Fish Species Research Articles

Sustainable fishing: a study on barrier traps in Indonesia

Fishermen from Indonesia are uncertain whether the timing and placement of Belats (guiding barrier traps) affects their catch. To answer this question and improve the long-term viability and productivity of the Belat fishery, this study described the catch composition, productivity, and efficiency of Belat in Tanjung Batu Village, Kotabaru Regency, Indonesia. Two Belats consisting of a leader net, playground, and chamber net, were used in this study: Belat-A was larger than Belat-B in both length and breadth. Belat-A was deployed at 2 km from the shoreline, while Belat-B was installed at 1.5 km away, starting at 10 a.m. over a 24-h and a 48-h period, respectively. Results showed that Belat-A outperformed Belat-B, capturing twice the number of catch (970 versus 460) and 1.6 times the weight (92.6 kg versus 59.1 kg) across ten fish species between 14-50 cm of total length. However, Belat-B achieved similar productivity rates in half the operational time, making it more time-efficient. All fish caught were fresh and marketable, while the method itself was considered environmentally friendly. Several factors that affected the Belat catch and recommendation for upcoming Belat studies are also discussed.

Diet and trophic structure of fishes in the Barents Sea: between empty and full stomachs - large individual variability follows a common pattern.

More than 27,000 stomachs from 70 species of fish were collected from the Barents Sea in 2015. Quantitative stomach content expressed relative to the body weight of the predator fish (g g-1 as %) varied by four to five orders of magnitude for six species with the largest sample size (Atlantic cod Gadus morhua, haddock Melanogrammus aeglefinus, Greenland halibut Reinhardtius hippoglossoides, long rough dab Hippoglossoides platessoides, polar cod Boreogadus saida, and Atlantic capelin Mallotus villosus). The quantitative stomach contents of individual fish followed a common and strict statistical relationship for predator species or groups of species (by families), and for prey categories across predator species. The common pattern was log-normal-like and was modelled with good fit by different types of right-skewed distributions, that is, variants of the Box-Cox, generalized inverse Gaussian, inverse gamma, or gamma distributions. The long tail in the high end reflects high variation with no clear sign of a plateau, as could be expected from the concept of a "full stomach". This is interpreted to reflect that high stomach contents are rare events that are sampled at low frequencies. The maximum recorded stomach content varied from 1% to 34% of body weight for 55 species of fish, being positively correlated (R2 = 0.45) with sample size. About a third of the stomachs were empty, and the low tail of the log-normal-like distribution represents the transition to empty stomachs. The amount of food in the stomachs was overall low compared to maximum values, with mean and median of 2.0% and 1.1%, respectively, for the 17,873 stomachs containing food. Supported by bioenergetic considerations, this suggests relatively low feeding rates of the various fish predators but sufficient to meet their energy demands.

Ontogeny of adenohypophyseal cells, pituitary gland development, and structure in adults of Astyanax lacustris (Teleostei, Characiformes): an emerging Neotropical model fish species.

Pituitary gland morphogenesis and the ontogeny of the adenohypophyseal (AH) cells of Astyanax lacustris are presented herein. This Characiformes species shows great ecological and commercial importance, and it has been increasingly used as animal model. For this study, A. lacustris specimens were collected from 0.5 to 120days after hatching (dah) (adults). The entire animal or its head was appropriately fixed, and after histological processing, the sections were subjected to histochemical and immunohistochemical reactions, using homologous and heterologous antibodies. The first AH cells of A. lacustris were detected at 1 dah by the immunostaining of prolactin (PRL)-producing cells. The morphology of the gland presented changes in shape throughout the development, starting with elongation but more oval at the end. The neurohypophysis was differentiated at 3 dah, along with the identification of adrenocorticotropic hormone (ACTH), melanotropic hormone (MSH), thyroid-stimulating hormone (TSH), and follicle-stimulating hormone (FSH)-producing cells. Identification of the immunoreactive cells to anti-luteinizing hormone (LH), anti-somatolactin (SL), and anti-growth hormone (GH) antibodies occurred at 5 dah. At 20 dah, an increase in pituitary proportions and the presence of the pituitary stalk were observed. At 60 dah, the pituitary gland already had the same shape and distribution of AH cells seen in the adult. The ontogeny of adenohypophyseal cells in A. lacustris corroborates the heterogeneity in the appearance of these cell types in teleosts and suggests that these hormones actively participate during the post-hatching development of this species, even before the establishment of all endocrine axes. Our findings contribute to understanding the morphogenesis of the hypothalamic-pituitary axis in South American teleosts, providing essential data for the development of future studies related to pituitary gland morphophysiology under normal or experimental conditions.

