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In the present study, the fish distribution and assemblage pattern in relation to environmental variables were studied in the canals of Indian Sundarbans. The Permutational analysis of variance (PERMANOVA) depicted the significant variation of water variables between the seasons (F = 10.40; p = 0.001), and stations (F = 1.96; p = 0.011). A total of 44 species belonging to 39 genera, 30 families and 16 orders were recorded with Cyprinidae (6 species) as the apex contributor. Significant temporal variations of fish Species Richness per sample (SRp) (p ≤ 0.05) were observed between pre-monsoon and monsoon season. By and large, fish assemblages did not portray the significant seasonal variation hinted towards the limited connectivity with tidal water through the sluice gate, thereby minimizing the movement of fish species between the canal and river. The fish assemblages pattern exhibited an overall 30% similarity among all the stations. The calculated value of Margalef richness (dʹ) and Shannon diversity (Hʹ) indices (4.42 ± 0.84 and 2.62 ± 0.18 for dʹ and Hʹ, respectively) indicating a moderate fish diversity in the canal system. The water variables such as temperature, dissolved oxygen, pH, salinity, specific conductivity, transparency, depth and water flow play important role in structuring the fish assemblages in the studied canals which were evident from the BIO-ENV module, and the distance-based redundancy analysis (db-RDA). Meagre seasonal variation of fish populations related to variations in species-specific adaptation to the prevalent ecological conditions. [ABSTRACT FROM AUTHOR]

Monitoring various Fish Species and its distribution of the species obtains a primary significance in receiving the insights to marine ecological-system. After this, visual classification of those species would aid in tracing out the movement and yield the patterns and trends in fish activities, which provides in depth knowledge of the species. Unconstrained under-water images pose highly variations because of the fish orientation changes, Light-intensities, similarity in fish patterns and fish shapes. This would create the greater challenge for Image-processing techniques in accurate classification of Fish species or the Fish classes. Hence, for this reason, Underwater Image Enhancement is implemented in combination of Morphological-operations in pre-processing method. The pre-processed image is then subjected to feature extraction process by using Speed-up Robust Feature algorithm. This is followed by Firefly Algorithm, applied for optimization of Region of interest selection in the selected-features. For the categorization of Fish-species, PatternNet is a technique which is employed, in classifying 10,000 marine fish-images to five categories (Dascyllus reticulatus, Plectroglyphidodon dickii, Chromis chrysura, Amphiprion clarkii, and Chaetodon lunulatus). The Efficiency of the proposed-framework is performed in terms of Classification accuracy, execution time, precision value, F-measure and recall factors with respect to various categories of fish species. The comparison of the proposed-framework is also assessed with the other existing methods. 98% of accuracy rate in classification was produced by the evaluation results of the proposed framework with a lesser average computation time of 3.64 s upon different tested images. Thus, the higher efficiency of the proposed framework is proved by the outcomes of the study. [ABSTRACT FROM AUTHOR]

After more than ten years of offshore wind farm (OWF) construction, the total installed capacity of China ranks first in the world. The effect of OWF on fish communities—to attract or banish—differs among fish species and wind farms. Studies on the effects of OWFs are limited in China and results from other regions may not be transferable due to different environmental and biological conditions. In October 2019, an acoustic survey was conducted in Jinwan OWF, outside the Pearl River Estuary, northern South China Sea, China, to assess the fish resources (biomass and abundance), community diversity, and distribution information of this area. According to the Index of Relative Importance (IRI), Harpadon nehereus and Brionobutis koilomatodon were the dominant fish species in the study area. The mean Shannon–Weiner diversity index was 1.74. The mean Margalef richness index and Pielou uniformity index were 2.51 and 0.84, respectively. The ABC curve indicated that the fish community was undisturbed. The mean acoustically-derived biomass and abundance densities were 195.40 ± 254.32 kg/km2 and 6506.83 ± 11,098.96 individuals/km2, respectively. The fishery resources had evident aggregate distribution patterns, and the southern part of the study area had more biomass than the northern part. Seven environmental factors were selected by canonical correspondence analysis (CCA) analysis to reveal the correlation between fish assemblages and environmental factors, including nitrate (NO3−), ammonium (NH4+), dissolved oxygen (DO), water depth, pH, Chlorophyll a (Chl a), and phosphate (PO4+). However, the CCA only accounted for 45.49% of the total variation, indicating that other unexplained stresses affect the fish assemblage in Jinwan OWF. This is the first study to examine the fish distribution patterns and community structures of the Jinwan OWF area. In addition, it will help all sectors of society to more scientifically and objectively understand offshore wind farm projects. In future studies, control areas with more trawl samples can be set up to explore the long-term impact of OWF facilities on local fish communities. [ABSTRACT FROM AUTHOR]

To unravel the effects of environmental factors on fishery resources in the bay, we conducted six biological and environmental surveys in the Laizhou Bay between 2013 and 2020. The findings of our study illuminated several key aspects: (1) The annual discharge of water and sediment from the Yellow River to Laizhou Bay exhibited notable variations, while concurrently, environmental factors including temperature, salinity, and suspended particle matter underwent fluctuations, yet remained within a relatively stable range overall. (2) A total of 8318 eggs and larvae belonging to 10 orders, 16 families, and 19 genera were collected. Significant interannual fluctuations had been documented in the species composition, abundance, and biodiversity of ichthyoplankton. Notably, both Shannon-Wiener diversity index and Pielou evenness index were significantly negatively correlated with suspended particle matter concentration. (3) The water and sediment discharge significantly positively correlated with the number of cold-temperature species. However, the sediment input negatively correlated with the number of continental shelf benthopelagic fish. (4) Redundancy and correlation analyses confirmed the strong link between spatial and temporal distribution of fish communities and environmental factors, with salinity and dissolved oxygen key for ichthyoplankton abundance. Our research offers a scientific foundation for targeted fishery protection and management, which is crucial for preserving the ecological functions of spawning grounds in the bay. [Display omitted] • Salinity and dissolved oxygen were key factors affecting ichthyoplankton abundance. • Biodiversity was significantly correlated with suspended particle matter and water depth. • The impact of water and sediment on certain species were pronounced. [ABSTRACT FROM AUTHOR]

The Brazilian North Coast (BNC) encompasses the intersection of multiple oceanographic features such as strong currents, a large continental shelf under the influence of the Amazon River freshwater and sediment outflow, extensive muddy and sand bottom, as well as a mesophotic reef system. As a result, the BNC hosts a diverse fish fauna, consisting of estuarine and freshwater species, including species endemic to the region. These fish species are distributed across a mosaic of megahabitats within the region. Here, we present the first comprehensive effort to understand the distribution patterns of ray-finned fishes and cartilaginous fishes among these different megahabitats. On 1891 samples, we recorded 616 species from 147 families distributed across five distinct megahabitats. The Continental Slope megahabitat had the highest number of families and consisted primarily of pelagic species, indicating its close association with the open sea. The Sand and Mud megahabitats exhibited high species richness and shared similar generalist fish families in terms of habitat use. The Amazon Plume megahabitat was characterized by freshwater and marine euryhaline species, emphasizing the influence of the Amazon River on the BNC's ecological dynamics. The Reef megahabitat had species closely associated with consolidated substrates and shared many species with the Sand megahabitat. This study offers valuable insights into fish species distribution and composition in the BNC, contributing to biodiversity assessments and conservation efforts in the region. • The Brazilian North Coast present a diverse fish fauna which is significantly influenced by the mosaic of megahabitats. • Species exhibit preferences for specific foraging substrates and/or are influenced by environmental factors. • The discharge of freshwater from the Amazon River mouth seems to play a direct role in defining the megahabitats boundaries. • The Amazon Plume megahabitat confirms the existence of a barrier for non-euryhaline species. • Amazon Plume megahabitat presenting the lowest percentage of species and families, which shows the selective character. [ABSTRACT FROM AUTHOR]

