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.

This study is the first to report the development and quality assessment of hilsa (Tenualosa ilisha) mince stock and of hilsa khichuri, a traditional rice and pulse dish incorporating this stock. The quality of the developed product was comprehensively evaluated through proximate composition, chemical spoilage indicators, and sensory analysis to determine its shelf life and nutritional quality over six months of frozen storage at − 25 °C. Proximate analysis revealed significant differences (p < 0.05) between fresh hilsa and hilsa mince stock. The mince stock showed reduced moisture (48.37 ± 0.42%) and significantly higher levels of protein (24.50 ± 0.07%), lipid (18.00 ± 0.25%), ash (3.00 ± 0.29%), and fiber (5.13 ± 0.27%), compared with fresh hilsa, indicated higher concentrations of these proximate compositions in the mince stock on a wet-weight basis. Chemical (TVB-N, TMA-N, PV, pH, histamine) and microbial (TVC) indices increased progressively and significantly (p < 0.05) throughout storage. Sensory evaluation by trained panelists indicated that both hilsa mince stock and hilsa khichuri remained acceptable up to the six months of storage. Hilsa mince stock resulted in progressive but acceptable deterioration of texture profile parameters (p < 0.05). This pioneering effort in preparing stable hilsa mince stock highlights its potential as a nutrient-rich value-added product from oily fish mince, supporting its commercial viability and contribution to fish-based food innovation.

The objective of this study was to compare the chemical properties of fresh hilsa (Tenualosa ilisha) and its processed products, namely powder and cube, in order to assess their nutritional profiles and highlight their potential as health-promoting foods. Proximate composition of the three products showed significant differences (p < 0.05) across all measured parameters. Processing markedly reduced moisture content while concentrating protein, lipid, ash, and fiber contents, thereby enhancing the nutritional density of the processed hilsa products. Significant variations (p < 0.05) were also observed in fatty acid composition, with processing altering the balance of saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA). Hilsa powder showed the most favourable omega-3/omega-6 ratio (5.96) and the highest EPA content, whereas fresh hilsa retained the highest DHA level and PUFA/SFA ratio (0.42), indicating superior lipid quality. The amino acid profiles also differed significantly (p < 0.05) among the three products, with hilsa powder and hilsa cube containing higher levels of essential amino acids (EAAs). Hilsa powder exhibited the highest EAA content (50.5%) and EAA/NEAA ratio (1.02), indicating superior nutritional quality. Processing enhanced key EAAs such as lysine, methionine, and leucine, while reducing certain NEAA. Fat-soluble vitamin contents varied significantly among fresh hilsa, hilsa powder, and hilsa cube, reflecting the effects of processing. Vitamin A was most concentrated in hilsa cube, while vitamin D remained relatively stable across all forms. However, vitamins E and K showed substantial losses after processing, particularly in hilsa powder, highlighting the need to optimize processing conditions for improved nutrient retention. Overall, this study provides valuable insights for the food industry in developing value-added hilsa products with enhanced nutritional and health benefits. The presence of high levels of DHA, EPA, EAAs, and vitamins in all three samples supports their potential contribution to human health.

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.