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The rosefin barb, Enteromius argenteus, as currently described, is a freshwater fish with a distribution that is geographically separated and divided into the northern population in the Kwanza River system in Angola, and the southern population in the Inkomati River system in South Africa and Eswatini. Due to this disjunct distribution pattern, it is likely that the two populations represent distinct species. mtDNA sequence data and detailed examination of morphometric characters revealed considerable genetic (2.8%–3.5%) and morphological differentiation of the two populations, suggesting their recognition as two distinct species. Enteromius crocodilensis is revalidated and redescribed for the southern population that is readily distinguished from E. argenteus by nonoverlapping circumpeduncular scale counts (12–13 vs. 14) and color pattern (presence of a conspicuous dark band along the midline vs. absence of characteristic melanin patterns). Phylogenetic analysis based on mtDNA cytochrome oxidase subunit I (COI) data places both E. argenteus and E. crocodilensis in a well‐supported clade that includes a number of morphologically similar sawfin barb species from southern and central Africa. [ABSTRACT FROM AUTHOR]

It is essential to understand the spatial distribution of a target species for effective stock management, particularly in the case of less mobile rock-dwelling species such as sea urchins. However, sea urchins exhibit an aggregated distribution within fishing grounds, thereby necessitating diving surveys at multiple sites to elucidate their spatial distribution at a fine scale. In Mikuni, Sakai City, Fukui Prefecture, Japan, female divers are well-acquainted with the underwater landscape and can determine the sea urchin catch per fishing ground. They also conduct voluntary fishery management for the sea urchin. Therefore, we enlisted female divers to report the sea urchin Hemicentrotus pulcherrimus catch during the 2020–2022 period and subsequently visualized the spatial distribution of these catches and estimated initial abundance using the Leslie method according to the fishing ground. The catch per unit effort did not decrease although the cumulative catch increased in many fishing grounds. This was because divers sensibly perceived the status of sea urchin stocks at each fishing ground through the dive fishery and they voluntarily controlled their fishing efforts to prevent stock depletion. Our results highlight that the catch data are often used for stock estimation but are influenced by fishermen's management of the fishery. [ABSTRACT FROM AUTHOR]

One of the hallmarks of invasive species is their propensity to spread. Removing an invasive species after establishment is virtually impossible, and so considerable effort is invested in preventing the range expansion of invaders. Silver carp (Hypophthalmichthys molitrix) were discovered in the Mississippi River in 1981 and have spread throughout the basin. Despite their propensity to expand, the 'leading edge' in the Illinois River has stalled south of Chicago and has remained stable for a decade. Studies have indicated that contaminants in the Chicago Area Waterway System (CAWS) may be contributing to the lack of upstream movement, but this hypothesis has not been tested. This study used a laboratory setting to quantify the role of contaminants in deterring upstream movement of silver carp within the CAWS. For this, water was collected from the CAWS near the upstream edge of the distribution and transported to a fish culture facility. Silver carp and one native species were exposed to CAWS water, and activity, behavior, avoidance, and metabolic rates were quantified. Results showed that silver carp experience an elevated metabolic cost in CAWS water, along with reductions in swimming behavior. Together, results indicate a role for components of CAWS water at deterring range expansion. [ABSTRACT FROM AUTHOR]

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The loss of freshwater fish habitats, exacerbated by climate change and dam constructions, poses a critical environmental concern. The upper Yangtze River basin, noted for its abundant fish fauna and concentrated dam development, serves as a crucial locale for investigating the impacts of climate shifts and dam construction. This study aims to disentangle the impacts of hydroelectric dams and climate change on fish habitat distribution by analyzing species presence data across different periods. Species distribution models were constructed using Maxent for Coreius guichenoti (a warm‐water endangered fish) and Schizopygopsis malacanthus (a cold‐water endangered fish). The model accuracy was assessed using the area under the curve of the receiver operating characteristic. Habitat distribution modeling and prediction for the pre‐dam period (1970–2000) and post‐dam period (2001–2020), as well as future climate change under two shared socioeconomic pathways scenarios, were conducted. The impacts of climate change and dam construction on the habitat suitability of two fish species were quantified. The results revealed dam construction predominantly diminished habitat suitability and range, with high‐suitability habitats in the post‐dam period decreasing by 56.3% (720.18 km) and 67.0% (1665.52 km) for the two fishes, respectively. Climate change would enhance the habitat suitability of Coreius guichenoti, while it would decrease the habitat suitability of Schizopygopsis malacanthus. The impact of dam construction is greater that of climate change for them. This study underscores the profound impacts of dam construction on fish habitats, particularly for cold‐water species, and highlights the critical need for habitat restoration in sustainable hydropower development. Our method of disentangling these factors also provides a new approach to evaluating environmental impacts in large river basins. [ABSTRACT FROM AUTHOR]

Fish spawning phenology is a major concern for conservation and fisheries management. New intensive data sources, such as GPS-based tracking data and high-resolution catch declaration data, are becoming increasingly available in the field of marine ecology. These data benefit from high spatiotemporal resolution and open new research avenues for investigating the interannual variability in fish phenology. In this paper, we demonstrate how an integrated species distribution model informed by commercial catch data combined with spatiotemporal dimension reduction methods known as empirical orthogonal functions (EOFs) can be used to synthesize spatiotemporal signals in fish reproduction phenology. Specifically, we address the following questions: (1) Can we identify seasonal spatial patterns that can be interpreted in terms of reproductive phenology and essential habitats? (2) Can we identify changes in reproductive phenology over time? (3) Are these changes related to environmental drivers? The analysis illustrates the reproductive phenology of three key commercial species in the Bay of Biscay (sole, hake, and sea bass). The EOF analysis emphasized strong seasonal spatiotemporal patterns that correspond to reproduction patterns and feeding patterns. Based on this methodology, we identified seasonal variations in the timing of reproduction, and we related these variations to sea surface temperature, a key driver of fish reproduction. [ABSTRACT FROM AUTHOR]

The Myxosporea subclass harbours cnidarians myxozoans adapted for parasitism that infect mainly fishes worldwide. A total of 159 myxosporean species were described in South American waters until December 2016. These species were distributed by 24 genera, infecting 114 different host species in seven countries. Here, we present an update of the species described in South American countries from January 2017 to the present date, or those for which molecular data were made available in GenBank during this period. A total of 105 species distributed by 13 genera, parasitizing 59 host species are depicted in tabulated format including the species characteristics. Reports of infection with these parasites were found only in Argentina, Brazil, Colombia, and Peru. The most common parasites were Myxobolus spp. and Henneguya spp., and freshwater fish were about four times more parasitized than saltwater ones. Thus, the knowledge of myxosporean diversity in South America seems to be shaped more by the presence of research groups in each country than by the continent's biogeographical conditions. In recent years, freshwater ecosystems in South America have become the site of discovery for a significant diversity of myxosporean genera previously associated with marine environments. [ABSTRACT FROM AUTHOR]

Sampling and sequencing marine environmental DNA (eDNA) provides a tool that can increase our ability to monitor biodiversity, but movement and mixing of eDNA after release from organisms before collection could affect our inference of species distributions. To assess how conditions at differing spatial scales influence the inferred species richness and compositional turnover, we conducted a paired eDNA metabarcoding and capture (beach seining) survey of fishes on the coast of British Columbia. We found more taxa were typically detected using eDNA compared to beach seining. eDNA identified more taxa with alternative habitat preferences, and this richness difference was greater in areas of high seawater movement, suggesting eDNA has a larger spatial grain influenced by water motion. By contrast, we found that eDNA consistently missed low biomass species present in seining surveys. Spatial turnover of communities surveyed using beach seining differed from that of the eDNA and was better explained by factors that vary at small (10–1000s meters) spatial scales. Specifically, vegetation cover and shoreline exposure explained most species turnover from seining, while eDNA turnover was not explained by those factors and showed a distance decay pattern (a change from 10% to 25% similarity from 2 km to 10 km of distance), suggesting unmeasured environmental variation at larger scales drives its turnover. Our findings indicate that the eDNA sample grain is larger than that of capture surveys. Whereas seining can detect differences in fish distributions at scales of 10s–100s of meters, eDNA can best summarize fish biodiversity at larger scales possibly more relevant to regional biodiversity assessments. [ABSTRACT FROM AUTHOR]

