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This study aimed to investigate the effectiveness of five natural plant extract compounds Curcumin (CUR); Eugenol (EUG), Cinnamaldehyde (CIN), Stigmasterol (ST) and Morin (MOR), on two species of Saprolegnia; Saprolegnia parasitica and S. australis. Selective compounds were screened for the minimum inhibitory concentration, first for anti-oomycetes activity and then mycelium growth inhibition, spore germination inhibition and colonisation test. Nitric oxide production and myeloperoxidase activity of the compounds were tested in head kidney leukocytes of rainbow trout, Oncorhynchus mykiss to assess the immunostimulatory potential. Molecular docking of effective compounds was carried out with effector proteins of S. parasitica to investigate the target binding sites. Among all, CUR could completely inhibit zoospore production and significantly (p ≤ .05) inhibit hyphal growth at 16 mg l−1 against S. parasitica and S. australis. CIN at the concentration of 50 mg l−1 completely inhibited hyphal growth of both Saprolegnia spp., although the zoospore production of S. parasitica and S. australis was reduced at 25 mg l−1 and 10 mg l−1. In the case of EUG, significant inhibition of the hyphal growth and germination of S. parasitica zoospores was observed at 50 mg l−1. ST and MOR did not show antioomycetes activity. The molecular docking results were consistent with in vitro studies, possibly due to the binding with the vital proteins (Plasma membrane ATPase, V-type proton ATPase, TKL protein kinase, Host targeting protein 1) of S. parasitica and ultimately inhibiting their activity. CUR and CIN showed increased nitric oxide production at the highest concentration of 250 and 256 mg l−1 but the value was not significant (p ≤ .05) with control. CUR showed significantly higher peroxidase activity (p ≤ .05) at a concentration of 256 mg l−1 though values were significantly similar with concentration from 16 to 128 mg l−1. The nitric oxide and total peroxidase activity of rainbow trout leukocytes in the case of CIN showed a significant difference only at 250 mg l−1 against the control. The results conclude that CUR, CIN showed the better anti-Saprolegnia activity and could be used as phyto-additives in aquaculture. Among all, the inclusion of CUR as phyto-additives will provide additional immunostimulatory activity.

Impact of osmoregulation on plasma sex steroid levels and gonadal histo-architecture was monitored to elucidate the effects of deviation from habitat salinity on gonadal recrudescence in an active reproductive season of an euryhaline fish Etroplus suratensis (pearlspot). Fish were maintained in three different salinities of 0 ppt Fresh Water (FW), 15 ppt Brackish Water (BW) and 30 ppt Sea Water (SW) for a period of 60 days. Plasma osmolality values were found to be significantly highest in SW-acclimated fish accompanied by highest levels of plasma K⁺ and Cl¯ ions. The progress of gonadal recrudescence was higher in BW followed by FW and SW as evident from the cellular features of gonads and increased level of plasma sex steroids, such as, in case of female and 11-keto Testosterone and Testosterone in case of males. Plasma cortisol levels were comparatively higher in fish of both sexes in SW group. Significantly high levels of cortisol in SW suggest its role in hypo-osmoregulation and associated stress. This study clearly reveals that salinity changes during the active reproductive phase can suppress the steroid-mediated gonad recrudescence maximally under hypo-osmoregulation in an euryhaline fish.

Three hydroponic media crushed stones (T1), river stones (T2), and floating raft (T3) were compared in an aquaponic system with common carp (Cyprinus carpio) and mint (Mentha arvensis). Fish effluents were used as plant nutrients while plants filtered water by stripping off the nutrients before returning to the fish tank. Fish growth, plant growth, and water quality parameters were used to evaluate the suitability of three different media. Growth performance of common carp and mint followed the relationship of crushed stones > floating raft > river stones with significant difference observed among all treatments. Total ammonia nitrogen (TAN) removal varied significantly among different treatments. The maximum TAN removal was observed in T1 (77.13%) followed by T3 (69.65%), and the minimum removal was observed in T2 (48.82%). Nitrate removal varied significantly among different treatments. The highest removal was observed in T1 (82.95%) followed by T3 (68.04%) and T2 (59.51%). Removal of phosphate was significantly lower in T2 (50.12%) when compared to T1 (67.85%) and T3 (70.71%). Biofilter performance (g m−3 day−1) of T2 (4.80) was significantly lower compared to T1 (7.13) and T3 (7.37). Crushed stone and floating raft were significantly efficient when compared to river stone medium in terms of nutrient removal and water quality maintenance for the fish culture. Considering all growth parameters, crushed stone media proved to be better when compared to other two media. Thus, medium selection could be a considerable factor when designing an aquaponic system.

