Net Fishing Research Articles

The main results of the research on the cultural layer of the Samarovsky Yam settlement (Khanty-Mansiysk)

In 2016, archaeological excavations were carried out for the first time in the settlement of Samarovsky Yam (Khanty-Mansiysk) directed by I.Yu. Chikunova. The cultural layers of the 17th–20th centuries have been studied. This publication introduces the information and materials obtained during the excavations, and the results of the analysis of fish remains. Evidence has been found of the great flood of 1771, which left a thick sterile layer. This layer separated the cultural deposits of the 18th century. Stratigraphic data, coupled with the analysis of distribu-tion of various finds of wood, leather, metal, and molded, pottery and glazed ceramic ware, make it possible, in support of archival data, to trace on specific material the economic structure and changes in the level of economy of the first Russian population of Samarovsky Yam. Archaeoichthyological material is also a valuable informative archaeological source. The fish remains helped to clarify the species, size, age, and time of catching fish in the past. The study of the fish bone and scale remains made it possible to establish that whitefish species predomi-nated in the net fishing of the population of the Samarovsky Yam.

Cormorant predation in fyke net fishing: The direct effects of a protected bird on coastal commercial fishing

The population size of great cormorants, Phalacrocorax carbo sinensis, has risen steeply in the Baltic Sea over the past 40 years. The growing population has resulted in polarized conflicts between conservation and coastal fisheries due to the losses cormorants may inflict on fisheries. Mitigation of the conflicts requires objective estimates of true losses to fisheries, but quantitative research on losses has been scarce. We used continuous video-recordings to systematically quantify cormorant visits and their activity at 15 fyke nets during the 2022–2023 breeding and post breeding seasons. More than 2400 h of video footage were recorded, in which cormorants were found for 664 h. We also quantified the frequency of fish injured by birds in coastal fishing catches using data from the EU Fisheries Data Collection Program including data from fyke nets and gill nets. Our results show that cormorants frequently foraged in open, floating fyke nets but relatively rarely in submerged nets, leading to significantly higher losses in the former. Monitoring data from fyke and gill net catches covering the entire Finnish coast revealed that the proportion of bird-injured fish in catches is very modest (0.5 %) but can be considerable in individual catches. Finally, results indicate that cormorant visits and the proportion of injured fish in the catch tend to increase when distance to the nearest cormorant colony decreases. We conclude that the losses caused by birds are generally modest, except in open fyke nets where cormorants may conduct hundreds of dives and catch dozens of fish a day. Our study shows that cormorant depredation is highly variable in time and space, but also partly manageable by selecting gear that conforms to local cormorant pressures. We underline the importance of systematic scientific research when measuring damage caused by cormorants and ask for evidence-based political strategies to mitigate perceived cormorant problems.

Assessing impact risk to tropical marine ecosystems from human activities with a Southeast Asian example

Abstract Society relies on intact marine ecosystems for ecosystem services such as nutrition, livelihoods, health and well‐being. Yet, to obtain these benefits, we carry out activities, introducing pressures to ecosystems, damaging and degrading habitats and reducing their capacity to optimally provide ecosystem services. Biodiversity and ecosystem services are consequently being lost globally but impact chains from these activities are poorly understood, especially in tropical marine ecosystems. We identified for the first time impact chains linking activities with pressures they introduce in five tropical coastal and marine habitats, specifically through application in four Southeast Asian case study sites. Using expert elicitation based on existing evidence, we weighted each impact chain according to pressure extent, frequency and persistence, and habitat resistance and resilience. Assigning each impact chain an impact risk score allowed identification of activities and pressures introducing most risk, and habitats most under threat. Of 26 activities we considered, we found fishing activities, specifically trawling, gill nets and seine nets introduce most risk, along with tourism and recreation. Litter and pollution were among the greatest pressures on habitats, with coral reefs being most vulnerable overall. Destructive fishing practices were associated with physical pressures like abrasion, smothering and siltation and total habitat loss, while tourism activities were associated with organic enrichment, litter and pollution. The risk levels depended on the habitat and on local case study context. Synthesis and applications: A contextualised risk‐based approach can help to prioritise sustainability issues for management in data‐poor regions by making use of a range of knowledge types from local experts to broader scientific knowledge. A multisectoral, and ecosystem‐based risk assessment can help decision makers to consider trade‐offs in marine resource management and highlight priorities transparently, where coordination of multiple administrative organisations, sectors and local actors is required to meet multiple sustainability objectives. Physical pressures from fishing activities combined with pollution from tourism indicate effective management requires a multi‐use zoning approach that not only considers impacts at the site of activities but also integrates regional coordination to tackle dispersive pressures from pollution or sediment disturbance that occur at a distance from the source.

