Inland Fisheries Research Articles

Перспективи промислового використання карася Київського водосховища

Purpose. Establishing modern parameters of Prussian carp population as a promising object for increasing commercial fish productivity of the Kyiv Reservoir. Methodology. The work is based on field materials obtained during the period 2019-2021 on the Kyiv Reservoir. Data collection and processing was carried out in accordance with generally accepted methods. Ichthyological material was collected from catches of the survey gill nets with mesh sizes of 30-120 mm and commercial gill nets with mesh sizes of 38-50 and 75-100 mm. A total of 1215 net-days of surevy and commercial nets were analyzed during the study period, of which 2372 specimens of Prussian carp were analyzed. Statistical data processing was carried out using MS Excel. Findings. The main parameters that characterize the commercial stock of Prussian carp of the Kyiv Reservoir in the context of optimizing the commercial fishing pressure on this species have been determined. It was found that the state of recruitment of the commercial stock of this species was satisfactory and the dynamics of its size-age structure indicated a low commercial fishing pressure, especially on the right wing of the variation series — the average annual fishing mortality in 2019-21 was φM=0.13. The majority of the commercial stock is steadily composed of age-6 to age-10 fish, the share of older age groups was consistently high, which led to fluctuations in the weighted average age in catches within 6.7...8.5 years. It was shown that the intensification of Prussian carp harvest (due to specialized fishing with nets with mesh size of 50 mm) would allow increasing catches in the Kyiv Reservoir by 52...65%. Originality. For the first time, a detailed description of Prussian carp of the Kyiv Reservoir is presented as an adventive species that quickly assimilates free econiches and requires scientifically based measures to localize its abundance. Practical value. Based on the processing of information on the state of stocks of Prussian carp as part of the source of commercial fishery of the Kyiv Reservoir, the procedure of intensification of its commercial exploitation was determined, taking into account both fishery and environmental aspects. Proposals regarding the quantitative characteristics of specialized fishery with nets with mesh sizes of 50-60 mm are included in the new edition of the Rules for commercial fishery in inland fisheries water bodies (parts thereof). Key words: Kyiv Reservoir, Prussian carp, size-age structure of the catch, commercial stock, specialized fishing.

Isolation and characterization of 17 polymorphic microsatellite loci with tri- and tetra-nucleotide repeat motifs for Ayu (Plecoglossus altivelis) using next-generation sequencing.

Ayu or sweetfish, Plecoglossus altivelis, an amphidromous fish ranging in the northwestern Pacific, is economically important inland fisheries and aquaculture resources. Genetic characterization of wild Ayu and derived culture seeds with competent molecular genetic markers is still insufficient for their sustainable use. Microsatellite DNA markers with larger repeat motifs (e.g. tri- and tetra-nucleotide motifs) are convenient and accurate compared with those having mono- and di-nucleotide motifs, but the latter motifs characterized most Ayu microsatellite markers developed previously. Here, we isolated and characterized 17 polymorphic microsatellite DNA markers with tri- and tetra-nucleotide repeat motif using next-generation sequencing. Alleles per locus varied from 6 to 23. The observed and expected heterozygosities ranged from 0.542 to1.000and 0.709to0.951, respectively. Polymorphic information content (PIC) of 15 out of the 17 loci were high (≧ 0.700), suggesting them to be highly informative. Twelve of the 17 loci were used for preliminary assignment test among three collections, and successfully allocated the examined fish to the original populations. The novel polymorphic microsatellite markers developed herein will be useful to examine the genetic diversity and population structure of wild Ayu and the effect of seed transplantation on native populations, providing a tool for conservation and sustainable adaptive management of this species.

Evaluation of the inland fisheries in Basrah province in Iraq during 2020-2021

The study was aimed to update the knowledge on the fish landings of the inland fisheries in Basrah province, Iraq. The species composition, species and total landings, and their trends in six landing sites throughout the study region were evaluated during the year 2020-2021. Species compositions were included seven cyprinids’ species, three cichlids’ species, three mullet’s species, and two species from sparids and silurids. The exotic species, C. carpio, tilapias species and C. auratus dominated the landings constituting 44.2% of the total catch, whereas the highly valued native species (M. sharpeyi, L. xanthopterus, C. luteus and A. grypus) forming only 12.4% of the total catch. The total landing reached 2,427.78 t in 2020 and 2,365.15 t in 2021, and these values were higher than what was recorded during the past years since the year 2009. This is due to the prevalence of aliened species and the increase in the fishing effort, such as the numbers of fishermen and fishing boats. Therefore, in fisheries management point of view, it is essential to enhance the stocks of the native species, minimize the dispersal and impacts of some exotic species, and activate the national regulating fishing, exploitation and protection of aquatic organisms to improve the inland fisheries.