Utilizing Invasive Pterygoplichthys pardalis as a Sustainable Fish Meal Substitute and Euphorbia hirta Extract Supplement: Effects on Growth Performance, Organosomatic Indices, Hematological Profiles, and Serum Biochemistry in Chinese Bullfrogs (Hoplobatrachus chinensis)

This research examined the efficacy of substituting commercial fish meal (CFM) with Pterygoplichthys pardalis meal (PPM) in Hoplobatrachus chinensis diets, with and without Euphorbia hirta extract (EHE) supplementation. The study utilized six dietary treatments: a control diet (0% PPM, no EHE) and five experimental diets with varying PPM levels (0%+, 25%+, 50%+, 75%+, and 100%+), each fortified with 300 mg/kg EHE. The experiment spanned 90 days. The analysis revealed that PPM exhibited superior amino acid profiles compared to CFM, both in quality and quantity, while CFM demonstrated higher fatty acid content. The growth metrics showed a significant decline only in the group receiving 100% PPM replacement with EHE supplementation. Most organosomatic indices remained consistent across the treatments, with the exception of intraperitoneal fat, which decreased in all EHE-supplemented groups. Blood parameters, including white blood cells, red blood cells, and hematocrit, along with serum proteins (total protein, globulin, and albumin), displayed an upward trend in all EHE-supplemented groups. The 50%+ and 75%+ PPM replacement groups exhibited significantly elevated serum glucose levels (p < 0.05). Liver enzymes (alanine transaminase and aspartate transaminase) showed no significant variations among the treatments. The results indicate that PPM can serve as an effective replacement for up to 75% of CFM in H. chinensis feed, without compromising their growth performance. Moreover, supplementing with EHE helps to enhance essential biochemical indices in the body, without adversely affecting liver function. This investigation offers valuable perspectives on the development of sustainable aquaculture feed and the potential application of invasive fish species in aquatic animal nutrition.

Assessment of Glyphosate Roundup Turbo (450 g/l) on Haemato-biochemical Indices of Freshwater African Catfish (Clarias gariepinus) Fingerlings

The escalating use of glyphosate-based herbicides in agricultural practices has sparked concerns regarding their potential ecological impact. This study undertakes a comprehensive investigation into the acute ecotoxicological effects of a brand-new glyphosate (Roundup Turbo 450 g/l) on haematology and biochemical indices of Clarias gariepinus a commercially vital fish species in Nigeria. Fish were exposed to 0.0 as control, 0.5, 0.7, 0.9 and 1.2 mg/l glyphosate for 96 hours in the laboratory. Water quality parameters monitored were temperature, pH, dissolved oxygen electrical conductivity, nitrate and nitrite. The blood, liver and gills were extracted and analyzed. Haematological and biochemical analyses revealed significant changes (P < 0.05) as concentration increases. The decrease in red blood cell, pack cell volume, haemaglobin and white blood cell was indicative of glyphosate-induced hematotoxicity. Biochemical analyses disclosed alterations in enzymatic activities within liver and gill tissues, including significant increase in alanine aminotransaminases, aspartate aminotransferase and alkaline phosphatase, suggesting hepatic and branchial dysfunction and decrease in total protein, globulin and albumin, showing enhanced disruption in protein synthesis. Glucose and albumin in liver were not detected. Behavioral observations indicated the fish heightened stress response, characterized by erratic swimming patterns, increased agitation, equilibrium loss, hyperactivity and skin erosion. The 96-hour LC50 value for this study was 2.50 mg/l and it highlights glyphosate roundup turbo’s potential to exert detrimental effects on Clarias gariepinus populations. These findings underscore the imperative for sustainable agricultural practices, judicious pesticide management, and rigorous environmental monitoring to mitigate the ecological risks associated with glyphosate use.