Despite efforts to use environmental DNA (eDNA), accurately quantifying fish populations remains a challenge. A recent eDNA approach provided reliable estimates of coastal fish population abundance, but it was not as effective for assessing spatial distribution due to a lack of eDNA samples relative to the study area. Therefore, we conducted a numerical case study to evaluate the ability of the eDNA approach to estimate fish (Jack mackerel) abundance and distribution based on the number of eDNA samples in a semi-enclosed bay (Jinhae Bay). Our study revealed that the eDNA approach can provide reliable estimates of fish abundance, even with knowledge of the eDNA concentration in just 1% of the study area. However, for estimating spatial distribution and fish school, significant estimates were obtained only when the eDNA concentration was identified in more than 70% of the study area. Our results confirm that the eDNA approach can reflect fish abundance but has limitations in estimating fish distribution. [ABSTRACT FROM AUTHOR]

Climate change and human activities, for example, dam construction, largely affect hydrologic and hydrodynamic processes of river‐lake system, and hence exerted serious pressure on its aquatic ecology. It's challenging to restore its ecological environment without systematic investigation and knowledge about the features of hydrodynamics, water quality, and aquatic ecology. This study conducted field surveys of hydrodynamic, water quality, and fish distribution in the Yangtze‐Poyang system, the largest river and largest fresh lake in China, to investigate the effects of hydrologic and hydrodynamic variations on fish population dynamics, especially the extreme drought and its effects were largely concerned. In two surveys, discharge decreased from 12,000 m3/s to less than 1,000 m3/s. Distinct differences on fish density, species composition, and populations connectivity between two surveys were observed. During high‐water, connecting channel secured effective transition of river‐lake habitats, its strong hydrological connectivity and flow heterogeneity supported great biodiversity and bidirectional populations connectivity. Limited flow space and elevated turbidity during low‐water confined fish to a few channel units with sufficient depth and width, increasing fish density up to 7 times greater than during high‐water, and seriously weakening ecological connectivity of the system. Furthermore, species interaction was intensified due to limited environmental capacity, periodic strategists were favored while opportunistic strategists visibly diminished, leading to a dramatic decline in species by nearly half. In the future with increasingly frequent extreme climate, engineering measures, for example, effective ecological project regulation, are needful to alleviate the drought problem, being of great significance for maintaining ecological connectivity within the river‐lake system. Key Points: Field surveys of hydrodynamics, water quality and fish population dynamics in the largest river‐fresh lake system in China were conductedStrong hydrological connectivity and flow heterogeneity during flood season promoted bidirectional fish connectivity and species diversityLimited flow space, turbid environment and intensified species interaction during dry season weakened fish connectivity and biodiversity [ABSTRACT FROM AUTHOR]

ABSTRACT Aim Location Methods Results Main Conclusions Shoaling of large oxygen minimum zones (OMZs) that form along eastern margins of the world's oceans can reduce habitat availability for some pelagic fishes. Our aim was to test the hypothesis that habitat compression caused by shoaling of the Pacific OMZ in tropical regions creates a boundary to the southern distribution of shortfin mako sharks (Isurus oxyrinchus) in the Eastern North Pacific Ocean.Eastern North Pacific and Western North Atlantic oceans.We compared environmental conditions between areas used by satellite‐tagged mako sharks in the Eastern North Pacific, encompassing the world's largest OMZ, to those used in the Western North Atlantic where no OMZ is present. In the Pacific we quantified the effects of temperature and dissolved oxygen (DO) on depth use and tested if sharks spent less time in areas with strong habitat compression over the OMZ than expected by chance.The southern distribution of sharks in the Pacific corresponded with the apex of OMZ shoaling in the North Equatorial Current. Sharks in the Atlantic occupied areas with warm surface temperatures (≥ 26°C) more often than the Pacific, and waters with these temperatures in the Atlantic had greater DO at depth. Sharks in the Pacific reduced time near the surface in warm temperatures and consistently avoided depths with low DO and spent less time in areas with strong habitat compression than expected by chance.The combination of warm surface temperatures and shoaling of the OMZ creates a soft boundary to mako shark movements in the Eastern North Pacific Ocean. The expected expansion of OMZs due to climate change could have considerable impact on future distribution of mako sharks and other pelagic fish. As such, development of species distribution models to predict the effects of climate change on pelagic fish distributions should incorporate oxygen availability. [ABSTRACT FROM AUTHOR]

Acoustic telemetry is a common tool used in fisheries management to estimate fish space use (i.e., occupancy) from a local habitat scale to entire systems. Numerous analytical models have been developed to estimate different aspects of fish movement from telemetry datasets, yet evaluations of model performance and comparisons among models are limited. Here, we develop a framework to evaluate model estimates of regional occupancy in large and fragmented systems using an acoustic receiver array in Lake Champlain. We simulated the tracks of 100 acoustically tagged fish using a random walk function and created detection events based on receiver positions and distance-based detection probability. Regional occupancy for the simulated data was estimated by six movement models that ranged in analytical complexity, and results were compared to the true distributions for each simulated track to evaluate model error. The six movement models included: (1) a basic residency index using detections alone; (2) a residency index using last-observation-carried-forward; (3) a centers of activity model; (4) linear and non-linear interpolations (i.e., least-cost paths); and (5 and 6) two dynamic Brownian bridge movement models generated using separate packages in R. We developed a model selection process to compare model performance and select the optimal analysis based on simulation error. This process showed significant differences in model performance among the six movement models based on model error. Overall, the model generating least-cost paths using linear and non-linear interpolations consistently provided the most accurate regional occupancy estimates. Based on these simulation results, we applied this model to a case study that evaluated patterns in the regional distribution of stocked lake trout (Salvelinus namaycush) in Lake Champlain, which demonstrated distinct regional occupancy of two stocked lake trout groups. These results demonstrate potential for large variability in interpretation of acoustic telemetry data for describing regional fish distribution dependent on the analytical method used. [ABSTRACT FROM AUTHOR]

This article aimed to enhance the management of the fish supply chain as a perishable commodity and to increase consumer trust. The fish supply chain begins with harvesting, whether from natural fisheries or the aquaculture sector, and extends through to marketing. It encompasses the hygienic practices of all involved parties, including suppliers, fishermen, retailers, storage facilities, distributors, transporters, and marketers. Proper hygienic handling is crucial, as inadequate practices can lead to cross-contamination at any stage of the supply chain. To improve fish quality, effective handling techniques must be applied. The use of appropriate equipment and facilities, such as cool boxes, refrigerated or insulated trucks, and boats loaded with ice, enhances the transport of fish. Improved transport methods offer several benefits to stakeholders in the fisheries sector. Consumers may be exposed to bacterial pathogens due to poor handling, washing with polluted water, or ingestion of raw or inadequately cooked fish. While most pathogens can be eliminated through adequate cooking and control measures at each stage of the supply chain, exposure to raw or undercooked fish poses a serious risk to consumer health. [ABSTRACT FROM AUTHOR]

In the Mediterranean, the bluespotted cornetfish Fistularia commersonii Rüppell, 1838, presents a minor socioeconomic impact and the assessment of any environmental impact requires more relevant data. The congeneric red cornetfish Fistularia petimba Lacepède, 1803, has expanded its distribution range within the basin but only small numbers have been reported to date. A total of 207 individuals of F. commersonii were collected between April 2021 and March 2022 from the Levantine coast of Rhodes and 92 more from various locations. Additionally, 13 individuals of Fistularia petimba were caught in March 2024 from the Aegean coasts of the island. We aim to assess the current progression of the population of the two cornetfish, the possible further exploitation of F. commersonii to boost the local fishing economy, their possible dietary overlaps and to add valuable biological and ecological data. In F. commersonii, male to female ratio (1:1.33) significantly departed from 1:1, with length–weight relationships exhibiting positive allometric growth. Six age groups were identified. The highest reproductive intensity was observed during summer. The onset of sexual maturity was estimated at 65.52 cm in total length (1.8 years). Longevity was estimated at 11.1 years with females growing larger than males. The exploitation rate (E = 0.47) indicated that the population is underexploited. The optimum and target fishing mortality were higher in comparison with the present fishing mortality (F = 0.48), indicating a potential for commercial exploitation of the species. For F. petimba, the sex ratio was 1:2.25. The species preys on crustaceans, followed by fish and molluscs. The finding of Vanderhorstia mertensi (Klausewitz, 1974) in the stomach content of both cornetfishes constitutes the second published record for Hellenic waters and the first for the Dodecanese Islands. [ABSTRACT FROM AUTHOR]