Development of Low-Resistance Coastal Stow Net Using Numerical Analysis and Model Experiments

In coastal stow net fishing, the heavy weight of a typical anchor (750–1000 kg) can increase the risk of capsizing the boat and crew member injury during hoisting operations. Thus, to prevent these accidents, a reduction in the anchor weight is required. One strategy to achieve this is to reduce the resistance force of the fishing gear used, which would allow lighter anchors to be employed. This requires the accurate estimation of the resistance force for various gear designs. Therefore, the resistance force and shape during the operation of two representative types of coastal stow nets currently employed in the Korean coastal stow net fishing industry were investigated using simulations and modeling experiments. The modeled fishing gear was divided into four sections according to the mesh size. Based on the results, the twine thickness was reduced in order to target areas of the gear where the greatest resistance was observed, while the front part of the gear was redesigned to prevent the front of the net from being pushed back into a suboptimal shape. The proposed low-resistance fishing gear has the potential to improve occupational safety in the coastal stow net fishing industry.

Quantifying non-target seahorse fisheries and domestic traditional medicine-based trade in Malaysia

Seahorses (Hippocampus spp.) are sold primarily for traditional medicine (TM) uses in Southeast Asia. Although Malaysia is reportedly an important global seahorse exporter, documentation on the current extent of seahorse catch and trade of seahorse-based TM within the country is limited. This study aimed to quantify patterns of seahorse bycatch, gear-specific biological parameters of caught seahorses, and trade characteristics in Malaysia. Questionnaire-based fisher and TM surveys were administered nationwide from March 2021 to March 2023. Seventy-one percent of fisher respondents (612 out of 860) reported catching seahorses, with gill or drift net fishers (73 %) more likely to have caught seahorses than trawlers (12 %). Significant spatial differences in species composition was observed between Peninsular Malaysia and Malaysian Borneo (Sabah state). The total estimated annual seahorse catch within Malaysia was approximately 3376 kg per year, with 77 % of the catch attributed to gill or drift nets and 23 % to trawling operations. Almost half (40 %) of traditional Chinese medicine (TCM) practitioners/ traders (n = 138), 3 % of Malay TM practitioners (n = 3), and 88 % of other TM traders (n = 7) reported selling seahorse species. This study is one of the first to quantify the often overlooked but critical contribution of small-scale fisheries, especially gill and drift nets, towards seahorse bycatch. The current supply volume and selling price of seahorses were observed to be relatively high, while the present-day demand was reportedly low. Almost half of TCM practitioners/ traders interviewed were still actively selling seahorses, indicating that there is still considerable demand. To ensure the sustainability of seahorse populations in Malaysia, efforts in both small-scale and trawl fisheries must be reduced while strictly enforcing seahorse trade regulations.

Assessing the vulnerability of Elasmobranch species in the Bay of Bengal: Insights from Lakkha gill net fishery of Bangladesh

