Conservation Of Fishery Resources Research Articles

Toward “climate-driven”: innovation on legislation of modern marine fisheries law under era of blue carbon

Abstract Over the past decade, there has been increasing interest in the blue carbon project, which uses marine activities and organisms to take up carbon dioxide from the atmosphere and store it in ocean. Important question in contemporary and future fisheries management is how to coordinate the relationship among the offshore fishery, the fisheries resource conservation and blue carbon projects. Through comparative studies and normative analysis, this study explores the legislative aims of some representative international and national fisheries legislation and their creative reforms in recent years. The legislative purpose of fisheries laws has traditionally been to keep fishery resources above the Maximum Sustainable Yield (MSY) standard, while marine carbon sink resource protection is marginally inadequate. Given that the blue carbon project is inseparable from future fisheries industry development, the protection of marine carbon sink resources needs to be incorporated into the legislative aim of fisheries law in the future.

Technology for the conservation of fishery resources in inland waters

Technology for the conservation of fishery resources in inland waters

Seasonal-Spatial Distribution Variations and Predictions of Loliolus beka and Loliolus uyii in the East China Sea Region: Implications from Climate Change Scenarios.

Global climate change profoundly impacts the East China Sea ecosystem and poses a major challenge to fishery management in this region. In addition, closely related species with low catches are often not distinguished in fishery production and relevant data are commonly merged in statistics and fishing logbooks, making it challenging to accurately predict their habitat distribution range. Here, merged fisheries-independent data of the closely related squid Loliolus beka (Sasaki, 1929) and Loliolus uyii (Wakiya and Ishikawa, 1921) were used to explore the construction and prediction performance of species distribution models. Data in 2018 to 2019 from the southern Yellow and East China Seas were used to identify the seasonal-spatial distribution characteristics of both species, revealing a boundary line at 29.00° N for L. uyii during the autumn, with the highest average individual weight occurring during the summer, with both larvae and juveniles occurring during the autumn. Thus, the life history of L. uyii can be divided into winter-spring nursery and summer-autumn spawning periods. L. beka showed a preference for inshore areas (15-60 m) during the summer and offshore areas (32.00-78.00 m) during the winter. High-value areas of both species included inshore areas of the southern Yellow and mid-East China Seas during the autumn, enlarging during the spring to include central areas of the survey region, before significantly decreasing during the summer. Therefore, this study provides both a novel perspective for modeling biological habitat distribution with limited data and a scientific basis for the adjustment of fishery resource management and conservation measures in the context of climate change.

PENGUATAN KAPASITAS NELAYAN PERIKANAN SKALA KECIL TENTANG LOG BOOK DAN KONSERVASI

Small-scale fisheries play a vital role in the economy and food security of both local and national communities. However, in carrying out their activities, they face various obstacles, including the weakness of human resource capabilities and the challenge of declining fishery resources. Therefore, efforts to improve the capacity of small-scale fishers are essential. This community service activity (PkM) aims to enhance the capacity of small-scale fishers in fish catch logbooks and fishery resource conservation to ensure business sustainability. This PkM was conducted by presenting material by resource persons, followed by discussions and question-and-answer sessions. The participants of this activity came from Tulehu, Waai, and Liang Villages in Salahutu District, Central Maluku Regency, which was held in Negeri Waai. For the fishers, the implementation of this PkM is very beneficial because they can gain knowledge and skills in using logbooks that have not been done so far. The completion of logbooks, which has become an obligation for fishers both nationally and internationally, is still unknown and not practiced by many fishers. After participating in this PkM, they understand the importance of filling out logbooks. In terms of conservation, fishers are already aware of fishery resource conservation by using environmentally friendly fishing gear. However, they still need assistance and capacity-building as fishers.

