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The bacterial population plays a crucial role in recycling the organic matter and metabolizing the toxic nitrogenous compounds under biofloc technology (BFT). The biofloc technology has been successfully implemented for several fish species, but not for shrimp culture in Bangladesh. The major objectives of this study were to determine the effects of stocking density on the growth performance of tiger shrimp Penaeus monodon under biofloc technology (BFT) rearing system using commercial probiotics and to investigate the abundance of total heterotrophic bacteria (THB) and vibrio-like bacteria (VLB) in different biofloc treatments and their water quality parameters. The experiment was conducted with three different stocking densities in three BFT tanks (2.5 × 2.0 × 1.0 m) with triplicate and three control tanks filled in clearwater. All these tanks were built with cement and can contain 5000 L of water. Visually healthy, disease-free P. monodon postlarvae (weighted 0.18 ± 0.02 g) were collected from a local hatchery and stocked in three different stocking densities, i.e., 400 PL/m3 (CW), 400 PL/m3 (BFT1), 450 PL/m3 (BFT2) and 500 PL/m3 (BFT3). Shrimps were fed four times a day with commercial feed (Biomer, 40 % crude protein) for 127 days. Significant differences (P < 0.05) in specific growth rate, food conversion ratio, and protein efficiency ratio of shrimp were found among the treatments and the control group. The overall final biomass in BFT1 (5.88 ± 0.12 kg m3) was significantly higher (P < 0.05) than that of other BFT groups and the control (3.40 ± 0.09 kg m3). The present findings showed that the biofloc technology with lower stocking density was reducing the total ammonia nitrogen, nitrite-N, and nitrate-N in water and significantly increased THB and reduced VLB populations.

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.

The recent incidence of loose-shell syndrome disease (LSSD) in grow-out shrimp ponds appears to be a major problem in Bangladesh. Therefore, the aims of our study were (i) to observe clinical signs of LSSD to confirm its incidence and (ii) to identify the probable causative agents for LSSD in shrimp. Sampling was conducted randomly from five LSSD-affected ponds and three non-affected ponds near Bakkhali River; ecological parameters were measured. A total of 180 healthy shrimps were used for this experiment, where LSSD-affected shrimp extracts were either injected into the shrimps or mixed with water in the experimental tanks. Finally, microbial examinations were performed to identify the possible LSSD causative agents from the infected individuals. The total shrimp production was higher in ponds with healthy populations (185 kg/ha) than from LSSD-affected ponds (126–146 kg/ha); the survival rate of shrimp at harvest was significantly different (p

This study examined the effects of an herbal extract composed of nine herbs i.e Aloe vera, Andrographis pariculata, Annona squamosa, Azadirachta indica, Citrus aurantifolia, Coriandrum sativum, Ocimum sanctum, Ollium cepa and Psidium guajava on growth, survival rate and immunoprotection against pathogenic Vibrio harveyi in the tiger shrimp Penaeus monodon. The petroleum ether, methanol and N-hexen extracts of different herbal plants were selected, processed and thoroughly mixed in equal proportions and added to the shrimp diets at a concentration of 1.0, 2.5 and 5.0 mL kg−1. After 60 days of feeding, shrimps were challenged with V. harveyi bacteria (1 × 107 cells mL−1), which were isolated and propagated from the infected shrimps. The shrimps fed on diets with methanolic extraction of 2.5 mL kg−1 had significantly (P

Chlorococcum sp . has been studied as its possibility for biofuel feedstock. This alga was grown in Zarrouk media. After harvesting, lipid extraction was done by pure n-hexane and mixture of chloroform: methanol (2 : 1)) and hexane: ethanol (3 : 1). Highest oil recovery (21.20%) derived from chloroform: methanol (2 : 1) solvent system from dry biomass whereas the lowest (2.83%) came from n-hexane: ethanol solvent system from wet biomass. GC/MS used for the analysis of extracted lipid revealed that, palmitic acid methyl ester (C 17 H 34 O 2 ), 9-octadecenoic acid methyl ester (C 19 H 36 O 2 ) were major contents of this biofuel. The acquired fatty acid profile indicates that Chlorococcum sp. could be used as promising biofuel feedstock in near future. Journal of Bangladesh Academy of Sciences, Vol. 40, No. 2, 147-153, 2016

Size frequency and length–weight relationships (LWRs) for three cephalopods, Indian squid Photololigo duvaucelii, needle cuttlefish Sepia aculeata, and spineless cuttlefish Sepiella inermis were studied. Specimens were caught from the coastal waters of Bangladesh (Moheshkhali Channel and Sonadia Island) using both trawl and marine set bag nets. The maximum dorsal mantle length for the Indian squid, needle cuttlefish, and spineless cuttlefish was recorded to be 228, 135, and 82 mm, respectively. The estimated growth coefficient b was 1.377 for Indian squid, 2.504 for needle cuttlefish, and 1.979 for spineless cuttlefish. The growth coefficient for these three species indicated hypoallometric growth from this region. No information has been published regarding size frequency and LWRs for these three cephalopods from the coastal waters of Bangladesh. The results of this study will be useful for the management and conservation of squid fisheries from the Bay of Bengal.