shaanxi Province, China. In total, 59 species were identified in eight orders, 19 families, and 40 genera. Cypriniformes and Perciformes were the main groups in the survey area, while Cyprinidae accounted for 50.85% of the total fish species. Rhinogobius similis (19%), Hemibarbus umbrifer (11%), Gnathopogon herzensteini (10%), Triplophysa stewarti (8%), and Zacco platypus (7%) were the dominant species. Eight rare and two exotic fish species were identified. Combined with analysis of historical data, the richness of fish identified using eDNA metabarcoding was significantly higher than that of fish captured in ground cages. Temperature, pH, and oxidation-reduction potential are the main environmental factors that affect the spatial distribution of fish communities. These results suggest that eDNA metabarcoding could be a new tool with broad application prospects; however, local databases must be improved. This study provides theoretical data and a methodological reference for protecting and managing fish diversity in the Qinling Mountains.

Fish identification in the Red Sea, particularly in Saudi Arabia, has a long history. Because of the vast fish diversity in Saudi Arabia, proper species identification is required. Indeed, identifying fish species is critical for biodiversity conservation, food and drug safety, and sustainable fishery management. Numerous approaches have been used to identify fish species, including conventional morphological identification, next-generation sequencing (NGS), nanopore sequencing, DNA barcoding, and environmental DNA analysis. In this review, we collected as much scientific information as possible on species identification in Saudi Arabia. Our findings suggest that the identification process has advanced and spread rapidly and broadly, as evidenced by the discovery of new fish species in Saudi Arabia. The advantages and disadvantages of each method were discussed as part of a comprehensive comparison. This study aimed to provide further scientific knowledge to promote the growth of fish diversity worldwide.

Fish surveys were conducted near artificial structures installed in eight streams flowing from the Nakdong River region to the east coast of Korea. As a result of the survey, a total of 20,000 individuals belonging to nine orders, 17 families, and 47 species were found. The dominant species was Zacco koreanus, and the subdominant species was Pungtungia herzi. Among the surveyed fish species, endangered species were Pseudobagrus brevicorpus (rank I) and Cottus hangiongensis (rank II). In addition, migratory fish species were Oncorhynchus keta, Plecoglossus altivelis, and Tribolodon hakonensis. As a result of community analysis, the highest diversity, dominance, richness, and evenness indices were Wangpi, Chuksan, Gokgang, and Janggi Stream respectively. The highest number of species was surveyed in Gokgang Stream (25 species). Alpha diversity, the number of species at each survey point in each stream, was the highest at a survey point in Wangpi Stream (20 species), and beta diversity, species at each stream survey point that does not overlap with nearby survey point, was the highest at survey points in Gokgang Stream (12 species). As a result of the similarity analysis, surveyed streams were divided into four groups: group 1 (Chuksan, Baeknok Stream), group 2 (Uljinnamdae, Wangpi, Yungdeokosip Steam), group 3 (Gokgang Stream), and group 4 (Janggi, Hoeya Stream). This study is expected to serve as basic data for managing the aquatic ecosystem of streams flowing from the Nakdong River region to the east coast.