Exploring Seasonal Variations in Fish Communities: A Study of the Yellow River Estuary and Its Adjacent Waters Using eDNA and Trawl Surveys

The Yellow River Estuary and its adjacent waters serve as crucial spawning, foraging, and nursery areas for marine organisms, possessing abundant biological resources. Monitoring fish communities provides a baseline for implementing the sustainable utilization of marine resources. In this study, data were collected from 15 spring surface and bottom sites and 17 summer surface sites using eDNA and trawl surveys. The results showed that 37, 40, and 35 fish species were detected using eDNA in the spring (surface and bottom) and summer (surface), respectively, with 38 fish species caught during summer trawling. The dominant species mainly belonged to Engraulidae of Clupeiformes in the spring and Gobiidae of Perciformes in the summer, characterized by smaller-sized, short-lived, and pelagic fish species. The summer surface communities exhibited higher diversity than the spring surface and bottom communities. NMDS analysis revealed a degree of seasonal differences in fish communities and that there may be a lack of vertical stratification in the spring communities. The pH and DO were identified as the key environmental factors affecting the fish community. Additionally, the combination of eDNA and trawl surveys was regarded as a superior survey method. Our study provides valuable information for understanding seasonal fish communities in the Yellow River Estuary and its adjacent waters, contributing to fishery resource management and conservation in the region.

Alternative splicing plays a nonredundant role in greater amberjack (Seriola dumerili) in acclimation to ambient salinity fluctuations

Alternative splicing (AS) is an important post-transcriptional mechanism for adaptation of fish to environmental stress. Here, we performed a genome-wide investigation to AS dynamics in greater amberjack (Seriola dumerili), an economical marine teleost, in response to hypo- (10 ppt) and hyper-salinity (40 ppt) stresses. Totally, 2267–2611 differentially spliced events were identified in gills and kidney upon the exposure to undesired salinity regimes. In gills, genes involved in energy metabolism, stimulus response and epithelial cell differentiation were differentially spliced in response to salinity variation, while sodium ion transport and cellular amide metabolism were enhanced in kidney to combat the adverse impacts of salinity changes. Most of these differentially spliced genes were not differentially expressed, and AS was found to regulate different biological processes from differential gene expression, indicative of the functionally nonredundant role of AS in modulating salinity acclimation in greater amberjack. Together, our study highlights the important contribution of post-transcriptional mechanisms to the adaptation of fish to ambient salinity fluctuations and provides theoretical guidance for the conservation of marine fishery resources against increasingly environmental challenges.

Selectivity in snow crab (Chionoecetes opilio) pot fishery: Effect of escape gap shape and size for conservation of fishery resources

Conical pots are commonly used fishing gear for capturing snow crab (Chionoecetes opilio). In these fisheries, optimal snow crab size selection is important for reducing unintended mortality of undersized individuals aiming at conserving fisheries resources and reducing sorting time onboard fishing vessels. Size selection in snow crab pot fisheries commonly takes place through pot netting meshes during deployment. The diamond mesh netting has varying opening angles affecting retention of snow crab of different sizes, and often large proportions of catches consist of undersized crab challenging natural resource conservation. Some commercial snow crab fisheries use rigid escape gaps in addition to mesh selection to improve size selectivity. In this study, we predict the size selection potential of escape gaps with different shape and size and investigated whether such additional size selection mechanism can have a potential to improve selectivity compared to mesh selection. Results showed that circular escape gaps have potential to provide sharper size selection compared to netting meshes and thus could be used to limit the capture of undersized snow crab which is relevant for management and conservation of snow crab resources. However, a similar positive effect cannot be obtained to the same extent with elliptical and rectangular escape gaps.

Genetic Structure and Diversity of Hatchery and Wild Populations of Yellow Catfish Tachysurus fulvidraco (Siluriformes: Bagridae) from Korea.

Yellow catfish Tachysurus fulvidraco is an important commercial fish species in South Korea. However, due to their current declines in its distribution area and population size, it is being released from hatchery populations into wild populations. Hatchery populations also produced from wild broodstocks are used for its captive breeding. We reported 15 new microsatellite DNA markers of T. fulvidraco to identify the genetic diversity and structure of its hatchery and wild populations, providing baseline data for useful resource development strategies. The observed heterozygosity of the hatchery populations ranged from 0.816 to 0.873, and that of the wild populations ranged from 0.771 to 0.840. Their inbreeding coefficient ranged from -0.078 to 0.024. All populations experienced a bottleneck (p < 0.05), with effective population sizes ranging from 21 to infinity. Their gene structure was divided into two groups with STRUCTURE results of K = 2. It was confirmed that each hatchery population originated from a different wild population. This study provides genetic information necessary for the future development and conservation of fishery resources for T. fulvidraco.

