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.

The study was conducted to identify the present status of fish biodiversity in the wetlands of Sylhet district for a period of 12 months from January 2014 to December 2014. It was done by questionnaire interviews (QI) of fishers, focus group discussions (FGD), and key informant interviews (KII) and secondary data collection. During the study period, a total of 58 fish species under 21 families were recorded. The species availability status was remarked in four categories and obtained as 24 commonly available, 16 moderately available, 18 rarely available species. Highest number of commonly available species was found in October to December and lowest number of commonly available species was observed in March to April. Among 54 threatened fish species listed by IUCN Bangladesh, about 30 species were found 10-15 years ago in those wetlands but only 23 were found during the study period. It is revealed that there has been gradual reduction of fish diversity in the wetlands of the area of Sylhet district and average fish catch per fisherman per day was also reduced. Community based fisheries management, fishing gears maintenance, sanctuary establishment and management, implementation of fish acts and regulations, stocking of fish fingerling in the open waters, dredging of beels and raising public awareness can play a great role in conserving fish biodiversity.

Food safety is currently a serious concern due to the health risks associated with food intake, particularly due to heavy metal contamination. Therefore, the present study was conducted to investigate the heavy metals concentration in water and fishes collected from Hakaluki haor, Bangladesh. Three important fish species, Labeo rohita, Cirrhinus cirrhosis, and Labeo calbasu, together with water samples, were analyzed for heavy metals (Pb, Cr, and Cd), respectively. Considering four seasons, namely the monsoon, post-monsoon, winter, and pre-monsoon, a total of 72 fish samples were collected from three fishing stations from June 2017 to May 2018. The results showed that the total mean concentration of metals in water (mg L⁻¹) was found to be in the order of Pb (0.125 ± 0.058) > Cr (0.026 ± 0.012) > Cd (0.001 ± 0.0002) within the maximum permissible limits set by the EU and WHO, except for Pb concentrations. Similarly, the total mean concentrations of Pb in fish (µg g⁻¹) were found in order of L. rohita (0.388 ± 0.291) > Cirrhinus cirrhosus (0.334 ± 0.236) > L. calbasu (0.251 ± 0.117) greater than the maximum permissible limits (0.3 µg g⁻¹) set by FIQC, except for L. calbasu. However, the mean concentrations of Cr and Cd in fish were found to be below the maximum permissible limits of FAO and FIQC, respectively. The quantity of heavy metal contamination in this haor indicates that the situation is worrying for the region’s biota and residents. However, to protect public health and reduce environmental risk, the appropriate authorities should oversee and monitor it with strong hands.

Scylla olivacea (Orange mud crab) is a second commercial invertebrate species exported from Bangladesh. Though a significant portion of exports are supported by aquaculture, their farming ultimately depends on their wild stocks. Unfortunately, unregulated exploitation has led to a significant decline in the natural biomass of this species, raising concerns about the sustainability of crab production in Bangladesh. The study aimed to assess the stock status of S. olivacea (Orange mud crab) from the Southwestern coastal water of Bangladesh. One-year length frequency (width frequency-WF for crustacean fishery) data were collected and analyzed using the LBB (Length-based Bayesian Biomass) and LB-SPR (Length-based spawning potential ratio) methods. The assessed width parameter depicted the exploitation of small-size individuals (W_c=< W_{c_opt}) of S. olivacea. The estimated B/B₀ (0.25) suggests that 75 % of the wild stock had already been harvested, and biomass cannot produce MSY. The mean estimates for SW_50 % and SW_95 % were 8.29 cm and 12.76 cm respectively, revealing the use of a small mesh-size net for crab harvesting. The assessed Spawning Potential Ratio (SPR) was 12 % which is below the SPR limit reference point (SRP) of 20 %. This research confirmed the overfished (F/M = 1.4) and overexploited (E = 0.58) status of S. olivacea in Bangladesh. To ensure the sustainability of coastal fisheries in Bangladesh, the authorities must take immediate management measures to control the overexploitation of this species.

To assess the current usage of aqua drugs and chemicals in enhancing the well-being of aquaculture in Khulna, Satkhira, and Bagerhat districts, a survey was conducted through questionnaire interviews involving 150 representative aquaculture farms. Spanning from January to June 2022 in Bangladesh, the survey encompassed six distinct sub-districts across three different districts. Various aquaculture systems, including finfish polyculture (FP), prawn (Macrobrachium rosenbergii) and finfish polyculture (PP), shrimp (Penaeus monodon) and finfish polyculture (SP), shrimp, prawn, and finfish polyculture (SPP), and semi-intensive shrimp culture (SS), were considered during the sampling process. The findings revealed the use of 123 aqua drugs and chemicals, classified into seven groups: water quality modifiers (31), disinfectants or sanitizers (13), oxygen supplier (12), therapeutics (10), probiotics (12), antibiotics (23), and feed supplements and growth promoters (22). Livelihood variables such as age, farm size, experience, education, training, source of water, water exchange frequency, crop duration, and production were recorded and analyzed to comprehend the current social context associated with shrimp farming. The diseases were categorized into viral, bacterial, fungal, parasitic, nutritional, and environmental with specific examples provided under each category.