Multi-omics dataset of individual variations in growth performance of large yellow croaker

Large yellow croaker (Larimichthys crocea) is a highly economically important marine fish species in China. However, substantial individual variations in growth performance have emerged as a limiting factor for the sustainable development of the large yellow croaker industry. Gut microbiota plays a crucial role in fish growth and development by regulating metabolic processes. To explore these dynamics, we employed metagenomics, transcriptomics, and untargeted metabolomics to comprehensively analyze the structure of the intestinal microbiome and its relationship with intestinal metabolism and host gene expression. We constructed association models for “gut microbiota–differentially expressed genes”, “differentially expressed genes–metabolites,” and “gut microbiota–metabolites.” Sequencing data and LC–MS/MS raw data have been deposited in NCBI and MetaboLights databases for public access. Our findings offer critical insights into the molecular mechanisms underlying growth variations in L. crocea and provide valuable data for the selective breeding of improved strains.

Microplastics in pelagic and demersal fishes from the Meghna River estuary, Bangladesh

Microplastics (MPs) were investigated in four fish species viz., paradise threadfin (Polynemus paradiseus), corsula mullet (Rhinomugil corsula), flathead sillago (Sillaginopsis panijus) and king gobyeel (Taenioides sandwipi), which were collected from the Meghna River estuary in Bangladesh. The gastrointestinal tracts (GITs) of fishes (n = 80 in total) were examined for the presence of MPs following alkali digestion, microscopic observation and μ-FTIR analysis. A total of 573 MPs were detected across all four fish species, indicating the presence of MPs in 81.3% of the fish samples. On average, there were 7.16 ± 4.33 MP items/fish, 2.16 ± 1.76 items/g of GIT and 0.15 ± 0.12 items/g of body weight. Polyethylene, polypropylene and nylon were the most abundant polymers, comprising 47%, 23% and 19%, respectively, according to μ-FTIR analysis. The majority of MPs were fibers (62.48%), with white being the dominant color. R. corsula demonstrated the highest number of MPs in the < 500 μm size range, suggesting that smaller particles are more bio-available to pelagic fish. The findings confirm the contamination of the Meghna River estuary by MPs, and their presence in local fish raises concerns about potential public health risks through the food chain.

Endemic and Invasive Species: A History of Distributional Trends in the Fish Fauna of the Lower New River Drainage

Invasive species are often central to conservation efforts, particularly when concerns involve potential impacts on rare, endemic native species. The lower New River drainage of the eastern United States is a watershed that warrants conservation assessment, as the system is naturally depauperate of native fish species and it is nearly saturated with non-native fish species: there are 31 natives, including at least nine endemic taxa, and 63 non-natives. For endemic taxa, we examined temporal distribution shifts (range expansions or contractions) based on percent change in the occupied watershed area. We contrasted these findings with time series analyses on distribution trends of non-native minnows (Leuciscidae) and darters (Percidae) based on growth curve models of the cumulative sum of the total area of occupied 12-digit hydrologic unit codes. We documented range reductions for six of nine endemic taxa. We determined that 11 of 18 non-native minnows and 6 of 8 non-native darters were invasive based on range expansions and associated invasion curve models. The endemic taxa are of conservation concern given the limited distribution ranges and documented population declines. Although among-species comparisons of range shifts do not support causal inference, documentation of changes in distribution ranges of endemic and invasive species is critical to inform conservation efforts.