Stock Assessment of the Commercial Small Pelagic Fishes in the Beibu Gulf, the South China Sea, 2006-2020.

Long-term variations in population structure, growth, mortality, exploitation rate, and recruitment pattern of two major commercial small pelagic fishes (CSPFs) (Decapterus maruadsi and Trachurus japonicus) are reported based on bottom trawl survey data collected during 2006-2020 in the Beibu Gulf, South China Sea. All individuals collected during each sampling quarter over a period of 15 years were subjected to laboratory-based analysis. In this study, the stock of D. maruadsi and T. japonicus inhabiting the Beibu Gulf was assessed using length-based methods (bootstrapped electronic length frequency analysis (ELEFAN)) to complete stock assessment in different fishery management periods (the division of fisheries management periods was based on China's input and output in the South China Sea offshore fisheries over 15 years, specifically divided into period I (2006-2010), period II (2011-2015), and period III (2016-2020)). The results showed that the mean body length, dominant body size, and estimated asymptotic length of two CSPFs decreased, whereas their growth coefficient decreased, indicating miniaturization and slower growth, respectively. Estimated exploitation rates and catching body length for two CSPFs indicated that both stocks in the Beibu Gulf were overexploited in period I and moderately exploited after 2011. These stocks were taking a good turn in status in period III, with the exploitation rate much lower than the initial period and reversing the downward trend in catching body length. Furthermore, the variations in the spawning season of the two CSPF stocks and their barely satisfactory expected yield indicated the complexity of the current fishery management in the Beibu Gulf. These results suggest that management measures to reduce fishing pressure may have a positive influence on the biological characteristics of those CSPFs in the Beibu Gulf; however, the stock structure already affected by overfishing will be a huge challenge for the conservation and restoration of fisheries resources in the future. Given that the current stocks of D. maruadsi and T. japonicus in the Beibu Gulf still have low first-capture body length (Lc) and high fishing mortality (F) (compared to F0.1), we identify a need to refine population structure by controlling fishing efforts and increasing catchable size, and more consideration should be given to the local fishery resource status in fisheries management.

Hydropower Plants and Ichthyofauna in the Tocantins–Araguaia River Basin: Challenges for Planning and Approaches to Ichthyofauna Conservation

The management of water resources is a complex issue, and the conservation of fish and fishery resources is a growing challenge given the increase in the number of hydroelectric projects in Brazilian river basins. This study describes the fragmentation of the Tocantins–Araguaia River Basin resulting from the installation of hydroelectric plants in operation and planned by the electricity sector until 2050, as well as its relationship with the conservation of fish fauna, especially long-distance migratory species. The hydroelectric projects in operation and planned were analyzed using data obtained from the National Electric Energy Agency. A literature review was carried out to assess the fish species of the Tocantins–Araguaia ecoregion, with an emphasis on long-distance migrants. In general, 75 hydroelectric dams are in operation, and a further 119 projects are in the electricity sector’s plans for construction by 2050 in the Tocantins–Araguaia ecoregion, including a stretch of the basin above the Tucurui dam, which will accentuate the fragmentation in the area. Of the 702 species found in the region, 31.1% are endemic, 6.1% are endangered, and several long-distance migratory species have had their populations restricted. Analysis of this information highlights the widespread impact on the ichthyofauna, affecting both species with a restricted distribution and migratory species with a long-distance distribution. The studies associated with the projects contribute to the advancement of knowledge, but they are only carried out after the works have been defined, which makes it difficult to plan conservation in advance. Transformations in the basin are imminent given the current changes and those expected in the coming years because of the electricity sector’s planning for the region. Considering the inseparable relationship between biodiversity and socio-environmental and cultural diversity, fish conservation is intrinsically linked to the conservation of socio-diversity and the effective participation of local communities from the start of the process. Fish depend on water, and people need both water and aquatic diversity. In conclusion, a well-structured and adaptative conservation plan, combined with the integration of effective fish routes, can contribute to the sustainable development of hydroelectric projects while safeguarding the biodiversity and ecological integrity of the Tocantins–Araguaia Basin.

