ABSTRACT The high cost of conventional culture media restricts large-scale cultivation of Ulva lactuca, highlighting the need for affordable nutrient alternatives. This study evaluated agricultural fertilizers, urea and diammonium phosphate (DAP), as nitrogen and phosphorus sources, respectively. Five treatments – urea (UE), DAP (DP), urea + DAP (UD), no urea (NU), and no phosphate (NP) – were tested under controlled laboratory conditions for 21 days with three replicates (n = 3). Growth, pigment content, gross primary productivity, and total antioxidant capacity were analyzed. Fresh weight increased 4.60, 2.97, and 4.06-fold in UE, DP, and UD treatments, respectively, compared to the control. UE and UD showed significantly higher gross primary productivity (p < .05). Regression analysis predicted a 13.85% biomass increase (R 2 = 0.79) under UD at 0.81:0.48 g L−1 (urea:DAP). These findings indicate that urea and DAP based formulations effectively enhance biomass and physiological performance under optimized conditions.

ABSTRACT In many parts of the world, rural communities rely heavily on indigenous fish species to meet their nutritional needs, underscoring the need for sustainable farming practices. Diet optimization and effective environmental management are essential to promoting the health and well-being of these fish during domestication. In this study, we evaluated the survival and growth of Macrognathus pancalus, a high-value benthopelagic and overexploited food fish, using various food materials: live tubifex, zooplankton, a combination of zooplankton and tubifex, and an artificial feed as a control. Additionally, we assessed different floor substrates as habitats—sand, mud, a combination of sand and mud, and a control without any substrate. The experiments were conducted in triplicate in reinforced plastic tanks over a 90-day period. The results revealed that fish (0.60 ± 0.08 g) fed with tubifex achieved significant growth of 1.89 ± 0.22 g (p < .05) with the higher survival (81.33 ± 2.31%), followed by those fed with a combination of mixed zooplankton and tubifex (1.38 ± 0.12 g). It was observed that fish (2.40 ± 0.75 g) in a water habitat without any substrate (control) achieved significant growth of 6.86 ± 2.60 g (p < .05), followed by those in a sandy habitat (5.21 ± 0.02 g). These findings suggest that feeding tubifex to fish in tanks without a floor substrate could be the most effective approach for the culture of this fish.

ABSTRACT The present study evaluated the growth and survival of pearlspot, Etroplus suratensis, under two rearing environments, freshwater (0 ppt) and constituted saltwater (10 ppt), which differed in calcium and magnesium concentrations due to the addition of raw sea salt in the constituted saltwater. A 60-day experiment (initial weight: 29 ± 2.5 g and stocking density: 20 fish/900 L) was conducted in duplicate in 1200-L fiber reinforcement tanks, each equipped with a biofilter. Water quality parameters and growth performance metrics of pearlspot were assessed in both treatments. Constituted saltwater exhibited substantially higher concentrations of calcium (38 mg/L), magnesium (285 mg/L) and total hardness (336 mg/L as CaCO3) compared to freshwater (calcium: 9 mg/L; magnesium: 42 mg/L; total hardness: 50 mg/L as CaCO3). Fish reared in constituted saltwater showed a significantly higher final mean weight (p < .05), daily weight gain (p < .01), percentage weight gain (p < .001) and condition factor (p < .001). Survival was also significantly higher (p < .05) in constituted saltwater, whereas mortality increased in freshwater, likely due to osmoregulatory stress. These findings highlight the importance of calcium and magnesium concentration in rearing water and support the use of raw sea salt to constitute saltwater at 10 ppt as a suitable medium for rearing E. suratensis in recirculatory aquaculture-based hatchery and nursery systems (RAS).