Composition of pelagic fish in commercial landings of the longline fishery in the Costa Rica Pacific during 2015-2021

Longline fishing in the Pacific of Costa Rica targets multiple species of large pelagic fishes and faces challenges in assessment due to lack of data. This study analyzes landing data of pelagic fish in this fishery using unconventional statistical methods, to better understand the dynamics and provide recommendations for improving data collection and analysis. Landing data reported during 2015-2021 were examined. A descriptive and comparative analysis of landings was conducted using Spearman correlation tests and Non-Metric Multidimensional Scaling (NMDS) to visualize patterns in catch composition. Permutational Multivariate Analysis of Variance (PERMANOVA) and Similarity Percentage Analysis (SIMPER) were employed to identify significant differences between fleet types, landing ports, months, and years, as well as species contribution to these differences. The annual mean total landing of large pelagic fish was 7531.01 tons, with 39.14% corresponding to sharks, 24.34% to billfish (Istiophoridae and Xiphiidae), 18.05% to mahi-mahi, and 14.94% to tuna. Statistically significant differences were found between fleet types, landing ports, months, and years. Shark landings were the least correlated (rho=0.36) and had the greatest influence on variation by fleet type. An increase in the similarity of catch composition by port since 2015 was observed. In addition, a shift towards increasingly less selective fishing over the study period was evident. Our findings highlight the urgent need for advanced research methodologies to address gaps in data collection for commercial fisheries in Costa Rica. Improving these methods is crucial to ensure that management policies are based on accurate and comprehensive information. Results highlight the need for a comprehensive strategy involving diverse stakeholders to improve our understanding and ensure the sustainability of fisheries and the preservation of marine ecosystems in Costa Rica.

Climate-Induced Changes in River Hydrological and Thermal Conditions in a Large Basin: Implications for Diadromous Fish Migration

Climate-induced changes in river conditions, such as water temperature and current velocity, can disrupt species migration patterns by altering the conditions encountered during migration. We assessed these impacts across the Loire River basin in Europe by compiling long-term fish passage data for three diadromous fish species at fishways, alongside reconstructed time series of water temperature and current velocity. We considered both water temperature and current velocity on days when migration was observed as ''suitable conditions'' for the species' upstream migration. Our findings for the 1963–2019 period revealed that trends in the frequency of suitable conditions for upstream migration were species-specific. For Atlantic salmon, particularly fall migrants, the frequency of suitable conditions has declined over time in certain areas. In contrast, the frequency of suitable migration conditions for both allis shad and sea lamprey has shown an overall increase across the basin. This study offers policy-makers and environmental managers valuable insights for developing effective, spatially explicit strategies to preserve diadromous fish populations amid ongoing climate change.

A Chromosomal-level genome assembly and annotation of fat greenling (Hexagrammos otakii)

Fat greenling (Hexagrammos otakii Jordan & Starks, 1895) is a valuable marine fish species, crucial for aquaculture in Northern China due to its high-quality meat and significant economic value. However, the aquaculture industry faces challenges such as trait degradation, early sexual maturity, and disease susceptibility, necessitating advanced genomic interventions for sustainable cultivation. This study presents the first chromosomal-level genome assembly of H. otakii, achieved using PacBio long-read sequencing and Hi-C technology. The assembly yielded a genome size of 682.43 Mb with a contig N50 size of 2.39 Mb and a scaffold N50 size of 27.83 Mb. The completeness of genome assessed by BUSCO is 96.99%. A total of 22,334 protein-coding genes were predicted, with 21,619 (96.80%) functionally annotated across various protein databases. This genomic resource is a step forward in supporting the breeding, germplasm conservation, and enhancement of H. otakii, facilitating genetic studies and the development of strategies for disease resistance and growth optimization in aquaculture.