Catch-per-unit-effort (CPUE) standardization is crucial for fishery stock assessment but often presents challenges due to spatial-temporal variations in species distribution and fishing effort. In this simulation study, we propose the use of customized artificial neural networks (ANNs) for modeling the spatial-temporal variations in CPUE standardization. This is achieved by encoding prior knowledge of the dependency structure between the variables into the architecture of the ANNs. We conducted numerical experiments on simulated data to compare our customized ANNs with Generalized Linear Models (GLMs), Generalized Additive Models (GAMs), and fully connected ANNs used in previous studies. Our simulated data cover three spatial-temporal dynamics scenarios with different degrees of species distribution shift over time: (1) steady fish distribution; (2) gradual directional shift over time; (3) sudden directional shift. In predicting the standardized CPUE in this simulation study, the customized ANNs demonstrated greater accuracy compared to the commonly used fully connected ANNs with an error reduction of over 70 %, more than 80 % compared to GLMs, and more than 40 % compared to GAMs, in terms of an error metric called the scaled mean absolute relative error. Our findings suggest that customized ANNs can serve as an alternative modeling tool alongside GLMs and GAMs in fisheries modeling. [ABSTRACT FROM AUTHOR]

When facing changes in the available forage fish composition and distribution, seabirds are expected to respond by switching their prey species and/or adjusting their key foraging areas. We studied chick-rearing Rhinoceros Auklets Cerorhincamonocerata at Teuri Island, Japan, across three successive years. We examined inter-annual and seasonal changes in their prey species by sampling bill-loads fed to chicks, and surveyed their foraging areas using GPS data-loggers. In 2020, auklets foraged on sand lance Ammodytes spp. in shallow coastal areas along the mainland, ~ 150 km from the colony. In 2021 however, they foraged on an alternative prey, age-0 Greenling Pleurogrammusazonus, in cool basin deep waters > 150 km away in the early season, and later switched to Herring Clupeapallasii caught in warm coastal waters. In 2022, they foraged on Anchovy Engraulisjaponicus in offshore and coastal waters < 150 km away. These changes in the auklets’ foraging areas mirrored the respective habitat of the dominant prey species in each case. In turn, these changes determined their foraging trip duration: the birds made longer trips in 2021 (45.5 h) than in 2020 (30.9 h) or 2022 (22.8 h). Longer overnight trips undertaken when auklets foraged in areas more than 130–180 km away from the colony, likely decreased chick meal frequency in this day-foraging/night-provisioning species. Although they could make longer foraging trips than day-foraging/day-provisioning species, the inter-annual variability of forage fish community might result in more frequent reproductive failure under the unconventional climate regime currently in place around Japan. [ABSTRACT FROM AUTHOR]

• The eDNA method exhibits higher taxonomic resolution and detection rates compared with traditional gillnet methods. • Gillnetting and eDNA survey methods resulted in significantly different fish communities. • The spatial distribution of fish species sampled by gillnetting was more dispersed than that using eDNA method. • The eDNA reads can to some extent indicate the abundance and biomass of fish assemblage. Environmental DNA (eDNA) technology, as an alternative to traditional gillnet surveys, has attracted widespread attention. However, comparisons between eDNA and traditional methods regarding biodiversity and community structure have not yet been fully elucidated. This study compared the ability of eDNA and gillnets for fish monitoring in a large deep reservoir (Qiandao Lake) in East China. The results showed that eDNA exhibited higher taxonomic resolution and detection rates, and significantly larger species diversity and richness indices compared with traditional gillnetting methods. Using abundance and biomass datasets from gillnets revealed significant differences in fish community composition between gillnetting and eDNA survey methods. Gillnet abundance was dominated by small-sized fish species, while gillnet biomass was dominated by larger-sized ones, and the prevailing species detected in eDNA reads included the dominant species from gillnet abundance and biomass, as well as a medium-sized invasive alien fish (Lepomis macrochirus). Non-metric multidimensional scaling (NMDS) showed that the spatial distribution in abundance of fish species sampled by gillnetting was more dispersed than that using eDNA. The explanatory power with the gillnet abundance and biomass together as predictor variables of the eDNA reads increased moderately compared with taking them separately, and the fitting degree of quadratic functions was also improved somewhat compared to linear equations when using biomass to predict eDNA reads. Furthermore, the key environmental factors affecting fish communities differed between the two methods. Current research indicates that eDNA has advantages over gillnets in detecting fish species diversity, and it is recommended to combine it with traditional sampling methods. Under natural aquatic ecosystem conditions, the eDNA reads may comprehensively reflect the biomass and abundance information obtained through gillnetting, but their relationship is complex and requires further research. This study will provide guidance for biodiversity monitoring. [ABSTRACT FROM AUTHOR]

The ocean sustains ecosystems that are essential for human livelihood and habitability of the planet. The ocean holds an enormous amount of carbon, and serves as a critical source of nutrition for human societies worldwide. Climate variability and change impact marine biogeochemistry and ecosystems. Thus, having state-of-the-art simulations of the ocean, which include marine biogeochemistry and ecosystems, is critical for understanding the role of climate variability and change on the ocean biosphere. Here we present a novel global eddy-resolving (0.1° horizontal resolution) simulation of the ocean and sea ice, including ocean biogeochemistry, performed with the Community Earth System Model (CESM). The simulation is forced by the atmospheric dataset based on the Japanese Reanalysis (JRA-55) product over the 1958–2021 period. We present a novel configuration of the CESM marine ecosystem model in this simulation which includes two zooplankton classes: microzooplankton and mesozooplankton. This novel planktonic food web structure facilitates "offline" coupling with the Fisheries Size and Functional Type (FEISTY) model. FEISTY is a size- and trait-based model of fish functional types contributing to fisheries. We present an evaluation of the ocean biogeochemistry, marine ecosystem (including fish types), and sea ice in this high resolution simulation compared to available observations and a corresponding low resolution (nominal 1°) simulation. Our analysis offers insights into environmental controls on trophodynamics within the ocean. We find that this high resolution simulation provides a realistic reconstruction of nutrients, oxygen, sea ice, plankton and fish distributions over the global ocean. On global and large regional scales the high resolution simulation is comparable to the standard 1° simulation, but on smaller scales, explicitly resolving the mesoscale dynamics is shown to be important for accurately capturing trophodynamic structuring, especially in coastal ecosystems. We show that fine-scale ocean features leave imprints on ocean ecosystems, from plankton to fish, from the tropics to polar regions. This simulation also offers insights on ocean acidification over the past 64 years, as well as how large-scale climate variations may impact upper trophic levels. The data generated by the simulations are publicly available and will be a fruitful community resource for a large variety of oceanographic science questions. [ABSTRACT FROM AUTHOR]