Transcriptomic profiling reveals the immune response mechanism of the Thamnaconus modestus induced by the poly (I:C) and LPS

Aquatic animals immune response to pathogenic is a hotspot and related to high-quality development of aquaculture industry and the conservation of fisheries resources. Thamnaconus modestus is an important commercial and economical species which is suffering from various pathogens but by now lack relevant research about revealing the immune response mechanism to the pathogens invasion. In the study, the polyriboinosinic polyribocytidylic acid [poly (I:C)] and Lipopolysaccharides (LPS), respective mimics of viral and bacterial infections, were used to demonstrate the immune response of the species via transcriptome analysis. The results showed that T. modestus had sensitive responses to the viral analog infection at 6 h and 48 h, and at 6 h, the first five major functional genes were NFKBIA, IL1B, JUN, IGH, FOS, and at 48 h, the genes were NFKBIA, IL1B, JUN, IGH, FOS. The genes IL1B, IRF3, PTGS2, THBS1 could helping the fish to fight against the bacterial infection in both the times. Similarly for the bacterial infection, the species had a sensitive response at 6 h, and the first five major functional genes were NFKBIA, JUN, FOS, L1B, GRIN2C. Our study provided an insight about the immune response mechanism of this species and demonstrated that if need for treatment of the virus and bacteria by the biotechnology, the artificial interferential time would be suggested before 6 h since the pathological features occur and the genes NFKBIA, JUN, IL1B, FOS, TRAF2, IL8, SOCS3, PTGS2 should be payed more attention.

Effects of CRISPR/Cas9-mediated dnd1 knockout impairs gonadal development in striped catfish

Clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 technology allows for the generation of loss-of-function mutations to enable efficient gene targeting to produce desired phenotypes, such as the production of germ cell-free fish. This technology could provide several applications for aquaculture and conservation of fisheries resources, such as the prevention of overpopulation in fish culture and gene flow from escaped farmed fish into wild populations and the production of germ cell-free recipient larvae for germ cell transplantation. This study aimed to develop CRISPR/Cas9 mediated dead-end 1 (dnd1) knockout techniques for striped catfish (Pangasianodon hypophthalmus). To optimise CRISPR/Cas9-induced dnd1 knockout, three single-guide RNAs (sgRNAs) were designed to target upstream sequences of start codon of the dnd1 gene. A combination of two concentrations of each sgRNA (100 and 200 ng/µl) and three concentrations of Cas9 (100, 250, and 500 ng/µl) was microinjected into fertilised striped catfish eggs. These sgRNAs/Cas9 could induce indel mutations and lower the primordial germ cell (PGC) numbers. Histological analyses indicated that sgRNA3 targeting upstream and nearest to the start codon at 200 ng/µL and Cas9 at 500 ng/µL showed the lowest PGC number. The reduction in PGC number was confirmed by in situ hybridisation using antisense dnd1 and vasa probes. All sgRNA/Cas9 combinations reduced the expression of dnd1, cxcr4b, dazl, nanos1, nanos2, and vasa, and the lowest expression levels were observed in gonads obtained from fish injected with 200 ng/µL sgRNA3 and 500 ng/µL Cas9 (P < 0.05). In addition, at 1 year of age, a significantly lower gonadosomatic index was observed in fish injected with all sgRNA and Cas9 at 500 ng/µL. Moreover, compared to the control fish, the ovaries and testes presented different morphologies in the sgRNA/Cas9-injected fish, that is, few previtellogenic oocytes in the ovary and spermatogonial cell-less testes. In conclusion, CRISPR/Cas 9 targeting dnd1 knockout at the upstream sequences of start codon was achieved, which resulted in the downregulation of dnd1 and lowered PGC number.