Evaluation of the influence of correcting for gillnet selectivity on the estimation of population parameters.

Gill nets are a common sampling technique in inland and marine fisheries. However, gill nets are size selective and may result in bias estimates of population parameters. As such, selectivity is commonly assessed using indirect estimation techniques. Indirect estimates of gillnet selectivity have been suggested to improve estimates of important populations metrics (e.g., total annual mortality), but this assertion has not been assessed. In the current study, we simulated hypothetical populations of channel catfish Ictalurus punctatus, lake trout Salvelinus namaycush, walleye Sander vitreus, and white crappie Pomoxis annularis and sampled the populations based on published gillnet encounter and retention probabilities. Total annual mortality and von Bertalanffy parameters were then estimated using unadjusted (not "correcting" for selectivity processes) and adjusted ("correcting" for selectivity processes) age and(or) length data to evaluate the value of accounting for gillnet selectivity when estimating these metrics. Our results indicate that adjusting for retention and encounter probabilities rarely leads to improved estimates of total annual mortality, K, and L∞. For instance, estimates of annual mortality of lake trout based on age data adjusted for retention probability resulted in an overestimate of A by 14.4%. As such, we suggest that analysis of gillnet selectivity only be used when specific questions are being addressed (e.g., catch-at-age models) or in situation when all processes contributing to gillnet selectivity (e.g., contact probability, size-specific availability) are known.

World Heritage, Hydropower, and Earth’s Largest Freshwater Fish

The Mekong River is one of the most biodiverse, productive rivers in the world, supporting more than 1000 fish species and the livelihoods of tens of millions of people. The spatial dynamics and population status of many Mekong fish species, especially megafishes, are poorly understood. Therefore, this information is rarely incorporated into environmental risk assessments for large infrastructure projects, such as mainstream hydropower developments, which have been accelerating rapidly in the Mekong Basin. In this study, we present initial findings from the ongoing, collaborative, transnational acoustic telemetry monitoring of nearly 300 tagged fishes representing 27 species, which yield important insights into the potential impacts that proposed hydropower dams would have on populations of ecologically and economically important fish species. Included in these data are more than ten months of hydrophone records tracking the location of a 300 kg giant freshwater stingray, Urogymnus polylepis (Bleeker, 1852), currently the world’s largest known freshwater fish, used to detect its migration behavior and distribution patterns. The telemetry data, combined with fisher surveys used to gather local ecological knowledge, provide evidence that the proposed dams would fragment the existing populations of this iconic species as well as those of other fish species that support river food web balance and local food systems. Furthermore, the existence of giant freshwater stringray populations and other unique megafauna reinforces the universal natural heritage value of the stretch of the Mekong River between the Lao People’s Democratic Republic/Cambodia border and the city of Kratie. This stretch of river is located between two proposed megadams, the 900 MW Stung Treng Dam and the 2300 MW Sambor Dam. However, the Cambodian Ministry of Environment has also proposed this area for designation as a UNESCO World Heritage Site (Biosphere Reserve). The documentation of the movement of migratory fishes through this reach of the river using acoustic telemetry, the surprising discovery of the world’s largest freshwater fish, the potential threat posed by dam construction, and the management ramifications of UNESCO World Heritage Site designation underscore the importance of scientific research and community involvement in landscape-scale development decisions. The decisions made today will affect the fate of this global biodiversity hotspot, the world’s most productive inland fisheries, and the livelihoods of millions of people throughout the Lower Mekong Basin.