Introduction: Investigating and assessing native fish diversity and conducting regional assessments of threats are vital for the conservation of aquatic biodiversity. For this specific study, the Daqing River basin in China was chosen as the research area. Field surveys were carried out between 2018 and 2019, supplemented by a review of pertinent literature and other records. Methods: To evaluate fish diversity, the following parameters are selected for analysis: Relative abundance (Pi), Frequency of occurrence (Fi), Margalef richness index (D), Shannon Wiener diversity index (H'), and Pielou evenness index (J').Relative abundance levels are categorized as follows: dominant species make up more than 10%, common species account for 1%--10%, and occasional species constitute less than 1%. Canoco 5.0 software was utilized to conduct Redundancy Analysis (RDA) on the fish species composition and environmental factors at 34 sampling sites. Results: The findings revealed that 85 fish species have been recorded in the basin, consisting of 78 freshwater species categorized into 8 orders, 17 families, and 59 genera, among which Cypriniformes comprised 64% of the total catch. The low proportion of threatened and endemic species was an important feature of the fish diversity of the Daqing River. Despite the theoretical presence of 85 species, field surveys managed to collect only 42 species, of which 33 were confirmed as naturally occurring within the basin. The average values of Margalef richness index, 22 Shannon Wiener diversity index and Pielou evenness index were 1.72, 2.04 and 0.80 respectively, signifying a low fish diversity with relatively uniform distribution across the sampled regions. Discussion: This study found that the community structure and diversity of fish were closely related to environmental factors, particularly water quality. Among these factors, ammonia nitrogen emerged as a significant determinant of fish diversity. High concentrations of ammonia nitrogen inhibit fish growth, endanger health, and can even lead to death. Additionally, dams and other water infrastructure also impact fish community structure and diversity. This baseline study can provide a basis for the protection and ecological restoration of fish resources in the Daqing River. [ABSTRACT FROM AUTHOR]

Biodiversity loss caused by biological invasions is an ecological problem on a global scale, and understanding the mechanism of biological invasion is the basis for managing non‐native species. The biotic resistance hypothesis proposes that species‐rich native communities are less susceptible to invasion because of the limited resources available to non‐native species, therefore comparing the resource utilization patterns of different communities can reveal the invasion mechanisms of specific non‐native species at the community level. We selected Lake Taihu, where icefish (Neosalanx taihuensis Chen) originated, and Lake Fuxian, where icefish invaded, as the research objects. We calculated the fish functional diversity indexes, including functional richness (FRic), functional evenness (FEve), and functional divergence (FDiv), to reflect differences in ecological niche and resource utilization based on four quarterly fish survey data from two lakes. The random forests model explored the relationship between functional diversity indexes and biotic and environmental variables. Our results showed that more diverse resource utilization (high FRic), more niche space (low FEve), and less competitive pressure (high FDiv) in Lake Fuxian were identified as the critical important factors for maintaining the current equilibrium state after successful invasion of icefish. The bottom‐up effects mainly affected the functional diversity indexes in Lake Fuxian. They differed from those in Lake Taihu and were primarily influenced by top‐down effects. Enhancing the top‐down effects in Lake Fuxian and limiting the zooplankton available to icefish are critical to controlling the invasion of icefish. This study offers a new perspective for studying the non‐native fish invasion mechanism, and provides scientific guidance for managing non‐native fish in Lake Fuxian. [ABSTRACT FROM AUTHOR]

Climate change is a major concern for the future of marine Arctic food webs. Diet shifts of seabirds can be used as indicators of environmental changes such as species compositions of food webs. However, studies on diets are often laborious and costly, while research in vulnerable Arctic environments benefits from short visits for data collection that minimize disturbance to Arctic wildlife and the environment. DNA-metabarcoding techniques are rapidly developing and could be used as an effective method of monitoring diet choice of seabirds. We tested DNA-metabarcoding on seabird faeces collected during short visits of typically around 30 min at breeding colonies of black-legged kittiwake Rissa tridactyla (3 colonies), Brünnich's guillemot Uria lomvia (2 colonies) and little auk Alle alle (3 colonies). DNA metabarcoding based on COI and 18S of a limited number of faeces samples revealed a wide spectrum of fish species and crustaceans in the diets of these species, comparable with or even exceeding diversity in diet composition found in conventional, more invasive techniques where birds are shot or caught and handled to obtain samples. While previous studies on diet choice of little auk, a crustacean specialist, mainly report small fractions of unidentified fish remains, DNA metabarcoding of faeces revealed a large variety of pelagic and benthic fish species supplementing its diet. We conclude that DNA metabarcoding of seabird faeces can be an effective attribute to diet studies supporting our understanding of changes in numbers and distribution of Arctic seabirds and their marine environment. [ABSTRACT FROM AUTHOR]

