Tropical hilsa shad, which is an anadromous fish migrating from the sea to spawn in freshwater river, constitutes an important fishery in some Asian and Middle East countries, particularly in Bangladesh. But, historical information on hilsa biology and ecology has confronted the scientists and policymakers with research and management challenges. We have reviewed both the old and recent findings on hilsa fishery to document the status of knowledge and potential gaps, necessary to comprehend for formulating a more effective fishery management plan. Thus, there has been a decline in hilsa catches in the riverine system associated with shift in fish migration routes, indiscriminate harvesting of brood and juvenile fish, and degradation of habitat. Specifically, the riverine hilsa catches peaked in the 1960s, declining thereafter, and became relatively abundant in marine waters since 1990s. Biological data indicated that hilsa goes through multiple reproductive cycles; therefore, a comprehensive understanding of reproductive biology, recruitment by various cohorts, stock abundance and habitats across the life cycle are necessary to accurately impose fishery regulatory measures, such as fishing ban in spawning season in Bangladesh. Moreover, domestication initiative is important for artificial seed production and mariculture development of hilsa that can not only offer economic return to small‐scale farmers but also reduce the growing pressure on capture fishery. Importantly, the arrangement of co‐management is found ideal as fishermen, scientists and managers can work jointly to improve the regulatory processes and to sustain the hilsa fishery over time.

Seaweeds can play an essential role in controlling antibiotic resistance for bacterial diseases. Three extracts of two brown seaweeds Padina tetrastromatica and Sargassum ilicifolium were investigated as growth promoters and to provide immune protection against Vibrio parahaemolyticus. Extracts of the two seaweeds were administered at 2.5 and 5 g kg⁻¹ with food for 45 days to Penaeus monodon juveniles. The maximum weight gain (6.28 and 7.08 g), specific growth rate (3.39 and 3.32%), and survival rate (78.45 and 82.45%) of the juvenile tiger shrimp were obtained at a dose of 5 g kg⁻¹ with P. tetrastromatica extracted by methanol and ethanol, respectively; which was significantly higher than the other solvents and control group (p < .01). On the other hand, methanol extract of both seaweeds had maximal antibacterial activity against V. parahaemolyticus with zones of inhibition ranging between 20.25 ± 1.00 and 22.00 ± 0.50 mm. The minimal time required for haemolymph clotting was with methanol extracted of P. tetrastromatica at 5 g kg⁻¹, which was significantly lower than the other groups (p < .05). After challenging with V. parahaemolyticus, the total haemocyte count (THC) in P. monodon treated with methanol-extract of P. tetrastromatica diet at 5 g kg⁻¹ was higher (5.42 × 10⁵ cells mL⁻¹) but not significantly different than the other diets (p > .05). However, the administration of 5 g kg⁻¹ methanol and ethanol extract of P. tetrastromatica improved growth performance and the immune capacity of P. monodon by increasing their phenoloxidase activity, superoxide anion concentration, and resistance against V. parahaemolyticus.

It is well understood that both untreated and partially treated wastewater comprise substantial amount of resources, which can be recovered and utilized for different purposes. Since Waste Water Treatment Plant (WWTP) is energy intensive and expensive, substantiating the WWTPs with Resource Recover Technologies (RRTs) will not only save a considerable amount of energy but also make the environment cleaner and safer. In line with this, this paper seeks to review several RRTS and to identify their limitations. Several effective nutrient recovery methods using both biota (e.g., microalgae, duckweed, aquatic macrophytes) and chemical processes (e.g., struvite precipitation and HAIX resin) are discussed in this study. The recovered nutrients can be used as fertilizer, animal feed and for production of protein rich by-products. In order to enhance the efficiency of nutrient recovery processes, several researchers suggest introducing hybrid system of nutrient recovery. On the other hand, biosolids, biogas, conserved heat, effluent flow, Microbial Fuel Cells (MFC), Microbial Electrolysis Cells (MEC) can potentially be employed to produce electricity and other forms of energy that can meet the demand of existing WWTPs. Moreover, the comparative analysis of these technologies in terms of advantages and disadvantages and their recovery potential has been discussed. The review analysis indicates that despite having limitations, several RRTs are being practiced mostly in developed world. Future research should focus on how to increase the efficiency of existing RRTs and identify innovative RRTs available in developing countries.

To understand the present status of fish diseases and their remedial measures taken by the fish farmers, a questionnaire survey and Participatory Rural Appraisal (PRA) tools including Focus Group Discussion (FGD) were conducted in seven districts of Bangladesh. In total 196 farmers were interviewed and nine FGD sessions were conducted. Disease occurs immediately after stocking (24%) and during the rainy season (21%) followed by cold season (19%). Mortality, abnormal swimming and feeding behavior, unusual appearance, some localized lesions and reduced growth are the main clue to recognize the fish disease. The most frequently observed diseases were epizootic ulcerative syndromes (18.72%) followed by tail and fin rot (13.19%), red spot (11.49%), gill rot (9.36%), parasitic disease (8.93%), broken prawn antennae (7.23%), and other environmental and nutritional diseases. To cure these diseases, farmers applied the following treatments: lime and potash, liming, lime and salt, lime alone, salt and potash, antibiotics, various chemicals, high doses of vitamin C, complete water exchange, and transport to another pond. This study showed that diseases can play important roles in freshwater aquaculture, but this role is often not recognized due to a lack of knowledge and veterinary backstopping services.Bangladesh J. Zool. 44(1): 111-122, 2016