In the domain of aquaculture, the act of feeding fish is a pivotal factor influencing both the growth of the fish and the associated cultivation costs. The implementation of intelligent feeding strategies is a crucial prerequisite for maintaining fish health and minimizing costs, with the accurate discernment of fish feeding behavior serving as the fundamental basis for the realization of such strategies. Addressing the issues of high data redundancy and substantial noise content inherent in the datasets utilized by existing identification models, as well as the intricate design and suboptimal execution efficiency of the model structures, this study introduces a two-stage framework for discriminating fish feeding behavior. In the initial stage, a re-parameterizable multi-scale object detection model is established, facilitating the acquisition of the spatial distribution of fish schools. This process effectively eliminates redundant data and noise, decouples the training and inference processes of the model, equivalently transforms the complex network training weights, and simplifies the inference process of the model. An analysis of the dataset characteristics is conducted, leading to the optimization of the model detector's design and a reduction in both the model parameters and computational requirements. In the subsequent stage, responding to the key data characteristics of the spatial distribution of fish schools, a lightweight behavior recognition model is designed. This model enables the rapid and accurate identification of fish feeding behavior. A plethora of experimental results demonstrate that the proposed method can achieve a high recognition accuracy (Acc 83.33%) while operating under the constraints of minimal model parameters and computations (6.45M Params, 8.135G FLOPs). This provides a robust model foundation for the industrial application of the algorithm, underscoring the significant potential of the proposed method in advancing intelligent feeding strategies in aquaculture. [Display omitted] • A comprehensive dual-phase analytical framework is introduced for examining feeding patterns. • An innovative method integrating multi-scale information fusion and lightweight reparameterization backbone is proposed. • A classification model is presented to capture temporal and spatial complexities in fish feeding behaviors. • Achieved 83.33% accuracy, providing compelling evidence of its proficiency in analyzing fish feeding behavior. [ABSTRACT FROM AUTHOR]

• Effective river management requires analysis of spatial distribution and habitat diversity. • Under normal flow the distribution of fish habitat is along the river channel while under flood flow is on the banks. • Two-dimensional habitat diversity construction model accurately simulates habitat diversity regardless of flow magnitude. Analyzing the spatial distribution and habitat diversity of river habitats not only helps us understand river ecology and guides effective management, but also informs efforts to create suitable habitats for fish and restore environmental diversity. Henceforth, we developed a Two-Dimensional Habitat Diversity Construction Model to predict and analyze the variation and spatial distribution of fish habitat types under the normal (for both dry and wet seasons) and flood flows (for different return periods). Shannon and Simpson Index, and Habitat Diversity Index (HDI) were used to assess the habitat diversity under normal and flood flow conditions. The simulation results showed that under normal flow, fish habitat distribution is along the channel while under flood flow it is more on the banks. Under average annual flow and high flow during the rainy season, 4.4 % and 20.51 % of water-covered areas, respectively, lack suitable habitats. For flood flows with return periods of 2 years and 100 years, 55.6 % and 73.36 % of water-covered areas do not support any habitat types. Regardless of the flow type, the model can reasonably evaluate the spatial distribution and habitat diversity of various habitat types in the river. Findings from this study will assist in conserving existing fish habitats, and in introducing missing/lacking habitats. In addition, it could provide a reference for creating ecological habitats for fish in rivers and restoring habitat diversity. [ABSTRACT FROM AUTHOR]

The lack of knowledge about freshwater biodiversity in remote areas like montane Andean rivers is noticeable and hinder the development of efficient conservation plans for aquatic ecosystems. Habitat requirements of tropical Andean fishes have been poorly analysed, despite the relevance of these ecological features on the fish conservation strategies. The present study aimed to examine fish assemblages along the altitudinal gradient in tropical Andean rivers and their relationship to habitat features to detect the most relevant abiotic factors and their implication on conservation. This study was conducted on a regional scale, along six basins located in tropical Andes (500 to 2,692 m a.s.l.). We studied fish diversity and distribution and their habitats along these elevation gradients. We found 6,320 specimens from 53 genera. Our analysis for the six most common and widely distributed genera (Astroblepus, Brycon, Bryconamericus, Chaetostoma, Pimelodella and Trichomycterus) underlines the relevance of hydromorphological variables on fish community structure in the Andean montane rivers, whereas human alterations seem to be less significant. These findings could be useful for current management and conservation strategies considering present threats over tropical montane rivers. [ABSTRACT FROM AUTHOR]

Tropical marine ecosystems are highly biodiverse and provide resources for small-scale fisheries and tourism. However, precise information on fish spatial distribution is lacking, which limits our ability to reconcile exploitation and conservation. We combined acoustics to video observations to provide a comprehensive description of fish distribution in a typical tropical environment, the Fernando de Noronha Archipelago (FNA) off Northeast Brazil. We identified and classified all acoustic echoes into ten fish assemblage and two triggerfish species. This opened up the possibility to relate the different spatial patterns to a series of environmental factors and the level of protection. We provide the first biomass estimation of the black triggerfish Melichthys niger, a key tropical player. By comparing the effects of euphotic and mesophotic reefs we show that more than the depth, the most important feature is the topography with the shelf-break as the most important hotspot. We also complete the portrait of the island mass effect revealing a clear spatial dissymmetry regarding fish distribution. Indeed, while primary productivity is higher downstream, fish concentrate upstream. The comprehensive fish distribution provided by our approach is directly usable to implement scientific-grounded Marine Spatial Planning. [ABSTRACT FROM AUTHOR]

The importance of vegetative habitat in influencing distribution patterns, species interactions, and biodiversity is well documented in marine ecosystems, yet most previous studies on macroalgal–fish relationships have focused on influences of density and identity of macroalgae, often ignoring how the unique physical structure provided by each alga contributes to patterns. We tested whether the distribution, abundance, and biomass of rocky reef fishes could be predicted as well or better by measures of physical structure of macroalgae than by species identity and abundance. Divers visually sampled fishes and macroalgae at seven sites spread over several km at Santa Catalina Island, California, over a 1-year period, to examine how the distribution patterns of fishes related to spatiotemporal differences in the macroalgal assemblage. We found that variation in the composition, density, and diversity of the fish assemblage was equally or better explained by macroalgal structure (total surface area and height) than by macroalgal species density. In contrast, biomass and vertical distribution of fishes were better predicted by macroalgal species identity and density than by macroalgal physical structure. Of the macroalgal attributes, surface area was the best predictor of fish abundance and multivariate assemblage structure (species and their densities). However, much of the spatiotemporal variation in the fish assemblage was not explained by macroalgae, indicating that even in habitats visually dominated by macroalgae, macrophytes are only one of many factors that drive spatiotemporal variation in community structure. Our results suggest that quantifying the physical structure provided by marine macroalgae can be more useful than macroalgal species identity in predicting some aspects of fish assemblage structure. [ABSTRACT FROM AUTHOR]