The elasmobranch population is declining in the Bay of Bengal of Bangladesh due to large-mesh gill net fishing, locally known as the Lakkha net, which primarily targets Indian threadfin (Leptomelanosoma indicum). This study was the first attempt to identify megafaunal bycatch in Lakkha fishing and assess its vulnerability using Productivity Susceptibility Analysis. A total of 40 elasmobranch bycatch species were identified, with sharks comprising 13 species from three families, while 27 rays belonged to six families, with the majority belonging to the Myliobatiformes order (60 %). Productivity and susceptibility scores were assigned to all identified species, with values ranging from 1.27 to 2.73 and 1.50 to 2.63, respectively. The target Lakkha fish exhibited the highest susceptibility score, followed by several pelagic sharks and eagle rays. Vulnerability assessment revealed that 31.7 % (n = 13) of species were highly vulnerable, while 43.9 % (n = 18) were classified as moderate, and 24.4 % (n = 10) were considered to have low vulnerability. All the high-risk megafauna species (n = 13) are classified as threatened by the global IUCN Red List. Sensitivity analysis highlighted susceptibility as a major contributor to species’ vulnerability. Alterations in susceptibility scores led to significant changes in the vulnerability status of many species. The overall data quality assessment indicated moderate data quality across species, with variability observed between productivity (76 % of species received a poor data quality score) and susceptibility attributes. However, vulnerability of these species can be reduced through adequate gear modification, shorter net deployment periods, adoption of safe discharge techniques, identification of critical habitats, and establishment of marine protected areas within this region. This study provides valuable insights into the species composition and vulnerability of elasmobranchs in the Lakkha gill net fishery, emphasizing the need for conservation measures to mitigate bycatch impacts on threatened species.

Let’s measure it: An approach of high-resolution estimates of bottom fixed net fishing effort at national level

Fisheries are one of the most important food sources for human consumption whilst being amongst the most impacting and extractive activities happening within the marine environment, which makes it imperative to properly manage this activity. To improve fisheries management, the precise quantification of fishing effort is of the outmost importance. Yet, present methods for effort estimation, especially at broad scales, are hampered by difficulties in data access and usually rely on coarse effort metrics or on costly data collection for quantifying fishing effort with higher resolution. In the present work, we propose an approach of high-resolution fishing effort estimates of net fishing, as length of nets operated by a given fleet, at the national level. It relies on sampling of effort, derived from classified and easy to access vessel tracking data – AIS, and fishery dependent data – logbook and landings data. The proposed methodology combines trip-based effort estimates, derived from AIS data, as a foundation to extrapolate the total fishing effort, through the number of fishing trips linked to official landings and logbook data. It is estimated that in the years from 2014 to 2020 an average of 180 200 km of static nets (gillnets and trammel nets), which corresponds to approximately 4.5 and 210 times the lengths of the equator and the Portuguese Atlantic coastline respectively, are used in Portuguese mainland waters each year, by a fleet of slightly more than 100 vessels. The presented methodology allows to quantify and study the variation of the nominal fishing effort, at country level, with a higher resolution than what is usually used and at very low cost. We argue that such methodologies need to be developed and explored in order to have better and more comprehensive estimates of fishing effort which will contribute and improve the sustainable management of fisheries and the marine environment.

Spawning migration and habitat characteristics of Labeobarbus species in the Gumara River and its tributaries, Lake Tana subbasin, Ethiopia

Information on the spawning migration and habitat use of migratory fish is critical to protect and restore threatened or endangered populations. Twenty-two individuals of three species, namely Labeobarbus platydorsus, L. megastoma, and L. truttiformis, were implanted with radio tags to study their spawning migration in the Gumara River and its tributaries between July and October of 2018 to 2021. Fourteen individuals were found at least twice throughout their migration, eleven moved upstream up to 41.0 and 44.4 river kilometers (rkm), and three were tracked when moving downstream. The upstream spawning movement of the tagged fish lasted 9 to 27 days, and their ground speeds ranged from 0.07 to 1.50 km h-1. The habitat use of untagged Labeobarbus specimens in the spawning sites was also assessed using fyke nets, cast net fishing, and data from fishermen’s catches. Labeobarbus truttiformis mainly exploited the Kizen tributary stream with gravel substrates and less turbid water for spawning. Several small-sized individuals of L. megastoma spawned in the Wonzuma and Dukalit tributaries. By contrast, larger-sized specimens of L. platydorsus and L. megastoma spawned in the main river channel at the riffles and the gravel/pebble size substrate. Destructive fishing using gillnet dragging, filtering, and damming/fencing has recently intensified at the spawning areas (~ 41.0 rkm to 45.0 rkm), which likely affects spawning populations. Therefore, we recommend that fishing in the main river channel and tributaries must be banned during the months of August, September, and October to safeguard and conserve the threatened Labeobarbus species.