ABSTRACT The dependence on fishmeal and fish oil in aquafeeds poses challenges to the long-term sustainability of aquaculture due to the pressure on limited marine resources. This study evaluated the potential of the microalga Haematococcus pluvialis (HP) as a partial substitute for fishmeal and a complete replacement for fish oil in the diet of black tiger shrimp (Penaeus monodon). Post-larvae (PL22) were reared for 56 days in a recirculating aquaculture system and fed five diets containing 0%, 8%, 12%, 16%, or 20% HP. Shrimp fed 12% HP showed significantly higher weight gain (1191.51%), daily weight gain (0.31 g day−1), and specific growth rate (4.56% day−1) compared with other dietary treatments (p < .05). Feed conversion ratio (1.09) and feed efficiency ratio (0.93) improved at 12% and 20% inclusion levels, respectively. Survival exceeded 95% at both levels, indicating that HP can effectively replace fish oil and partially replace fishmeal in shrimp feed.

ABSTRACT This study examined the effects of a novel phytobiotic-based functional additive (Apex®) supplementation on the growth performance and disease resistance of the brown-marbled grouper. The experimental design consisted of three treatments: a control (0% additive), a medium-dose (0.3%), and a high-dose (0.7%) treatment, all applied over a 90-day period. Each treatment contained 75 fish with an initial weight of 8.3 g, replicated in three hapas. The results showed that supplementation with the additive significantly enhanced weight gain, specific growth rate, total length, and condition factor, as well as improved feed conversion ratio. Additionally, fish receiving dietary Apex® demonstrated reduced prevalence, intensity of ectoparasites, and Vibrio sp. loads, while showing increased levels of red and white blood cells, hematocrit, hemoglobin, lymphocytes, and monocytes. This study highlights the positive effects of novel phytobiotic additives on growth, immune response, and disease resistance in grouper aquaculture, supporting their potential application for sustainable fish farming.

ABSTRACT Vibriosis, a bacterial disease, is considered a significant threat to the sustainability and economic viability of shrimp production. The present study evaluated the application of a predatory bacterium to control the population growth of pathogenic Vibrios in Pacific whiteleg shrimp (Penaeus vannamei). The predatory bacterium was identified as Bacteriovorax sp. OP175948.1 based on the 16S rRNA sequence. The Vibrio-inhibitory activity of Bacteriovorax sp. was evaluated using two independent trials with P. vannamei, exposed to two pathogenic Vibrios, including Vibrio parahaemolyticus and Vibrio harveyi. Each trial was conducted in five treatments, including a negative control, a positive control, and a treatment with Bacteriovorax sp. applied at 102, 104, and 106 plaque-forming units mL−1 (PFU mL−1). Results indicated that shrimp infected with V. parahaemolyticus and V. harveyi, and then treated with Bacteriovorax, showed a 6-fold increase in survival for V. parahaemolyticus and a 3-fold increase for V. harveyi, relative to the control. The shrimp treated with 104 to 106 Bacteriovorax sp. improved survival associated with a significant decline in Vibrio spp. counts in the shrimp tissues and rearing water. The Bacteriovorax sp. should be used as a practical strategy to prevent Vibrio-associated mortalities in P. vannamei aquaculture.

ABSTRACT Technologies currently employed for land-based seaweed cultivation are cost-intensive and wasteful of resources. Hence, the present study examined natural and synthetic materials as growth substrates for a sustainable on-land production of Ulva spp. In total, 16 materials were qualitatively evaluated regarding their usability represented as availability, durability, reusability, and adherence, as well as growth of algae on the selected materials. The results of spore adhesion and mobility indicated that loofah sponge, clay pellets, and polyurethane foam were most suitable for algal adhesion. Synthetic materials generally exhibited low toxicity and high durability but low usability, as algal spores clogged the materials. In contrast, natural materials exhibited increased vulnerability to mechanical stress, leading to reduced durability and low reusability. Furthermore, toxic effects that might have inhibited movement and attachment of spores were more likely to occur from natural materials due to degradation processes during the tests.