Lake Victoria is the second-largest freshwater lake in the world, and fish from the lake are a vital food resource for millions of people living around it. The silver cyprinid (Rastrineobola argentea) , a small schooling pelagic species known in Tanzania as "dagaa" contributes ca. 55% to the total annual catch (ca. 0.51 million tonnes (MT) in 2014). The acoustic target strength (TS, dB re 1 m2) of dagaa, a key factor for biomass estimation, is however not well described, and is a major source of uncertainty in biomass estimation. In this study, we developed a Kirchhoff-ray mode (KRM) model to predict the TS of dagaa at standard fisheries survey frequencies. The model was based on the morphology of the body and the dual-chambered swimbladder, as obtained from X-ray images of fish ranging in total length (TL) between 2.8 and 5.4 cm. The results suggested that the swimbladder (which comprises 2.6 to 8.2% of body volume) accounts for ca. 65 to 90% of the total backscattering at 120 kHz. The predicted TS was highly dependent on tilt angle, varying by 14.0 dB at 120 kHz across the tilt range 65–115˚ (where 0˚ is head up and 180˚ is tail up), and TS variability with tilt generally increased with increasing frequency. The tilt angle of acoustically tracked individual fish indicated a distribution of tilt angles with a mean and s.d. of 93.5 and 15.1°. Our model suggested a new tilt-averaged TS–TL relationship for dagaa [ |$T{S}_{120\ kHz} = 19.49\log ({TL}) - 70.3$| ], which leads to a TS 1.5 dB higher than the value in the relationship presently used to estimate stock biomass. The new relationship will lead to a substantial reduction (by ca. 30%) in estimated biomass. The discrepancies between the mean relative frequency response of the in situ measurements of backscatter from dagaa and the KRM model predictions were in the range of -2.9–3.1 dB at frequencies from 45 to 250 kHz. The KRM modelling and in situ broadband measurements of dagaa will be beneficial for acoustic identification and behavioural studies of dagaa, and will enable improved biomass assessment, thereby underpinning sustainable long-term management. [ABSTRACT FROM AUTHOR]

The choice of temporal resolution has high importance in ecological modeling, which can greatly affect the identification of the main drivers of an organism's distribution, considering the spatiotemporal dynamism of environmental predictors as well as organisms' abundance. The present study aimed to identify the spatiotemporal distribution patterns of Caspian Kutum, Rutilus frisii, along the southern coast of the Caspian Sea, north of Iran, evaluating multiple temporal resolutions of data. The boosted regression trees (BRT) method was used to model fish catch distribution using a set of environmental predictors. Three temporal scales of data, including seasonal, sub‐seasonal, and monthly time frames over the catch season (October–April), were considered in our modeling analyses. The monthly models, utilizing more detailed data scales, exhibited the highest potential in identifying the overall distribution patterns of the fish, compared to temporally‐coarse BRT models. The best models were the BRTs fitted using data from March and April, which represented the final months of the catch season with the highest catch levels. In the monthly models, the main determinants of the Kutum's aggregation points were found to be dynamic variables including sea surface temperature, particulate organic and inorganic carbon, as opposed to static topographic parameters such as distance to river inlets. Seasonal and sub‐seasonal models identified particulate inorganic matter and distance to river inlets as the predictors with the highest influence on fish distribution. The geographical distributions of fish biomass hotspots revealed the presence of a stable number of fish aggregation hotspot points along the eastern coast, while some cold‐spot points were identified along the central and western coasts of the Caspian Sea. Our findings indicate that utilizing fine time scales in modeling analyses can result in a more reliable explanation and prediction of fish distribution dynamics. The investigated approach allows for the identification of intra‐seasonal fluctuations in environmental conditions, particularly dynamic parameters, and their relationship with fish aggregation. [ABSTRACT FROM AUTHOR]

Simple Summary: We employed environmental DNA (eDNA) metabarcoding to assess fish biodiversity in three river basins in Beijing. Across all the 67 sampling sites, we identified a total of 60 fish taxa, with an average of 33.0 taxa per site. Of these, 20 taxa (33.3%) were non-native, distributed across 11 orders, 13 families, and 17 genera. We observed geographical homogenization among the native fish species, whereas non-native taxa exhibited varied geographical distributions—some taxa were widely distributed across river basins while others were restricted to specific sites or basins. Simple linear regression analyses revealed positive correlations between the number of taxa and species richness for both native and non-native taxa. Co-occurrence network analysis indicated positive relationships among both native and non-native taxa, with only two negative relationships involving one native and two non-native fish taxa. Rapid urbanization and its associated human activities have facilitated the colonization and spread of non-native species, rendering urban ecosystems, particularly in megacities such as Beijing, highly susceptible to biological invasions. This study employed environmental DNA (eDNA) metabarcoding to evaluate the biodiversity and geographical distribution of non-native fish, as well as their interactions with native fish species, across three river basins in Beijing pertaining to the Daqing River, the North Canal, and the Ji Canal. Across all the 67 sampling sites, we identified 60 fish taxa, representing 11 orders, 23 families, and 40 genera, with an average of 33.0 taxa per site. Of these, 40 taxa were native, accounting for only 47.1% of the historically recorded native fish species. Additionally, we detected 20 non-native fish taxa, spanning 11 orders, 13 families, and 17 genera. Native fish exhibited geographical homogenization across the basins, while non-native taxa displayed varied geographical distributions. Non-metric multidimensional scaling (NMDS) and analysis of similarities (ANOSIM) revealed no significant variation in the non-native communities across the river basins. Although most of the non-native taxa were widespread, some were restricted to specific sites or basins. The North Canal exhibited significantly lower non-native biodiversity compared with the Ji Canal across all alpha diversity indices. Simple linear regression analyses indicated positive correlations between the number of taxa and species richness for both native and non-native taxa. Interestingly, species co-occurrence analyses revealed predominantly positive interactions among both native and non-native species pairs, with only two negative relationships involving one native and two non-native taxa. This study provides insights into the biodiversity and geographical distribution of non-native fish in Beijing and establishes a baseline for future biomonitoring and conservation efforts. The findings underscore the need for further investigation into the mechanisms and dynamics of biological invasions within urban environments in Beijing. [ABSTRACT FROM AUTHOR]

In intelligent fisheries, accurate fish detection is essential to monitor underwater ecosystems. By utilizing underwater cameras and computer vision technologies to detect fish distribution, timely feedback can be provided to staff, enabling effective fishery management. This paper proposes a lightweight underwater fish detection algorithm based on YOLOv8s, named HRA-YOLO, to meet the demand for a high-precision and lightweight object detection algorithm. Firstly, the lightweight network High-Performance GPU Net (HGNetV2) is used to substitute the backbone network of the YOLOv8s model to lower the computational cost and reduce the size of the model. Second, to enhance the capability of extracting fish feature information and reducing missed detections, we design a residual attention (RA) module, which is formulated by embedding the efficient multiscale attention (EMA) mechanism at the end of the Dilation-Wise Residual (DWR) module. Then, we adopt the RA module to replace the bottleneck of the YOLOv8s model to increase detection precision. Taking universality into account, we establish an underwater fish dataset for our subsequent experiments by collecting data in various waters. Comprehensive experiments are carried out on the self-constructed fish dataset. The results on the self-constructed dataset demonstrate that the precision of the HRA-YOLO model improved to 93.1%, surpassing the original YOLOv8s model, while the computational complexity was reduced by 19% (5.4 GFLOPs), and the model size was decreased by 25.3% (5.7 MB). And compared to other state-of-the-art detection models, the overall performance of our model shows its superiority. We also perform experiments on other datasets to verify the adaptability of our model. The experimental results on the Fish Market dataset indicate that our model has better overall performance than the original model and has good generality. [ABSTRACT FROM AUTHOR]