Disappearing fish: Grey seal depredation in a Baltic net fishery

Grey seals (Halichoerus grypus) in the Baltic Sea commonly attempt to steal fish captured in net fisheries. Seal depredation reduces economic yields for small-scale net fishers in a region already highly impacted by the collapse of important fish stocks. Visible damages in looted nets consist of injured fish with bite marks, or holes in the gear, but additional losses from seals eating entire fish without leaving a trace can often remain unnoticed. In this study, we estimated the daily rates of injured and of stolen fish in a commercial gillnet fishery operating off coast of Bornholm in the Central Baltic Sea in 2021–2022. Our results show that the Atlantic cod (Gadus morhua) is generally preferred over other target species [here, European plaice (Pleuronectes platessa), European flounder (Platichthys flesus), and turbot (Scophthalmus maximus)]. Although the observed ratio of 5.65 cods disappearing for each cod retrieved with seal bite marks is similar to a study from the 2000’s, we show that average daily cod disappearance rates are linked to the duration a gear is left soaking in the same location.

Quantification and mitigation of bottom-trawling impacts on sedimentary organic carbon stocks in the North Sea

Abstract. The depletion of sedimentary organic carbon stocks by the use of bottom-contacting fishing gear and the potential climate impacts resulting from remineralization of the organic carbon to CO2 have recently been heavily debated. An issue that has remained unaddressed thus far regards the fate of organic carbon resuspended into the water column following disturbance by fishing gear. To resolve this, a 3D-coupled numerical ocean sediment macrobenthos model is used in this study to quantify the impacts of bottom trawling on organic carbon and macrobenthos stocks in North Sea sediments. Using available information on vessel activity, gear components, and sediment type, we generate daily time series of trawling impacts and simulate 6 years of trawling activity in the model, as well as four management scenarios in which trawling effort is redistributed from areas inside to areas outside of trawling closure zones. North Sea sediments contained 552.2±192.4 kt less organic carbon and 13.6±2.6 % less macrobenthos biomass in the trawled simulations than in the untrawled simulations by the end of each year. The organic carbon loss is equivalent to aqueous emissions of 2.0±0.7 Mt CO2 each year, roughly half of which is likely to accumulate in the atmosphere on multi-decadal timescales. The impacts were elevated in years with higher levels of trawling pressure and vice versa. Results showed high spatial variability, with a high loss of organic carbon due to trawling in some areas, while organic carbon content increased in nearby untrawled areas following transport and redeposition. The area most strongly impacted was the heavily trawled and carbon-rich Skagerrak. Simulated trawling closures in planned offshore wind farms (OWFs) and outside of core fishing grounds (CFGs) had negligible effects on net sedimentary organic carbon, while closures in marine protected areas (MPAs) had a moderately positive impact. The largest positive impact arose for trawling closures in carbon protection zones (CPZs), which were defined as areas where organic carbon is both plentiful and labile and thereby most vulnerable to disturbance. In that scenario, the net impacts of trawling on organic carbon and macrobenthos biomass were reduced by 29 % and 54 %, respectively. These results demonstrate that carbon protection and habitat protection can be combined without requiring a reduction in net fishing effort.

New insights into the impact of leachates from in-field collected plastics on aquatic invertebrates and vertebrates