DNA barcoding of invasive Gambusia holbrooki Girard, 1859 and Atherina boyeri Risso, 1810 inhabiting Upper Euphrates River Basin, Türkiye

The main contributor to Türkiye’s abundant freshwater fish biodiversity is its geographic location. This fauna consists of endemic, native, and non-native fish species. The introduction of Gambusia holbrooki Girard, 1859 to Lake Amik in the 1920s for the biological control of malaria was the first introduction of nonnative species to Türkiye. Atherina boyeri Risso, 1810 and other nonnative fish species have recently been introduced to Türkiye’s freshwaters. In this research, the first records of invasive Gambusia holbrooki (Keban Dam Lake, in Elazığ Province) and Atherina boyeri (Karakaya Dam Lake, in Elazığ Province) are cited from the Upper Euphrates River Basin in the Eastern Anatolia Region of Türkiye. In situ electrofishing equipment was used to gather the specimens. Fish muscle samples were used to extract genomic DNA, which was then used to barcode the mitochondrial cytochrome c oxidase subunit I (COI) gene to identify different species of fish. The identification of invasive fish species using DNA barcoding is an effective technique, as evidenced by the comparison of amplified COI sequences to the BLAST database.

Exploitation and Mortality of the West African Fiddler Crab (Uca Tangeri) in Mbo River, Niger Delta, Nigeria

Studies on the exploitation and mortality of the crab Uca tangeri in Mbo river of Akwa Ibom State, Nigeria, were conducted for 12 consecutive months. Exploitation was calculated to be -1.62. The negative value could imply that the species is not fished or under-fished. Length-frequency data was analyzed using FISAT software. Using the Shepherd’s method, asymptotic length (L∞) was 3.99cm, while the Von Bertalanffy Growth Function (VBGF) K was 0.10. Meanwhile, the Powell-Wetheral plot estimated asymptotic length (L∞) was 3.58cm and Z/K was 0.72yr-1. The natural mortality(M) of Uca tangeri was 0.71yr-1. However, using length-converted catch curve, total mortality (Z) was estimated to be 0.27yr-1. The instantaneous fishing mortality (F) was calculated to be -0.44yr-1, indicating that it was not a highly fished species.

Floodplain forests drive fruit-eating fish diversity at the Amazon Basin-scale

Unlike most rivers globally, nearly all lowland Amazonian rivers have unregulated flow, supporting seasonally flooded floodplain forests. Floodplain forests harbor a unique tree species assemblage adapted to flooding and specialized fauna, including fruit-eating fish that migrate seasonally into floodplains, favoring expansive floodplain areas. Frugivorous fish are forest-dependent fauna critical to forest regeneration via seed dispersal and support commercial and artisanal fisheries. We implemented linear mixed effects models to investigate drivers of species richness among specialized frugivorous fishes across the ~6,000,000 km2 Amazon Basin, analyzing 29 species from 9 families (10,058 occurrences). Floodplain predictors per subbasin included floodplain forest extent, tree species richness (309,540 occurrences for 2,506 species), water biogeochemistry, flood duration, and elevation, with river order controlling for longitudinal positioning along the river network. We observed heterogeneous patterns of frugivorous fish species richness, which were positively correlated with floodplain forest extent, tree species richness, and flood duration. The natural hydrological regime facilitates fish access to flooded forests and controls fruit production. Thus, the ability of Amazonian floodplain ecosystems to support frugivorous fish assemblages hinges on extensive and diverse seasonally flooded forests. Given the low functional redundancy in fish seed dispersal networks, diverse frugivorous fish assemblages disperse and maintain diverse forests; vice versa, diverse forests maintain more fish species, underscoring the critically important taxonomic interdependencies that embody Amazonian ecosystems. Effective management strategies must acknowledge that access to diverse and hydrologically functional floodplain forests is essential to ensure the long-term survival of frugivorous fish and, in turn, the long-term sustainability of floodplain forests.