In order to accurately estimate the distribution of Trachinotus ovatus in marine cages, a novel method was developed using omnidirectional scanning sonar and deep-learning techniques. This method involved differentiating water layers and clustering data layer by layer to achieve precise location estimation. The approach comprised two main components: fish identification and fish clustering. Firstly, omnidirectional scanning sonar was employed to perform spiral detection within marine cages, capturing fish image data. These images were then labeled to construct a training dataset for an enhanced CS-YOLOv8s model. After training, the CS-YOLOv8s model was used to identify and locate fish within the images. Secondly, the cages were divided into water layers with depth intervals of 40 cm. The identification coordinate data for each water layer were clustered using the DBSCAN method to generate location coordinates for the fish in each layer. Finally, the coordinate data from all water layers were consolidated to determine the overall distribution of fish within the cage. This method was shown, through multiple experimental results, to effectively estimate the distribution of Trachinotus ovatus in marine cages, closely matching the distributions detected manually. [ABSTRACT FROM AUTHOR]

The research of hydrographic variability can be performed using geospatial analyses of habitats that explicitly represent the distribution of physicochemical factors in different periods. In the present study, water characteristics were recorded monthly in four interdecadal sampling campaigns (1980, 1998, 2010, and 2016) in Terminos Lagoon. Based on these records, geostatistical methods and multivariate spatial analyses were conducted to describe the lagoon's spatiotemporal changes, testing the distribution of fish community attributes. Interpolation of physicochemical factors revealed directional trends of change indicative of an influence of environmental characteristics seasonality, represented in the principal components by spatial gradients on estuarine condition (PC1, salinity: 52%), habitat complexity (PC2, depth: − 63%), and water quality (PC3, pH: − 55%). The spatial classification of habitats by hierarchical clustering resulted in different environmental units representing discrete hydrographic zones (Ward's cut-off height: 0.004), such that five zones were formed in the cold fronts season (a highly hydrodynamic period) instead of four as in the rainy and dry seasons. Concordant distribution patterns of fish community attributes with the identified hydrographic zones were observed (p ≤ 0.05), suggesting that ichthyofauna responded differently to ecological variability at the seasonal scale and sorted spatially according to the local environmental heterogeneity. Overall, the continuous and discrete spatial structures found in the Terminos Lagoon provide spatially explicit scenarios of the estuarine seascape, a deep insight into the realized niche of the fish assemblages by zones in different seasons, and hydrographic characterization data to parameterize multiscale fishery models. [ABSTRACT FROM AUTHOR]

Marine sediments are among the largest carbon reservoirs on the planet and play a key role in the global cycling of organic matter. Bottom fisheries are the most widespread anthropogenic physical disturbance to seabed habitats, prompting NGOs and governments to act on regulating mobile bottom-contacting fishing gear. However, the scientific evidence of the effects of bottom trawling on sediment biogeochemistry is highly diverse and presents contrasting results. Here we present a global harmonized dataset of 71 independent studies that assess the effects of demersal fisheries on sedimentological (i.e. grain size, porosity) and biogeochemical (i.e. organic carbon, phytopigments, nutrient fluxes) properties: the Demersal fishery Impacts on Sedimentary Organic Matter (DISOM) database (Paradis, 2023; 10.3929/ethz-b-000634336). We identify considerable gaps, namely in the geographical extension of the data; coverage of environmental predictors (i.e. seasons); fishing descriptors such as the availability of true controls, quantification of fishing effort, and distribution of fishing gear types; and biogeochemical variables that study the remineralization of organic matter. Future studies should address these data gaps to enhance the comprehensiveness of the dataset. With this harmonized database, we aim to allow researchers to explore the effects of demersal fisheries in variable environmental settings to disentangle the effects of this disturbance and provide efficient management strategies. [ABSTRACT FROM AUTHOR]

Emerging fishing activity due to melting ice and poleward species distribution shifts in the rapidly‐warming Arctic Ocean challenges transboundary management and requires proactive governance. A 2021 moratorium on commercial fishing in the Arctic high seas provides a 16‐year runway for improved scientific understanding. Given substantial knowledge gaps, characterizing areas of highest uncertainty is a key first step. Marine ecosystem model ensembles that project future fish distributions could inform management of future Arctic fisheries, but Arctic‐specific variation has not yet been examined for global ensembles. We use the Fisheries and Marine Ecosystem Intercomparison Project ensemble driven by two Earth System Models (ESMs) under two Shared Socioeconomic Pathways (SSP1‐2.6 and SSP5‐8.5) to illustrate the current state of and uncertainty among biomass projections for the Arctic Ocean over the duration of the moratorium. The models generally project biomass increases in more northern Arctic ecosystems and decreases in southern ecosystems, but wide intra‐model variation exceeds projection means in most cases. The two ESMs show opposite trends for the main environmental drivers. Therefore, these projections are currently insufficient to inform policy actions. Investment in sustained monitoring and improving modeling capacity, especially for sea ice dynamics, is urgently needed. Concurrently, it will be necessary to develop frameworks for making precautionary decisions under continued uncertainty. We conclude that researchers should be transparent about uncertainty, presenting these model projections not as a source of scientific "answers," but as bounding for plausible, policy‐relevant questions to assess trade‐offs and mitigate risks. Plain Language Summary: As the Arctic Ocean gets warmer, melting ice is opening up new opportunities for fishing. However, we don't know where fish will go and how they can be managed sustainably. An important first step is to figure out which unknowns we can solve quickly with more research, and what is so uncertain that we will have to make decisions without ideal information. In this paper, we looked at uncertainty in a set of global models that predict how fish populations might shift in the next 10–25 years. Overall, these models show that fish populations might increase in the northern parts of the Arctic while decreasing in the south. But the models make very different predictions, and some disagree on whether fish populations will increase or decrease in certain areas. A major source of uncertainty is how sea ice will change, and how ocean life will respond. Therefore, this is a priority area to invest in long‐term research and better models. Overall, these models are too uncertain to rely on for specific management decisions about Arctic fishing. Instead, scientists and decision makers can use them to shape more informed discussions about potential trade‐offs and risks of future fishing in the Arctic. Key Points: Variation and disagreement in marine ecosystem model projections are too high to be informative for near‐term Arctic fisheries managementInsufficient inclusion and knowledge of sea ice cover and sea ice productivity dynamics are major drivers of uncertaintyResearchers should be transparent about uncertainty and risk; present model projections as the basis for hypotheses and scenario planning [ABSTRACT FROM AUTHOR]

The article explores the icthyofaunal diversity in selected lakes of Somwarapete taluk of Kodagu district in Karnataka, India. The study calculates the diversity of fishes and distribution of fish species and evaluates the endemism of the fishes. It identifies fish abundance belonging to different genera and families including Cyprinidae, Channiadae and Claridae taxa.

Mercury contamination from gold mining in the Amazon poses significant environmental and health threats to the biome and its local populations. The recent expansion of non-industrial mining areas has severely impacted territories occupied by traditional communities. To address the lack of sampling data in the region and better understand mercury dynamics, this study used the probabilistic model SERAFM to estimate the mercury distribution and bioaccumulation in fish. The analysis covered 8,259 sub-basins across three major Amazonian basins: the Branco, Tapajós and Xingu rivers. The findings revealed increasing downstream mercury levels, with notable accumulations in the main watercourses influenced by methylation processes and mining releases. The projected concentrations showed that an average of 27.47% of the sub-basins might not comply with Brazilian regulations, rising to 52.38% in the Branco and Tapajós river basins separately. The risk assessment of fish consumption based on the projections highlighted high mercury exposure levels among traditional communities, particularly indigenous populations, with an average of 49.79% facing an extremely high risk in the Branco and Tapajós river basins. This study demonstrated SERAFM's capacity to fill information gaps in the Amazon while underscoring the need for enhanced data collection, culturally sensitive interventions and regulatory updates to mitigate mercury contamination in gold mining-affected areas. [ABSTRACT FROM AUTHOR]

