Seed stunting is widely practiced in aquaculture to ensure year-round availability of quality juveniles; however, its effects on carcass quality and biochemical composition during post-stunting grow-out remain inadequately understood. This study evaluated the influence of stunting on carcass traits and nutrient composition of catla (Labeo catla) during the compensatory growth phase. Stunted and non-stunted juveniles were produced through photoperiod manipulation using 6 h light:18 h dark (6L:18D) and 12 h light:12 h dark (12L:12D) regimes, respectively, and subsequently reared in earthen ponds for 240 days. At harvest, stunted fish attained a mean body weight of 590.33 ± 73.50 g, while non-stunted fish reached 753.33 ± 52.04 g. Stunted catla exhibited significantly lower (p < 0.05) dressed, headless dressed, and skinless dressed yields (82.64%, 50.76%, and 46.80%, respectively) compared to non-stunted fish (83.52%, 53.83%, and 50.70%). Among offal traits, stunted fish showed a higher head percentage (31.37%) and a lower digestive tract percentage (7.82%) (p < 0.05). Fillet cutability revealed marginally higher meat yield (72.12%) and lower bone content (19.53%) in stunted fish. The mid-body region contributed the highest edible meat proportion in both groups. Biochemical analysis indicated significantly lower moisture content in stunted fish, while crude protein and lipid levels were comparable between treatments. Overall, stunting did not adversely affect nutrient accretion or meat quality during compensatory growth, highlighting its potential for improving seed management without compromising product quality. These findings support improved stunting protocols and provide a reference for assessing nutritional effects in other cultured fish species.

A ready-to-eat fish pickle was developed from Pangasianodon hypophthalmus, and its storage stability was evaluated at room temperature (28–32 °C) and under refrigeration (5–8 °C) for six months. Quality changes were monitored through total volatile base nitrogen (TVB-N), peroxide value (PV), pH, total plate count (TPC), and sensory acceptability. TVB-N, PV, and TPC increased progressively under both conditions, with higher deterioration at room temperature. Sensory acceptability decreased from 8.8 to 3.1 at room temperature and to 6.4 under refrigeration. The product remained acceptable for four months at room temperature and six months under refrigerated storage.

A portable thermal aquarium was custom-designed in this study to assess the physiological response of Genetically Improved Farmed Tilapia (GIFT) to acute thermal stress. The design included a modified aquarium heater and temperature controller unit, equipped with an external temperature sensor. A total of 144 fish (average weight: 27.13 ± 0.19 g) were assigned to three groups, viz., Control (28 °C), and two acute thermal stress exposed group (34 °C and 36 °C), with exposure durations of two and twelve hours (n=4 replicates/group) in temperature-controlled aquariums. The impact of acute thermal stress was assessed by measuring liver metabolism, stress hormones, and enzyme activities. Results revealed significant alterations (p < 0.05) in serum cortisol, T3, and T4 levels in fish exposed to thermal stress. Similarly, liver enzyme activities including SOD, CAT, GPx, GST, and GR, along with the brain AChE activity, were markedly elevated under thermal stress. The portable thermal aquarium designed for this study proved to be cost-effective, versatile, and adaptable to tanks of varying volumes. This study also highlights the importance of simulation studies to understand thermal stress-related perturbations in fish. The use of portable thermal aquariums offers a means to replicate warming scenarios in aquaculture systems.

Aeromonas spp. are responsible for causing hemorrhagic septicemia resulting in significant mortalities in carp aquaculture. Among the different species, Aeromonas veronii is considered as a significant pathogen and is second only to A. hydrophila in causing severe economic losses to freshwater fish farmers. The present study was carried out to isolate and identify A. veronii from freshwater fishes in Andhra Pradesh, India. In addition, both in vivo and in vitro pathogenicity assays were performed to assess its virulence. A total of 95 A. veronii strains were meticulously isolated from 80 [Labeo rohita (n=40), Catla catla (n=40)] fish samples and subjected to biochemical tests (API 20E system), PCR confirmation (amplification of 16S rRNA gene), and virulence gene profiling. The strains exhibited a genetic diversity ranging from four to eight virulence genes, with a prominent genotype (ahy+, ahp+, enol+, lip+, alt+, hly+) observed in 28% of the isolates. In vivo pathogenicity analysis indicated that 72% of the strains exhibited hemolytic activity, which was strongly associated with the presence of aer+, hly+, and ahyB+ genes. Furthermore, in vivo challenge experiments demonstrated that even Aeromonas strains with as few as four virulence genes (ahy+, enol+, aer+, alt+) were capable of inducing over 90% mortality. These findings strongly imply that the pathogenicity of A. veronii is more significantly influenced by the synergistic effect of virulence genes rather than their total number. The high virulence of A. veronii poses a serious threat to the freshwater aquaculture, underscoring the need for enhanced monitoring and management strategies.

Microbial fermentation improves the nutritional value of plant ingredients by decreasing the natural toxicants and reducing the complexity of the nutrients. The current study was conducted to replace soybean meal (SM) with yeast (Saccharomyces cerevisiae) fermented rain tree seed meal (FRTSM) and to evaluate its effect on the growth, nutrient utilisation, carcass composition, digestive enzymes activity, and degree of digestion of tilapia fry (Oreochromis niloticus). Five iso-nitrogenous and iso-lipidic diets were formulated with replacing SM (0, 25%, 50%, 75% and 100%) with FRTSM and was denoted as FRTSM0 (Control, without FRTSM), FRTSM25, FRTSM50, FRTSM75 and FRTSM100. The feeding experiment was conducted for 60 days in FRP tanks of 150L capacity taking twenty tilapia fry (6.27±0.09 g) per tank in triplicates. The tilapia fed with FRTSM0 diet showed significantly higher (P<0.001) final weight, weight gain and weight gain percentage compared to other treatments. The quadratic regression analysis showed that replacing up to 37 and 38.64% of SM with FRTSM led to optimal specific growth rate (SGR) and weight gain. The FRTSM0 diet-fed group also showed lower body moisture content and increased body protein content. The quadratic regression analysis revealed that digestive enzymes, nutrient digestibility, and serum biochemical parameters were optimized with less than 20% replacement of SM. Despite notable enhancements in nutritional status and a decrease in antinutritional factors, replacing SM with FRTSM did not emerge as a superior ingredient choice. However, it is important to highlight that a cautious replacement of 38% SM with FRTSM can be achievable in the Nile tilapia diet.