Emergent patterns of reef fish diversity correlate with coral assemblage shifts along the Great Barrier Reef

Escalating climate and anthropogenic disturbances draw into question how stable large-scale patterns in biological diversity are in the Anthropocene. Here, we analyse how patterns of reef fish diversity have changed from 1995 to 2022 by examining local diversity and species dissimilarity along a large latitudinal gradient of the Great Barrier Reef and to what extent this correlates with changes in coral cover and coral composition. We find that reef fish species richness followed the expected latitudinal diversity pattern (i.e., greater species richness toward lower latitudes), yet has undergone significant change across space and time. We find declines in species richness at lower latitudes in recent periods but high variability at higher latitudes. Reef fish turnover continuously increased over time at all latitudes and did not show evidence of a return. Altered diversity patterns are characterised by heterogeneous changes in reef fish trophic groups across the latitudinal gradient. Shifts in coral composition correlate more strongly with reef fish diversity changes than fluctuations in coral cover. Our findings provide insight into the extent to which classic macroecological patterns are maintained in the Anthropocene, ultimately questioning whether these patterns are decoupling from their original underlying drivers.

Effects of Feed Supplementation With Fulvic Acid on the Systemic and Mucosal Protective Mechanisms of Juvenile Rainbow Trout (Oncorhynchus mykiss).

Rainbow trout (Oncorhynchus mykiss) is an important fish species raised in aquaculture, but it is susceptible to stress, infections diseases. The present study aimed to determine the effects of fulvic acid feed addition on the systemic and mucosal protective mechanisms of juvenile rainbow trout and to elucidate the underlying molecular mechanisms of changes in the gut. Rainbow trout (4.30 ± 0.6 g) diet was supplemented with different levels of fulvic acid: 0% (Control), 0.5%, 1% and 2%. At the end of 8-week feeding trial, growth parameters such as final weight gained weight (%), SGR (F1%) increased, and FCR (all levels) decreased significantly compared to the control group. We found that the activity of lysozyme, glutathione peroxidase, and catalase in the serum were significantly improved, especially after the addition of 0.5% and 1% of fulvic acid. At the same time, the immunoglobulin concentration in the skin mucus was increased with 0.5% supplementation. However, the expression of tnf-α, il-6 and gpx in the intestine was strongly upregulated after supplementation with 2%, indicating oxidative stress and inflammation with this level of fulvic acid inclusion. Furthermore, the mucus lysozyme activity was reduced at this concentration, which can increase the susceptibility to pathogen invasion. The results suggest that adding 0.5%-1% of fulvic acid to the feed of juvenile rainbow trout can help to improve their immune and antioxidative defenses and thereby support the wellbeing of fish.

Does the Fishery or Climate Change Drive Commercial Catches in a Shallow Eutrophic Lagoon?

ABSTRACTClimate change has significantly affected the Curonian Lagoon, the largest coastal lagoon in Europe, which is of great economic importance to fisheries and tourism. We modeled how environmental factors and fisheries affected recruitment and subsequent catches of pikeperch (Sander lucioperca L.) and common bream (Abramis brama L.) in the lagoon. Recruitment, catch per unit effort (CPUE), environmental variables, and fishery catch, and effort were used to construct Bayesian belief networks (BBNs) for both fish species. Catches of pikeperch and common bream depended more on fishing effort than recruitment. Environmental factors (temperature and riverine discharge) were only weakly related to catches of pikeperch and common bream. Changes in salinity and temperature are expected to have only minor direct effects on populations of pikeperch and common bream.

ATL_FISHREF: A 12S mitochondrial reference dataset for metabarcoding Atlantic fishes frequently caught during scientific surveys in the Bay of Biscay

