Stocking density is one of the critical factors that influence the production and health status of fish in aquaculture practices. In this 60-day trial, effect of different stocking densities (70, 140, 210, 280 and 350 fish/m 3 ) on growth performance, digestive enzyme activity, body composition and gene expression of Asian seabass, Lates calcarifer, was studied using Recirculating Aquaculture System by following completely randomized design with four replications. Asian seabass (5.20 ± 0.10 g) were randomly distributed in 20 tanks, each of 500-L capacity, and fed four times a day (6:00, 12:00 18:30 and 23.00 h). The study found that growth performance and feed utilization efficiency were significantly decreased with increasing stocking density. A significantly higher survival (95.00 ± 1.25%) was recorded in the low stocking density group (70 fish/m 3 ). On the other side, fish reared in higher stocking densities (140, 210. 280 and 350 fish/m 3 ) displayed lower digestive enzyme activities, such as protease, amylase, lipase and cellulase. There is a significant density-dependent decrease in crude protein deposition in the fish body and the study found significantly higher protein (19.12 ± 0.10%) content in the 70 fish/m 3 . The relative gene expression of GH/ IGF axis and myostatin (MSTN) was significantly down-regulated and up-regulated, respectively, with the increasing stocking density. Overall, the study found that the increasing stocking density produced chronic stress which negatively affected the growth performance of the fish. Therefore, the study suggests that rearing of Asian seabass at a stocking density of 70 fish/m 3 in a recirculatory aquaculture system could improve the growth performance, metabolic and molecular activities of the fish.

Escherichia coli is the most extensively used organism in recombinant protein production. It has several advantages including a very short life cycle, ease of genetic manipulation and the well-known cell biology etc. which makes E. coli as the perfect host for recombinant protein expression. Despite many advantages, E. coli also have few disadvantages such as coupled transcription and translation and lack of eukaryotic post-translational modifications. These challenges can be overcome by adopting several strategies such as, using different E. coli expression vectors, changing the gene sequence without altering the functional domain, modified E. coli strain usage, changing the culture parameters and co-expression with a molecular chaperone. In this review, we present the level of strategies used to enhance the recombinant protein expression and its stability in E. coli.

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Background: Antimicrobial resistance (AMR) is a rising concern in the global aquaculture sector due to the rampant prophylactic use of antibiotics. This study is aimed to determine the AMR pattern in freshwater ornamental fishes. Methods: Fish pathogens were isolated and identified from infected Guppy and Molly collected from ornamental fish farms. Antibiotic susceptibility testing (ABST) using disc diffusion with 36 antibiotics was performed following the disc diffusion method. The resistance gene cassettes such as Class 1 and Class 2 integron were also detected from resolved isolates. Result: Fish pathogens were isolated and identified as Aeromonas hydrophila, A. dhakensis, A. veronii, A. sobria, Bacillus subtilis, Comamonas testosteroni, Edwardsiella tarda, Enterobacter cloacae, Enterococcus faecalis, Kurthia gibsonii and Klebsiella aerogenes. Shannon Weiner diversity index of resolved isolates was found to be 1.366 and 2.101 for Guppy and Molly, respectively. ABST results showed an elevated resistance pattern for A. veronii, E. faecalis (Guppy), K. aerogenes, B. subtilis, E. faecalis, C. testosteroni (Molly) with higher multiple antibiotic resistance indexes ( greater than 0.33). Meanwhile, all the recovered isolates were susceptible to sulphafurazole, enrofloxacin, norfloxacin and ciprofloxacin. Detection of class 1 integron in genomic and plasmid DNA reminds the rapid spread of the AMR gene through horizontal gene transfer.

Background: There is a gap that we will need to use innovative solutions to produce more food and nutrition. RAS is a continuous water-flowing system that can induce schooling behaviour, a phenotypic character seen in Asian seabass that could help cut down cannibalism at a certain level. Stocking density is one of the critical factors affecting the growth, survival and health status of animals, which can influence the antagonistic behaviour pattern, hierarchical phenomena and cannibalistic nature of Asian seabass during the early life stage. Methods: A 60-day trial was conducted to evaluate the effect of different stocking densities (70, 140, 210, 280 and 350 fish/m3) on biochemical and stress gene expression of Asian seabass (Lates calcarifer) reared in Recirculating Aquaculture System by following a completely randomized design with four replications. Result: The study found that fish reared at 350 fish/m3 had significantly higher haemoglobin and red blood cells. In the case of biochemical parameters, total protein, Albumin and Globulin were lower in 70 fish/m3 and Blood Urea Nitrogen, cholesterol and triglycerides were significantly higher in 350 fish/m3 treatment. The relative gene expression of HSP70, HSP90A and GST was significantly upregulated with the increasing stocking density. The study suggests that the rearing of Asian seabass at a stocking density of 70 fish/m3 in a recirculatory aquaculture system could improve the growth performance and metabolic and molecular activities of the fish.