Climate warming is one of the facets of anthropogenic global change predicted to increase in the future, its magnitude depending on present-day decisions. The north Atlantic and Arctic Oceans are already undergoing community changes, with warmer-water species expanding northwards, and colder-water species retracting. However, the future extent and implications of these shifts remain unclear. Here, we fitted a joint species distribution model to occurrence data of 107, and biomass data of 61 marine fish species from 16,345 fishery independent trawls sampled between 2004 and 2022 in the northeast Atlantic Ocean, including the Barents Sea. We project overall increases in richness and declines in relative dominance in the community, and generalised increases in species' ranges and biomass across three different future scenarios in 2050 and 2100. The projected decline of capelin and the practical extirpation of polar cod from the system, the two most abundant species in the Barents Sea, drove an overall reduction in fish biomass at Arctic latitudes that is not replaced by expanding species. Furthermore, our projections suggest that Arctic demersal fish will be at high risk of extinction by the end of the century if no climate refugia is available at eastern latitudes. Using a joint species distribution model fitted to 61 species, this study shows that the habitat of Arctic fish might be hugely reduced in the next decades, and potentially eliminated from the Barents Sea. Boreal species are shown to expand their habitat, leading to increased species richness in the area and a diversification of dominance, but this might not increase overall biomass. [ABSTRACT FROM AUTHOR]

While the spatial distribution pattern of fish is increasingly used for toxicological test of chemicals or wastewater, no ideal parameter is available for quantitative assessment of spatial distribution, especially uneven distribution with multiple hotspots. Here, to develop a quantitative assessment parameter for spatial distribution, the zebrafish were exposed to ethanol, pentylenetetrazole (PTZ), paraquat dichloride (paraquat) and wastewater, followed by a behavioral test in a narrow tank. Behavioral data was acquired and analyzed by idTracker and MATLAB. By comparing the effects of all treatments on behavior parameters, we confirmed that the spatial distribution was more easily altered rather than general locomotor parameters, e.g. 0.7–70 mg/L PTZ and 5–20 mg/L paraquat being effective for altering spatial distribution but having little effects on general locomotor parameters. Based on the heatmap, i.e., the cumulative proportion of grids and that of frequency in grids, we calculated the behavioral Gini coefficient (G b) for quantitative assessment of fish spatial distribution. The Gini coefficient ranged from zero to 1, with larger values meaning poorer evenness of spatial distribution. Of note, G b showed smaller coefficient of variations (CV) with 3%-19% between replicate tanks in all treatments than the highest frequency (4%-79%), displaying well robustness. Especially, G b addressed the challenge of the complicated heatmap with multiple hotspots. Overall, the behavioral Gini coefficient we established is an ideal parameter to quantitatively assess spatial distribution of fish shoal, which is expected to be applied in toxicity testing for chemicals and wastewater and automatic quality monitoring for surface water and aquaculture water. [Display omitted] [ABSTRACT FROM AUTHOR]

In an ever-changing environment, detecting shifts in the spatial distribution of marine fish and understanding the relative importance of climate change and biotic factors impacting fish distributions can improve fisheries management. Coincident with the significant increase in Haddock (Melanogrammus aeglefinus) abundance to a historically high levels on Georges Bank (GB) in the last decade, extreme ocean temperature increase was also observed in this region. In this study, the possible seasonal and inter-annual spatial distribution changes of haddock were investigated with >50 years of bottom trawl survey data collected in spring and fall on GB. These data were analyzed using models with spatial, different temporal, and spatio-temporal autocorrelation structures. To characterize the directional changes in haddock spatial distribution, the Center of Gravity (CG) and Area of Occupancy (AO) in each season were estimated from the best model selected by Akaike Information Criteria (AIC). The results showed substantial range expansion/contraction and distribution changes in both spring and fall over time. The relative role of density dependence, age structure, and climate change in affecting haddock distribution was evaluated using a generalized additive model (GAM). It was found that density-dependent habitat selection made the greatest contribution to the variations of AO in both seasons, which is consistent with the MacCall's Basin model theory. Rising ocean temperatures played a major role in shaping a northward distribution shift in fall. GB is the southern edge of haddock distribution in the Northwest Atlantic, continued warming from climate model projections in the next 50 years in this region could make it difficult to define stock boundaries between GB and adjacent Canadian and US domestic management areas. This would subsequently impact fishery management of haddock. [ABSTRACT FROM AUTHOR]

Changes to Earth's climate affect organisms globally; in marine systems, these impacts are seen through warming water temperatures, ocean acidification, hypoxia and frequent marine heatwaves. These effects may lead to the movement of species to more favourable conditions. While climate‐driven movement is well studied at the adult stage, how the early life stages of marine fish will respond to future variability is less clear. Many fish species are constrained by specific spawning locations or phenology. Spawning in certain locations allows for local retention of offspring, while precise timing can facilitate transport of offspring to nursery locations through seasonal circulation patterns. Our research investigates how changing oceans impact the location and timing of spawning of Bering Sea groundfishes over the next century. We used ROMS SST and SSS model output and NOAA survey data in species distribution models to hindcast and project distributions and centre of gravity for eggs and larvae of six groundfish species. Our analyses found that most of our study species exhibit flexible geography. However, the speed and direction of egg and larval movement did not track the speed and direction of their respective thermal niches. Hence, the projected distributional patterns of adult stages may be limited by their early life stages. This response is likely to be mirrored globally by other species with planktonic eggs and larvae. These results indicate that life history considerations are critical for the management of commercially important species, as effects on early life stages are strongly connected to the success or failure of adult populations. [ABSTRACT FROM AUTHOR]

Herein, we present a diverse record of dinoflagellate cysts from the lignite-associated sedimentary succession (belonging to the Akli Formation) at Sonari Lignite Mine, Barmer Basin, Rajasthan State, western India. The dinoflagellate cyst assemblage implies a Danian to Ypresian age for the investigated succession and argues that the deposition of lignitic sequences along India's western margin is not coeval. We also identify two vertebrate (dominantly fish-yielding) units within the studied Akli Formation succession. The Ypresian fish genera (mainly represented by dental remains) include Ginglymostoma, Jaekelotodus, Brachycarcharias, Pycnodus and Myliobatis while the Selandian-Thanetian fish dental remains include Dasyatis. A discontinuous distribution of fish fauna during the early Paleogene (based on the temporal and spatial data) within the lignite-associated sedimentary successions of western and north India allows us to infer the prevalence of separated realms with variably restricted palaeoenvironmental conditions. Overall, the faunal evidence is indicative of dominantly estuarine to shallow marine conditions with enhanced freshwater influence during the Thanetian as compared to the Danian. Our study also argues in favour of the earliest appearance of dinoflagellate cyst Apectodinium in the near-equatorial region of the Tethys Ocean during the early Paleocene. (within Danian). [ABSTRACT FROM AUTHOR]

In order to investigate the relationship between the surface distribution of fish larvae and juveniles and environmental factors in the Philippine Sea in summer, surface horizontal trawl surveys were conducted with large larvae and juvenile fish nets (diameter 1.3 m, mesh 0.5 mm) at 50 sampling stations in the Philippine Sea (11°N-19°N, 129°E-138°E) during the summer of 2022. A total of 38 159 fish larvae and juveniles, belonging to 14 orders, 21 families, and 56 species were collected. The dominant species in the daytime collection were Thunnus albacares and Encrasicholina punctifer, while the dominant species in the nighttime collection was Encrasicholina punctifer, so the co-dominant species was Encrasicholina punctifer, which accounted for 97.05% of the total number of samples collected. The total mean density of fish larvae and juveniles at each station was 292.43 ind./1 000 m³, with a mean density of 17.61 ind./1 000 m³ collected during the daytime and 526.54 ind./1 000 m³ collected during the nighttime, indicating significant differences in diel distribution. The stations with higher densities were mainly located in the sea near 15 N, and all sample were collected at night. Canonical correlation analysis showed that the environmental factors affecting the distribution of fish larvae and juveniles were, in descending order, sea surface salinity, sea surface temperature, and dissolved oxygen. The distribution of the dominant species Encrasicholina punctifer was mainly influenced by sea surface salinity and dissolved oxygen. The study shows that the fish larvae and juveniles in the Philippine Sea have a rich species composition with uneven surface distribution and significant differences in diel distribution. This study can provide a scientific basis for the assessment, conservation and utilization of fishery resources in the Philippine Sea. [ABSTRACT FROM AUTHOR]