The impact of leachates from micronized beached plastics of the Mediterranean Sea and Atlantic Ocean on coastal marine ecosystems was investigated by using a multidisciplinary approach. Chemical analysis and ecotoxicological tests on phylogenetically distant species were performed on leachates from the following plastic categories: bottles, pellets, hard plastic (HP) containers, fishing nets (FN) and rapido trawling rubber (RTR). The bacteria Alivibrio fischeri, the nauplii of the crustaceans Amphibalanus amphitrite and Acartia tonsa, the rotifer Brachionus plicatilis, the embryos of the sea urchin Paracentrotus lividus, the ephyrae of the jellyfish Aurelia sp. and the larvae of the medaka Oryzias latipes were exposed to different concentrations of leachates to evaluate lethal and sub-lethal effects. Thirty-one additives were identified in the plastic leachates; benzophenone, benzyl butyl phthalate and ethylparaben were present in all leachates. Ecotoxicity of leachates varied among plastic categories and areas, being RTR, HP and FN more toxic than plastic bottles and pellets to several marine invertebrates. The ecotoxicological results based on 13 endpoints were elaborated within a quantitative weight of evidence (WOE) model, providing a synthetic hazard index for each data typology, before their integrations in an environmental risk index. The WOE assigned a moderate and slight hazard to organisms exposed to leachates of FN and HP collected in the Mediterranean Sea respectively, and a moderate hazard to leachates of HP from the Atlantic Ocean. No hazard was found for pellet, bottles and RTR. These findings suggest that an integrated approach based on WOE on a large set of bioassays is recommended to get a more reliable assessment of the ecotoxicity of beached-plastic leachates. In addition, the additives leached from FN and HP should be further investigated to reduce high concentrations and additive types that could impact marine ecosystem health.

Environmental DNA metabarcoding reflects spatiotemporal fish community shifts in the Scheldt estuary

Estuarine ecosystems face increasing anthropogenic pressures, necessitating effective monitoring methods to mitigate their impacts on the biodiversity they harbour. The use of environmental DNA (eDNA) based detection methods is increasingly recognized as a promising tool to complement other, potentially invasive monitoring techniques. Integrating such eDNA analyses into monitoring frameworks for large ecosystems is still challenging and requires a deeper understanding of the scale and resolution at which eDNA patterns may offer insights in species presence and community composition space and time. The Scheldt estuary, characterized by its diverse habitats and complex currents, is one of the largest Western European tidal river systems. Until now, it remains challenging to obtain accurate information on fish communities living in and migrating through this ecosystem, consequently confining our knowledge to specific locations. To explore the potential of eDNA based monitoring, we simultaneously combine stow net fishing with eDNA metabarcoding, to assess spatiotemporal shifts in the Scheldt estuary's fish communities. In total, we detected 71 fish species in the estuary using eDNA metabarcoding, partly overlapping with historic fish community data gathered at the different study locations and in contrast to only 42 species using stow net fishing during the same survey period. Community compositions found by both detection methods varied among sampling locations, driven by a clear correlation to the salinity gradient. Limited effects of sampling depth and tide were observed on the eDNA metabarcoding data, allowing a significant reduction of the eDNA sampling effort for future eDNA fish monitoring campaigns in this study system. Our results further demonstrate that seasonal shifts in fish species occurrence can be detected using eDNA metabarcoding. Combining eDNA metabarcoding and stow net fishing further enhances our understanding of this vital waterway's diverse fish populations, allowing a higher resolution and more efficient monitoring strategy.

Simulation Of An Automatic Fish Netting Tool With Continuous Servo Motor Drive, Hc-Sr04 Distance Sensor And Button, Using Arduino Mega

The current fish harvesting system is still not optimal and requires a lot of human power . In every fish farming place, we can see that the fish netting system still uses manual nets, lots of people, and takes a long time. This affects the turnover / income and profit from the fish empowerment business. Therefore, to increase time efficiency, human energy, turnover and profit, this tool is a solution for every fish empowerment location. Because this tool is designed with an automatic system with a continuous servo motor, HC-SR04 distance sensor, push button, with an Arduino Mega base. button as the input command, the empowerer only needs to input the button (push button) to start harvesting cultivated fish, so that this work becomes more efficient in time, human energy, and influences the increase in turnover and business profits.