Significant decline of water pollution associated with inland fishery across China

Water pollution seriously threatens the sustainable development of fisheries in China. To inform effective pollution control policies, a comprehensive understanding of the fishery environment status is needed. However, nationwide data on the temporal changes of major pollutants in the fishery waters of China are scarce. This study collected data on the major water pollutants, including total nitrogen, total phosphorus, heavy metals, and total petroleum hydrocarbons (TPHs), from 2003 to 2017 to evaluate dynamic changes in the inland fishery water environment across China. We discovered that the levels of four heavy metals (Cu, Zn, Pb, and Cd) and TPH decreased during the 15-year period, corresponding to the reduced national discharge of pollution sources from 2003 to 2015. However, nitrogen and phosphorus levels in the inland fishery waters showed no significant changes during this period. A comparative analysis of water quality in different periods indicated that these improvements were highly associated with effective measures for water pollution control in China. In addition, the decline in pollution was consistent among the three regions of China (north, west, and southeast) from 2003 to 2017, while southeast China exhibited the weakest pollution mitigation among the three regions. These findings suggest that the inland fishery water quality improved during 2003–2017, but still faced eutrophication risk.

Outlay of inland fishery cooperatives for fishery resource enhancement in Japan

Outlay of inland fishery cooperatives for fishery resource enhancement in Japan

Environmental risks of organic fertilizer with increased heavy metals (Cu and Zn) to aquatic ecosystems adjacent to farmland in the northern biosphere of Japan

In Abashiri, Hokkaido, northern Japan, composted sewage sludge (CSS) containing a large amount of zinc (Zn) and copper (Cu) is used as fertilizer in agriculture. The local environmental risks of Cu and Zn from such organic fertilizers were studied. The study area, especially the brackish lakes located near the farmlands, is important for inland fisheries. The risks posed by heavy metals to the brackish-water bivalve, Corbicula japonica, was therefore investigated as an example. First, the long-term effect of CSS application in agricultural fields was monitored. Second, using pot cultivation, factors influencing Cu and Zn availability in the presence of organic fertilizers were evaluated under different scenarios of SOM content. In addition, the mobility and availability of Cu and Zn in organic fertilizers were evaluated in a field experiment. In the pot cultivation, both organic and chemical fertilizers increased the availability of Cu and Zn with a decrease in pH, possibly caused by nitrification. However, this decrease in pH was inhibited by higher SOM content, i.e. SOM mitigated the heavy metal risk from organic fertilizer. In the field experiment, potato (Solanum tuberosum L.) was cultivated using CSS and pig manure (PM). As observed in the pot cultivation, the applied chemical and organic fertilizers increased the soil-soluble and 0.1 N HCl-extractable Zn with increased nitrate. Considering the habitat and the LC50 values of C. japonica that were lower than the concentration of Cu and Zn in the soil solution phase, there is no significant risk from heavy metals in the organic fertilizers. However, the Kd values for Zn were significantly lower for CSS or the PM-applied plot in the field experiment soil, indicating a higher Zn desorption rate from organically fertilized soil particles. The potential risk of heavy metals from agricultural lands under changing climate conditions must therefore be monitored carefully.

Bauran Pemasaran Pada Usaha Rekreasi Pemancingan Nagaya Desa Kotapulu

The purpose of serving in the village with the mission of building a rural economy through the potential in the village is the fisheries sector, as well as to broaden business actors' insight into the application of the marketing mix. The potential in Kotapulu Village is in the fisheries sector. Nagaya fishing is one of the businesses as a means of community recreation. The development of inland fisheries in Central Sulawesi Province has quite large potential for freshwater and brackish water fisheries resources, which if managed optimally can provide a sizeable contribution to the region. Technical data collection is carried out through counseling, interviews and documentation that can answer existing problems. , and so on the data were analyzed descriptively qualitatively. From the results of this study, the Marketing Mix) or 7 P which consists of: Product, Price, Place, Promotion, Process, Physical Environment used in the Nagaya fishing recreational business is in accordance with the existing procedures, while for application in the field there are several obstacles that arise in terms of Promotion, so that the Marketing Mix is not going well.