Transboundary freshwater fish are critical for both biodiversity and community well‐being but face alarming overexploitation in shared rivers. Such rivers greatly aid the livelihood and nutrition of local people on both sides of shared borders. However, a lack of understanding of resource dynamics and utilization patterns hinders sustainable management of resources. We investigated spatiotemporal fish assemblages along the River Atrai, a transboundary river between India and Bangladesh. The socioeconomic status of fishers was quantified from personal interviews and group discussions to estimate the exploitation trajectory of piscine resources. Fish assemblages varied significantly among locations and seasons. Species diversity was highest downstream and lowest upstream. Spatiotemporal fishery exploitation aligned with fish diversity among sites and seasons, with fishers preferring to fish in downstream areas during the post‐monsoon season. Fishers were economically weak, with limited sources of income. Therefore, adequate integrated management plans should be implemented to ensure resource resilience in a transboundary pocket, sustainably supporting the livelihood of concomitant fishers. [ABSTRACT FROM AUTHOR]

Understanding the distribution of species is highly important for optimizing future conservation priorities and strategies at the regional scale. Relatively little attention has been given to multi-taxon aquatic biota in extreme alpine environments. We examined the spatial and temporal patterns of alpha and beta diversity, site-specific contributions to beta diversity and assembly mechanisms of four taxonomic groups (fishes, macroinvertebrates, zooplankton and phytoplankton) from the source to the estuary of the Za'gya Zangbo River above 4500 m AMSL (above mean sea level) on the northern Qinghai-Tibetan (Q–T) Plateau. A total of 4 fish species, 45 macroinvertebrate taxa, 17 zooplankton taxa and 56 phytoplankton taxa were found in the study area. No consistent patterns in taxonomic richness were observed across taxa from upstream to estuary. The fish communities had the lowest dissimilarity between communities, the phytoplankton community had the highest dissimilarity in the dry season, and the macroinvertebrate community had the highest dissimilarity in the wet season. The relative importance of the turnover and nestedness components varied considerably across taxa and along spatial gradients. The diversity patterns of macroinvertebrate, zooplankton and phytoplankton communities were significantly correlated with several environmental factors, whereas only the beta diversity of fish was correlated with altitude. Stochastic processes dominated in shaping the macroinvertebrate communities whereas deterministic processes dominated the assembly of the phytoplankton communities. Weak congruence of diversity patterns across taxonomic groups suggested that biological groups cannot serve as reliable surrogates for one another and that multiple biological groups should be included in the biomonitoring of high-altitude rivers on the Q‒T Plateau. The relatively unique species in the upstream area and estuary of the Za'gya Zangbo River harbor should receive more attention in future conservation and management schemes. [ABSTRACT FROM AUTHOR]

The diverse deep-sea order Stomiiformes includes 457 species of mesopelagic and bathypelagic fishes with a remarkable diversity of structures associated with feeding, locomotion, and bioluminescence. This study investigates their patterns of body-shape evolution using geometric morphometry in an ecological and phylogenetic context. A total of 473 specimens from 56 different species in 48 genera representing all five families were photographed and 14 homologous landmarks and 50 semilandmarks were marked on the digital images. A principal component analysis (PCA) visualized body-shape variation, and morphological disparity analysis evaluated differences in variance among species in relation to their dietary classes, habitat partitioned by depth, and the presence or absence of diel vertical migration. The study also tested phylogenetic and ecological signals. The PCA revealed that variation in fin size and position, particularly for the dorsal and anal fins, accounted for the most important axis of variation among species. Changes in relative body size and body depth also contributed to morphological diversity. There is a trend toward body elongation in relation to depth distribution, with the meso-bathypelagic species having more elongated bodies than those restricted to the mesopelagic zone. Piscivorous and generalist species exhibit higher morphological disparity when compared to zooplanktivorous species, and meso- to bathypelagic species exhibit higher morphological disparity when compared to strictly mesopelagic species. A high phylogenetic signal indicates that morphological diversification within the Stomiiformes fits the expectations of Brownian evolution, in which the degree of shared ancestry rather than similarity of ecological niche predicts anatomical similarity. However, the current dataset may lack the statistical power to uncover any causal relationship between shifts in depth, diet, or migration and the shape diversification of stomiiforms. [ABSTRACT FROM AUTHOR]