Polyacrylonitrile microfibers pose a significant threat to the early-stage survival of zebrafish

Microplastic pollution, especially microfibers (MFs), presents a critical global environmental challenge in natural water bodies. Yet, research on the toxic effects of MFs, particularly during early fish development, is limited. This study aimed to investigate MFs' toxic effects and mechanisms on early-stage zebrafish. Zebrafish embryos were exposed to varying concentrations of polyacrylonitrile microfibers (PanMfs) for 7 days. Results revealed PanMfs adhering to the embryos' surface, with higher concentrations accelerating heart rate and causing pericardial edema in post-hatching larvae. Larvae ingested PanMfs, leading to their accumulation in the intestines and increased levels of reactive oxygen species (ROS) and mitochondrial quantity. Notably, lipid metabolism and calcium ion related signaling pathways underwent significant changes. Low concentration MFs affected glycometabolism pathways, with potential roles for aldob and cacng1a, exhibiting pronounced increases in ROS levels. High concentration of MFs had the most profound impact on signal transduction-related pathways, and possibly triggering micromitophagy and apoptosis in zebrafish intestinal epithelial cells through the Kras/MAPK signaling pathway, with potential roles for kras and mapk9. Although ROS increase was somewhat alleviated, it resulted in decreased survival rates and restricted growth in high concentration of MFs group. These findings highlight the significant threat of MFs to the early survival of fish. MFs pollution prevention and control hold great significance in the conservation of fishery resources.

Assessing larval fish diversity and conservation needs in the Luzon strait using DNA barcoding

IntroductionAccurate species identification and biodiversity assessment of larval fish are essential for effective management and conservation of fisheries resources, as it allows for the estimation of parent stocks, assessment of future recruitment, and prediction of spawning and nursing grounds. However, traditional morphology-based identification methods have inherent limitations, highlighting the need for accurate and efficient techniques to address these challenges effectively. The Luzon Strait, a crucial channel connecting the South China Sea to Western Pacific Ocean, is renowned for its fish biodiversity. However, our knowledge of the biodiversity status of larval fish species in this region remains insufficient.MethodsHere we employed DNA barcoding to assess larval fish species diversity in the Luzon Strait and adjacent waters. We investigated the species composition, diversity, and geographical distribution of larval fish communities in the region. Moreover, we assessed habitat types, human uses, and IUCN conservation status of each larval fish species.ResultsA total of 385 larval fish individuals were collected from 15 stations, and 354 individuals were successfully barcoded and identified, representing 147 species from 93 genera, 44 families, and 22 orders. The interspecific Kimura 2-parameter (K2P) divergence exhibited a significant increase of approximately 55-fold higher than intraspecific divergence. The phylogenetic neighbor-joining tree confirmed the distinct lineages for each taxonomic level, demonstrating the feasibility of DNA barcoding. We observed notable variations in fish species diversity and community composition among sampling stations. Non-metric multidimensional scaling analysis revealed greater diversity and dissimilarity of larval fish community compositions in the western regions compared to the eastern regions. This pattern corresponded to the grouping based on the path of the Kuroshio current, suggesting its influence on the fish community structure. Additionally, economically valuable species were identified at these stations, highlighting their ecological significance as potential spawning or nursery grounds for larval fish. We also examined the habitat type, human use, and conservation status of each larval fish species, providing comprehensive insights into their ecological significance and conservation needs.DiscussionThe establishment of a local DNA sequences database through DNA barcoding will greatly enhance the accuracy of species identification in environmental DNA (eDNA) metabarcoding applications. Altogether, this study offers valuable information for identifying important spawning and nursing grounds of fish populations, thereby supporting sustainable management and conservation of fisheries resources in this region.

Artisanal fisher knowledge on the impacts of destructive and illegal practices on the Southern Coast of Bahia, Brazil

Destructive fishing practices (DFP) and illegal, unreported, and unregulated (IUU) activities result in significant marine ecosystem effects, such as habitat destruction, biomass reduction, bycatch, and waste of resources. They also generate socioeconomic impacts on artisanal fisher coastal populations. Both DFP and IUU are linked to fisheries management system failures and the impossibility of marine surveillance. In this context, from an Ethnoecological approach, the aim of this study was to analyze the local ecological knowledge of fishers from Ilhéus (Bahia), Northeastern Brazil, regarding DFP and IUU fisheries. A total of 59 interviewees pointed to decreased resource catches in recent years, citing increasing fishing efforts and certain types of gear as the main reasons. They also claim that local fishers and fishers from other Brazilian regions have been using banned equipment, such as compressors and lobster nets. In turn, although permitted by law, shrimp trawling and gillnet fishing were reported as being excessively applied and identified as destructive fisheries. Surprisingly, longline fishing was one of the most reported as responsible for excessive catches and for causing decreases in Common dolphinfish catches. This study reinforces the importance of including the knowledge of local fishers and their participation to contribute to fisheries management and resource conservation. In this context, some recommendations are highlighted to reduce the impacts of harmful practices and improve regional fisheries management, summarized as: (i) policy improvement; (ii) fishing monitoring; (iii) incentives; and (iv) enforcement.