Aim: Unravelling the ecological and historical factors that underlie species distributions has challenged ecologists for a long time. Thus, our objective is to understand the role of environmental variables explaining the distribution of three major eco‐evolutionary groups of inland fishes (Darlington's divisions: primary, i.e. strict freshwater; secondary, i.e. salt‐tolerant; and peripheral, i.e. diadromous and marine origin), and how these variables are related to fish traits. Location: Iberian Peninsula. Taxon: 51 native and 17 alien inland fish species from the Iberian Peninsula. Methods: We modelled distributions of the most common inland fish species across the Iberian Peninsula to compare the importance of different predictors among the three Darlington's divisions and between native and alien species. To explore the importance of specific environmental variables in determining the distribution of different traits of inland fish, variable importances obtained from species distribution models were subjected to a redundancy analysis. Results: Darlington's divisions differ significantly in salinity tolerance, in distribution overlap, in the importance of distribution predictors and associated life‐history traits. Topographic and climatic variables were generally more important than land use and anthropogenic factors in explaining fish distributions. We found significant differences in the importance of variables explaining the distribution of native vs. alien species and especially among Darlington's divisions. River basin was most important for primary native and many alien species. Increasing mean temperature and damming were positively associated with the presence of tolerant, large‐bodied and warm‐water alien species from more hydrologically stable habitats. Main conclusions Despite marked differences in the distribution patterns of native and alien species, evolutionary and introduction histories as well as seawater tolerance are central factors explaining the current distribution of inland fishes. Darlington's divisions proved useful for addressing ecological and biogeographical questions at broader spatial scales. [ABSTRACT FROM AUTHOR]

Bengawan Solo River is heavily modified into reservoirs and dams. Starting from Karanganyar to Sragen District, mass fish deaths happen up to 3-4 times a year due to organic matter pollution. The research was conducted to determine water quality during the rainy season (April 2020) and the dry season (August 2020). Samplings were carried out in three zones: the upstream zone (I) in Sukoharjo District, Central Java; the middle zone (II) in the Solo City, Karanganyar, and Sragen District, Central Java; and the downstream zone (III) in Ngawi and Bojonegoro District, East Java. Results showed that the waters of Bengawan Solo in zone I were not affected by waste. After reaching zone II, there was a heavy pollution effect. In zone III, the water quality has returned to normal levels (recovery). The fish species in zone I were dominated by exotic fish such as Nila (Oreochromis niloticus) and Jambal Sius (Pangasianodon hypothalamus). The fish species in zone II was dominated by Sapu sapu (Pterygoplichthys pardalis). In zone III were dominated by native fish species such as Jendil (Pangasius polyuranodon), Seren (Cyclocheilichthys enoplos), Bendol (Barbichthys laevis), Wader (Rasbora spp.), Keting (Barbonymus gonionotus), Daringan (Mystus microcanthus), and Tagih (Hemibagrus nemurus). [ABSTRACT FROM AUTHOR]

Reservoirs are thought to contain three zones (riverine, transition and lacustrine) emerging from environmental gradients from the river to the dam where zooplankton are predicted to peak in the transitional zone. Few high spatial resolution studies, however, have surveyed zooplankton distribution in reservoirs, leading to limited knowledge regarding longitudinal abundance and composition of zooplankton. Using 44 samples from river to dam in a 35.7 km long reservoir, we explore spatial variability in zooplankton density, biomass, composition and relative bottom-up to top-down control. Broadly, density and biomass increased from the river to the dam. Variation occurred in the location and frequency of peaks among groups. Divergence between per unit volume and area within groups highlighted the importance of depth. Richness and turnover between sites were both greatest near the river. The ratio of zooplankton to phytoplankton biomass varied longitudinally, with a low near 20% of the distance from the river to the dam indicating spatial variability in bottom-up versus top-down control. This study highlights the complexity of longitudinal zooplankton composition and distribution in reservoirs and provides insight into reservoir ecosystem complexity and function, with important consequences for water quality, fish distribution, and productivity. [ABSTRACT FROM AUTHOR]

Reservoir cascades have cumulative effects on fish assemblages that can be less pronounced with the presence of incoming free-flowing tributaries. However, it is still poorly understood how the effects of cascade reservoirs on fish communities are driven. This study aimed to assess the fish assemblage distribution along two long free-flowing rivers that enter the first two reservoirs in cascade within the upper Grande River basin. Fishes were collected bi-monthly throughout 1 year along this cascade and were evaluated by composition and richness of native and non-native species. The transitional areas between the rivers and the first reservoir presented the highest richness. An increase of non-native species was observed from the uppermost (Rivers) to the downmost (lower reservoir) region. Although the seasonality did not influence fish composition in the Camargos-Itutinga cascade system, discharge-related variables (water level, transparency, and temperature), together with the position along the gradient, were the main drivers of the variation on fish assemblage's structure. The results reinforce the role of cascade systems in the increase of non-native species, as well as the importance of free-flowing rivers in structuring the fish fauna in such conditions. [ABSTRACT FROM AUTHOR]

Temperature and salinity often define the distributions of aquatic organisms. This is at least partially true for Delta Smelt, an imperiled species endemic to the upper San Francisco Estuary. While much is known about the tolerances and distribution of Delta Smelt in relation to these parameters, little is known regarding the temperature and salinity preferences of the species. Therefore, the temperature and salinity preferences of sub-adult Delta Smelt were investigated across a wide range of thermal (8–28 °C) and salinity (0–23 ppt) conditions. Replicates of ten fish were allowed to swim between two circular chambers with different temperature or salinity, and the distribution of fish between the chambers was recorded. We found that Delta Smelt showed no temperature preference below 15 °C, a modest aversion to the warmer tank from 15 to 28 °C, and a strong aversion to the warmer tank with elevated mortality at temperatures above 28 °C. Delta Smelt also preferred lower salinities, and this preference became more pronounced as salinity increased toward 23 ppt. These results indicate that Delta Smelt can tolerate high temperatures and salinities for a short time, and that their preferences for lower temperature and salinity strengthens as these variables increase. [ABSTRACT FROM AUTHOR]

For both conservation and management purposes, it is important to identify the natal origin of migratory individuals entering a river, particularly in genetically spatially structured species like brown trout (Salmo trutta) where the migrant ecotype (called sea trout) can originate from different populations. Nonetheless, little attention has been paid to the spatial distribution of non‐local fish at the level of an entire river catchment. The objective of the study was to quantify the proportion of non‐local sea trout entering a river catchment (i.e., straying rate) and estimate the spatial extent of their upstream migration. Here, the authors considered dispersal in three distinct rivers, taking advantage of 10 sampling sites. Sea trout, either trapped or rod‐caught, were genotyped and genetically assigned to their source populations using appropriate baselines. Based on 1437 sea trout fish classified as local or non‐local, the authors empirically demonstrate that straying rate declines in each river as distance from the coast increases in a non‐linear fashion. Straying rate exceeds 50% near the mouth, and then decreases gradually to reach <10% 40–50 km inland. A similar spatial pattern is found in the three rivers investigated suggesting an underlying common behaviour of non‐local sea trout. The data and results presented here suggest that straying in is far more constrained spatially than first expected. The majority of non‐local sea trout were found within the first 25 km of the estuary in the three rivers investigated. [ABSTRACT FROM AUTHOR]

