Explore the vast range of titles available.

Eutaeniichthys cf. gilli Jordan & Snyder, 1901 (Gobiidae), an estuarine goby with a high risk of vulnerability, is documented for the first time in Vietnam, representing the recent southernmost and westernmost range of distribution of the species. A single specimen measured 26.7 mm in standard length (SL) was collected during the summer from the intertidal flat area near the mouth of the Red River at Xuan Thuy National Park, Vietnam. The collection was conducted during high tide using a small seine net in an area characterized by scattered mangrove trees and a mixed sandy and muddy bottom with shrimp burrows. This goby is characterized by a very elongate and slender body with three short spines in the first dorsal fin and a stripe of melanophores extending along the side throughout its entire length. The photographic, meristic, and morphometric data of the specimen are provided to aid in resolving the ambiguity of taxonomic studies of gobies in Vietnam.

Skipjack tuna is the main target for commercial fisheries in the Luwu District, Bone Bay. The fish catching is performed all year long, so the overharvesting of this species tends to increase. The goal of the study is to analyze the performance skipjack tuna fishing gear (pole and line, hand line, and seine net) based on four aspects: biological, technical, social, and economical. Design the of study is direct observation in the field using interview method to choice respondent as like owner of fishing boat and other people choice each skipjack fishing gear. The analysis used scoring methods. Result of the study indicated that the pole and line was the optimal choice in technical and economical aspect, but hand line the optimal in biological and social aspect. The main priority of fishing gears in succession was first pole and line, second hand line and last seine net. The conclusion was that the fishing gear of pole and line had the best performance than others fishing gear in District Luwu. The fishing gear was also suitable to be continued and developed in the future because its profitable and short time in payback periods.

Surf zones of sandy beaches are crucial environments for numerous fishes but one of the most challenging habitats when it comes to sampling, due to high-energy currents and waves. In this study, we compared the efficiency of 2 methods currently used to sample the biodiversity of shallow surf zone fish communities: the traditional method of beach seine nets and the more recently introduced surf zone Baited Remote Underwater Video Stations (surf-BRUVS). We ap plied both sampling strategies at 67 sites along 27 sandy beaches with different environmental characteristics in southeastern Brazil.We compared overall abundance, species richness, and beta (turnover) and functional trait diversity recorded from both methods. Our results showed that seine nets captured a higher species richness, greater abundance, greater functional richness and more functionally singular species than surf-BRUVS, particularly in areas with low wave energy. Beta diversity analyses, however, showed a clear difference in assemblage composition detected by each method regardless of environmental conditions, mainly driven by species turnover and variations in abundance. Only seine nets captured small species (<10 cm total length), while surf-BRUVS were more effective in recording larger species. Our results suggest that shallow surf zone assemblages sampled with surf-BRUVS and beach seine nets are almost totally taxonomically and highly functionally divergent, and the application of both methods provides complementary results. Additionally, the non-extractive nature of surf-BRUVS presents an opportunity for sampling vulnerable areas or species. However, when using a single method, researchers should take into consideration each method’s biases and be aware that biodiversity may be underestimated for certain groups.

To address the key principles and deliverables identified in South Africa's National Freshwater (Inland) Wild Capture Fisheries Policy and Implementation Plan, and the paucity of information on inland small-scale fisheries, a small-scale fisheries pilot research project was implemented at Krugersdrift Dam, Free State Province, South Africa. This paper presents the results of a 12-month seasonal study and pilot research project, with notes on the socio-economic benefit to communities and value of freshwater fish as a natural resource. Nine unemployed youth from Ikgomotseng, a small rural town in close proximity to the dam, attended a basic course on small-scale fisheries development, with only five still actively involved by the end of the research period. Three long-lines to which sixty 6/0 circular hooks on snoods were attached, a beach seine net and three double-ended Dutch type fyke nets were used to harvest fish. The long-lines selected exclusively for sharptooth catfish Clarias gariepinus, while catches from the beach seine net were dominated by common carp Cyprinus carpio, C. gariepinus and moggel Labeo umbratus. Catch rates based on the total weight of all species caught during the study period varied from 3 147 kg for long lines, 3 363 kg for the beach seine net and 251 kg for fyke nets. Although fishing was limited to 1 week per month during the experimental phase, results indicate an average monthly income of 6 255.48 ZAR-fisher (1) can be expected based on 20 days of harvesting fish per month. Investigations of the price the fishers sold their catch for indicated that C. carpio was sold at 28 ZAR-kg (-1), C. gariepinus at 17 ZAR-kg (-1), and L. umbratus at 24 ZAR-kg (-1). The methodology and gear used during this study may serve as a blueprint for the further development of small-scale fisheries in the Orange-Vaal river system in South Africa. KEYWORDS freshwater fish job creation rural development inland fisheries