In the Eastern Tropical North Pacific Oxygen Minimum Zone (ETNP‐OMZ), fish larvae undergo development amidst highly variable dissolved oxygen environments. As OMZs expand, understanding the implications of low‐oxygen environments on fish development becomes increasingly relevant for fisheries management and ecosystem modeling. Using horizontal zooplankton tows to track five oxygen levels (oxic [200 μmol/kg], hypoxic [100 μmol/kg] suboxic [10 μmol/kg], anoxic [<1 μmol/kg], and deep [10 μmol/kg at ~ 1000 m depth]), this study analyzed the three‐dimensional distribution of fish larvae and adults across the ETNP‐OMZ. Results revealed a wide midwater anoxic core, extending from Costa Rica to Baja California, that was almost devoid of fish larvae (< 1 larvae/1000 m3). Early larval stages primarily inhabited the oxic and hypoxic levels above the core, while postflexion and transformation stages occurred across a wider oxygen gradient, including the deep level below the anoxic core. Epipelagic species (e.g., Auxis sp.) were predominantly found in the surface oxic level, whereas coastal‐demersal species (e.g., Bregmaceros bathymaster, Ophidion spp.) were prevalent in the hypoxic level above the core. Meso‐bathypelagic species (e.g., Diogenichthys laternatus, Cyclothone spp.) were present throughout the study area, including below the anoxic core as transformation larvae and juveniles. These findings indicate that a vertical expansion of anoxic waters in OMZs could further constrain the habitat of epipelagic species, while also affecting the ontogenic vertical movements of meso‐bathypelagic species. [ABSTRACT FROM AUTHOR]

Small-scale fisheries exhibit unique, diverse, and varied characteristics in each region. These distinctive traits render small-scale fisheries challenging to regulate centrally. This research aims to compare the characteristics of land-based and island-based small-scale fisheries in Southeast Sulawesi Province. Data were collected through structured interviews involving 445 respondents from two distinct areas: North Konawe, representing land-based fisheries, and Konawe Islands, representing island-based fisheries. Both qualitative (questionnaire data) and quantitative analyses were conducted using R software. Proportion data were tested using the R ggstatsplot package, while word cloud analysis utilized the R wordcloud package. The analysis of fishing ground distribution hotspots was performed using QGIS software version 3.30. The research findings demonstrate differences across various aspects, including education levels, boat sizes, fishing frequency, monthly income, and types of captured fish. Furthermore, the study highlights that island-based small-scale fisheries hold a higher income potential compared to their landbased counterparts. These differing characteristics serve as essential considerations in developing policies that support sustainable management of small-scale fisheries based on the needs of local communities. [ABSTRACT FROM AUTHOR]

Lotic fish species distributions are frequently predicted using remotely sensed habitat variables that characterize the adjacent landscape and serve as proxies for instream habitat. Recent advancements in statistical methodology, however, allow for leveraging fish assemblage data when predicting distributions. This is important because assemblage composition likely provides better information about instream habitat compared to landscape-derived metrics and therefore may improve predictions. To better understand the value of using multi-species fish data in species distribution modeling, we fit two conditional random fields (CRF) models to quantify the relative importance of fish assemblage co-occurrence, landscape-derived habitat variables, and interactions between these two predictor groups (i.e., effects of co-occurrence could be context-dependent) at over 1200 stream catchments in Pennsylvania, USA. We first compared predictive performance of CRF models against traditionally used single-species logistic regressions (generalized linear models; GLMs) and found that inclusion of fish assemblage data often improved predictive performance. The multi-species CRF models performed significantly better at predicting occurrence for 63% of species with an average percent increase in AUC of 25% compared to GLMs. Furthermore, the CRF identified species co-occurrences as more informative, and thus relatively more important, at predicting occurrence than the other effect types. The CRF also suggested that allowing these biotic effects to be context-dependent was important for predicting occurrence of many species. These findings illustrate the value of fish assemblage data for landscape-scale species distribution modeling and leveraging this information can improve predictions and inferences to help inform the management and conservation of freshwater fishes. [ABSTRACT FROM AUTHOR]

Changes in fish habitat induced by dam construction in the downstream river have been well documented in an increasing body of literature. Fish habitats in the backwater zone of dams have undergone dramatic changes, which have still remained poorly understood. This study aims to provide a more complete understanding of fish habitat distribution and clarify fish habitat utilization patterns in the upstream dam in order to adopt effective remediation activities. This study was conducted in the Three Gorges Dam (TGD) as it is the world's largest installed capacity hydropower station, with a backwater zone length of about 660 km. Four major Chinese carp (FMCC) were selected as target fish species, and fish habitat distribution upstream of TGD was assessed by integrating the swimming ability and environmental preference of different fish species into their critical life stages. Assessment results at different life stages of the target fish species showed that June was a critical period for spawning activities FMCC in the fluctuating backwater zone of TGD. The riverbank was an important feeding habitat for FMCC, and the high‐velocity flow in the centre of the channel exceeded the limits of the swimming ability of target fish. The fish habitat distribution in the fluctuating backwater zone of TGD was heavily affected by runoff from April to September and by dam operation from October to March of the next year. This work provide valuable information about river conservation and management in the upstream of TGD. [ABSTRACT FROM AUTHOR]

Objective: Automatic feeders are commonly used in aquaculture, but the feed delivery pattern cannot be adjusted to accommodate a variety of rearing unit sizes. For those few feeders that can be adjusted, their use has been limited because of initial costs, availability, and other issues. This paper describes modification to a commercially available fish feeder (Texas Hunter Products 31.75‐kg [70‐lb] Lake and Pond Directional Fish Feeder) to effectively provide feed to different‐sized ponds. Methods: This feeder has a 14‐m fish feed distribution pattern, making it unusable for smaller ponds. To reduce the distance of fish feed projected from the feeder, a resistor (rheostat) was installed in series with the fan motor. Result: The rheostat reduced the power to the fan motor, thereby decreasing the feed projection distance. In addition, because the rheostat was adjustable, the resistance—and the resulting power to the fan motor—could be easily changed, making it possible for the same feeder to be used in different‐sized ponds while using approximately the same amount of power from the battery and solar panels. Conclusion: This modification was inexpensive and relatively easy to perform. The feeders reliably dispensed feed in a number of small ponds during an 8‐month evaluation period. Impact statementThis paper describes an inexpensive and relatively easy to perform modification to a commercial fish feeder so that it can effectively dispense feed in small rearing ponds. [ABSTRACT FROM AUTHOR]

This study investigates the behavior of chubs (Squalius cephalus) of mid-body length (9.7–15.6 cm) with respect to turbulent flow conditions in a pool representing an experimental vertical slot fishway. Velocity and turbulence were characterized using PIV data. The influence of turbulent flow on fish behavior was assessed through the number of successful fish passage attempts, the associated passage times, and the spatial distribution of fish in the pool. Turbulence conditions were modified by the addition of one or three vertical rigid cylinders inside the pool. The results show that these adaptations may facilitate the passage of chubs. Results provide valuable insights and information to understand the relationship between fish behavior and hydraulic conditions, especially in the context of improving the design of fishways. [ABSTRACT FROM AUTHOR]

Production of energy is a foundation of life. The metabolic rate of organisms (amount of energy produced per unit time) generally increases slower than organisms' mass, which has important implications for life organization. This phenomenon, when considered across different taxa, is called interspecific allometric scaling. Its origin has puzzled scientists for many decades, and still is considered unknown. In this paper, we posit that natural selection, as determined by evolutionary pressures, leads to distribution of resources, and accordingly energy, within a food chain, which is optimal from the perspective of stability of the food chain, when each species has sufficient amount of resources for continuous reproduction, but not too much to jeopardize existence of other species. Metabolic allometric scaling (MAS) is then a quantitative representation of this optimal distribution. Taking locomotion and the primary mechanism for distribution of energy, we developed a biomechanical model to find energy expenditures, considering limb length, skeleton mass and speed. Using the interspecific allometric exponents for these three measures and substituting them into the locomotion-derived model for energy expenditure, we calculated allometric exponents for mammals, reptiles, fish, and birds, and compared these values with allometric exponents derived from experimental observations. The calculated allometric exponents were nearly identical to experimentally observed exponents for mammals, and very close for fish, reptiles and the basal metabolic rate (BMR) of birds. The main result of the study is that the MAS is a function of a mechanism of optimal energy distribution between the species of a food chain. This optimized sharing of common resources provides stability of a food chain for a given habitat and is guided by evolutionary pressures and natural selection. [ABSTRACT FROM AUTHOR]

