Journal of Applied Ichthyology最新文献

The present investigation was carried out in the Bhairab River, situated in the southwestern part of Bangladesh, with the aim of evaluating the impact of stocking densities on the growth performance and survival rate of Lates calcarifer (Bloch, 1790) in floating cages. In addition, the study aimed to determine the optimal stocking density for cage farming. Seabass fry, measuring an average length of 18.7 ± 2.19 cm and weighing 69.57 ± 4.86 g, were placed in nine cages. The cages were made of knotless polythene nylon net with a mesh size of 01 cm and had dimensions of 3.5 × 3 × 1.5 m. The fry were stocked at three different densities: 3, 6, and 9 individuals/m³. Their growth performance was observed every 2 weeks for a period of 6 months. The fry were nourished with live fish, equivalent to 10%-5% of their body weight. After a period of 180 days in a grow-out culture, the seabass fry achieved a length of 32.43 ± 0.57 cm and a weight of 504.56 ± 89.95 g when there were 3 individuals/m³. At a density of 6 individuals/m³, the seabass fry had a length of 29.94 ± 0.58 cm and a weight of 447.78 ± 52.76 g. Finally, at a density of 9 individuals/m³, the seabass fry had a length of 26.50 ± 0.69 cm and a weight of 331.49 ± 73.39 g. The growth exhibited allometric patterns and was not influenced by the stocking density. The survival rate was relatively greater at lower (97%) and moderate (95%) stocking levels; however, the production was significantly (p < 0.05) higher at the moderate stocking density. Lower and moderate stocking densities resulted in increased weight gain and specific growth rate (SGR). The findings of the current investigation suggest that a density of 6 individuals per cubic meter of L. calcarifer is suitable for cage culture in flowing water environments.

Length‒weight relationships (LWRs) and length‒length relationships (LLRs) were estimated for 63 and 58 freshwater fish species, respectively, captured in the Itaipu Reservoir, Paraná River Basin, Paraná State, Brazil. Sampling was carried out from March 1987 to July 2024 at 63 professional fishing sites within the reservoir’s area of influence. Statistically clear differences in LWR between sexes were detected in 26 species. Isometric growth (b = 3) was identified in 29 species. The b-value ranged from 1.14 to 3.89, with an average of 2.68 (SE ± 0.04) across all species. For LLR, the b-value ranged from 0.713 to 1.440, with an average of 1.12 (SE ± 0.01) across all species, with statistically clear differences between sexes observed in 19 species. In 16 species, females were larger than males. This study provides the first LWR references for 13 species and LLR references for 22 species, as well as new maximum total length records for 39 species and maximum total weight records for 41 species. These estimates are crucial for managing fish stocks and developing models related to fish growth, reproduction, and fisheries.

Aquaculture genomics, genetics, and breeding are pivotal disciplines that enhance the efficiency and sustainability of fish farming. The advanced genomic technologies, including whole genome sequencing (WGS), genome-wide association studies (GWAS), and CRISPR/Cas9 gene editing, have revolutionized our understanding of the genetic foundations of economically important traits in aquaculture species. These technologies enable the identification of genetic markers linked to growth, disease resistance, and environmental adaptability, facilitating the development of improved breeding strategies. Marker-assisted selection (MAS) and genomic selection (GS) are now integral to breeding programs, allowing precise selection of desirable traits and accelerating genetic gain. Despite these advances, several challenges remain, including the need for extensive phenotypic and genomic databases, the complexity of polygenic traits, and ethical considerations surrounding genetic modifications. Furthermore, integrating these genomic tools into practical breeding programs necessitates bioinformatics infrastructure and expertise. This review provides a comprehensive overview of the present status of aquaculture genomics and genetics, highlighting key technological advancements and their applications in breeding programs. It also discusses the challenges faced by the industry and outlines future research priorities, such as enhancing genomic resources for under-researched species, improving phenotypic data collection accuracy, and developing sustainable breeding practices. By addressing these challenges and leveraging genomic insights, the aquaculture industry can significantly improve productivity, sustainability, and resilience, contributing to global food security and economic growth.

This study explored the distribution, diversity, and morphological characteristics of some Labeobarbus species in the Gumaro River from August 2021 to January 2023. A total of 348 specimens, belonging to 12 species, were collected from three sites. Catches were dominated numerically (85.5% of the total catch) by Labeobarbus nedgia, Labeobarbus intermedius, Labeobarbus beso, and an unidentified species that appeared to be a potential hybrid. Abundance, distribution, and Shannon diversity values differed between sites, possibly due to the presence of natural barriers. To characterize the potential hybrid species, 28 morphometric and 13 meristic characteristics were measured and compared with most closely related species, including L. nedgia and L. beso. Principal component analysis (PCA) was used to compare the morphometric characteristics of these three groups only for fresh specimens. Morphometric characterization of the unidentified species showed that some characteristics had a common identity with both L. nedgia and L. beso, indicating potential hybridization. However, some morphometric characteristics, particularly the head and mouth profiles, indicated a significant difference between L. nedgia, L. beso, and the putative hybrid species. Most meristic characteristics were similar between the known and unidentified species. Therefore, this potentially hybrid species needs molecular characterization to confirm its genotypic identity. An expanding presence of instream barriers within the Lake Tana tributaries may be leading to increased potential for hybridization among its endemic Labeobarbus species.