Carbon footprint and associated environmental impacts of fisheries on the Pulicat region, Southern India: A preliminary study

The current research analyzed carbon emissions resulting from fossil fuel consumption in the Pulicat region. This area is home to approximately 3500 motorized boats dedicated to fishing activities. Through this comprehensive study, we assessed the fuel consumption and subsequent carbon emissions within the motorized fishing sector. Our investigation revealed that traditional fishing methods in Pulicat Lake consumed 148,515 L of fuel whereas fishing methods along the Pulicat coast consumed a substantial 1650,429 L of fuel during the study period spanning from June 2022 to May 2023. In total, the Pulicat region accounted for the consumption of 1798,944 L (1547.1 metric tonnes (MT)) of fuel, contributing a mere 0.00004% to the global fuel consumption levels attributed to the small-scale fishing sector. Furthermore, the cumulative CO2 emissions resulting from fishing activities in the Pulicat region amounted to 4731.23 MT, representing a 0.001% of the overall CO2 emissions attributed to the Indian fishing sector. Remarkably, the Pulicat region emitted 1.05 MT of CO2 to capture 1 t of fish during the study period. The average CO2 emissions of fish stood at 1.08 MT of CO2/ ton of fish. Our analysis revealed that October 2022 recorded the highest carbon emissions per ton of fish at 1.45 MT of CO2 whereas May 2023 exhibited the lowest carbon emissions at 0.54 MT of CO2/ ton of fish. Within the Pulicat region, the use of crab lift net fishing methods in the lake (0.10 MT of CO2 per ton of fish) and purse seine techniques along the coast (0.65 MT of CO2/ ton of fish) emerged as the most energy-efficient fishing methods among the various alternatives. This study offers an in-depth exploration of carbon emissions originating from the Pulicat region’s fishing activities, providing valuable insights into the environmental impact of this crucial sector.

Technical and financial analysis of 1 GT Gill net fishing in Teluk Lancar Village, Bantan District, Bengkalis Regency, Riau Province

This research was conducted in February 2023 at Teluk Lancar Village, Bantan District, Bengkalis Regency, Riau Province, to know fishermen's techniques in carrying out fishing activities using gill nets with 1 GT boats and how the business feasibility of fishermen using gill nets with boats 1 GT using the survey method. The results showed that the fishermen's technique of operating gill nets in Teluk Lancar Village measured the water's depth; after that, the net was used and thrown to the right of the ship while moving backward (setting). Furthermore, within 1 or 2 hours, the crew lifted the nets in the water onto the ship and moved forward. Fishermen's investment in business activities is IDR 27,600,000.00. The total costs incurred in fishing business activities amount to IDR 92,190,000.00/year, the income received by fishermen is IDR 113,352,000.00/year, the revenue that fishermen have obtained is IDR 21,162,000.00/year, the results of calculating business feasibility based on the formula Revenue Cost of Ratio (R/C), Payback Period of Capital (PPC), and Financial Rate of Return (FRR) this business is feasible to continue and also develop.

Design of Home Decoration Products from Leftover Fishing Nets Coated with Latex: Product Designs Reflecting the Identity of the Southern Region Communities in Thailand

Design of Home Decoration Products from Leftover Fishing Nets Coated with Latex: Product Designs Reflecting the Identity of the Southern Region Communities in Thailand

Traditional games for physical fitness: an experimental study on elementary school students

Maintaining optimal physical fitness is crucial for students to combat fatigue during activities, allowing them to concentrate on their studies during the learning process at school. Consequently, physical fitness is a fundamental aspect of health that warrants careful consideration. The objective of this study is to enhance students' abilities and promote good physical fitness through the utilization of traditional games. The research employed a pre-experimental design with a one-group pretest-posttest approach. Modified traditional games, including sodor carts, fish nets, and balloon racing, were applied as the treatment.The results of the treatment demonstrated a significance value of 0.000, indicating a notable increase in students' physical fitness after engaging in learning activities through traditional games. This improvement is attributed to the traditional games, which effectively engage children in learning, fostering active participation and contributing to the enhancement of physical fitness. Consequently, the conceptualization of physical learning within the framework of traditional games proves to be applicable and effective. Keywords: Physical Fitness, Traditional Games, Elementary School, Children's Games

Valuation of the Bar Reef Marine Sanctuary from the Perception of the Visitors


 
 