Fish identification in the Red Sea, particularly in Saudi Arabia, has a long history. Because of the vast fish diversity in Saudi Arabia, proper species identification is required. Indeed, identifying fish species is critical for biodiversity conservation, food and drug safety, and sustainable fishery management. Numerous approaches have been used to identify fish species, including conventional morphological identification, next-generation sequencing (NGS), nanopore sequencing, DNA barcoding, and environmental DNA analysis. In this review, we collected as much scientific information as possible on species identification in Saudi Arabia. Our findings suggest that the identification process has advanced and spread rapidly and broadly, as evidenced by the discovery of new fish species in Saudi Arabia. The advantages and disadvantages of each method were discussed as part of a comprehensive comparison. This study aimed to provide further scientific knowledge to promote the growth of fish diversity worldwide. [ABSTRACT FROM AUTHOR]

This study evaluates the relative and combined effectiveness of seaweed rafts and light traps in attracting juvenile fish, focusing on diel variations in juvenile fish assemblage in the tropical coastal waters of Gaolong Bay, Wenchang City, Hainan Province. Sampling was conducted in May 2023 during various time periods using self-made artificial drifting seaweed rafts and light traps. The nonparametric Kruskal–Wallis was employed to compare the diversity and catch per unit effort of juvenile fish across different time periods and sampling methods. The Permutational Multivariate Analysis of Variance, heatmaps, and Principal Coordinates Analysis were used to analyze and visualize the differences between juvenile fish assemblages. Our findings indicate that light traps were particularly effective during nocturnal periods, capturing a diverse array of species and achieving the highest richness and evenness indices. Seaweed rafts demonstrated the lowest diversity indices, largely due to the dominance of specific species, which likely contributed to the competitive exclusion of other species. Seaweed rafts showed significant effectiveness during noon, providing critical habitat and shelter that attracted juvenile fish despite the lower diversity. While each method demonstrated specific advantages, their combined approach did not significantly improve juvenile fish aggregation compared to the individual method. These findings underscore the importance of considering diel and tidal cycles in the selection of sampling methods, as aligning the method with the time of day can greatly enhance the accuracy of biodiversity assessments, leading to more informed conservation and management strategies for tropical coastal waters. [ABSTRACT FROM AUTHOR]

This study elucidated the composition and diversity characteristics of the main fish species in the Pingzhai Reservoir by collecting and analyzing environmental DNA (eDNA) samples from the reservoir and comparing them with data from traditional fishery resource surveys. The results showed that eDNA technology detected 43 fish species spanning 37 genera, 5 orders, and 11 families. Importantly, no significant difference in fish diversity was observed among the surveyed sites, and the potential of eDNA technology in studying fish diversity in the Pingzhai Reservoir was discussed. A total of 29 species distributed across 18 genera, 3 families, and 3 orders were captured using traditional resource surveys. Overall, 21 fish species were detected using both methods, constituting 48.8% of the total fish population. Cypriniformes were the most prominently detected order in both methods. Among all the fish species, the most abundant in the Pingzhai Reservoir were the free-range fish species Hypophthalmichthys molitrix and Hypophthalmichthys nobilis, which have the largest sequence abundance in the eDNA investigation, in addition to the detection of exotic species, such as Micropterus salmoides and Oreochromis niloticus. Compared with traditional investigation methods, eDNA technology offers several advantages, including high sensitivity, minimal ecological impact, superior data accuracy, and low cost, making it suitable for fish diversity research in fishery resources investigations. This study enhances our understanding of fish diversity in the Pingzhai Reservoir and provides crucial basic information to support the ecosystem management and restoration efforts of the reservoir. [ABSTRACT FROM AUTHOR]

