Fisheries College and Research Institute

The study was conducted during January, 2023 to December, 2024 at Tirunelveli, Tuticorin and Kanyakumari district of Tamil Nadu, India to investigate the biodegradability of effluents collected from semi-intensive aquaculture systems operating in Tamil Nadu based on biodegradability index calculated from Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD). BOD indicated the oxygen needed to biologically degrade organic matter; COD measured both biodegradable and nonbiodegradable organic matter. The BOD/COD ratio (Biodegradability index) averaged 0.46, showing that the wastewater exhibited moderate biodegradability, implying that biological treatment was feasible but microbial seeding might enhance efficiency. Seasonal peaks in May correlated with increased feed input and organic waste accumulation; lower values in October and November reflected reduced production. Regression analysis identified a quadratic polynomial as the best predictor of BOD from COD, underscoring the value of mathematical models for monitoring wastewater quality. This study demonstrated that integrating BOD and COD data with statistical tools could improve effluent management. Expanding sustainable aquaculture would require implementing treatment technologies suited to effluents with moderate biodegradability. The findings provided baseline information for designing effluent treatment plants, optimizing microbial consortia and informing policy on discharge standards.

The present study evaluated the effect of different stocking densities on the growth performance, cannibalism and survival of Asian seabass (Lates calcarifer) fry reared in an indoor recirculating aquaculture system (RAS). Fry (25 days post-hatch) were stocked at three densities: 100T1, 200T2, and 300(T3) individuals per m3 and reared for 50 days under controlled conditions. Growth parameters, water quality, cannibalism rate and survival were monitored throughout the study. Water quality parameters remained within acceptable limits across treatments, although slight variations were observed with increasing density. Fish reared at the lowest density (T1) exhibited significantly higher growth performance, with maximum length gain (8.40±0.95cm), weight gain (10.2 ± 0.16g) and better feed conversion efficiency. In contrast, higher stocking densities (T2 and T3) resulted in reduced growth and feed efficiency. Cannibalism rate increased significantly with density, reaching the highest value in T3(13.55 ± 2.84%), while survival rate decreased from 96.54 per cent in T1 to 86.45 per cent in T3. The results indicated that lower stocking density improves growth performance, reduces cannibalism and enhances survival in Asian seabass fry under RAS conditions. Optimizing stocking density is therefore critical for sustainable and efficient nursery rearing of seabass.

This study investigates the length-weight relationships and length-frequency distributions of four gastropods Neripteron violaceum, Clithon oualaniense, Pirenella cingulata, and Telescopium telescopium collected from the Muthupet mangroves in Tamil Nadu. A total of 823 specimens were collected by handpicking within the quadrant. The values of the growth coefficient (b) varied from 2.42 in T. telescopium and 3.34 in N. violaceum. The results indicated that C. oualaniense, P. cingulata, and T. telescopium displayed negative allometric growth, whereas N. violaceum showed positive allometric growth. The coefficient of determination (r2) ranged from 0.662 (C. oualaniense) to 0.933 (P. cingulata).The length-weight associations for C. oualaniense and N. violaceum, which were not previously available in SeaLife Base, are determined for the first time in the current study. The study provides baseline data on gastropod resources in the Muthupet mangroves, supporting population assessment, ecological understanding and conservation oriented management of these species.

Soybean meal (SBM) remains a primary protein source in aquafeeds. This study investigated the potential of winged bean (Psophocarpus tetragonolobus) meal as a SBM replacement in diets for butter catfish (Ompok bimaculatus) juveniles (mean weight: 1.24 ± 0.23 g). A response surface methodology (RSM) optimized processing conditions to minimize antinutritional factors (ANFs) in winged bean meal (WBM), resulting in minimized tannin (4.14 ± 0.018 mg/g at 40 min, 110°C), phytate (0.414 ± 0.0009 mg/g at 31.67 min, 104.5°C) and trypsin inhibitor activity (70.8 ± 0.06% inhibition at 20 min, 90°C). Experimental diets containing 30% crude protein and varying levels of WBM substitution (0%, 25%, 50%, 75% and 100%) were fed for 70 days. Growth performance, measured by weight gain, was significantly higher in the 25% substitution group (p < 0.05) but not significantly different from the control at 50% substitution. Quadratic regression analysis predicted an optimal inclusion level of 15.10% for maximizing weight gain. Survival rates did not differ significantly among treatments (p > 0.05). Feed utilization was most efficient in the 25% substitution group. Haematological and immunological parameters indicated improved fish health at the 25% substitution level. Flesh quality attributes, including texture profile analysis, pH and antioxidant activity, were superior in the 25% group compared to other treatments. However, colour enhancement was more pronounced at higher inclusion levels (≥50%). While flesh pH and antioxidant activity suggested potential stress at higher winged bean inclusion levels, the 25% group showed improved values compared to the control. These findings suggest that WBM can potentially replace up to 50% of SBM in butter catfish diets, offering a promising alternative protein source. This study provides preliminary data on the feasibility and prospects of utilizing WBM in O. bimaculatus diets.

Biodiversity loss is expanding at an unprecedented rate, owing to habitat degradation, overexploitation, pollution, and climate change. Key Biodiversity Areas (KBAs) play an essential role in conservation and spatial planning to reduce the detrimental effects of biodiversity loss. The present study examined the spatio-temporal variations in fish diversity within selected zones of the Point Calimere Wildlife Sanctuary Key Biodiversity Area (PCWSKBA) from January 2023 to December 2024. In this study, 255 species from 39 orders and 85 families were identified. Escualosa thoracata (Valenciennes, 1847) was the most abundant fish species, comprising 7% of the total number of fish collected, followed by Eleutheronema tetradactylum (Shaw, 1804) (4%) and Mugil cephalus Linnaeus, 1758 (3.8%). The diversity indices revealed that Kodiyakarai Wetland (KW) had the highest species richness and abundance. Simultaneously, the SC recorded lower diversity due to anthropogenic pressure and environmental constraints. The post-monsoon season had the greatest seasonal diversity, which corresponded to the input of nutrients from monsoon rain. The K-dominance curve indicated that the samples from 2023 exhibited a higher concentration of dominance than those from 2024. Redundancy analysis (RDA) revealed that dissolved oxygen, salinity, and phosphate nutrient levels significantly influenced fish distribution across various zones. This study suggests that increasing phosphate and organic matter levels may enhance productivity by promoting algal growth and by providing a food source for fishes. However, excessive nutrient enrichment can lead to eutrophication, depletion of oxygen levels, and promotion of opportunistic species that ultimately disrupt the ecosystem balance. Therefore, it is essential to implement measures to reduce nutrient runoff and organic pollution to prevent oxygen depletion and protect the biodiversity and ecological health of the PCWSKBA. Sustainable land-use practices and enhanced water quality monitoring can help mitigate nutrient overload while preserving the productivity and diversity of aquatic ecosystems.