Assessment of benthic diversity and estuarine ecological quality is becoming increasingly important. Estuaries are not only highly productive and variable environments, but they are also areas of high anthropogenic perturbations. In this study, benthic macrofauna were sorted, identified and analyzed from a freshwater-dominated tropical estuary along the Bay of Bengal to assess their community structure, distribution and functional guilds, and to uncover the environmental drivers influencing their distributional patterns. Results revealed that the studied physio-chemical variables (DO, pH, alkalinity and temperature) were significantly varied (p < 0.05) among the sites. Capitella sp. was dominant (18%) of the forty morphospecies recorded, indicating organic richness of the area. The ANOVA results revealed that macrobenthic density differed significantly (p < 0.01) between the study locations, and diversity indices (Shannon diversity index, H′) also differed significantly (F_4,12 = 5.89; p = 0.02). The benthic density decreased from the head to the mouth, which could be related to salinity fluctuations and large freshwater discharges. Upstream sites were completely segregated from downstream and mid-estuarine sites, according to cluster analysis (CA). The SIMPER results clarified the site grouping pattern, showing that Mysis-1 spp., Capitella spp. and Nephtys-1 were the most significant contributors. From the communities, five functional trophic groups were identified where deposit feeders were the most dominant (66.44%). Most of the macrobenthos had strong positive correlations with DO (r = 0.92) and water temperature (r = 0.86) and a negative correlation with soil pH (r = −0.28), per correlation and CCA analyses. Individually, soil pH (r = 0.88) and alkalinity (r = 0.898) showed strong positive correlation with Capitella sp. and Chironomus sp.2. The above results indicate that macrobenthos of this estuary do not follow the usual pattern of spatial distribution, and they are structured by DO, alkalinity and soil pH. In addition, dominance of some pollution indicator species (Capitella sp. and Chironomus sp.) and deposit feeders indicates a poor ecological condition of the estuary.

Biodiversity assessment is important for evaluating community conservation status. The haor basin in Sylhet Division represents a transitional zone with high species availability, rare occurrences and endemism. As a result, this study aims to describe the haor-based freshwater fish composition, including habitat, trophic ecology, availability and conservation status. Semi-structured questionnaires were used to collect data on fish samples through focus group discussions, field surveys, and interviews with fisheries stakeholders on a monthly basis. We identified 188 morpho-species, of which 176 were finfish and 12 shellfish, distributed into 15 orders and 42 families where 29%, 42%, 15%, and 14% species were commonly available, moderately available, abundantly available, and rarely available, respectively. Cypriniformes was the dominant order in both total species and small indigenous species identified. Approximately 45.34% of species were riverine, 31.58% floodplain residents, 12.55% estuarine, 2.83% migratory, and 7.69% were exclusively hill stream residents. Carnivores and omnivores were the most dominant trophic groups. A total of 87.76% species were used as food, 12.23% as ornamental and 6.91% as sport fish. Approximately 50 species were threatened (7 critically endangered, 23 endangered and 20 vulnerable) at the national level, most of them belonging to Cypriniformes and Siluriformes. Based on endemism, 16 species were endemic of which Sygnathidae, Cobitidae, Olyridae, Cyprinidae and Balitoridae fell under the threatened category. Minimizing intense fishing efforts, banning indiscriminate fishing and destructive fishing gear, initiating fish sanctuaries and beel nurseries, and implementing eco-friendly modern fishing technology are suggested to conserve the threatened species. This study represents a guideline for assessing the availability and conservation of freshwater fish in the Sylhet belt and serves as a reference for decision-makers in order to allow for the sustainable exploitation of fisheries resources within an ecosystem-based framework.