As key indicator species for aquatic ecosystem health under cascade hydropower development, shifts in fish diversity directly reflect the cumulative impacts of hydropower projects on river connectivity, hydrological regimes, and habitat integrity, providing critical evidence for assessing ecological equilibrium and formulating conservation strategies. To assess the effects of hydropower development on the fish community structure and resource status in the mid-reach of the Beipan River and optimize the ecological sustainability of cascade hydropower operations, a field survey was conducted between the Mamaya hydropower station and the Dongqing hydropower station from 2020 to 2023. The results revealed that 2776 fish samples were recorded during the survey period, representing 38 species from 31 genera, 9 families, and 4 orders. Analysis of the relative importance index revealed Onychostoma sima as the dominant species, with a significantly higher index than those of the other species. Across the study period, the Margalef richness index (D_Ma), Shannon–Wiener diversity index (H^′), Pielou evenness index (J), and Simpson index (C) ranged from 4.790 to 5.758, 0.064–0.083, 0.822–0.895, and 0.908–0.950, respectively, with peaks observed in 2021. The abundance–biomass comparison curve (ABC) suggested an undisturbed fish community structure in 2020, transitioning to moderate disturbance from 2021 to 2023. The length–weight relationships (LWRs) of 28 fish species were analyzed. The LWRs of the four species in the Beipan River Basin have not been previously documented, and the maximum lengths of the seven species were recorded for the first time. When a value in the LWR associated with fish fertility was used as an indicator to assess changes in fish status and nutrition between 2020 and 2023, the 10 largest species presented the highest A values from 2020 to 2021, followed by a decline from 2022 to 2023. The construction of cascade hydropower stations is considered the main driving factor of fish habitat change, fish diversity, and fish resources in the Beipan River. The establishment of aquatic germplasm resource protection areas, strengthening law enforcement, controlling the sand mining period, and monitoring, rescuing, and breeding rare and endemic fish in river basins are suggested. This study supplemented the basic data of fish resources in the middle reaches of the Beipan River. It proposed suggestions for enhancing fish diversity protection to provide protection measures and a basis for the protection of fish resources for power stations and river basin managers.

Aquatic ecosystems, essential for global biodiversity and human health, are increasingly threatened by hydraulic engineering projects. This study examines the impact of waterway regulation on fish communities in the Jiujiang section of the Yangtze River using environmental DNA (eDNA) technology. Water samples were collected from multiple locations within and outside the construction areas during the low and high water periods (HWPs) of 2022 and 2023. The results reveal differences in fish community composition and diversity between construction and nonconstruction areas, as well as between low and HWPs. Notably, fish diversity was higher during HWPs, with Cyprinidae being the predominant family in the study area. Canonical correspondence analysis (CCA) identified pH and water temperature as key environmental factors affecting fish communities. This study demonstrates the effectiveness of eDNA technology in monitoring aquatic ecosystems and provides valuable insights for the sustainable management and conservation of regulated waterways. The findings highlight the necessity of long-term ecological monitoring to address the negative impacts of hydraulic engineering projects.

Hypophthalmichthys molitrix and Hypophthalmichthys nobilis are economically important freshwater fish species in China. During resource surveys in the Xiangluzhou section of Xiangjiang River, Changsha, in 2020, fish suspected to be natural hybrids of H. molitrix and H. nobilis were identified. To confirm this, we employed morphological and molecular analyses of H. molitrix, H. nobilis, and their suspected hybrids. Morphometric results revealed that most countable and measurable traits of suspected hybrids (n = 29) were intermediate between those of H. molitrix (n = 30) and H. nobilis (n = 26). However, the traits were slightly biased toward those of H. molitrix, representing an intermediate, transitional form indicative of hybridization. Genome resequencing followed by principal component analysis and population structure analysis indicated that the genetic composition of the suspected hybrids (n = 9) was intermediate between H. molitrix (n = 10) and H. nobilis (n = 9), containing nuclear genetic material from both species. These results confirmed the suspected hybrids as true hybrids of H. molitrix and H. nobilis. COI gene barcoding results showed that the suspected hybrids (n = 28) formed a single clade in the haplotype network and shared haplotypes exclusively with H. molitrix (n = 29), indicating that H. molitrix was the maternal parent. Furthermore, the asymmetric hybridization pattern suggested potential influence of physicochemical factors, such as water temperature, water quality, and flow velocity, which affect the affinity between sperm and egg cells. We propose that the natural hybridization of H. molitrix and H. nobilis originates from genetic exchange. The influence of Xiangjiang River’s unique aquatic ecological environment and hydraulic engineering projects, which have led to changes in flow regimes and the degradation of spawning grounds, have further altered the species’ ecological reproductive habits and disrupted reproductive isolation and natural hybridization. This study provides direct empirical evidence of natural hybridization between H. molitrix and H. nobilis within their native ranges in China through morphological and molecular research methods, thereby complementing previous hybridization inferences based on genomic data. These findings offer a novel view on fish hybridization theory.