Ecological processes that are behind distributions of species that inhabit isolated localities, complex disjunct distributions, remain poorly understood. Traditionally, vicariance and dispersion have been proposed as explanatory mechanisms that drive such distributions. However, to date, our understanding of the ecological processes driving evolution of ecological niches associated with disjunct distributions remains rudimentary.Here, we propose a framework to deconstruct drivers of such distribution using World's most widespread freshwater fish Galaxias maculatus as a model and integrating marine and freshwater environments where its life cycle may occur. Specifically, we assessed ecological and historical factors (Gondwanan vicariance, marine dispersion) and potential dispersion (niche‐tracking) that explain its distribution in the Southern Hemisphere.Estimated distribution was consistent with previously reported distribution and mainly driven by temperature and topography in freshwater environments and by primary productivity and nitrate in marine environments. Niche dynamics of G. maculatus provided evidence of synergy between vicariance and marine dispersion as explanatory mechanisms of its disjunct distribution, suggesting that its ecological niche was conserved since approximately 30 Ma ago.This integrated assessment of ecological niche in marine and freshwater environments serves as a generic framework that may be applied to understand processes underpinning complex distributions of diadromous species. [ABSTRACT FROM AUTHOR]

Machine learning occupies a central position in the modeling of fish distribution patterns. The augmentation of explanatory variables in fish habitat through many kinds of observational methodologies necessitates the discernment of an optimal combination of these variables for fish distribution modeling. We proposed a feature selection technique, recursive feature elimination with cross-validation (RFECV), to determine optimal variables combinations for yellowfin tuna distribution in the Pacific Ocean. Four tree-based models, random forest, eXtreme Gradient Boosting, Light Gradient Boosting Machine, and categorical boosting driven by RFECV, were developed using comprehensive fisheries and biotic/abiotic data. Habitat variables including sea temperature, dissolved oxygen concentration, chlorophyll-a concentration, sea salinity, and sea surface height were identified as significant features by all models. The models were trained using the corresponding selected variables, and these trained models were employed to predict the spatiotemporal distribution of yellowfin tuna from 1995 to 2019. The results obtained could inform useful knowledge for the sustainable exploitation of yellowfin tuna in the Pacific Ocean and furnish a benchmark of feature selection for machine-learning-based distribution modeling of other pelagic species. [ABSTRACT FROM AUTHOR]

The management and conservation of faunas at regional scales depend on current data on species diversity and distribution. Relative to the ichthyofauna of West Virginia, few studies have recently documented the richness and distribution of fishes in the state, with even the most comprehensive publications rarely discussing either the conservation status of individual fishes or historical sportfish stockings. In this paper, we review the state's historic sportfish stockings. We also clarify inconsistent published data and present new information for several species, delete 3 species from the West Virginia ichthyofaunal list, and add 35 species representing extant or extirpated populations. Lastly, we provide a checklist of 195 species by major drainage of West Virginia's fishes, including their origin (i.e., native or introduced). [ABSTRACT FROM AUTHOR]

Hydropower plants (HPPs) create barriers across rivers and fragment aquatic ecosystems, river reaches and habitats. The reservoirs they create slow the flowing water and convert the riverine into lacustrine ecosystems. The barriers created by HPPs interrupt the seasonal migrations of many fish species, while the reservoirs drive away fish species that are dependent on flowing water habitats. This paper assesses the distribution of fish species in the 3S rivers—Sekong, Sesan and Sre Pok, in Cambodia, Laos and Viet Nam—using IUCN Red List-assessed species distribution by HydroBasin Level 8 from the freshwater reports of the Integrated Biodiversity Assessment Tool (IBAT) and their connectivity with the Mekong. There are currently 61 commissioned dams in the 3S basins and a further 2 under construction, 23 of which are larger than the 30 MW installed capacity. A further 24 HPPs are proposed or planned in these basins. The changes in connectivity caused by the dams are measured by adapting the River Class Connectivity Index (RCICLASS); the original connectivity of the 3S basin taking into account the two major waterfalls in the Sesan and Sre Pok rivers was estimated at 80.9%. With existing dams, the connectivity has been reduced to 23.5%, and with all planned dams, it is reduced further to 10.9%. The resulting re-distribution of fish species occurring throughout the 3S basins is explored, by focusing on migratory guilds and threatened and endemic fish species. With all dams built, it is predicted that the total numbers of species in HydroBasins above the dams will be reduced by 40–50%. The Threatened Species Index is estimated to fall from over 30 near the confluence of the three rivers to less than 10 above the lowest dams on the 3S rivers. The analysis demonstrates how widely available global and regional datasets can be used to assess the impacts of dams on fish biodiversity in this region. [ABSTRACT FROM AUTHOR]

Artisanal fishing is an important subsistence practice in freshwater habitats worldwide, but overexploitation threatens the conservation of several nontarget species including crocodylians. We investigated the effects of artisanal fishing on the distribution of a population of broad‐snouted caiman (Caiman latirostris) inhabiting the Tapacurá reservoir, within the highly altered and threatened Atlantic Forest biome.We conducted spotlight surveys to detect caimans and gillnets deployed in the reservoir from April 2015 to June 2022. We evaluated temporal differences in gillnet encounter rates and the relationship between caimans and gillnet distribution.Gillnet encounter rates remained consistent year‐round, while caiman encounter rates were highest near gillnets, especially in the river channel and in forested margins. Caimans are opportunistic predators attracted by tangled fish in gillnets and likely prefer habitats with increased fish abundance.Future research should continue monitoring the interaction between caimans and fishing and include local communities in conservation efforts. [ABSTRACT FROM AUTHOR]

Day and nighttime autumn fish abundance and biomass were studied in the pelagic and littoral zones of Lake Sauka in Latvia. Both pelagic methods (hydroacoustics and trawling) revealed significantly higher fish abundance and biomass during the day than at night, especially in deeper zones (below 3 m). Roach (Rutilus rutilus) and Eurasian perch (Perca fluviatilis) dominated the trawl catches during the day, while roach and ruffe dominated at night. Fish smaller than 14 cm strongly dominated in both the trawl catches and hydroacoustic observations. Our hydroacoustic sampling found inhomogeneous pelagic distributions of fish aggregated in big shoals during the day. In the littoral zone, which was sampled by beach seining, both the abundance and biomass were significantly higher at night than during the day. Roach, bleak, and European perch usually dominated in beach seine catches during the day and at night. The daytime pelagic biomass found by hydroacoustics was 62 kg/ha and it decreased to approximately 11 kg/ha at night. The littoral biomass found by beach seining was diurnally opposite, 4 kg/ha during the day and 37 kg/ha at night. It is obvious that diurnal horizontal migrations between pelagic and littoral zones, and shoaling behavior during the daytime are common patterns in the shallow Lake Sauka during the autumn. The study of the spatial distribution of fish is extremely important for the establishment of an appropriate monitoring plan for the purposes of the Water Framework Directive with regard to the morphometry of the lake, the geographical location, and the sampling period of the year. This study also shows that the combination of completely non‐invasive hydroacoustic and other methods that are invasive (trawls, beach seines) but not as destructive as gillnets, which are normally used for scientific fish monitoring in Europe, could be a future way forward for fish monitoring. [ABSTRACT FROM AUTHOR]

Muncar is the largest fish landing which produced Bali Sardinella (Sardinella lemuru) in Banyuwangi. Sardinella was caught by purse seine. During fishing by purse seine, target species was Bali Sardinella while another catch was called bycatch. Some researchers indicated that bycatch was one factor affecting fish stock depletion. The aim of this research was to investigate catch composition and size distribution of dominant fish caught by purse seine. Result of observation at 10 fishing trip indicated that catch of purse seine was dominated by Bali Sardinella (Sardinella lemuru) which total account of 3.360 fishes or 77,83 % as a target catch, and the bycatch is layang (Decapterus ruselli) about 596 fishes or 13,77%, and slengseng (Scomber australasicus) about 363 fishes or 8,40%. The size of lemuru who caught in this research is between 12-21 cm. Dominant caught at size 14-15 cm about 2.032 fishes (46,97%), and a least caught at >18 cm about seven fishes (0,16%). The size of layang who caught in this research is between 13-25 cm. Dominant caught at size 19-20,5 cm about 255 fishes (5,20%), and a least caught at size 23,5-25 cm about one fishes (0,02%). The size of slengseng who caught in this research is between 13-28 cm. Dominant caught at size 23-25 cm about 143 fishes (3,30%) and least caught at size 27-28 cm only two fishes (0,04%). [ABSTRACT FROM AUTHOR]

