This research aimed to investigate the present status of disease prevalence and usage of aqua drugs for various aquaculture operations in the Narsingdi region of Bangladesh. Data were collected through the market survey, preset questionnaire interview, personal contact, and participatory rural appraisal tools. Amongst the respondents, the maximum percentages were found practicing mixed cultures of carp, tilapia, and pangas. The respondents suggested that epizootic ulcerative syndrome, saprolegniasis, streptococcosis, tail and fin rot and bacillary necrosis are common fish diseases in the area. About 140 drugs of different companies used in aquaculture for different purposes such as disease treatment, growth enhancement, water quality improvement, toxic gas removal, improvement of feed conversion ratio. Zeolite, rotenone, disinfectant, oxygen precursors, ammonia reducers, and probiotics were applied for pond preparation, water, and soil quality maintenance, while 30 different antibiotics were used for the purpose of treatment. Among the available antibiotics, oxytetracycline, ciprofloxacin, enrofloxacin, erythromycin, sulphadiazine, and trimethoprim were found extensively used by the fish farmers. Four enzymes and eighteen growth promoters were identified as being utilized to enhance digestion and boost up the production. This study elicited various issues connected with application and administration of such aqua chemicals, including farmers’ ignorance about their usage, proper doses, application methods, withdrawal period, and the human health concerns associated with their irresponsible use. However, the consequences of these chemical products to the environment, animal health, and human health required further study for the betterment of mankind.

Tanguar Haor (TH), an ecologically critical area (ECA) and a Ramsar site of worldwide significance, is an essential wetland ecosystem for the Bangladesh’s economic, ecological, social, and cultural aspects. Fish, aquatic plants, amphibians, reptiles, birds, and mammals are notable among the floral and faunal compositions found in this haor. Unfortunately, unsustainable exploitation of its natural resources poses a serious threat to the TH ecosystem. Therefore, the broad objective of this study was to review the status of fish biodiversity along with the driving factors of biodiversity loss and the management issues of the TH ecosystem. A total of 143 species of fishes (137 indigenous and 6 exotic) under 35 families, and 12 orders were documented during the last two decades. Species diversity of the haor has been changed over time due to the effects of climatic, anthropogenic, socioeconomic, and policy related drivers. Furthermore, high dependency on fisheries resources, poverty, and the lack of empowerment to manage the TH fishery were responsible for fish diversity decline. Therefore, ecosystem based co-management through active participation of local community, establishment of balanced fishing tactics, and strengthening alternative livelihoods for highly depended poor harvesters are strongly recommended for the proper management of this valued wetland ecosystem. Furthermore, this review proposes immediate and useful conservation initiatives for the studied wetlands, including comprehensive stock assessment, establishment of gene banks and fish sanctuaries, a combination of input and output control, and regulation with the ECA and RAMSAR guidelines.

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.

Seaweeds are grown for their use in food and other sectors, however heavy metals (HMs) contamination raises serious issues for the environment and public health. This study focuses on seaweed samples (Hypnea musciformes and Gracilaria lemaneiformis) collected from the Rezu Khal seaweed culture site, Cox’s Bazar coast, Bangladesh. HMs and minerals were determined using Atomic Absorption Spectrophotometry (AAS). Among the elements examined, H. musciformes displayed the highest mean concentrations of minerals and HMs, including Magnesium (Mg) (8663.00 ± 2302.06 mg/kg), Copper (Cu) (10.59 ± 1.61 mg/kg), Iron (Fe) (7566.29 ± 2842.47 mg/kg), Manganese (Mn) (9.93 ± 2.88 mg/kg), Zinc (Zn) (29.54 ± 7.51 mg/kg), and Nickel (Ni) (11.77 ± 2.63 mg/kg). Conversely, G. lemaneiformis exhibited the highest levels of Calcium (Ca) (798.14 ± 143.40 mg/kg), Lead (Pb) (3.91 ± 1.74 mg/kg), and Chromium (Cr) (0.59 ± 0.30 mg/kg). Specifically, Mg was prominently abundant in H. musciformes, while Cawas more prevalent in G. lemaneiformis. Both seaweed types contained Pb and Cr. None of the elements was significantly different between the species (p < 0.05). The consumers are not exposed to any carcinogenic or non-carcinogenic risks related to these concentrations, according to the evaluation of carcinogenic and non-carcinogenic risks.

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.