 Bar Reef is a diverse ecosystem with near shore coral reefs, sea grass beds and associated ecosystems with over 120 coral species and over 300 fish species reported from the surrounding sea. It has been declared as a marine sanctuary by the Department of Wildlife Conservation in 1992. Despite of the efforts it is subjected to over exploitation by extractive users, destructive fishing practices and visitor pressure on the ecosystem. The study sought to value the ecosystem degradation prevailing in the bar reef from the perception of the visitors using choice experiment method. Different attributes for the choice experiment were identified using two focus group discussions and 10 key informant interviews held prior to the mail survey. Identified attributes were level of plastic accumulated, use of illegal fishing nets, level of crowding and monetary contribution. An orthogonal main effect design was generated and 9 choice cards were prepared, each with 4 different attributes. Randomly selected 250 visitors were interviewed onsite during January to June 2021 and conditional logit model was used to analyze the significance of their preferences. Paying LKR 1,000, reducing crowding the beach area by 15% and reduction of plastic and polythene by 50% were the significant factors according to the results obtained at α=0.01. People are willing to pay LKR 1,001.18 if plastic pollution can be reduced by 50%. People are willing to pay LKR 998.92 if the crowding of the beach can be reduced by 15%. The results of this research emphasize the importance of protecting this habitat to the relevant stakeholders. Further, this research will enable to introduce new policies and practices so that sustainability of the ecosystem can be ensured.
 Keywords: Ecosystem sustainability, Choice experiment, Conditional logit, Marine plastic pollution, Visitor access management
 
 

ОСОБЕННОСТИ НЕРЕСТОВЫХ МИГРАЦИЙ ПРОХОДНЫХ ВИДОВ РЫБ КАСПИЙСКОГО МОРЯ ЧЕРЕЗ МОРСКОЙ СУДОХОДНЫЙ КАНАЛ ЗА ПЕРИОД 2001–2022 ГГ.

Background. Anadromous species of sturgeons, salmonids and clupeids inhabiting the Caspian Sea migrate to their spawning grounds predominantly through the Volga-Caspian Sea Shipping Canal (VCSSC), which hydrological and hydrographic features have an effect on the abundance dynamics of the anadromous fish species. Along the entire delta sea edge, the Volga-Caspian Sea Shipping Canal (around 200 km in length) provides the conditions required for fish migration. Relevance. The current decrease in the Caspian Sea level and extensive accumulation of the fluvial and marine drift sediments impede navigation due to insufficient depth of the waterway and affect the entering of the anadromous breeders. This work is aimed at the assessment of the VCSSC use by sheefish, black-spined herring, beluga sturgeon, Russian sturgeon and stellate sturgeon during various seasons within 2001–2022 time range. Methods. Trawling and net fishing have been conducted in the marine part of the canal. Based on the data from seine catches in the river, the seasonal dynamics of fish migrations has been identified. Results. Despite the existence of extensive riverine network of the River Volga Delta suitable for the entering of anadromous fish species (Kirovsky, Belinsky, Igolkinsky, Karaysky and other banks), the Volga-Caspian Sea Shipping Canal (Main Bank) provides the anadromous fish species with a primary transit waterway to their spawning grounds—up to 90 % sheefish and black-backed herring breeders out of the total spawning stock abundance. The share of stellate sturgeon migrating along this waterway is 76–78 %, for the Russian sturgeon it is 83–85 %, and for beluga sturgeon it is 90–95 % of the spawning populations in the year of their entering into the Volga River. In recent years, the ecosystem of the Volga River has been developing in the context of low water content, which leads to the decrease in the water level of fish passage channels and tj a weakened flow, which, exacerbated by abiotic factors, in turn results in the reduction in the spawning stock abundance and decline in the yield of juveniles of the anadromous fish species [1]. Conclusion. During their pre-spawning season, sturgeons, sheefish and anadromous herring use the Volga-Caspian Sea Shipping Canal as the main migratory passageway to their spawning grounds. After the spawning, the canal provides juveniles and mature breeders with the passageways to the feeding sites in the Northern Caspian Sea. Sturgeon juveniles and the individuals skipping the spawning actively feed in the marine part of the canal [2].

Analysis of Trawl Net Fishing of Antarctic Krill in a Polar Ice Area

Analysis of Trawl Net Fishing of Antarctic Krill in a Polar Ice Area