Species invading non‐native habitats can cause irreversible environmental damage and economic harm. Yet, how introduced species become widespread invaders remains poorly understood. Adaptation within native‐range habitats and rapid adaptation to new environments may both influence invasion success. Here, we examine these hypotheses using 7058 SNPs from 36 native, 40 introduced and 19 farmed populations of tench, a fish native to Eurasia. We examined genetic structure among these populations and accounted for long‐term evolutionary history within the native range to assess whether introduced populations exhibited lower genetic diversity than native populations. Subsequent to infer genotype–environment correlations within native‐range habitats, we assessed whether adaptation to native environments may have shaped the success of some introduced populations. At the broad scale, two glacial refugia contributed to the ancestry and genomic diversity of tench. However, native, introduced and farmed populations of admixed origin exhibited up to 10‐fold more genetic diversity (i.e., observed heterozygosity, expected heterozygosity and allelic richness) compared to populations with predominantly single‐source ancestry. The effects of introduction to a new location were also apparent as introduced populations exhibited fewer private alleles (mean = 9.9 and 18.9 private alleles in introduced and native populations, respectively) and higher population‐specific Fst compared to native populations, highlighting their distinctiveness relative to the pool of allelic frequencies across tench populations. Finally, introduced populations with varying levels of genetic variation and similar genetic compositions have become established and persisted under strikingly different climatic and ecological conditions. Our results suggest that lack of prior adaptation and low genetic variation may not consistently hinder the success of introduced populations for species with a demonstrated ability to expand their native range. [ABSTRACT FROM AUTHOR]

The identification of multiple facets of biodiversity (e.g., phylogenetic and functional) can help to understand how evolutionary and ecological mechanisms shape the assembly of biological communities.Here, we employed multiple regressions and variance partitions to investigate the effects of environmental conditions, connectivity and space on aspects of the functional and phylogenetic facets of fish fauna in tropical headwater streams of the Xingu River basin, in Eastern Amazonia.We found that the functional and phylogenetic diversities of fish communities are related to local environmental conditions and stream connectivity in the drainage network, with marked differences occurring between the rainy and dry periods. Furthermore, we discovered that functional uniqueness was influenced mainly by environmental factors, whereas phylogenetic uniqueness had a more complex relationship with the influence of local environmental factors and connectivity.Our findings indicate that the fish assemblages of small headwater streams of the Xingu River basin share a close phylogenetic history. This is probably because of the climatic and environmental stability experienced by Amazonian ichthyofauna over evolutionary time.Our findings emphasise the role of niche‐based processes in shaping the unique functional composition of fish assemblages in headwater streams, and highlight the importance of environmental heterogeneity in maintaining the ecological integrity of these freshwater ecosystems. [ABSTRACT FROM AUTHOR]

A decline in diversity from the equator to the poles is a common feature of Earth's biodiversity. Here, we examine body shape diversity in marine fishes across latitudes and explore the role of time and evolutionary rate in explaining the diversity gradient. Marine fishes' occupation of upper latitude environments has increased substantially over the last 80 million years. Fishes in the highest latitudes exhibit twice the rate of body shape evolution and one and a third times the disparity compared to equatorial latitudes. The faster evolution of body shape may be a response to increased ecological opportunity in polar and subpolar oceans due to (1) the evolution of antifreeze proteins allowing certain lineages to invade regions of cold water, (2) environmental disturbances driven by cyclical warming and cooling in high latitudes, and (3) rapid transitions across depth gradients. Our results add to growing evidence that evolutionary rates are often faster at temperate, not tropical, latitudes. [ABSTRACT FROM AUTHOR]