The distribution of species depends on the relationship with other species and the influence of abiotic factors, modulated by long‐term evolutionary and biogeographic processes. Polychaetes and fish are important components of the biota that inhabit estuarine systems, coexisting in various habitats, although the relationship between these groups and their responses to environmental variables is poorly understood. This study aimed to assess the concordance between fish and polychaete communities in three zones (inner, middle, and outer) of a tropical bay and to determine environmental influences on these communities. The raised hypothesis is that benthic fish is associated with polychaetes and that these taxonomic groups respond differently to environmental conditions. Environmental characteristics were the main drivers determining the occurrence of fish species and polychaetes families; however, no consistent relationship was observed between fish and polychaetes. Sediment granulometry seems to be an essential driver in determining polychaetes and fish distribution while turbidity and phosphorus were also important for fish. The three zones differed in both water physicochemical and sediment (nutrients and granulometry) variables, which determined their uses by different fish and polychaetes species. Only one fish species, the gerreid Eucinostomus argenteus showed a weak but significant association with the Goniadidae and Spionidae polychaetes, which may be associated with similar environmental preferences of both taxa. The lack of a consistent relationship between benthic fish and their likely invertebrate prey may be associated with the small spatial scale of this study and the early fish life stages. Most fish in shallow coastal areas are still in their early life, feeding mainly on polychaetes and other benthic macroinvertebrates, and as the area is shallow, planktonic organisms may be included in their diet, thus relieving predation pressure on benthic organisms. These findings are important to unveil relationships among different taxonomical groups and their environment. [ABSTRACT FROM AUTHOR]

Thai traditional fermented fish products (Plaa-som) from four provinces (Ubon Ratchathani, Surin, Sisaket, and Khon Kaen) in the northeast part of Thailand were collected and analyzed to determine their salt content, total acidity, and pH. Yeasts in all samples were isolated and identified to the genus and species level based on sequence analysis of the D1/D2 of the large subunit (LSU) rRNA gene and the internal transcribed spacer (ITS) region. The results revealed that the salt content, total acidity, and pH values are in the range of 2.01–6.9%, 0.62–1.9%, and 4.4–6.57%, respectively. Moreover, 35 strains of yeast were isolated and identified as eight genera, namely Candida, Diutina, Filobasidium, Kazachstania, Pichia, Saccharomyces, Torulaspora, and Yarrowia with 17 species. The ascosporogenous yeast, Kazachstania, was the most dominant genus found and was widely distributed among the fermented food samples. In addition, a new strain of yeast, Kazachstania surinensis, was also discovered in Plaa-som samples. Thus, this study is the first to report the presence and wide distribution of these yeasts in fish fermentation products. [ABSTRACT FROM AUTHOR]

The Socotra Cormorant (Phalacrocorax nigrogularis) is a regionally endemic seabird that is vulnerable due to human disturbance and habitat degradation. This study aimed to predict the potential current and future marine distribution of the species under different climate change scenarios using environmental variables affecting distribution using MaxEnt. Occurrence data were collected over several years using satellite tagged adults in the Arabian Gulf. The current model showed large areas of high suitability, mainly in the Arabian Gulf and in the Red Sea, where 31,300 km2 or 48% of total highly suitable areas existed. These areas are currently not utilized by the species. The future model predicted a sharp decline in suitable areas with 73% loss under the SSP5-8.5 climate change scenario of 2050 (extreme scenario). Nevertheless, the Red Sea is predicted to still hold considerable moderately suitable areas. Suitable areas increased around the Socotra archipelago. The model did not include biological variables due to lack of fish distribution data. Two variables, namely, mixed layer thickness and sea floor depth, explained most of the species' distribution. These variables significantly influence nutrient cycling and forage fish distribution patterns, which in turn influence seabird distributions. Thus, the model could be useful in predicting the distribution of Socotra cormorants. However, the model outcomes should be interpreted with caution as potential areas of future expansion of the species to be further tested and validated. Conserving these areas as a precaution might encourage the Socotra Cormorant to colonize the region and persist in the future under the most extreme climate change scenarios, given that small forage fish that are eaten by the species are abundant in the predicted areas outside of the Arabian Gulf. [ABSTRACT FROM AUTHOR]

The Guadalquivir River Basin is one of the largest in the Iberian Peninsula and has a remarkable freshwater biodiversity. Although many studies on hydrological regimes or water quality have been conducted in this basin the biodiversity of freshwater fish, as well as their distribution and conservation status, has never been globally addressed as in other Iberian basins. In this context, we synthesized information on freshwater fish using field procedures and a bibliographic search. Fish distribution patterns at different spatial scales and general environmental conditions were analyzed as well as the conservation status of the fish community. We documented the presence of 40 species (20 native and 20 exotic) in the basin during the 20th century until today. However, we only captured 18 species during the field sampling, with a prevalence for any native species of less than 23% (except Luciobarbus sclateri). The highest species richness was found in mid reaches, while the lower reaches had very low diversity values. Around 50% of species are threatened; according to the IUCN, several species are declining at an alarming rate and others are probably extinct and/or their current status is unknown. Human disturbances during the last few decades have caused serious changes in fish distribution and consequently to their conservation status. Hydrological alterations, intensive agriculture and introduced species are probably the principal reasons for Guadalquivir's ichthyofauna imperilment. Our study indicates an urgent and real need to identify important areas for fish conservation to guarantee a minimum fish biodiversity conservation over the long term, as well as effective strategies for fish recovery where it still is possible. [ABSTRACT FROM AUTHOR]

This paper is analyzes the faunistic composition and quantitative characteristics of aquatic communities in the mountain lakes of the Torgovaya River basin (Subpolar Urals) with special focus on the distribution of Siberian fish and invertebrate species. Aquatic communities of seven mountain lakes have been studied; three of them can be considered as glacial refugia inhabited by the resident form of Arctic grayling. Four species of amphibiotic insects have been identified in the chyme of two grayling species; their main range is in Siberia. The zoobenthos included 16 large taxa; among them, nematodes, entomostracans, and chironomids were dominant in abundance and dipteran and stonefly larvae were dominant in biomass. Twenty eight taxa typical for the fauna of the European northeast of Russia have been identified in the zooplankton. The recorded patterns of distribution of the local aquatic fauna are determined mainly by the glacial history of the Urals. It is assumed that rheophilic benthic invertebrates of Siberian origin colonized the Torgovaya riverbed in the postglacial period. [ABSTRACT FROM AUTHOR]

Knowledge of the fishes of northern New York can help with conservation planning and landscape interpretations. This report draws from fish surveys from the 1930s to 2018 to summarize and interpret the distribution of fishes in the region surrounding and including the Adirondacks. The study area, with its broad elevational gradient, includes lowland and upland ecoregions, for which we compare fish assemblages. Lowlands are the waters downstream of historic barriers to migration into the uplands (elevations of 62–215 m, depending on landscape slope). Uplands are the waters at higher elevations than the lowlands (above 168 m) that include the transitional and Adirondacks' elevations (above 305 m). In total, 114 fish species and 2 hybrids have been documented in northern New York; for the sake of convenience, the hybrids are tabulated as species here. Of the 116 taxa, 111 are in lowlands. Eighty percent are native to New York State, although patterns of nativity differ between the lowlands and the uplands. Specifically, natives make up 80% of the lowland group and 51% of upland group. Many of the species that are native to the lowlands do not occur naturally in the uplands, becoming widespread there only after transferal or stocking. The continued expansion of non-native species has caused changes in fish communities and losses of native species. In the uplands, 3 native species have been lost and 3 others dramatically reduced. In the lowlands, there has been relatively little change in species status over time. Brief annotations are provided for each of the 116 taxa, including summaries of recent studies, changes in their status before and after December 1989, and proposed conservation classifications. [ABSTRACT FROM AUTHOR]