Intestinal microbiota of the four omnivorous fishes revealed by 16S rRNA metabarcoding from the habitats of oyster reefs

The habitats of oyster reefs had played various ecological services functions, as an important means of marine ecological restoration and fishery resources conservation, which had been widely used worldwide. And the characteristics of microbial communities would be inevitably affected by habitat of oyster reefs. The aim of this study was to reveal the relationship between oyster reefs and the intestinal microbiota of fish (Takifugu ocellatus, Acanthopagrus latus, Clupanodon thrissa, and Mugil cephalus). Here, based on 16S rRNA sequencing, this research analyzed the microbial communities of fishes gut in the oyster reefs from the most crucial estuary economic zone in Southern China. It was significantly lower that the bacterial alpha-diversity in the fish intestines than in the sediments of oyster reefs. The non-metric multidimensional scaling (NMDS) and analysis of similarities (ANOSIM) results showed that intestines microbiota of T. ocellatus and A. latus were more homologous to sediments microbiota, but intestines microbiota of C. thrissa and M. cephalus were more similar to the water microbiota. There were obvious differences in the contribution of oyster reefs habitat to intestinal microorganisms of four fishes. Source tracking analysis as well reached the similar conclusion. For instance, contribution of water to T. ocellatus and A. latus was lesser than sediments, which was related to their benthic habits. Based on the differences in microbial community compositions, the functional prediction analysis had demonstrated that special functional pathways and independent core indicators had been formed separately from oyster reefs and fish intestines. Overall, these findings highlighted the characteristics of microbial diversity and functions from the omnivorous fish living in oyster reefs habitats. This research proposed new insights into the function of oyster reefs habitats, which have enriched the ecological service value of oyster reefs from microbial ecology and provided a reference for the application of oyster reefs habitats in other estuaries.

THE Local Wisdom as a Form of Development Principles of Environmental Sustainability in Indonesia

Abstract. This research is important to obtain the concept of developing the Principles of Environmental Sustainability in Indonesia, in order to preserve the marine environment againts various forms ofviolations in the field of marine fisheries. The Principle of Environmental Sustainability is a moral approach and emphasizes more on preventive measures in the preservation of the environment in general and in particular the marine environment. For conditions in Indonesia, there is a potential for local wisdom of the community of an area spread throughout the archipelago as a form of real efforts to involve the community in the preservation of the marine enviroment. This research was carried out using a normative juridical approach, qualitative legal analysis with legal interpretation methods, and literartur studies. The inclusion of Local Wisdom in the preservation of the marine environment is an important instrument as a form of Development of Environmental Sustainability Principles. The existence and role of local wisdom of coastal communities that are evenly distributed throughout the archipelago conceptually have the opportunity to be included as a form of the developing the Principles of Environmental Sustainability in order to support the effectiveness and efficiency of monitoring the conservation of marine fishery resources.

Comparative footprint studies of single and multiday trawl fishing along Ratnagiri coast, Maharashtra, India