Kaptai Lake, the largest artificial reservoir in Southeast Asia, is home to a diverse fish fauna that supports thousands of livelihoods and is distinguished by multi-species and multi-gear fisheries. In Kaptai Lake, the gear-based catch composition, catch rate and distribution pattern are little known. From August 2020 to April 2021, a nine-month study was conducted in five upazilas using direct catch assessment surveys and fishing effort surveys from four fishing gears, namely seine nets, gill nets, lift nets, and push nets. A total of 49 morpho-species from 22 families were found, with three species from the Clupeidae accounting for 93.63 % of the catch in all gear combined. The total catch composition and CPUE were higher in seine nets (75.07 %, 13.86 ± 1.8 kg/gear/trip respectively) and lower in lift nets (4.97 %, 1.01 ± 0.21 kg/gear/trip) and showed significant differences among gears, except sampling sites whereas CPUE was higher in Naniarchar for seine nets (17.29 ± 8.89 kg/gear/trip) and lower in Langadu for lift nets (0.62 ± 0.25 kg/gear/trip). Seine nets captured more species, and the number of species increased significantly as CPUE increased. Our study assessed four gears that targeted different fish species with little overlap in leading species; seine nets and gill nets primarily targeted Clupeidae (96.53 % and 41.69 %, respectively), whereas lift nets and push nets primarily targeted Cyprinidae and Palaemonidae (38.93 % and 99.37 % respectively). The observed abundance and variety of fish species captured in gill nets suggest a significant overlap in the selectivity of this fishing method with that of lift nets. Due to the varying contributions of sites and gears, the nMDS ordination pattern reveals a weak spatial variation in catch composition. According to the SIMPER results, Bagridae, Gobiidae, and Ambassidae were the most significant contributors to site grouping patterns across all gears. Furthermore, the findings indicate that the catch composition does not follow the typical pattern of spatial variation. By implementing measures to eliminate or decrease the usage of small mesh nets, there is expected to be a corresponding decrease in the capture of small fish. Additionally, this action will help mitigate the issue of overlapping selectivity among the current fishing gears. Our findings provide baseline data on the potential efficacy of gear limitation and suggest a gear-based management strategy.

The Burmese dry fish market in Cox’s Bazar sadar is a traditional hub for a variety of dried fish products in coastal Bangladesh, playing a crucial role in local fisheries-based livelihoods and trade. This study offers a comprehensive review of commercial diversity, processing methods, drying times, pricing structures, and marketing channels based on a one-month field survey. Data were gathered from 15 retail shops through systematic observation and semi-structured interviews with experienced traders and shop owners. A total of 58 different dried fish products were documented, representing at least 24 scientifically identified taxa along with numerous market variants distinguished by size, processing level, and presentation form. Whole and near-whole products dominated the market, indicating limited post-harvest modification beyond initial preservation. Sun-drying was identified as the main processing technique, reflecting its low cost and reliance on suitable climatic conditions, while salt-curing was also widely employed to extend shelf life and improve product stability. Less common methods, including mechanical drying, premium processing, and fermentation, highlighted specialized products and higher value addition. Drying times varied significantly, from 1–2 days for quickly processed products to 120–150 days for fermented items such as puti shidol, illustrating species- and method-specific processing characteristics. Retail prices showed considerable variation (BDT 300–5,500 kg⁻¹), mainly determined by species type, product size, salting method, and perceived quality. The marketing system operated on multiple levels, involving fishermen, beparis, processors, wholesalers (aratdars), and retailers before reaching consumers, tourists, and regional traders. Overall, the market reflects a highly diverse, economically structured, and value-driven system influenced by biological, technological, and market factors. The findings of this study provide valuable insights for improving value chain efficiency, supporting sustainable fisheries-based livelihoods, and informing policy and market interventions to enhance the quality, profitability, and competitiveness of dried fish products in coastal Bangladesh.

This study investigated diversity, availability, current status, population trend, threats and conservation status of SIS in floodplain-rich haorbasin from September 2017 to April 2018. A total of 140 SIS belonging to 35 families and 89 genera were collected from 43 sampling sites (10 in arats/wholesale fish markets, 16 in retail markets, and 17 in fishing locations). Cypriniformes were the most diverse group. 47%, 29%, 14% and 9% of species were moderately available, commonly available, rarely available and abundantly available, respectively. Fish belonging to Cypriniformes and Siluriformes were under moderately available and rarely available categories. Carnivorous was dominant group (49%). National and global population trends of 44% and 13% recorded fish were declining (Perciformes, Siluriformes and Clupeiformes were dominant), whereas most of the species don't have enough biological informationstatus. Out of the 140 species, 4 belong to `critically endangered`, 18 `endangered` and 14 `vulnerable` at national level, beside the order Osteoglossiformes, Sygnathiformes and Cypriniformes were more threatened. Additionally, Mastacembelus oatesiiand Rita ritawere endangered and Channa orientalisand Barilius dogarsinghiwere vulnerable at the global level. Indiscriminate fishing, poisoning, illegal fishing, siltation, pollution and invasive species posed the greatest threat to fish diversity. Climatechange is hard to predict and drastically changing fish habitats and putting SIS at risk. Eco-friendly modern fishing technology, restoration, and potent conservation measures are urgently needed at multiple scales to conserve the fish fauna.