Determining a suitable stocking density of fish for an ambient condition is very important for economic benefit in cage aquaculture, which is not yet tested for many species in Sylhet district of Bangladesh. Therefore, current research was conducted in order to explore the effect of various stocking densities on growth and production performances of mono-sex Nile tilapia cage aquaculture in an open running water body, the Gurukchi River. Considering maximizing economic benefit, it is the first instance of such research in the Sylhet district of Bangladesh. In the three treatments (T₁, T₂, and T₃), fingerlings were stocked at 40, 60 and 80 fish/m³, respectively with initial weights of 39.51 ± 0.91, 39.61 ± 0.71 and 38.54 ± 0.57g, respectively. Fish were fed with commercial floating pellet feed at 8-4% of their body weight. The results showed that growth performance of Nile tilapia significantly decreased with increasing stocking density. The mean total yields were 13.25 ± 0.48, 18.43 ± 0.88 and 22.76 ± 0.63 kg/m³ in T₁, T₂ and T₃, respectively, which showed significant variations (p < 0.05) among treatments. The benefit-cost ratio analysis revealed that T₁ (1.512 ± 0.022) and T₂ (1.499 ± 0.063) were significantly (p < 0.05) higher than T₃ (1.191 ± 0.071), with no significant differences observed between T₁ and T₂. Notably, a significantly higher (p < 0.05) net profit was observed in T₂ than in T₁ and T₃. Overall, 60 fish/m³ stocking density was the best stocking density for commercial cage aquaculture of tilapia in a riverine environment of the north-eastern Bangladesh.

Colistin (polymyxin E) is widely used in animal and human medicine and is increasingly used as one of the last-resort antibiotics against Gram-negative bacilli. Due to the increased use of colistin in treating infections caused by multidrug-resistant Gram-negative bacteria, resistance to this antibiotic ought to be monitored. The study was undertaken to elucidate the molecular mechanisms, genetic relationships and phenotype correlations of colistin-resistant isolates. Here, we report the detection of the mcr-1 gene in chicken-associated Salmonella isolates in Bangladesh and its in-silico functional analysis. Out of 100 samples, 82 Salmonella spp. were isolated from chicken specimens (liver, intestine). Phenotypic disc diffusion and minimum inhibitory concentration (MIC) assay using different antimicrobial agents were performed. Salmonella isolates were characterized using PCR methods targeting genus-specific invA and mcr-1 genes with validation for the functional analysis. The majority of the tested Salmonella isolates were found resistant to colistin (92.68%), ciprofloxacin (73.17%), tigecycline (62.20%) and trimethoprim/sulfamethoxazole (60.98%). When screened using PCR, five out of ten Salmonella isolates were found to carry the mcr-1 gene. One isolate was confirmed for Salmonella enterica subsp. enterica serovar Enteritidis, and other four isolates were confirmed for Salmonella enterica subsp. enterica serovar Typhimurium. Sequencing and phylogenetic analysis revealed a divergent evolutionary relationship between the catalytic domain of Neisseria meningitidis lipooligosaccharide phosphoethanolamine transferase A (LptA) and MCR proteins, rendering them resistant to colistin. Three-dimensional homology structural analysis of MCR-1 proteins and molecular docking interactions suggested that MCR-1 and LptA share a similar substrate binding cavity, which could be validated for the functional analysis. The comprehensive molecular and in-silico analyses of the colistin resistance mcr-1 gene of Salmonella spp. of chicken origin in the present study highlight the importance of continued monitoring and surveillance for antimicrobial resistance among pathogens in food chain animals.

A checklist of the native fishes of the Dhanu River and adjacent waters at Mithamain Upazila under the Kishoreganj district of Bangladesh is prepared with details on their availability, conservation status, habitat preferences, population trends, and threats. Data were collected monthly by field survey, focus group discussions, and personal interviews by using a semi-structured questionnaire and a pictorial check list of fish species. A total of 91 indigenous fish species of 59 genera belonging to 29 families under 11 orders were documented where 17.6%, 27.5%, 31.9%, and 23.1% species were abundantly available, commonly available, moderately available, and rarely available, respectively. Among those, 24 fish species (26.4%) were under the threatened category (3 critically endangered, 11 endangered, and 10 vulnerable) according to the IUCN Bangladesh. Notably, the globally threatened Cirrhinus cirrhosus, Channa orientalis, and Wallago attu were available in the study area. Fish population trends of 24.2% and 59.3% of the entire fish species were found in decreasing trends at the global and national level, respectively. The leading threats to the fish diversity were indiscriminate overfishing followed by fishing by dewatering of wetlands, the katha fishing method, the use of deprecated fishing gears, etc. Minimizing anthropogenic impacts, enacting fishing laws, installing and managing fish sanctuaries, and raising public awareness can be effective for the conservation of existing fisheries resources.

Fish sanctuary is considered as an important structural management tool for restoring fish biodiversity and enhancing fisheries production. Therefore, this study was conducted in the Ratargul Swamp Forest (RSF) of Bangladesh to evaluate the impact of a fish sanctuary on native fish biodiversity in and around the forest ecosystem. The investigation was carried out through focus group discussions, personal interviews, and direct catch assessments during fishing operations by the local fishers. After two years of study, 65 species of indigenous fishes were recorded for 46 genera under 23 families covering 9 orders, where Cypriniformes and Cypriniidae are the dominant order and family, respectively. After the establishment of the fish sanctuary, there was an increasing tendency of fish population was observed in the RSF and the adjacent Shari-Goyain and Kapna Rivers. In the RSF, fish diversity indices such as Simpson dominance index (D), Shannon-Wiener diversity index (H), Margalef richness index (d), and Pielou evenness index (J) varied from 0.12-0.09, 2.77–2.98, 6.15–6.14, and 0.66–0.71, respectively indicating species diversity enrichment in the final year compared to baseline assessment year which is supposed to be associated with the impact of fish sanctuary establishment. That assumption is further supported by remarkable increase in average fish catch (11.38%). Local fishers and people adjacent to RSF perceive that sanctuary became useful for protecting biodiversity, increasing fish production as well as improving their livelihood conditions.

This study aimed to investigate the seasonal and spatial variations in water quality parameters and determine the main contamination sources in the Shari-Goyain River, Bangladesh. Therefore, surface water was sampled monthly from six sampling sites, where six water quality parameters were evaluated. Data were analyzed by applying the Canadian Council of Ministers of the Environment (CCME) water quality index (WQI) and multivariate statistical methods. The results reveals that most of the examined water quality parameters crossed the acceptable range, and significant variations were observed spatiotemporally (p < 0.05). Based on the CCME WQI value, the water quality of the river is classified as poor to marginal with a score range between 33.40 and 51.30. This range of values demonstrates that the river’s water quality is far from desirable for aquatic life and that it is being impacted and deteriorated by external drivers. Principal component analysis (PCA) retained two principal components (Factors 1 and 2), explaining about 79.17% of the total variance in the studied parameters and identified acidic pollution sources. Cluster analysis also reveals relative differences in water quality throughout sites and seasons, which supported the CCME WQI and PCA. Finally, Kruskal-Wallis one-way analysis of variance by ranks has identified coal mine drainage (CMD) as the main pollutant source for the Shari-Goyain River. In order to mitigate the CMD impact on land and water, different nature-based solutions are proposed, particularly passive mine water treatment approaches through constructed wetlands that could also mitigate the transboundary waters problem.