ABSTRACT This study evaluated the effects of artificial salinization strategies on the growth, water quality, and health status of Pacific white shrimp reared in a synbiotic nursery system. Four treatments were established: low-cost salt mixture with freshwater at salinity 3 g L−1 (LCSM), commercial salt mixture with freshwater at salinity 3 g L−1 (CS), seawater diluted to salinity 3 g L−1 (DS), and control; seawater at salinity 36 g L−1 (SW). Experimental units (60 L) were stocked with 2000 shrimp m−3 (12.0 ± 1.0 mg). The LCSM, CS, DS, and SW resulted in a similar final weight (0.84 g, 0.84 g, 0.72 g, and 0.65 g, respectively). However, survival rates were lower in the LCSM treatment (70%) compared to the SW (90%). Our results demonstrated that despite low survival in the LCSM treatment, all low-salinity treatments provided good ionic profile, water quality, and shrimp growth.

ABSTRACT The present study was conducted to assess the effects of fresh and 30%, 40%, and 50% of dry Azolla pinnata as supplementary diets with the basal feed on the growth performance, growth-related gene expression, and antioxidant enzymes of Nile tilapia (Oreochromis niloticus) under normal conditions. Also, we evaluated their protective impact on these parameters against the toxicity of a heavy metal mixture (Cu, Pb, and Zn) for 5 weeks. An average initial body weight of O. niloticus, which was used, was 31.5 ± 1.5 g. Three replicates were used for each treatment (10 fish/replicate). The results showed that O. niloticus exposed to heavy metals (HMs) and fed on fresh and 40% and 50% of dry A. pinnata had high significant levels of ghrelin, leptin, and the insulin-like growth factor gene (IGF-1) compared to untreated exposed fish (p < .05). Further, fresh and 40% and 50% of dry A. pinnata significantly decreased the accumulation of Cu, Pb, and Zn in the liver, intestine, and muscles of fish (p < .05). In addition, they led to a significant increase in antioxidant enzyme activities (p < .05) and reduced oxidative stress induced by heavy metal toxicity. Ultimately, our study concluded that the basal feed enriched with fresh and 40% and 50% of dry A. pinnata can effectively provide protection for O. niloticus against the toxic effects of HMs.

ABSTRACT Aquaculture species are often exposed to disease challenges and environmental stress, necessitating the use of natural dietary supplements to enhance health and productivity. This study evaluated the effect of Ganoderma lucidum polysaccharide (GLP) on the growth performance, intestinal enzyme activity, serum antioxidant capacity, and disease resistance of the Chinese soft-shelled turtle (Pelodiscus sinensis) against Aeromonas hydrophila infection. A commercial diet (50% crude protein) was supplemented with GLP (50% purity) at 0 (GLP0), 2.5 (GLP25), 5 (GLP50), 7.5 (GLP75) and 10 (GLP100) g/kg feed. A total of 450 soft-shelled turtles (4.00 ± 0.20 g) were randomly stocked into five concrete tanks (1.2 × 0.4 × 0.3 m) in triplicates and fed thrice daily (8:00, 13:00 and 18:00) at a feeding rate of 3–5% body weight for eight weeks, which was adjusted weekly. At the end of the feeding trial, the soft-shelled turtles were challenged with A. hydrophila (2.0 × 107 CFU/ml) by intraperitoneal injection. The results showed that the soft shelled turtles fed GLP50, GLP75 and GLP100 diets had significantly improved weight gain, specific growth rate, feed conversion ratio and survival (%) compared to those fed the control diet (p < .05). All GLP diets significantly enhanced intestinal trypsin and lipase activities, while the GLP50, GLP75 and GLP100 diets also improved intestinal α-amylase activity compared to the control (p < .05). The turtles fed GLP50 and GLP75 diets displayed significantly enhanced serum total superoxide dismutase activity compared to the control (p < .05). GLP supplementation significantly increased serum catalase and glutathione peroxidase activities while reducing serum malondialdehyde content (p < .05). The cumulative mortality decreased significantly at all levels of GLP supplementation after A. hydrophila challenge (p < .05). Polynomial (quadratic) regression analysis indicated optimum GLP levels of 8.33 g/kg for final body weight, 7.56 g/kg for trypsin activity, and 13.52 g/kg for glutathione peroxidase activity. In conclusion, dietary GLP supplementation enhanced growth, digestive enzyme activities, antioxidant capacity, and disease resistance in Chinese soft-shelled turtles, demonstrating its potential as a functional feed additive in aquaculture.