Marine sponges have recently emerged as efficient natural environmental DNA (eDNA) samplers. The ability of sponges to accumulate eDNA provides an exciting opportunity to reconstruct contemporary communities and ecosystems with high temporal and spatial precision. However, the use of historical eDNA, trapped within the vast number of specimens stored in scientific collections, opens up the opportunity to begin to reconstruct the communities and ecosystems of the past. Here, we define the term 'heDNA' to denote the historical environmental DNA that can be obtained from the recent past with high spatial and temporal accuracy. Using a variety of Antarctic sponge specimens stored in an extensive marine invertebrate collection, we were able to recover information on Antarctic fish biodiversity from specimens up to 20 years old. We successfully recovered 64 fish heDNA signals from 27 sponge specimens. Alpha diversity measures did not differ among preservation methods, but sponges stored frozen had a significantly different fish community composition compared to those stored dry or in ethanol. Our results show that we were consistently and reliably able to extract the heDNA trapped within marine sponge specimens, thereby enabling the reconstruction and investigation of communities and ecosystems of the recent past with a spatial and temporal resolution previously unattainable. Future research into heDNA extraction from other preservation methods, as well as the impact of specimen age and collection method, will strengthen and expand the opportunities for this novel resource to access new knowledge on ecological change during the last century. [ABSTRACT FROM AUTHOR]

A growing body of evidence indicates that the global diversity of freshwater fishes has not been fully documented. Studies of freshwater fishes that were previously thought to be morphologically variable have revealed the existence of deeply divergent lineages, with many distinct species. In southern Africa a number of Enteromius species exhibit either exceedingly wide or divided distribution patterns that should be rare for freshwater fishes with limited dispersal opportunities between river systems. One such species is the sidespot barb, Enteromius neefi. As currently defined, E. neefi has a disjunct distribution that is divided between rivers in the northeast escarpment in South Africa and Eswatini, and tributaries of the Upper Zambezi in Zambia and southern Congo in the Democratic Republic of Congo, with a large geographic gap between these two populations. With the use of molecular and morphological methods, the level of divergence between the two populations was examined, and a new species was described from the Steelpoort River in the Limpopo River system of South Africa. Findings from this study provide further evidence for a number of taxonomic problems within the goldie barbs of southern Africa, and some taxonomic rearrangements are proposed for this group. [ABSTRACT FROM AUTHOR]

Aim: Surf zones are crucial nursery habitats for the early life stages of fish species associated with typical coastal ecosystems. However, little is known about the temporal patterns and drivers of fish assemblages in tropical surf zones. This study aimed to assess the (1) main changes in fish community structure throughout 1 year, (2) seasonal dynamic patterns in fish assemblages, and (3) key factors influencing fish assemblages in the tropical surf zones. Location: Gaolong Bay, Wenchang City, Hainan Island, China. Methods: Fish sampling was conducted monthly from June 2021 to May 2022 using a beach seine net. Fish species were identified using both morphological and molecular analyses. Kruskal–Wallis test, analysis of similarity, non‐metric multidimensional scaling analysis, and similarity percentage analysis were used to investigate the temporal fish assemblage patterns. Generalised additive models and canonical correspondence analysis were used to assess how environmental variables influence fish assemblages. Results: We identified 83 fish species, which were grouped into three ecotypes based on their primary habitat: coral reef‐seagrass‐associated species (CS) (35), mangrove‐estuarine‐associated species (ME) (30), and common coastal‐estuarine‐associated species (CE) (18). Most captured individuals were juveniles, and fish abundance and diversity were highest in May. Most CS species were abundant between March and May. ME and most CE species were dominant from June to August, and Mugilidae (CE) was abundant between October and February. Furthermore, surf fish assemblages were substantially influenced by tidal level, water temperature, conductivity, pH, turbidity, and dissolved oxygen. Conclusions: Juvenile fish were abundant in May and fish species with three ecotypes alternate in the surf zones throughout the year. Counter to much current thinking, March maybe the spawn peak of most fish species in the studied area, and we suggest that the fishing ban period could start from March instead of May in the inshore areas of Hainan Island. [ABSTRACT FROM AUTHOR]