Quantifying the fish harvest from inland aquatic ecosystems is a major prerequisite for effective fisheries management. However, rigorous efforts are lacking in this direction due to erratic fishing patterns, isolated landing sites, and nonattendance of fishermen. Moreover, there is an urgent need of systematic evaluation of aquatic resources from Ramsar sites, which are wetlands of international importance. In this direction, the finfish harvest of the Vembanad estuary, a Ramsar site of international importance in Kerala state, India was estimated on a monthly basis from June 2019 to May 2020, covering ten major fish landing centres. The exploited finfish fishery was estimated as 867 tonnes, comprising 88 species from 48 families and 71 genera. Cichlids (19.50%), catfishes (12.40%), anchovies (10.10%), mullets (8.52%), and cyprinids (3.70%) were the major groups in the fishery. The landings included one endangered (EN) ( Himantura uarnak ) and 4 vulnerable (VU) ( Rhizoprionodon acutus, Hyporhamphus xanthopterus, Channa diplogramma, and Horabagrus brachysoma ) fish species. The major fish species in the fishery were Etroplus suratensis (90.46 t), Oreochromis mossambicus (65.56 t), Arius maculatus (57.97 t), Ehirava fluviatilis (56.34 t), and Stolephorus commersonnii (53.24 t). Gill nets (66.80%) were the dominant fishing gear in the estuarine fishery, followed by stake nets (21.32%), seine nets (6.70%), and Chinese dip nets (2.55%). The highest landings were recorded during the pre-monsoon season (40.43%), while the lowest during the monsoon (26.99%). The study revealed a decline (68%) in the finfish landings, from 2647.1 t (1988–89) and 1192.17 t (2012–13) to 867.13 t (2019–20), which might have been due to depletion of microhabitats and mangrove areas, compositional changes in water and soil, siltation, pollution, microplastics contamination, urbanization in the Kochi city, a reduction in estuarine area and mean depth, and over-exploitation. Therefore, there is an urgent need for management actions, including protection of natural microhabitats, mesh size regulation, the implementation of catch quotas and total allowable catch, artificial stocking of edible indigenous fish species, prevention or elimination of alien fish species and the declaration of fish protection zones, to protect the largest Ramsar site along the west coast of India.

Typified by heterogeneous habitats, large rivers host diversified communities throughout their course. As the spatial organisation of fish communities within these ecosystems remains little studied, longitudinal gradients and spatial heterogeneities of fish diversity were analysed in the large temperate St. Lawrence River, Canada. We used two distinct datasets obtained from either seine nets or gillnets from governmental standardised fish surveys (1995–2012) consisting of a total of 299,662 individuals from 76 fish species captured in 1,051 sites. Results from diversity indices and multivariate analysis revealed a gradual downstream increase in taxonomic diversity, and a gradual change of the community structure along the river. In addition, we observed different fish communities within fluvial lakes and corridors and found significant differences in fish community structure between opposite shores. The fish communities described along the river using seine nets are spatially more heterogeneous than when described using gillnets. This discrepancy is likely resulting both from the more mobile species targeted by gillnets and sampling sites located farther from the shallower shoreline habitat targeted by seine nets. The organisation of fish communities stresses the need to implement science-based policies and actions to preserve biodiversity and restore communities distributed over large heterogeneous ecosystems.

The dynamics of fishing nets can be estimated by modeling and numerically computing the forces acting on them. However, the dynamic models of fishing nets are highly nonlinear owing to the significant influence of hydrodynamic forces acting on the net. Therefore, if there are unknown parameters that define the state of motion in the model, it is often difficult to achieve high accuracy in the numerical simulations of fishing gear and evaluate its dynamics. To address this issue, a method is proposed for estimating these unknown parameters by integrating a nonlinear Kalman filter into a fishing net dynamics model. This study aimed to estimate the hauling velocity of large- and medium-sized purse seine fishing nets, which can be a challenging parameter to measure. The calculations are based on the data obtained from a research operation conducted by the Marine Fisheries Research and Development Center in 2019 using the purse seine fishing vessel “Taikei Maru No. 1”. The time series of the hauling-net velocity was estimated based on the results of the estimation experiment. These results allowed the estimation of the hauling velocity and calculation of the net dynamics during the hauling process. This shows that net dynamics simulation is possible even with unknown parameters.