Accurate abundance estimates are crucial for evidence‐based fisheries management. In rivers, drift dive counting and electrofishing are commonly used for quantifying fish abundance. However, the likelihood that fish are detected by these counting methods is affected by a range of factors, with substantial potential implications for the outcomes. Fish behavior and distribution also differs with light intensity, yet diel variation in abundance estimates produced by common enumeration methods has received little attention. Here, we present a comparison of diurnal and nocturnal counts of the landlocked population of Atlantic Salmon Salmo salar, known as "småblank," and Brown Trout Salmo trutta in a Norwegian river. Six drift dive transects and 12 electrofishing sites were surveyed at day and night in early autumn. During drift dives, småblank were exclusively observed at night. Brown Trout were observed by snorkelers both day and night but in significantly higher numbers at night (six times more Brown Trout per 100 m at night versus in the day). Catch per unit effort of backpack electrofishing was significantly higher at night than at daytime for both småblank and Brown Trout older than age 0 (202% and 108% higher, respectively). We argue that differences in drift dive counts were mainly caused by fish hiding in the substrate during the day and being more active at night, resulting in diel differences in detection rate. Further studies are needed to determine whether differences in electrofishing catches were caused by diel fish migrations or higher catchability at night. [ABSTRACT FROM AUTHOR]

Copyright of South China Fisheries Science is the property of South China Fisheries Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Food & Machinery is the property of Food & Machinery Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper investigates the ecological-economic sustainability of coral reef socio-ecological systems under fishing and environmental pressures. To achieve this, a dynamic, spatially explicit, multi-species, multi-fleet fisheries model is developed. Stochastic environmental shocks are assumed to alter coral cover and consequently the entire coral reef social-ecological system. The model is calibrated using ecological, socio-economic and environmental data in French Polynesia. Four exploratory fishing strategies and a goal-seeking strategy entitled Stochastic Multi-Species Maximum Sustainable Yield (SMMSY) are compared in terms of ecological-economic outcomes and sustainability of the socio-ecological system. The SMMSY turns out to promote ecological-economic sustainability. It is characterised by a global increase in fishing effort pointing to the relative current under-exploitation of the fishery. SMMSY balances the trophic level of catches after natural shocks and sustains the fundamental herbivore grazing process. SMMSY strategies are also more diversified in terms of temporality, gears, spatial distribution of fishing and target species. [ABSTRACT FROM AUTHOR]

Monitoring carnivore populations requires sensitive and trustworthy assessment methods to make reasonable and effective management decisions. The Eurasian fish otter Lutra lutra experienced a dramatic population decline throughout Europe during the twentieth century but is currently recovering in both distribution range and population size. In Austria, most assessments on otter distribution have applied a modified version of the so-called "British" or "standard" method utilizing point-wise surveys for otter spraints at predefined monitoring bridges. In this study, we synthesize several recent statewide assessments to compile the current otter distribution in Austria and evaluate the efficiency and sensitivity of the "monitoring bridge" approach in comparison to the "standard" method. The otter shows an almost comprehensive distribution throughout eastern and central Austria, while more western areas (Tyrol and Vorarlberg) are only partially inhabited, likely due to a still ongoing westward expansion. Furthermore, the bridge monitoring method utilizing presence/absence information on otter spraints reveals itself to be a time- and cost- effective monitoring tool with a tolerable loss of sensitivity for large-scale otter distribution assessments. Count data of spraints seem to be prone to observer bias or environmental influences like weather or flooding events making them less suitable for quantitative analyses. [ABSTRACT FROM AUTHOR]

Environmental DNA (eDNA) is increasingly used to noninvasively monitor aquatic animals in freshwater and coastal areas. However, the use of eDNA in the open ocean (hereafter referred to OceanDNA) is still limited because of the sparse distribution of eDNA in the open ocean. Small pelagic fish have a large biomass and are widely distributed in the open ocean. We tested the performance of two OceanDNA analysis methods—species-specific qPCR (quantitative polymerase chain reaction) and MiFish metabarcoding using universal primers—to determine the distribution of small pelagic fish in the open ocean. We focused on six small pelagic fish species (Sardinops melanostictus, Engraulis japonicus, Scomber japonicus, Scomber australasicus, Trachurus japonicus, and Cololabis saira) and selected the Kuroshio Extension area as a testbed, because distribution of the selected species is known to be influenced by the strong frontal structure. The results from OceanDNA methods were compared to those of net sampling to test for consistency. Then, we compared the detection performance in each target fish between the using of qPCR and MiFish methods. A positive correlation was evident between the qPCR and MiFish detection results. In the ranking of the species detection rates and spatial distribution estimations, comparable similarity was observed between results derived from the qPCR and MiFish methods. In contrast, the detection rate using the qPCR method was always higher than that of the MiFish method. Amplification bias on non-target DNA and low sample DNA quantity seemed to partially result in a lower detection rate for the MiFish method; the reason is still unclear. Considering the ability of MiFish to detect large numbers of species and the quantitative nature of qPCR, the combined usage of the two methods to monitor quantitative distribution of small pelagic fish species with information of fish community structures was recommended. [ABSTRACT FROM AUTHOR]

Chlorophyll-a (Chl-a) change details derived from HY-1C/D images in the waters of the Zhoushan archipelago were analyzed. A new Chl-a inverse model was built based on the relationship between the in situ Chl-a and the combination of red, blue and green bands of the coastal zone imager (CZI). Chl-a as well as fishery resources were analyzed. The results showed the following. (1) The Chl-a concentration in the waters of the Zhoushan archipelago was mainly in the range of 0.5~6 μg/L. High Chl-a area distributed in the west side of the study area, with a value of 3.5~5.5 μg/L. The Chl-a concentration in the east side of the study area was relatively lower, with a value of 0.5~2 μg/L. Chl-a around the islands was higher than that in the area far away from the islands. In addition, Chl-a concentration increased obviously downstream of the island. (2) The spawning ground of many fish in the waters of the Zhoushan archipelago was abundant, and its spatial-temporal variation was consistent with the change of Chl-a. (3) The islands interacted with the current, inducing upwelling upstream and vortex streets downstream. The complex hydrodynamic environment promoted a vertical exchange of water bodies, thereby resulting in an increase in suspended sediment concentration, nutrients, Chl-a and attracting fish. [ABSTRACT FROM AUTHOR]

An abundance of studies in marine systems have documented species range shifts in response to climate change, and many more have used species distribution models to project species ranges under future conditions. However, there is increasing interest in moving beyond a single‐species focus to understand how species redistribution alters ecosystem dynamics via changes in trophic interactions. We employed spatiotemporal models to characterize decadal‐scale changes in spatial overlap between the distribution of juvenile walleye pollock Gadus chalcogrammus and the distributions of four of its groundfish predators: arrowtooth flounder Atheresthes stomias, Pacific cod Gadus macrocephalus, Pacific halibut Hippoglossus stenolepis and adult walleye pollock. These fishes represent ecologically and commercially important species in a rapidly changing sub‐Arctic ecosystem, the eastern Bering Sea, Alaska, USA. We then examined whether changes in spatial overlap corresponded to changes in predation, using spatiotemporal models of predator stomach contents. We found marked shifts in spatial overlap between juvenile pollock and two predators (arrowtooth flounder and Pacific halibut) over 34 years, with changes in overlap corresponding to increases in population‐scale predation pressure. By contrast, we did not find clear relationships between spatial overlap and predation for Pacific cod and adult pollock, the two predators for which juvenile pollock constitute a much smaller diet proportion. Our findings highlight the complexity of predicting predation dynamics for generalist marine species and suggest a need for better process‐based methods for understanding the potential future ecological impacts of coupled species range shifts. However, simple metrics of spatial overlap between relatively specialized predators and their prey offer promise as a means to integrate predictions from species distribution models into ecosystem‐based fisheries management. [ABSTRACT FROM AUTHOR]

