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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.

It is increasingly recognized that Estuarine Set Bag Net (ESBN) is very popular gear in the coastal fishing community of Bangladesh. In order to reveal the species composition of the ESBN catch and to study the impact of environmental parameters on the spatio-temporal variation of fish assemblages, a one-year baseline survey was conducted in coastal waters of the Moheshkhali Island, northern Bay of Bengal, Bangladesh. A total of 59 taxa were identified of which 47 were finfishes, 7 were shrimps and 5 were from other categories i.e. crab, holothruim, lobster, squid and squila. Among them, 54 species were commonly distributed in all four seasons and stations with 23 and 24 species were found dominant to the total communities in different seasons and sites, respectively. Similarity percentage analysis revealed significant variation in structure and composition of total communities in temporal and spatial scale: (1) the highest (89.33%) and lowest (70.10%) average species similarity was observed in monsoon and winter, respectively; (2) the average species similarity was found highest in Sonadia (88.30%) and lowest in Nalbila (74.83%). SIMPER analysis demonstrated that the contributory species (i.e. Crab, Squid, Pampus chinensis, Chirocentrus nudus, Ascetes sp. Penaeus monodon, Metapenaeus brevicornes, Arius sp., Tenualosa ilisha, Uranoscopus sp., Machrobrachium ruddis, Gerres filamentosus, Coillia dussumieri, Squila, Glossogobius giuris, Rastrelliger kanagurta, Rhynchorhamphus georgii, Chirocentrus nudus, Ascetes sp., Metapenaeus brevicornes, Tenualosa ilisha, Uranoscopus sp., Rhynchorhamphus georgii, Penaeus indicus) varied among different sites and seasons. One-way ANOVA and Canonical Correspondence Analysis (CCA) revealed that the total communities were significantly driven by temperature, salinity, pH, DO and water transparency. Multivariate analyses showed that the diversity of ESBN fishery is high in this Island. These findings signify that this coastal zone is one of the nursery grounds and highly diversified for many marine fishes.

Oceanic marine plastic contamination was an increasingly global issue due to increased demand. This has a significant effect not only on marine biodiversity, but also on public safety and numerous infectious diseases found in both aquatic and human species. A huge amount of money was spent worldwide on plastic waste. In the 1940s, plastics development began and is increasing massively. This crucial analysis intends to accomplish goals such as defining plastic materials, origins, detecting aggregation, and validating appropriate techniques to analyze plastic abundance spatio-temporal trends. This further addresses the possible impacts of plastics on marine species, humans, and future chemical emission control strategies together with advice. Plastics are primarily distributed along the coasts and mid-ocean vortex in large amounts. The broad variety of plastics, as eaten by aquatic animals finds their way to the human body through the food chain. Research articles should help learn the origins, deterioration mechanisms, and harmful effects of plastics on both the human body and the ecosystem. Until recently, the science community and politicians have generally ignored plastic waste, but ecological implications, as well as plastic pollution’s economic/health effects, have now gained greater global interest.