PRESENT STATUS, PROSPECTS AND CONSERVATION OF HILSA, Tenualosa ilisha (CLUPEIFORMES: CLUPEIDAE) FISHERY IN BANGLADESH

Belonging to the family Clupeidae, hilsa shad Tenualosa ilisha (Hamilton, 1822) is an important fish species in the South and Southeast Asia, especially in Bangladesh. Due to its unique nature, the fish has gained national and international demands for its nutritional values, taste qualities, special aroma and high delicacy, and provides livelihoods to the millions of fishers directly or indirectly along the coastal and riverine stretches in its range of natural distribution. It is considered as the national and most important commercial fish species of Bangladesh and contributes significantly to the national economy. In this study, an attempt is made in evaluating the data currently available on hilsa to determine the impact of the current management approaches and improvement strategies of this important fishery. Hilsa is found primarily in marine and estuarine environments, but it has been declining gradually over the last 30 years, reaching a low point in 1991-1992 and continuing until 2002-2003. Recognizing the declining trend of hilsa, the government took action to increase production by implementing regulations on jatka (juvenile) catch and restrictions on brood hilsa catch during the breeding season. As a result, total hilsa catch increased from 2.55 million MT (metric ton) in 2003-04 to 3.94 million MT in 2015-2016. Under the Protection and Conservation of Fish Act of 1950, Hilsa production peaked in 2016-2017, with a total of 4.96 lakh metric tons. Hilsa management techniques contribute 12.9% of all fish produced, while in Bangladesh, the rate of increase in hilsa production is 25.69%. The annual increase of total hilsa production climbed from 3.5% to 9.0% after 2015 as a result of the government's general management activities, payments for ecosystem service (PES) and the environmental management strategies, resulting in annual total hilsa production of 5.50 lakh MT in 2019–2020. A number of recommendations for effective management of the hilsa fisheries that might be implemented into the national policy are elicited in order to improve the situation because the current hilsa management plan has an impact on the conservation of this important fishery to a greater extent in commensurate with its national and international demands

Diversity of bacterial communities in the Sundarbans mangrove, Bangladesh, with special focus on pathogens affecting aquatic organisms

The Sundarbans, located in Bangladesh, is the world's largest mangrove forest with a rich and diverse microbial community. The main objective of this study was to use 16S rRNA sequencing to identify the bacterial community in the Sundarban mangrove forest, particularly pathogenic bacteria to aquatic organisms. This study conducted in Bangladesh collected 225 samples of soil, water, fish, and shellfish from five locations with a typical mangrove environment. All samples underwent genomic DNA extraction, quantification, gel documentation, and subsequent sequencing. Sanger sequencing was then carried out, followed by sequencing 11 concentrated samples using the universal bacterial primer 16S rRNA. The study found 872 bacterial species, 94 genera, 38 families, and 6 phyla. Pseudomonades or proteobacteria accounted for 92% of the phylum composition, with firmicutes, bactericides, cyanobacteria, Verrucomicrobia, and actinobacteria also present at smaller percentages. Chromatiaceae had the highest species count (20.3%), followed by Ectothiorhodospiraceae (15.5%), Methylococcaceae (12.3%), Moraxellaceae (10.7%), Thiotrichaceae (8.7%), Idiomarinaceae (5.4%), and smaller groups. All the species that were identified were gram-negative bacteria and were found in different environments, mainly halophilic ones. Based on 16 s rRNA sequencing, additional experimental and clinical data, as well as NCBI (BLAST), approximately 49.3% of the 872 bacterial species are typically harmless and not classified as pathogenic. The pathogenic characteristics of 24.9% of the species are still unidentified. 13.4% showed either pathogenic or non-pathogenic characteristics (a bacterium as having the potential to exhibit pathogenic or non-pathogenic characteristics in certain circumstances), while 8.4% were exclusively pathogenic, potentially capable of causing disease. Also, the bacterial species are categorized as 2.6% non-highly pathogenic (a bacterium can still have a significant impact on health, especially in weakened immune systems or other underlying health conditions), 1.3% sometimes pathogenic and 0.1% potentially pathogenic (a bacterium don't always cause disease). Sequence analysis, combination of phylogenetic, biochemical characterization (data were not shown), and other experimental validation conclude a genetic baseline of bacterial community, this research may serve as a valuable reference for future ecological and taxonomical studies as well as addressing further research scope on bacterial diversity found in the Sundarbans mangrove of Bangladesh

Bacteriophage and non-pathogenic Vibrio to control diseases in shrimp aquaculture

The study aimed to address the recurring outbreaks of microbial diseases in shrimp aquaculture in Bangladesh the study focused on the utilization of bacteriophages and non-pathogenic Vibrio. The bacteriophages were isolated from sewage water sample collected from shrimp farm, hatchery, and the JUST campus. The bacteriophages were tested for their ability to infect different Vibrio strains in order to assess their bacteriolytic activity. Non-pathogenic Vibrio strains were obtained from suspected diseased isolates collected from the south-western region of Bangladesh through PCR amplification. In laboratory tests, the bacteriophages successfully infected 91 % of the tested Vibrio strains (19 out of 21 strains). In the experimental unit, shrimp treated with phage prophylaxis and phage treatment demonstrated notable protection against AHPND and was able to survive a deadly bacterial challenge. A total of 35 suspected diseased isolates were tested, and PCR amplification revealed 6 non-pathogenic Vibrio strains. In field trials, cultured bacteriophages were applied at a concentration of 1.5×106 PFU/ml, while non-pathogenic Vibrio was applied at 5×105 CFU/ml. The trials showed increased protection against infections and no severe deaths during the adaptive research phase. The cultured shrimp were analyzed morphologically and showed a muscle gut ratio greater than 4:1. No abnormal deformities were observed in their appendages or overall body, suggesting their overall health and well-being. The bacteriological tests conducted on the shrimp samples (application of bacteriophages and non-pathogenic Vibrio) revealed that 18 % of them were infected with bacteria, primarily Vibrio cholerae, Vibrio parahaemolyticus, and other bacterial species. Despite this, the infections did not lead to a disease outbreak; PCR amplification showed negative results for AHPND, White Spot Syndrome Virus (WSSV), and Enterocytozoon hepatopenaei (EHP). The results highlight the potential of using bacteriophages and non-pathogenic Vibrio as a sustainable solution for preventing and controlling microbial diseases in shrimp aquaculture. Furthermore, this study will contribute valuable insights into the development of alternative strategies to combat antibiotic resistance and promote the growth of the shrimp industry in Bangladesh