Trawl fishing is widely recognised as the most productive and industrious fishing method in the world. Due to the importance of trawl fisheries along the Ratnagiri coast of Maharashtra, the present comparative study was undertaken on single and multiday trawl fishing in the region. In this study, monthly variations in fishing depth, catch per hour (CPH), discard per hour (DPH), spatio-temporal species distribution and spatial prediction of catch-discard of 136 trawl hauls were analysed. Single and multiday trawlers were operated from 15°53’24’’N to 18°00’36’’N latitude and 72°55’55’’E to 73°25’48’’E longitude within a depth range of 10 to 64 m in the Arabian Sea. For the multiday trawlers, maximum CPH of 68.30 kg h-1 was recorded in October 2015, while single day trawlers recorded CPH of 42.70 kg h-1 in November 2015. Average DPH for multiday and single day trawlers were recorded as 7.66 and 3.84 kg h-1 respectively. The study found that CPH and DPH were significantly (p&lt;0.05) higher in multiday trawlers than single day trawlers. Based on spatial mapping, high fishing pressure was observed in the area south-west off Ratnagiri. Our results highlighted the need for suitable strategies for conservation and management of fisheries resources to achieve long-term sustainability in the region. Keywords: Catch, Discard, Diversity, GIS mapping

Geo-spatial distribution and trends of trawl catch and bycatch off the south Konkan coast, Maharashtra, India

Trawl fishing is well-known for its high catch rate, but due to its non-selective nature, it is now widely acknowledged to have an impact on biodiversity and habitat. The geographical and temporal aspects of trawl catch, bycatch, discard, and ichthyofaunal trawl diversity along the south Konkan coast of Maharashtra, India, are contemplated in the current study. The data of 177 georeferenced trawl hauls, towed between 15°53’38”N to 17°34’52”N latitude and 72°54’29”E to 73°25’48”E longitude, revealed that maximum bycatch (70–110 kg/haul) and discard (60–110 kg/haul) regions were found towards the southern direction, near ecologically sensitive estuarine areas off the south Konkan coast, Maharashtra. The post and pre-monsoon seasons were found to be much more productive in terms of catches, while the post-monsoon and winter seasons had the highest species diversity 38.15% and 33.86%, respectively, with the winter season having higher discard rates. In the present study, bycatch contributed nearly 49% of the total catch, with the maximum catch per hour recorded in October (62.20 kg) and the discard per hour in January (14.59 kg). There were 134 different species of fish and shellfish recorded, and the family Carangidae (8.21%) was prominent in terms of species richness, followed by Penaeidae (6.72%), Clupeidae (5.22%), Engraulidae (5.22%), and Sciaenidae (4.48%). The results of various biodiversity indices confirmed that the studied region is blessed with rich and evenly distributed biodiversity. The mapped predictive values of trawl fishing showed a high fishing pressure zone towards the south off the Maharashtra coast, and it highlighted the need for suitable strategies for the conservation and management of fisheries resources to achieve long-term sustainability in that region.

Effects of water temperature on swimming performance of Siniperca knerii Garman under the Yuanshui River cascade development

We examined the swimming parameters and oxygen consumption rate at four temperature levels (15，20，25 and 30°C) of Siniperca knerii Garman (11.81 ±2.21 cm, 26.4 ± 6.28g) from Yuanshui River for 30 days to analyze the ecological adaptability of the typical fish and the conservation of fishery resources from the Dongting Lake water system. Their relationship was also analyzed, and the results showed an approximately linear increasing trend of the fish’s critical swimming speed and preferred swimming speed with the change of temperature (P&lt;0.05). In contrast, the induction velocity of fish decreased with the increase in water temperature. The relative induction velocities of the fish at four temperatures were (1.16±0.07), (0.94±0.06), (0.86±0.07), and (0.70±0.09) BL/s (Body Length/s). The preferred swimming speed was (1.86±0.04), (2.23±0.35), (2.65±0.28), and (2.74±0.33) BL/s. The relative critical speed was (2.58 ±0.32), (3.31±0.41), (4.31±0.52), and (5.22±0.48) BL/s. According to oxygen consumption rate at different temperatures, four nonlinear function models of the relationship between oxygen consumption rate of water temperature and swimming speed behavior parameters were obtained by nonlinear fitting. The model proved that the oxygen consumption rate, tail beating frequency, and respiratory rate increased with the increase in swimming speed. The higher the temperature, the more significant the changes were. The results showed that water temperature significantly affected the swimming characteristics of juvenile Siniperca knerii Garman. The changes were due to physiological and biochemical regulation with temperature and environmental changes. This experiment provided essential data support for the adaptive mechanism of sports physiology and ecology of typical fishes in the Yuanshui River.