Food Security Status and Its Determinants among Inland Fishing and Non-Fishing Rural Households in Sekhukhune District Municipality, Limpopo Province

Background: Inland fisheries are considered to have the potential to reduce food insecurity and malnutrition globally. However, its contribution has been unrecognized. The study aimed to analyze the determinants of food security status among households involved and uninvolved in inland fisheries in Sekhukhune District Municipality (SDM), Limpopo Province.
 Methods: A total of 115 households were interviewed following snowball, purposive, and simple random sampling techniques. Descriptive statistics, Household Food Insecurity Access Scale (HFIAS), and Multinomial Logistic Regression (MLR) were used as data analysis tools. These tools were used to obtain the socio-economic characteristics of households and the determinants of food security status.
 Results: A total of 72 households were identified as fishers, while 43 households were not fishers. Moreover, the results confirm that there was no significant difference in the food security status of households involved in inland fisheries and those who were not involved; however, most of them were mildly food insecure. Additionally, total household income, marital status, level of education and type of agricultural activity determine the food security status of households involved in inland fisheries and those who were not involved.
 Conclusion: The integration of inland fisheries and other sectors is necessary to address household food insecurity related issues.

-I fish, therefore I monitor: Participatory monitoring to assess inland small-scale fisheries.

Analysis of small-scale inland fisheries (SSIFs) is often highly dispersed and tends not reflect the true magnitude of their contribution to society. This is partly due to the insufficient attention given to this sector by the relevant authorities, in addition to its highly diverse characteristics, with complex patterns of operation in a wide range of systems, often in remote areas. Here, by integrating fishers as participatory fishery monitors, we provide fishery-dependent estimates of yields, the biological attributes of the fish species, and the spatiotemporal dynamics of the fisheries of lakes on the floodplain of the São Francisco basin in northeastern Brazil. As the fishers were willing participates in the monitoring, the results revealed well-structured artisanal fishing activities, with the lake system providing high-profile fish harvests from both monthly and annual perspectives. The spatial distribution of fishing effort reflected the adaptation of the fishers to the flood cycle of the river, in order to maintain high fishery productivity throughout the year. The results also indicate that participatory monitoring can help to overcome knowledge gaps and provide a database that is readily applicable to management needs at both local and regional scales. As Brazil is one few world's nations that no longer have national fishing monitoring program, participatory monitoring represents a low-cost solution for the credible and useful data on small-scale fisheries. It would thus appear to be extremely worthwhile to invest in the empowerment of communities in order to overcome the historic vulnerability of productive sector and the food security of the populations that depend on these fisheries.

Biological and life-history parameters for Labeo rosae Steindachner, 1894 and Oreochromis mossambicus (Peters, 1852) from Flag Boshielo Dam, Olifants River, South Africa

Inland fisheries contribute towards food security for rural communities living close to large aquatic systems. However, sustainable inland fisheries rely on accurate biological information for the target species at the proposed fishery location. In this study, the biological information for Labeo rosae Steindachner, 1894 and Oreochromis mossambicus (Peters, 1852) were determined at Flag Boshielo Dam, Olifants River system, Limpopo province, as part of a larger study to evaluate a small-scale gill net fishery at this impoundment. Nine fish surveys were conducted from February 2016 to April 2017 using mixed sampling gears. Labeo rosae exhibited positive allometric growth (b > 3) while O. mossambicus displayed negative growth (b < 3). For L. rosae, the asymptotic length was 391 mm L ∞, and the length-at-50% sexual maturity 165.8 mm. For O. mossambicus, the asymptotic length was 420 mm L ∞, and the length-at-50% sexual maturity 166.5 mm. Both species population stocks showed signs of exploitation. Total mortality for L. rosae was 0.57 yr−1 with a fishing exploitation of 0.21 yr−1, while total mortality of 0.78 yr−1 and fishing exploitation of 0.50 yr–1 were estimated for O. mossambicus. The biological data collected, apart from the length–weight parameters for O. mossambicus, are suitable for conducting a fisheries assessment for these species at Flag Boshielo Dam.