Five sampling campaigns were conducted in the water columns of River Sabaki and Tana in Kenya, Between October 2021 and January 2023, covering a 1-year cycle, at four sites in River Sabaki (2.5 km, 3.05 km, 3.51 km, and 4.52 km) and River Tana (1.5 km, 1.8 km, 2.0 km, and 2.5 km) distant from the river mouth. The ebb and flood tides were sampled to calculate net plastic litter fluxes. Two 6350-µm seine nets were deployed in two replicates per sampling point. Factor and cluster analysis were used to investigate plastic litter sources for both rivers. The influences of rainfall on plastic abundance and mass were explored using permutational linear models. A total of 15,318 plastic litter items weighing 1.37 kg were recorded in River Sabaki, and 3741 plastic litter items weighing 0.95 kg in River Tana. The top ten captured plastic litter types sorted by abundance and mass were mostly plastic fragments. The annual net plastic litter flux to the ocean through River Sabaki amounted to 1,277,120.63 items year −1 by abundance and 22.30 kg year −1 by mass. For River Tana, the same fluxes were 207,550.76 items year −1 , and 28.09 kg year −1 , respectively. In River Sabaki, significant impacts of rainfall on plastic abundance and mass were found. River Sabaki’s pollution sources included upstream reaches, fishing activities, and littering by locals and tourists. River Tana’s major pollution sources were illegal dumpsites, littering, fishing, and recreational activities. This research can guide combat plastic pollution in the rivers and ultimately the ocean.

We evaluated the influence of hydrological phases and limnological variables on the taxonomic composition and functional diversity of fish associated with aquatic macrophytes in a floodplain lake of Amazon Basin, Brazil. Sampling was conducted using seine nets across the four phases of the local hydrological cycle (rising, high-water, receding, and low-water) during the year 2018 in Lake Maicá. The species were identified and classified into four functional groups on the basis of their ecological traits (migration, life history strategy, feeding habits, and swimming performance/microhabitat use). A total of 6075 individuals were captured, representing nine orders, 26 families, and 104 species. The fish assemblages underwent changes in both taxonomic and functional structure in response to the hydrological phases and limnological variables (pH, temperature, dissolved oxygen, and water transparency), with an increase in functional diversity during the receding water and low-water phase. During the low-water period, there was an increase in the abundance of fish with life history strategies at equilibrium, small periodic species as well as invertivores, piscivores, short-distance migrants, and residents. In contrast, the rising and high-water phases contributed to higher abundances of young fish (larvae and juveniles) and medium-distance migratory fish. The synergy among these factors acts as an environmental filter in the structure of the local ichthyofauna, allowing species with antagonistic ecological traits to coexist, maintain their populations, and reduce competition for space and food under varying environmental conditions during the four phases of the annual hydrological cycle. The information presented is essential for identifying priority areas for the conservation of fish assemblages, which represent the primary source of animal protein and income for the region, and for understanding the mechanisms responsible for changes in the taxonomic and functional structure of fish in Amazonian floodplain lakes.

The temporarily open-closed (TOCE) Seekoei Estuary, on the warm temperate coast of South Africa, has been subject to various anthropogenic modifications such as impoundments, water abstraction, causeway construction, and artificial breaches that have impacted its estuarine functioning. To determine the impact of these combined factors on the fish community, the Seekoei Estuary was sampled twice per season over 2 years, which included a hypersaline phase. A total of 92,026 fishes, comprising 12 families and 25 species, were caught from five different habitat types using a 30 m × 1.7 m seine net (10-mm mesh aperture). The catches were dominated by the exclusively estuarine species Gilchristella aestuaria (81.0%) (Clupeidae), followed by the estuarine and marine Atherina breviceps (11.4%) (Atherinidae) and the marine estuarine-dependent Rhabdosargus holubi (5.1%) (Sparidae). Fish catch-per-unit effort (CPUE) were similar among seasons and sites; however, species richness was highest (d = 1.24) at the site directly below an obstructing causeway hindering fish migration. Additionally, reoccurring hypersaline conditions due to low freshwater inflow and artificial breaching have resulted in frequent fish kills of mainly marine origin species, creating an anthropogenically mediated ecological trap. The current anthropogenic alterations require amelioration for the conservation of the fish and the ecological functioning of this estuary. Rehabilitation to restore functioning is important for estuaries globally, especially estuaries with low inflow.