AbstractThe biodiversity crisis driven by anthropogenic pressures significantly threatens marine ecosystems. The rate of climate change and anthropogenic impacts outpace our traditional observation tools' capabilities, underscoring the urgency for new assessment methods. Environmental DNA (eDNA; DNA traces released by organisms) metabarcoding, a non‐invasive method widely developed over the last decade, represents a promising biomonitoring tool thanks to a large spatio‐temporal coverage, high detection of rare species and its time and cost‐effectiveness. However, capturing fish diversity using eDNA requires genetic reference databases, currently lacking. Improving reference databases relies on opportunistic sampling enabling the reporting of sequences for new species. The data provided here consists of barcoding 86 species of fishes over the 12S mitochondrial DNA gene. We generated 156 sequences of the mitochondrial 12S gene adapted to the “Teleo” barcodes from fishes sampled in the Bay of Biscay (BoB; Northeast Atlantic, France) between 2017 and 2019. In addition, we provided each individual the barcode details (Genbank accession number, chromatograms), a photograph, 5 ecomorphological measures and 11 life‐history traits documenting ecological functions (e.g., dispersion, habitat use, diet). Furthermore, we provided the sampling metadata (e.g., date, time, gear, coordinates, depth) and environmental variables measured in situ (e.g., conductivity, water/air temperature). This data set is valuable to improve the Northeast Atlantic eDNA genetic database, thus helping to better understand the effects of environmental forcing in the BoB, a transition zone housing mixed assemblages of boreal, temperate, and subtropical fish species susceptible to display variability in functional traits to adapt to changing conditions. The detailed Metadata for this abstract published in the Data Article section of the journal is available in MetaCat in JaLTER at https://jalter.diasjp.net/data/ERDP-2024-09.

Pacific ocean perch and Atka mackerel research in the Pacific waters of the Northern Kuril Islands and Eastern Kamchatka in February-April 2024

The aim: obtain data on the biology, distribution and abundance of the Pacific ocean perch, Atka mackerel, by-catch species, and monitor aquatic biological resources.The methods: in the course of specialized fishing, fishing information was collected and ichthyological work was carried out according to the generally accepted methodology.The newness: expeditionary work is a continuation of many years of scientific research on the state of commercial populations of valuable fish species in the western part of the Bering Sea and Eastern Kamchatka and the North Kuril Islands.Results: concentrations of Pacific perch were noted in the area of Cape Kamchatsky, Cape Kronotsky, and in the area of Shiashkotan and Onekotan islands. The largest catches were recorded at Cape Kronotsky (2.25–5 tons/hour of trawling). The average length of the beaked perch decreased from north to south from 39 cm to 37 cm, weight — from 868 g to 681 g. The main concentrations of the Atka mackerel were noted in the area of Cape Afrika and Cape Kamchatsky (the largest catches are 8–10 tons/hour of trawling), at Kronotsky (5–9 tons/hour trawling) and Shiashkotan Island (15–40 tons/hour trawling). The average length of the Atka mackerel was 38–39.6 cm with a weight of 635–752 g.The practical significance: the results of this work will be taken into account when developing and updating materials for forecasting the total allowable and recommended catch and recommendations for efficient fishing.

Diversity of Ichthyofauna and their Abundance in Ghaghara River, Siwan District, Bihar, India

The Ghaghara River, a significant tributary of the holy River Ganga, travels across northern India., providing essential water resources for agriculture, communities and biodiversity. The river's fish diversity is vital for maintaining local ecological balance and supporting livelihoods. Fish biodiversity and different diversity indices were evaluated in the study area from August 2021 to July 2022. Data was collected from four locations namely Darauli (S-1), Rakauli (S-2), Phulwariya (S-3) and Semariya (S-4) of the Ghaghara River and we found 61 species belongs to 47 genera, 21 families and 07 orders. Cypriniformes were the most common order, accounting for 42% of fish species, followed by Siluriformes (31%), and Perciformes (18%). The most prevalent family is Cyprinidae, which accounts for 39.3% of the fish fauna (24 species), followed by Bagridae (06 species) and Sisoridae (4 species). Total number of individuals, relative abundance (percentage catch), minimum and maximum size of each species were calculated. However, the river’s aquatic ecosystems, particularly its fish populations are increasingly under threat due to human activities, including habitat degradation, pollution, overfishing and the construction of hydropower projects. This study aims to assess the fish diversity of the Ghaghara River and explore the current conservation challenges and opportunities.