The study provides information on the diversity, assemblage structure, distribution pattern, and composition of fish at several sampling locations along the river Diyung. In this study, fish fauna was collected from 8 selected stations of the river from January 2019 to December 2020. A total of 81 different fish species were identified, divided into 10 orders, 24 families, and 52 genera. The orders Cypriniformes, Siluriformes, Anabantiformes, and Synbranchiformes accounted for 88.88% of the total fish population and the remaining 12.12% is being contributed by other orders. The family Cyprinidae was found to be the most prevalent (40.74%). Minnows and barbs contributed the most (30.49%) among the 11 common groups of fishes identified. According to the IUCN status, 11.11% were near threatened (NT), 2.44% each of vulnerable and data deficient, 1.23% were endangered (EN), 6.17% were not evaluated (NE), and 76.54% were least concerned (LC). The Margalef species richness, Shannon-Weiner diversity indices showed higher diversity in the middle and lower stretches of the river. Subsequently, cluster analysis divided the samples into two different groups by sample sites. Group 1 comprised sites S6, S7, and S8 representing the lower stretches of the river and Group 2 comprised stations S1, S2, S3, S4 and S5, all of which were located in the middle and upper stream. The Canonical Corresponding Analysis revealed that environmental parameters have varied connotations with the fish occurrence, indicating species-specific adaptive potential. The parameters like temperature, turbidity, Dissolved Oxygen (DO) and velocity exhibited a positive correlation with fish abundance. Longest K-dominance curve formed at the station S-4 indicating the highest fish abundance. The findings will aid in the development of a reasonable exploitation and protection strategy for freshwater fish in the Diyung river. [ABSTRACT FROM AUTHOR]

In the context of climate change, the current rise in temperature, changes in precipitation, and extreme weather events are exceptional and impact biodiversity. Using the Mann–Kendall trend test, change-point analysis, and linear mixed models, we investigated the long-term trends (1978–2022) of water temperature and flow in the Po River, Italy's largest river, and examined changes in the fish community over the same period. Our findings indicate that the daily water temperature of the Po River increased by ~4 °C from 1978 to 2022, with a significant rise starting in 2005. The river's daily discharge showed higher variability and decreased from 2003 onwards. The number of days per year with water temperatures above the summer average increased steadily by 1 day per year, resulting in over 40 additional days with above-average temperatures in the last four decades. The number of summer days above the seasonal average water temperature was the most influential factor affecting fish diversity. Total fish species richness and native species richness significantly decreased between 1978 and 2022 with the increasing number of days above the summer average water temperature, while non-native species increased. Our results demonstrate that the Po River is experiencing significant impacts from global warming, affecting freshwater communities. [ABSTRACT FROM AUTHOR]

BACKGROUND AND OBJECTIVES: The coasts around West Java, Indonesia are prospective fishing grounds due to their commercial fish diversity. The presence of neighboring settlements discharging waste, including microplastics, poses a threat to the estuarine ecosystem. This study aimed to quantify and classify microplastics in the tissues of Mugil cephalus, Eleutheronema tetradactylum, and Scatophagus argus. METHODS: This study takes place in the estuary of the Blanakan River, Subang Regency, an area renowned for its wide variety of commercially valuable fish. Four fish sampling sites were identified according to the predominant land use, with settlements in the upper reaches, ponds in the central area, and mangrove forests in the lower reaches. Fish samples were taken the gastrointestinal tract, gills and muscle to calculated the microplastic content and identify its shape and size. Raman spectroscopy was applied to verify the polymer of microplastic. Statistical analysis was conducted to evaluate variations in microplastic levels at the individual level across these fish species. FINDINGS: The findings indicated the presence of microplastics in the muscle, gastrointestinal tract, and gills of three commercially caught fish from Blanakan, with the muscle being identified as the edible part and the gastrointestinal tract and gills as the non-edible parts. The microplastics were classified according to shape and size and were found in the following order of abundance: Mugil cephalus, Scatophagus argus, Eleutheronema tetradactylum. Mugil cephalus contained the most microplastics (210.8 particles per individual), with the lowest amount recorded in Eleutheronema tetradactylum (41.9 particles per individual). The tissues of Eleutheronema tetradactylum exhibited varying levels of microplastic contamination, with the highest concentration found in the gastrointestinal tract, followed by the gills and muscles. In contrast, in the tissues of Mugil cephalus and Scatophagus argus, microplastics were found in the following order of abundance from high to low: muscle, gastrointestinal tract, gill. The muscle of Mugil cephalus contained the highest microplastic concentration (28.71 particles per gram wet weight), while the lowest was recorded in the muscle of Eleutheronema tetradactylum (3.42 particles per gram wet weight). Microplastics ranging from 300 to 1000 micrometers in size, in the form of fibers and fragments, were commonly found in fish tissues. CONCLUSION: Microplastic content is found most abundantly in the gastrointestinal tract and muscle. This indicates that feeding and ingestion play a role in the entry of microplastics into the fish's body. Given that the fish falls under the category of commercial and consumption fish, there is a significant concern regarding environmental pollution caused by microplastics and the potential health hazards linked to its consumption. [ABSTRACT FROM AUTHOR]