Accurate estimates of abundance are a cornerstone for resource managers to make effective decisions for fish conservation. However, multiple sampling methods often are required to sample fish communities, and ignoring the detection process can create substantial bias in latent state parameter estimation (e.g., abundance, survival). We developed a joint-species N-mixture model that integrated snorkel, seining, and electrofishing surveys to estimate factors affecting native and non-native fish distributions in the Santa Ana River, California. We found through data integration that native Santa Ana sucker (Catostomus santaanae) and arroyo chub (Gila orcuttii) were most abundant in wide stream channels, and the abundance of both native fishes were negatively correlated with non-native largemouth bass (Micropterus salmoides). Our results highlight the power of integrating multiple data sets into a single analysis and incorporating among-species correlation into abundance modeling. Our results also highlight a pattern of native fish declines that coincides with an expanding largemouth bass population, a concern for the management of native aquatic communities within the Santa Ana River. [ABSTRACT FROM AUTHOR]

Pre-planning for a rational survey design is essential to improve the reliability and efficiency of the acoustic assessment of fishery resources in large water bodies. In this study, we compared the differences in acoustic estimates of fish resources between triangular and parallel transect designs in the Three Gorges Reservoir (TGR, China), aiming to provide a reference for fishery acoustic survey planning in such canyon-shaped reservoirs. We conducted hydroacoustic surveys using an echosounder (SIMRAD EY60, 120 kHz) in the Yangtze mainstream near the dam and an adjacent tributary with triangular and parallel designs. The independent samples t-test showed that the acoustic estimates of fish density were not significantly different between these two types of survey designs for both mainstream and tributary. The Fisher's exact test indicated that there was no significant difference in fish size distributions, as measured by target strength (TS), between survey designs either. In view of reducing time spent in nearshore areas to improve efficiency and ensure safety, we recommend that the triangular design with reliable coverage be given priority for hydroacoustic sampling in the TGR and similar canyon-shaped reservoirs, especially when sampling at night. [ABSTRACT FROM AUTHOR]

Exact knowledge of the physical structures of different river sections that govern their ecological structure and function is essential for the efficient conservation and management of riverine ecosystems. Eleven Andean river basins (Maipo, Rapel, Mataquito, Maule, Itata, Biobío, Toltén, Valdivia, Bueno and Puelo) comprise large scale latitudinal and altitudinal gradients and accommodate 71% of the Chilean population that strongly depend on their ecosystem services. Here, based on 16 hydrogeomorphic variables (on basin, valley and channel scales), we assessed the riverine landscapes (Functional Process Zones; FPZs) of these river basins using a top-down multivariate statistical approach. Two steep valley and downstream slope FPZs, three sinuous FPZs and two braided FPZs emerged in 8906 river sections. The proportion of the occurrence of FPZs was characterised by a clear latitudinal pattern which is strongly related to the proportions of each river basin within the large morphostructural units of Chile. As such, the proportion of each river basin within the Andes Cordillera, Central Valley and Coastal Cordillera is a strong driver of the fluvial geomorphology and, thus, of the FPZs' arrangement in each river network. FPZ classification captured geomorphic diversity that coincided with the latitudinal and altitudinal gradients of Chilean Andean river basins strongly related to the hydrological characteristics of the assessed river basins and large scale spatial distribution of fish fauna endemism. As such, the identified large geomorphic units (FPZs) that are strongly tied up with hydrology and ecology hierarchies of riverine landscape provide robust operational tools that can be instrumental for river ecosystem monitoring and management at a basin scale. [ABSTRACT FROM AUTHOR]

Introduced fish are a widespread ecological threat in originally fishless high mountain lakes. However, basic distribution data are largely missing for most high mountain regions.Using time‐consuming standard methods (e.g. Nordic standard fishing nets) to assess fish distribution and relative densities at a relevant spatial scale can be impracticable, because of the large number of high mountain lakes. To overcome this problem, alternative rapid monitoring methods would be helpful.Visual encounter survey (VES) is a candidate method that enables observing fish from the shoreline. It takes only minutes to implement and is already widely used for amphibian monitoring in high mountain lakes and ponds. VES was evaluated as a method for monitoring introduced salmonids and cyprinids (the most widespread fish families) in 52 high mountain lakes.The probability of detecting both families by VES rapidly approaches 100% as the relative densities of fish increase, and false absences are restricted to populations living at low relative densities. VES also provides simple indications about fish relative densities, distinguishing between high‐density and low‐density populations.As VES usually does not enable fish species identifications, we propose VES as a useful method to describe large fish distribution inventories, not needing high taxonomic detail, but necessary for planning large‐scale conservation measures. [ABSTRACT FROM AUTHOR]

Francisella orientalis is an important bacterial pathogen of marine and freshwater fish with worldwide distribution. Fish francisellosis is a severe subacute to chronic granulomatous disease, with high mortalities and high infectivity rates in cultured and wild fish. To date, there is no approved vaccine for this disease. In this study, we evaluated the efficacy of a defined F. orientalis pathogenicity determinant protein A (pdpA) mutant (ΔpdpA) as a live attenuated immersion vaccine against subsequent immersion challenge with the wild‐type organism. Immunized Nile tilapia Oreochromis niloticus were protected (45% relative percent survival) from the lethal challenges and presented significantly lower mortality than nonvaccinated and challenged treatments. Although serum IgM was significantly higher in immunized fish, similar bacterial loads were detected in vaccinated and nonvaccinated survivors. In conclusion, although the F. orientalis ΔpdpA is attenuated and effectively stimulated an adaptive immune response, the low relative percent survival and high bacterial persistence in survivors of immunized and challenged treatments indicates low suitability of ΔpdpA as a mucosal vaccine for tilapia under conditions used in this study. [ABSTRACT FROM AUTHOR]

The Pacific saury (Cololabis saira) is one of the most commercially important pelagic fishes in Asia–Pacific countries. The oceanographic environment, especially the Oyashio Current, significantly affects the distribution of Pacific saury, and may lead to variations in their migration route and the formation of fishing grounds in Japanese coastal region and the high seas. In this study, six oceanographic factors, sea surface temperature (SST), sea surface chlorophyll-a concentration (SSC), sea surface salinity (SSS), sea surface height (SSH), mixed layer depth (MLD), and eddy kinetic energy (EKE), were associated with the monthly catch per unit effort 1 (monthly CPUE1, ton/vessel) and the monthly CPUE2 (ton/day) of Pacific saury from Chinese fishing vessels during the optimal fishing periods (September–November) in 2014–2017. The gradient forest analysis showed that the performance of monthly CPUE1 was higher than monthly CPUE2 and SST was the most important oceanographic factor influencing monthly CPUE1, followed by EKE. The generalized additive model indicated that SST, SSH, and EKE negatively affected monthly CPUE1, whereas SSC, SSS, and MLD induced dome-shaped increases in monthly CPUE1. The distributions of fishing locations are likely to form along Offshore Oyashio current and meanders, especially in October and November. Synchronous trends in the relationship between the intrusion area of the Oyashio and relative abundance variation index suggest that an increase in the intrusion area of the Oyashio causes more Pacific saury to migrate to the Japanese coastal region, and vice versa. These findings extend our understanding of the effects of the oceanographic environment on Pacific saury. [ABSTRACT FROM AUTHOR]