Pesticides are widely used in aquaculture farms against ectoparasites. However, due to the development of resistance in ectoparasites against the traditional pesticide formulations, pesticides are being applied at a higher dose or in combinations. Nano formulation of pesticides with enhanced properties is a viable option to reduce the volume of traditional pesticides applied in aquaculture. Hence, the present study developed a nano formulation of the pesticide cypermethrin and evaluated the toxic effects in the fish Hypselobarbus pulchellus. The acute toxicity study recorded the mortalities at 24h intervals for 96h. The 96h LC50 value was estimated to be 0.003 mg L-1. Chronic toxicity studies were also conducted exposing H. pulchellus to sublethal concentrations for 45 days. The brain acetylcholine esterase activity was significantly reduced (p ˂ 0.05) in the cypermethrin nano formulation exposed fish. The nano formulation exposure also caused a significant increase in the liver and kidney superoxide dismutase activity. Elevated catalase and glutathione-s-transferase levels were observed in the liver and gills, with no conspicuous change in the kidneys. The serum enzymes aspartate aminotransferase and alanine aminotransferase were elevated significantly by cypermethrin exposure. The serum triglycerides, cholesterol, and protein content were reduced significantly. Similarly, the red blood cell, haematocrit, haemoglobin, and platelet count also showed significant reduction on cypermethrin exposure. These findings on the toxic impacts may help to understand the effect of micro-formulated antiparasitic drugs in fin fish.

Bacteria are ubiquitous in nature, live on animate and inanimate surfaces playing diverse roles and act as either beneficial or harmful organisms. The present study focuses on developing a simple and cost-effective method for long-term storage of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible Staphylococcus aureus (MSSA). The method involves drying bacterial cultures viz., nine MRSA strains and one MSSA strain, on gelatin-impregnated filter paper strips. A 12% nutrient gelatin medium was used for maintaining and storing the bacterial cultures. The results showed that the bacteria preserved on the gelatin-paper strips remained viable for up to a year at temperatures of 4°C, -20°C, or -80°C.Further, the bacterial cultures survived for over a month at room temperature (30±2 °C). This practical, user-friendly technique offers an affordable solution to store and transport bacterial cultures, making it particularly beneficial for labs with limited resources or storage space.

Hyaluronic acid (HA) is a valuable bioactive polysaccharide that has numerous applications in the nutricosmetic and cosmetic industries. The tremendous increase of jelly fish in fishing environments has led to a huge global demand for better ways to utilize the organism. The present study investigated the potential for extracting hyaluronic acid from the jelly fish, Acromitus flagellates. The extracted powder was fine, hygroscopic and off-white in colour. The viscosity was measured at different concentrations of 1 mg/ml to 5 mg/ml and at the highest shear rate studied (450 s-1), the maximum viscosity obtained was 1.85cp. Fourier Transform Infrared Spectroscopy (FTIR) confirmed the structure of hyaluronic acid with the presence of disaccharide repeats of D-glucuronic acid (GlcUA) and N-acetylglucosamine (GlcNAc) adjoined alternatively by β-1,3 and β-1,4 glycosidic bonds. The UV-Visible spectroscopic absorption data of the extracted sample showed similar characteristics when compared to the standard. Protein contamination was not observed in the SDS PAGE analysis. The moisture retention ability of the extracted hyaluronic acid, as estimated by in vitro analysis, was better than glycerol up to 4h. Hence, Acromitus flagellates is an ideal candidate for extraction of hyaluronic acid that can be applied in cosmetic and pharmaceutical formulations.

Chitosan and sodium alginate are important natural polymers that are abundant in marine sources. Chitosan is generated from chitin by chemical N-deacetylation and is made up of poly-β-(1→4)-2-amino-deoxy-D-glucopyranose. It is found in the shells of crustaceans, insects, fungi, and also in the scales of fishes. Sodium alginate is a derivative of alginic acid found mostly in marine brown algae, made up of 1,4-β-d-mannuronic (M) and α-l-guluronic (G) acids. Chitosan and sodium alginate are natural, non-toxic, biocompatible and biodegradable polysaccharides. Thus, they have a wide range of uses in food packaging, biomedical applications, and are used to make biodegradable films in various compositions. This review covers chitosan and sodium alginate-based films with various combinations of polysaccharides, protein, essential oil, plant extract and synthetic materials. The incorporation of these materials has improved the physical, mechanical, barrier, antioxidant and antimicrobial properties of the films.

Stake net fishing in Vembanad Lake plays a vital role in the local economy and to food security. The study analysed the cost and return and seasonality of stake net fishery in Vembanad Lake, Kerala, India. It faces significant challenges threatening its sustainability. High-value prawns comprise of 65% of landings from fishery and account for more than 70% of the revenue realisation. The annual net profit is less than Rs.2 lakhs per stake net unit which again is shared among the crew of 3 to 4 members, which is only nominal considering the fishing effort. The average catch during lean months is currently reported to be as low as 9.49 kg per unit. The net present value of stake net fishing unit was computed as Rs.10.26 lakhs. The study points to seasonality in fish landings.