The field of fish microbiome research has rapidly been advancing, primarily focusing on farmed or laboratory fish species rather than natural or marine fish populations. This study sought to reveal the distinctive gut bacteriome composition and diversity within the anadromous fish species Tenualosa ilisha (hilsa), which holds the status of being the national fish of Bangladesh. We conducted an analysis on 15 gut samples obtained from 15 individual hilsa fishes collected from three primary habitats (e.g., freshwater = 5, brackish water = 5 and marine water = 5) in Bangladesh. The analysis utilized metagenomics based on 16S rRNA gene sequencing targeting the V3-V4 regions. Our comprehensive identification revealed a total of 258 operational taxonomic units (OTUs). The observed OTUs were represented by six phyla, nine classes, 19 orders, 26 families and 40 genera of bacteria. Our analysis unveiled considerable taxonomic differences among the habitats (freshwater, brackish water, and marine water) of hilsa fishes, as denoted by a higher level of shared microbiota (p = 0.007, Kruskal-Wallis test). Among the identified genera in the gut of hilsa fishes, including Vagococcus, Morganella, Enterobacter, Plesiomonas, Shigella, Clostridium, Klebsiella, Serratia, Aeromonas, Macrococcus, Staphylococcus, Proteus, and Hafnia, several are recognized as fish probiotics. Importantly, some bacterial genera such as Sinobaca, Synechococcus, Gemmata, Serinicoccus, Saccharopolyspora, and Paulinella identified in the gut of hilsa identified in this study have not been reported in any aquatic or marine fish species. Significantly, we observed that 67.50% (27/40) of bacterial genera were found to be common among hilsa fishes across all three habitats. Our findings offer compelling evidence for the presence of both exclusive and communal bacteriomes within the gut of hilsa fishes, exhibiting potential probiotic properties. These observations could be crucial for guiding future microbiome investigations in this economically significant fish species. [ABSTRACT FROM AUTHOR]

This paper reports the presence of the common dolphinfish, Coryphaena hippurus, in Argentinian waters for the first time, with a specimen collected by experienced sport fishermen near Mar del Plata (38°S). This finding also represents the first record of a species from the Coryphaenidae family in Argentinian waters. The collection of these specimens coincided with sightings of other rarely-seen pelagic and oceanic fish species during the same period, providing further evidence supporting the influx of subtropical fish species from warmer Brazilian waters. These observations highlight the need for continued monitoring of fish populations and their distribution and the ecological dynamics within the region. [ABSTRACT FROM AUTHOR]

Environmental DNA (eDNA) is an effective tool for describing fish biodiversity in lotic environments, but the downstream transport of eDNA released by organisms makes it difficult to interpret species detection at the local scale. In addition to biophysical degradation and exchanges at the water–sediment interface, hydrological conditions control the transport distance. A new eDNA transport model described in this paper considers downstream retention and degradation processes in combination with hydraulic conditions and assumes that the sedimentation rate of very fine particles is a correct estimate of the eDNA deposition rate. Based on meta‐analyses of available studies, the particle size distribution of fish eDNA (PSD), the relationship between the sedimentation rate and the size of very fine particles in suspension, and the influence of temperature on the degradation rate of fish eDNA were successively modelled. After combining the results in a mechanistic‐based model, the eDNA uptake distances (distance required to retain 63.21% of the eDNA particles in the riverbed) observed in a compilation of previous experimental studies were correctly simulated. eDNA degradation is negligible at low flow and temperature but has a comparable influence to background transfer when hydraulic conditions allow a long uptake distance. The wide prediction intervals associated with the simulations reflect the complexity of the processes acting on eDNA after shedding. This model can be useful for estimating eDNA detection distance downstream from a source point and discussing the possibility of false positive detection in eDNA samples, as shown in an example. [ABSTRACT FROM AUTHOR]

The study reports on the capture of a new-born specimen of shortfin mako shark Isurus oxyrinchus Rafinesque, 1810 off Karantina islet coast, Urla, Izmir (north Aegean Sea). This specimen measured 761 mm in total length and weighed 2900 g. The historical and recent captures of the species in the area shows the presence of new-born, juvenile and adult males and females. The distribution of these specimens suggests the potential occurrence of a nursery ground in the same area. To preserve the extirpation of the species throughout the area where it finds favourable environmental parameters to live, a management plan should be conducted to ensure the establishment of a viable population in the Turkish marine waters. [ABSTRACT FROM AUTHOR]

Few studies have been done on the interspecific relationship between fishes species, an important part of mangrove wetlands. In 2022-2023, a sampling survey was conducted on the mangrove tidal gully fish in the estuary area of Haishan Town, Raoping County, Guangdong Province in spring, summer, autumn and winter, and the composition of fish species in the mangrove wetland was studied. The aim of this study was tried to elucidate the response relationship between the distribution and interspecific relationships of wetland fish and the effects of environmental factors by calculating the spatiotemporal niche width and interspecific overlap values. The results showed that a total of 14 species belonging to 12 families and 6 orders were identified, including 6 dominant species (IRI≥500), 3 common species (500>IRI≥100), 2 rare species (100>IRI≥10) and 3 occasional species (IRI<10). The spatiotemporal niche width of the fish in mangrove tidal gullies ranged from 0.000 to 2.428, with a large variation range, including 1 species of wide niche species (Bij≥2.0) (Oreochromis niloticus), 2 species of medium niche species (1.0≤Bij<2.0)(Odontamblyopus rubicundus and Bostrichthys sinensis), and the remaining 11 species narrow niche species (00.6) were highly significant overlapped (0.6), accounting for 47% of the total logs, and 21 pairs (0.3< overlap value <0.6) were significant overlapped, accounting for 23% of the total logs, and the two pairs accounted for 70% of the total logs. The highest spatiotemporal niche overlap values were found in Siganus oramin and Periophthalmus cantnensis (up to 0.956), while the lowest non-overlap values were included in O. niloticus and Platycephalus indicus, B. sinensis and P. indicus, and Paraplagusia bilineata and P. indicus, all with the value of 0. BIOENV analysis showed that the most suitable combinations of environmental factors for fish abundance in the study area were water temperature, salinity, pH and chlorophyll a content, which the correlation coefficient is 0.475, and the RELATE test results were significant (R=0.461, P<0.05), indicating that these four environmental factors were important in affecting fish distribution. In general, the spatiotemporal niche of fish in the mangrove wetland of Raoping Haishan town was dominated by narrow niche species, and the spatiotemporal niche overlap between different fish species was significant and meaningful. The water temperature, salinity, pH and chlorophyll a content of the water body were important environmental factors affecting the distribution of fish in the wetland in the forest area. [ABSTRACT FROM AUTHOR]

With the global population growth and increasing demand for high-quality protein, aquaculture has experienced rapid development. Fish culture management and feed supply are crucial components of aquaculture. Traditional baiting management relies on experiential judgment and regular observation, which often leads to inefficient baiting practices and wastage. To address these issues, intelligent bait casting decisions have emerged. Leveraging advanced artificial intelligence algorithms, intelligent bait casting decisions can overcome most drawbacks of traditional bait management and enhance breeding efficiency. However, most of the current intelligent baiting decisions are focused on using methods such as image processing and target detection to identify different feeding actions and patterns. These methods do not discuss based on video streams and do not consider the changes in fish behavior during the baiting process. Therefore, we proposed a real-time analysis method based on the density distribution of fish feeding behavior (FishFeed). Firstly, this method upgrades the input mechanism, not only handling static images but also capable of real-time video stream analysis. Secondly, by evaluating the fish school density distribution through a new intelligent baiting strategy, this method can monitor the feeding behavior of fish school during the baiting process in real time. Finally, we constructed a dataset for fish school density analysis (DlouFishDensity) that includes a wealth of video and image frames, providing a valuable resource for research. Experimental results indicate that our algorithm outperforms MCNN, improving MAE by 1.63 and 1.35, MSE by 1.92 and 1.58, and reducing prediction time by 2.56 seconds on the same dataset. By implementing real-time analysis of fish feeding behavior density distribution, our method offers a more efficient and effective approach to baiting management in aquaculture, contributing to improved breeding efficiency and resource utilization. [ABSTRACT FROM AUTHOR]