A survey was conducted to identify fish fauna related to the dominant habitats, viz., (i) Honduwa Lake (stagnate water), (ii) estuarine area with mangroves, (iii) freshwater marshy area with floating aquatic vegetation, (iv) canals, and (v) river, in the Dedduwa estuary of southern Sri Lanka. Thirty-nine species of fish including two endemics (to the island) were identified, including members of major migratory families such as Anguillidae and Megalopidae. Based on the abundance of species, the Bray-Curtis similarity index indicated a clear separation of the canal and freshwater marsh, with other studied areas. Similarly, the taxonomic diversity of the canal and freshwater marsh was high, indicating high variation and diversity of the species and genera. Protection of mangroves and related habitats is important to maintain the stability and long-term existence of fish fauna in the estuary. Effective monitoring is proposed for detecting and eliminating illegal encroachments, mangrove clearance, and illegal fishing activities. Moreover, improving the knowledge and awareness among members of the local community, politicians, and environment officers about the importance of the region's biodiversity implementing strong policies, and creating a strong responsible stakeholder bond are required to ensure the long-term sustainability of the estuary. [ABSTRACT FROM AUTHOR]

The fish detection task is an essential component of marine exploration, which helps scientists monitor fish population numbers and diversity and understand changes in fish behavior and habitat. It also plays a significant role in assessing the health of marine ecosystems, formulating conservation measures, and maintaining biodiversity. However, there are two main issues with current fish detection algorithms. First, the lighting conditions underwater are significantly different from those on land. In addition, light scattering and absorption in water trigger uneven illumination, color distortion, and reduced contrast in images. The accuracy of detection algorithms can be affected by these lighting variations. Second, the wide variation of fish species in shape, color, and size brings about some challenges. As some fish have complex textures or camouflage features, it is difficult to differentiate them using current detection algorithms. To address these issues, we propose a fish detection algorithm—FishDet-YOLO—through improvement in the YOLOv8 algorithm. To tackle the complexities of underwater environments, we design an Underwater Enhancement Module network (UEM) that can be jointly trained with YOLO. The UEM enhances the details of underwater images via end-to-end training with YOLO. To address the diversity of fish species, we leverage the Mamba model's capability for long-distance dependencies without increasing computational complexity and integrate it with the C2f from YOLOv8 to create the Mamba-C2f. Through this design, the adaptability in handling complex fish detection tasks is improved. In addition, the RUOD and DUO public datasets are used to train and evaluate FishDet-YOLO. FishDet-YOLO achieves mAP scores of 89.5% and 88.8% on the test sets of RUOD and DUO, respectively, marking an improvement of 8% and 8.2% over YOLOv8. It also surpasses recent state-of-the-art general object detection and underwater fish detection algorithms. [ABSTRACT FROM AUTHOR]