The relationships between environmental factors and fish density are closely related, and species distribution models (SDMs) have been widely used in exploring these relationships and predicting the spatial distribution of fishery resources. When exploring the prediction of the spatial distribution of species in different seasons, the method of choosing the appropriate approach to the season will help to improve the predictive performance of the model. Based on data collected from 2015 to 2020 during a survey off southern Zhejiang, the Tweedie-GAM was used to establish the relationship between the density of Decapterus maruadsi and environmental factors at different modeling approaches. The results showed that water temperature, salinity and depth were the main factors influencing D. maruadsi, and they operated through different mechanisms and even resulted in opposite trends of density in different seasons. Spatially, the two modeling approaches also differed in predicting the spatial distribution of D. maruadsi, with the seasonal model showing a higher density trend in inshore waters than in offshore waters in spring but showing the opposite trend in summer and autumn, which was more consistent with the actual spatial distribution of the resource. By analyzing the effects of two different approaches on the prediction of fishery resources, this study aims to provide research ideas and references for improving the predictive performance of SDMs. [ABSTRACT FROM AUTHOR]

This study provides baseline data on the mullid fish assemblages based on their morphometries on a shelf of the most oligotrophic water of the Mediterranean Sea, Antalya Gulf. The distribution of fish abundances, biomasses, total length, sex composition, growth parameters, and ecological fish assemblages was studied along three transects (each had a series of bottom depths of 10, 25, 75, 125, and 200 m) between spring 2014 and winter 2015, representing the winter, spring, summer and autumn seasons. Four different species of the Mullidae family: the red mullet (Mullus barbatus), the striped red mullet (M. surmuletus), the golden-banded goatfish (Upeneus moluccensis) and the Por’s goatfish (U. pori) were found and subjected to distributional analyses. Excluding M. surmuletus, all of the mullid fish were commonly and abundantly found. There was a definite depth segregation among their distributions, but no seasonal differences occurred. Mediterranean meadows are attractive areas for mullid species, especially for M. surmelatus. The spatial distributional pattern of U. pori was in complete contrast to that of M. surmuletus. Overall, the females (F) outnumbered the males (M) significantly in space (region and depth) and time (season). The morphometric parameters (length-related and growth parameters) were estimated to increase comparatively from east to west in the Mediterranean Sea. Ecologically, the mullid assemblages depended on the seafloor depth, bottom type (habitat and sedimentary characteristics), water productivity and dissolved oxygen content and salinity, and benthic composition. [ABSTRACT FROM AUTHOR]

[Display omitted] • Gill monogeneans on Neotropical cichlid fish were studied. • Species of Gussevia , Trinidactylus , and Scadicleithrum were identified. • The high diversity of cichlid monogeneans was revealed. • Divergent lineages of Sciedicleithrum from South America and Mexico were inferred. • Host switch and duplication were the main coevolutionary events for monogeneans. Host-parasite coevolution is one of the main topics of the evolutionary biology of host-parasite associations. The majority of monogeneans parasitizing fish exhibit a high degree of host specificity. As a result, their evolutionary history might be intertwined with that of their fish hosts. The Cichlidae represent a diverse group of secondary freshwater fish with disjunctive distribution. Host-specific dactylogyrid monogeneans commonly parasitize cichlid fish. Their high diversity is associated with the main areas of cichlid distribution, i.e., Neotropical America and Africa. Nevertheless, the parasite fauna of cichlids from Neotropical America is still underexplored. A total of 31 cichlid species were examined for the presence of monogeneans, with 20 of them being parasitized. On these cichlids, 30 monogeneans belonging to the genera Gussevia , Trinidactylus , and Scadicleithrum were identified, 17 of them potentially representing new species for science. Phylogenetic analyses revealed three monophyletic groups of Neotropic cichlid monogeneans. Genus Gussevia was monophyletic, while Sciadicleithrum resulted polyphyletic. Sciedicleithrum from South America and Sciadicleithrum from Mexico represented two divergent lineages. The plesiomorphic Neotropical cichlid host group for dactylogyrid monogeneans was Cichlini, from which the representatives of other Neotropical cichlid tribes were colonised. Cophylogenetic analyses revealed a statistically significant cophylogenetic signal in the investigated host-parasite system, with host switch and duplication representing the main coevolutionary events for monogeneans parasitizing Neotropical cichlids. This scenario is in accordance with previous studies focussed on dactylogyridean monogeneans parasitizing freshwater fish in Europe and Africa. [ABSTRACT FROM AUTHOR]

Factors including human dispersal, climate change and varied environmental stressors are altering fish species distributions. Range expansions are producing new records of freshwater species which were rare or previously absent from regional jurisdictions (states, provinces and territories). Simultaneously, species are facing declines and local extirpations in some areas of their distribution. The Resist‐Accept‐Direct (RAD) framework can provide guiding principles for how declining, newly arrived, or range expanding freshwater fishes should be managed and how range‐wide trends can be considered in local management and conservation decisions. We examine the principles of the framework and provide an example decision tree which is applied to examples ranging from resisting the establishment of potentially harmful non‐native fishes, to accepting and providing refuge to those species threatened in other parts of their ranges, to directing the migration of fishes which improve ecosystem services. Applying this framework may improve coordination between agencies aiming to improve the resilience of freshwater ecosystems. [ABSTRACT FROM AUTHOR]

Copyright of South China Fisheries Science is the property of South China Fisheries Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Qilian Mountain Basin, on the north-eastern edge of the Qinghai-Tibet Plateau (QTP), supports a high diversity of native and endemic fish. However, the detailed species inventory and distribution patterns concerning fish in the whole Basin remain unknown, which hinders the conservation of biodiversity and assessment of ecological health. We compiled a comprehensive species richness and distribution database of freshwater fish in the Qilian Mountain Basin, based on field investigations and exhaustive data collection from 50 rivers or lakes. Then, we elucidated a distribution pattern using clustering and ordination analyses based on a β matrix with species presence/absence data. A total of 79 freshwater fish species within eight orders, 17 families and 42 genera were recorded. The Qilian Mountain Basin could be grouped into six systems, which match the six Basins (i.e. Heihe River Basin, HHR; Qaidam Basin, QDM; Qinghai Lake Basin, QHL; Shule River Basin, SLR; Shiyang River Basin, SYR; Yellow River Basin, YR), based on the fish distribution pattern. Additionally, the spatial pattern of species distribution showed the distance decay of taxonomic similarity. Our results demonstrate that riverine connectivity resulting from historical processes plays a vital role in shaping the freshwater ichthyofauna of High Central Asia. These findings will be valuable for future systematic conservation of fish in the Qilian Mountain Basin. [ABSTRACT FROM AUTHOR]