Evaluation of the inland fisheries in Basrah Province during 2020-2021, Iraq

The purpose of the study was to provide up-to-date information on inland fisheries landings in Basrah province, Iraq. During 2020-2021, the species composition, species and total landings, and trends at six landing locations in the research region were assessed. There were seven species of cyprinids, three species of cichlids, three species of mullet, and two species of sparids and silurids. The foreign species C. carpio, tilapias species, and C. auratus dominated landings, accounting for 44.2% of the entire catch. In contrast, the highly prized native species (M. sharpeyi, L. xanthopterus, C. luteus, and A. grypus) accounted for just 12.4%. In 2020 and 2021, the total landings reached 2,427.78 t and 2,365.15 t, respectively, greater than the previous years since 2009. This is attributable to the frequency of alien species and the rise in fishing effort, as measured by the number of fishermen and fishing vessels. Improving inland fisheries requires enhancing the stocks of native species, minimizing the dissemination and impacts of some exotic species, and activating national regulations governing fishing, exploitation, and conservation of aquatic life from the fisheries management perspective.&#x0D;

Trickier than it first appears: investigating opportunities to increase small fish production and availability from culture-based inland fisheries in West Bengal, India

Trickier than it first appears: investigating opportunities to increase small fish production and availability from culture-based inland fisheries in West Bengal, India

Size-age population structure of an endangered and anthropogenically introgressed northern Adriatic population of marble trout (Salmo marmoratus Cuv.): insights for its conservation and sustainable exploitation.

Salmonid species are main actors in the Italian socio-ecological landscape of inland fisheries. We present novel data on the size-age structure of one of the remnant Italian populations of the critically endangered marble trout Salmo marmoratus, which co-occurs with other stocked non-native salmonids in a large glacial river of the Lake Maggiore basin (Northern Italy-Southern Switzerland). Like other Italian native trout populations, the Toce River marble trout population is affected by anthropogenic introgression with the non-native brown trout S. trutta. Our sample includes 579 individuals, mainly collected in the Toce River main channel. We estimated the length-weight relationship, described the population size-age structure, estimated the age-specific growth trajectories, and fit an exponential mortality model. A subset of the sample was also used to measure numerical and biomass density. The estimated asymptotic maximum length is ~105 cm total length (TL). Mean length at first maturity is ~55 cm TL, and mean length at maximum yield per recruit is ~68 cm TL. Approximately 45-70% of the population are estimated to die annually, along with a fishing annual mortality of ~37%, with an exploitation ratio of ~0.5. The frequency distribution of length classes in a sample collected by angling shows that ~80% of the individuals that could be retained according to the current recreational fishing regulations likely never reproduced, and large fish disproportionally contributing to recruitment are fished and retained. We identify possible overfishing risks posed by present regulations, and propose updated harvest-slot length limits to mitigate such risks. More detailed and long-term datasets on this system are needed to more specifically inform the fishery management and monitor the effects of any change in the management strategy on the size-age structure of the marble trout population of the Toce River.

Transboundary Fisheries Management in Kavango–Zambezi Transfrontier Conservation Area (KAZA-TFCA): Prospects and Dilemmas

Inland fisheries in the Kavango–Zambezi Transfrontier Conservation Area (KAZA-TFCA) offer food security to the riverine communities across the region. They also contribute towards the attainment of the United Nations’ Sustainable Development Goals 1 and 15, which aim to alleviate poverty and maintain biodiversity conservation. Despite this significant role, the fisheries have suffered severe declines in the previous decades due to multiple factors, such as overfishing and poor legislation. Furthermore, climate change is exerting pressure by altering the ecology and productivity of the river systems. The unprecedented challenges of the COVID-19 pandemic have further constrained management efforts. Attempts to address these challenges have pointed towards transboundary fisheries management as a silver bullet in moving towards sustainable fisheries management. However, the implementation of this strategy in the region has encountered numerous roadblocks, thereby subjecting the river ecosystem to a wider environmental threat, with dire consequences on livelihoods. This paper reviews existing management and governance structures together with key informant interviews to elicit primary and secondary data essential for management at the regional level. The study identifies conflicting regulations, and inadequate policies and institutions across the region as major bottlenecks affecting the successful implementation of transboundary fisheries management. Finally, the paper offers some suggestions for the improvement of fisheries management in the region.