This paper explores the aquaculture and fisheries’ potentials within the ecologically critical areas (ECAs) of the Sundarbans, Bangladesh, highlighting their socioeconomic importance and the urgent need for sustainable management practices. As the largest mangrove forest globally and a UNESCO World Heritage Site, the Sundarbans is a biodiversity hotspot and a vital source of livelihood for millions, rich in various aquatic species, including finfish and shellfish. However, the region faces significant challenges such as climate change, habitat degradation, and unsustainable fishing practices, which threaten its ecological balance and fisheries resources. Current fisheries’ management is hindered by inadequate conservation efforts and limited aquaculture practices, particularly in breeding and seed supply of economically important species. Unsustainable juvenile collection methods exacerbate the depletion of local fish stocks, posing further risks to biodiversity. The study underscores the need for comprehensive research initiatives aimed at enhancing breeding technologies, developing sustainable aquaculture practices, and promoting community engagement in resource management. Recommendations include establishing hatcheries for commercially important species to produce high-quality seed, thereby alleviating pressure on wild populations and strengthening the local economy. The paper advocates for the implementation of Integrated Coastal Zone Management (ICZM), community-based resource management, and enhanced legal frameworks to support sustainable aquaculture. By adopting a multistakeholder approach that balances environmental conservation, economic development, and social equity, the Sundarbans can realize its potential for sustainable fisheries and aquaculture, ultimately improving livelihoods and fostering ecological resilience. The paper calls for proactive, scientifically informed strategies to navigate the complexities of aquaculture, fisheries, and ecological health in this critical region.

A total of ten species of freshwater small indigenous fish species (SIFS) were examined in order to study their length–weight relations (LWRs), condition factors (K_R), and form factors (a_3.0) caught by a small-scale fishery from the Babu Mondoler beel, a wetland ecosystem in northwestern Bangladesh. In addition, the form factor (a_3.0) was calculated for ten freshwater fish species in worldwide habitats. The samples were collected between June 2021 and May 2022 with various fishing equipment and traps, including box traps, cast nets, and gill nets. The study focused on the following species: Ailia coila (Hamilton, 1822), Amblypharyngodon mola (Bleeker, 1854), Channa punctata (Bloch, 1793), Channa straita (Bloch, 1793), Esomus danricus (Hamilton, 1822), Eutropiichthys vacha (Hamilton, 1822), Gagata cenia (Hamilton, 1822), Labeo catla (Hamilton, 1822), Lepidocephalichthys guntea (Hamilton, 1822), and Macrognathus aculeatus (Bloch, 1786). Total length (TL) was strongly correlated with body weight (BW) (p < 0.001). The slope b was between 2.55 and 3.38, with 7 species experiencing negative allometric growth, 1 species experiencing positive allometric growth, and 2 species experiencing isometric growth. The mean relative condition factor (K_R) ranged from 0.9746 ± 0.0870 (Channa punctata) to a maximum of 1.0344 ± 0.2101 (Ailia coila) as a benchmark of the well-being of individuals of the various species in the same ecosystem. In our studied ecosystem, we observed a form factor (a_3.0) ranging from 0.0025 to 0.0151. The results on LWRs, condition factors, and form factors are important baseline data for monitoring the status of fish populations, detecting environmental stress, and sustainable management. Therefore, habitat action is required to reduce the growth-affecting stressors on these SIFS.

This study investigated the length-weight relationship (LWR) of 16 fish species from the Upper Tietê Basin under the influence of the Atlantic Forest biome, aiming to provide updated morphometric data and contribute to the knowledge of Neotropical ichthyofauna. 2811 specimens were collected and distributed across five orders and 10 families. Standard length ranged from 0.8 to 24.5 cm, and weight from 0.01 to 34.19 g. The parameters a and b of equation W = a·L^b were estimated, revealing that most species exhibited allometric growth, with one isometric species (Astyanax lacustris), seven with negative allometry, and eight with positive allometry. The b values ranged from 2.579 (Imparfinis piperatus) to 3.651 (Phalloceros reisi), the latter being the only one outside the typical range of 2.5 < b < 3.5. The Bayesian analysis proposed by Froese indicated morphological deviations for Hyphessobrycon multifasciatus (α outside the expected range) and a lack of specific classification for Cambeva iheringi, Geophagus iporangensis, and Osteogaster aenea. An apparent scarcity of geographically delimited studies in the basin was evident, hindering broader comparisons. Only Phalloceros reisi presented compatible data, with mean, standard-length values similar to those reported in the literature. Also noteworthy is Pseudotocinclus tietensis, a threatened species that exhibited positive allometry (b = 3.2595), suggesting favorable environmental conditions for its growth in the studied basin. The results highlight the importance of regional morphometric studies as tools for monitoring and conserving ichthyofauna, especially for species whose morphometric characteristics had not yet been documented for the Upper Tietê Basin.