Parentage‐based tagging using mothers balances accuracy and cost for discriminating between natural and stocked recruitment for inland fisheries

AbstractHatchery programmes are frequently used to supplement inland fisheries, yet achieving successful management outcomes often requires information on stocked versus naturally reproduced fish abundance. Parentage‐based tagging – genetically assigning offspring to their parents – has potential to be an effective approach for distinguishing stocked and naturally reproduced fish. However, several challenges may limit its application to inland fisheries, including genetic relatedness among populations that can affect identification accuracy and high costs of genotyping large broodstocks. Here, we demonstrate the efficacy of parentage‐based tagging based on broodmothers in the Lake Ontario Chinook Salmon fishery, which uses thousands of broodparents and has potential for substantial relatedness between stocked and naturally reproduced fish. Restricting parent sampling to broodmothers reduced costs by two‐thirds, was logistically pragmatic, and achieved &gt;95% accuracy in distinguishing stocked from naturally reproduced salmon. Combined, these results highlight the potential wide applicability of parentage‐based tagging for assessing stocking programmes in inland waters.

Viability of side-scan sonar to enumerate Paddlefish, a large pelagic freshwater fish, in rivers and reservoirs

Recreational-grade side-scan sonar (SSS) has become an invaluable tool for inland fisheries, particularly when characterizing underwater habitat, but it is being increasingly used for enumerating large-bodied (> 1 m total length [TL]) aquatic fauna. We used SSS in river and reservoir environments to evaluate methods for identifying and counting Paddlefish Polyodon spathula, a large pelagic planktivore of recreational and economic importance that can exceed 2 m in length and weigh over 70 kg. We assessed accuracy and precision among readers to identify Paddlefish by assigning confidence scores (1–3; with 3 being more confident) to sonar images of a ballistics-gel filled fiberglass replica Paddlefish. Readers varied in their confidence scores for the replica Paddlefish and no reader could identify the target beyond 25 m from the transducer. Afterwards, we used SSS to survey several kilometers of a reservoir during summer residency and a large river during springtime spawning migrations. Two readers counted Paddlefish images in the SSS recordings and we estimated population size in the surveyed area with distance sampling. In the reservoir, the number of Paddlefish counted ranged from 172 to 184. In the river, the number of Paddlefish counted ranged from 165 to 617. The exponential model of distance was most-supported for detection in both environments, except there was support for a half-norm distribution for one reader in the river. In the reservoir, abundance estimates were statistically similar between readers at approximately 1500 (7/ha) in the total scanned area. In the river, similar abundance estimates were obtained with the half-norm model from one reader compared to the exponential model of the other reader, resulting in approximately 1500 individuals (30/ha) in the surveyed area. The application of SSS to count Paddlefish has some clear advantages to traditional methods, such as gill netting, and can be done at multiple times of the year. Distance sampling methods compensated for differences in counts among readers, indicating distance sampling can produce similar abundance estimates even when variation in counts exists among readers.

Response of fish stocks in Lake Victoria to enforcement of the ban on illegal fishing: Are there lessons for management?

Most small-scale inland fisheries in the Global South prohibit fishing gear with smaller meshes than is legally permitted. Nonetheless, in most instances, this is not strictly enforced. But starting in 2017, Uganda and Tanzania ramped up enforcement on Lake Victoria. We used time series hydro-acoustic data to determine whether the strict enforcement achieved the management goal of increased biomass (t) of commercial species and an increase in the biomass of big Nile perch (>50 cm). The biomass for 2018–2021 (under strict enforcement) was expected to be greater than in 2007–2017 (prior to strict enforcement). The biomass of key species fluctuated annually, but no spatial or temporal differences in biomass associated with strict enforcement were evident. Similarly, the biomass of big Nile perch did not increase. Our findings suggest that mesh sizes may have limited influence on fish biomass dynamics in Lake Victoria, and that high primary productivity of the lake, high turnover rates of fish species, and limited compliance by fishers likely counteract the effects of high fishing effort on biomass and size structure of fish. Therefore, the high cost of strict top-down enforcement and the societal cost of lost lives, jobs, and livelihoods may not be justified.

Differences of soundness of management and structure of expenditure of Japanese inland fishery cooperatives by differences of fishing grounds

内水面では漁場も採捕の対象となる魚種も多様であり，漁業協同組合（漁協）の経営もそれに対応して多様である。本研究では2017事業年度の全国の571の内水面漁協の業務報告書を用いて内水面漁協を7類型に類型化し，経営の安全性と支出の構造の違いを分析した。その結果，全ての類型の漁協で安全性は高いが，安全性の高さは人件費の額が小さいことによって維持されており，経営改善のためには収支の規模を拡大する必要があること，またアユおよび渓流魚の利益率を改善する必要があると考えられた。