An 18-months field trial was performed to explore the effect of duration of stunting on growth, digestive enzymes and carcass quality in Chanos chanos. Milkfish fry (weight of 1.25 ± 0.03 g and length of 5.53 ± 0.03 cm) were stocked in earthen ponds of 0.02 ha, in triplicate, for different duration of stunting, viz., 4 months (Treatment-1; T4), 8 months (Treatment-2; T8) and 12 months (Treatment-3; T12) and a normal seed (Control; C) separately. In the stunting phase, fish were stocked at higher stocking density (0.2 million/ha) and fed de-oiled rice bran at sub-optimal level. Post-stunting or re-feeding phase commenced immediately after completion of respective stunting duration and fish were reared for the rest of the period to complete the total rearing period of 18 months. In post-stunting, fish stocking density was adjusted to (5000 pieces/ha) and fed at an optimum level (3%). At the end of stunting phase, the study found a significant reduction in growth, survival, digestive enzymes activity, except protease in the T4 group, and carcass nutrients composition of stunted fish. However, in the initial phase of post-stunting, T8 group exhibited an elevated specific growth rate (5.00 ± 0.092%/day), body weight gain (80.82 ± 1.28 g), amylase (0.585 ± 0.021 U/mg protein), protease (5.48 ± 0.13 U/mg protein), and lipase activity (7.92 ± 0.32 U/mg protein). All stunted fish groups displayed a compensatory growth response in post-stunting, but a complete growth compensation was observed in T8 group, which resulted in better feed conversion ratio (3.03 ± 0.04) feed efficiency ratio (0.33 ± 0.01), protein efficiency ratio (1.91 ± 0.03), survival (91.38 ± 0.07%) and digestive enzyme activities. Similarly, at the end of post-stunting, carcass analysis revealed a complete restoration of nutrients in stunted fish and significantly higher protein content in T8 group. Further, the study found lower meat and higher bone contents in normally reared fish than the post-stunted fish which revealed the carcass quality improvement in post-stunted fish thus indicates superiority of the stunting process over normal rearing. Overall, the study suggests that stunting of milkfish, for 8 months (T8), positively affects its growth, survival, digestive enzyme activities and carcass quality which in turn, shall help to overcome the contemporary challenges in milkfish culture.

In this study, we investigated the effect of dietary Bacillus circulans PB7 (BCPB7) and fructoligosaccharide (FOS), used singly or in combination for evaluation of growth, immune and physiological status of Labeo rohita (rohu) juveniles reared under low pH and normal pH for 60 days. Experimental fishes were distributed in two sets such as one set continuously exposed to low pH (5.5) and other reared under normal pH (7.0), and fed with four iso-nitrogenous diets viz. basal (control), Bacillus circulans PB7 (BCPB7, 106 cfug−1), 1% fructooligosaccharide (FOS) and their combination. The effect of such pre, pro and synbiotics dietary treatments on growth performance (weight gain, specific growth rate, feed conversion ratio and protein efficiency ratio), immune response (hematological indices, serum biochemistry, lysozyme, NBT activity), antioxidative status in the form of antioxidant enzyme (catalase, superoxide dismutase, glutathione-S-transferase), acetylcholine esterase (AChE), Na+ K+ ATPase and stress bio-markers (cortisol, glucose and HSP-70) were examined. The group treated with low pH and fed with control diet (without supplementation) was found to be inhibited (p

This study investigated the effect of dietary supplemented synthetic, and shrimp shell meal (SSM) derived natural astaxanthin combination on growth, digestive and metabolic enzyme activities, antioxidative status, physio-metabolic responses, and skin colouration of high valued discus (Symphysodon aequifasciatus) advanced juveniles reared in captive condition. Four isonitrogenous (50 % crude protein), isolipidic (9% ether extract), and isocaloric (around 400 kcal digestible energy/100 g) experimental diets viz. Control (only synthetic astaxanthin, without SSM), T1 (15 % SSM + synthetic astaxanthin), T2 (20 % SSM + synthetic astaxanthin), T3 (25 % SSM + synthetic astaxanthin) were prepared and fed to satiation level twice daily for 90 days. Results indicated significantly (P

The false clown fish, Amphiprion ocellaris is a promising candidate species in the global marine aquarium trade. The lack of sustainable hatchery production and the over-exploitation from the wild cause severe threats to their natural population. Environmental factors influence the survival and existence of aquatic animals, and the temperature is one of the most crucial factors determining survival, especially during the early embryonic developmental stages. The present study evaluated the effect of temperature on embryonic development by exposing the fertilized eggs to varying temperature (26 °C, 27 °C, 28 °C, 29 °C, and 30 °C). Temperature significantly (P

Carotenoprotein, a complex of carotenoids and protein, extracted from shrimp shell waste can be an effective source of carotenoid as well as antioxidant in fish diets. In the present study, the nutritional potential of carotenoprotein extracted from shell wastes of Parapeneopsis stylifera on growth, physiometabolic changes and coloration in high-value ornamental fish, oscar (Astronotus ocellatus) was assessed in a 120 days feeding trial. Four iso‑nitrogenous (30–31% CP) and isolipidic (11.34–11.55% CL) diets were formulated with graded levels of carotenoprotein inclusion like 0%, 5%, 10% and 15% and designated as Control, T1, T2 and T3 respectively. At the end of the feeding trial, growth indices such as final body weight, weight gain, and specific growth rate indicated that fish fed with 10 and 15% levels of carotenoprotein incorporated diet showed higher growth compared to control and T1. Oxidative stress enzymes like SOD and Catalase were lower in 15% and 10% carotenoprotein incorporated diets respectively in both gills and liver. Stress indicators like serum glucose and cortisol activity were found to be higher in control than in diets with 10% (T2) as well as 15% (T3), suggesting the stress-reducing ability of the carotenoprotein in fish feed. Relatively higher respiratory burst activity in fishes of T3 group indicated higher immunity status of the fish. Quantitative colour values in terms of redness, chroma in the fin region as well as carotenoid content in scale, skin and muscle of fish were higher in T2 (10% carotenoprotein incorporated diet) as compared to T3 (15% carotenoprotein incorporated diet). Overall, this study clearly showed that dietary incorporation of as little as 10% carotenoprotein is advisable to ornamental fish farmers for enhanced growth, colouration, as well as antioxidant activity in this popular high value ornamental fish for maximizing their profit.

Temperature can influence sex differentiation in gonochoristic fish with a genetic sex-determination system (GSD). The precise effect of high temperature on sex remains unknown in a eurythermal carp (Cyprinus carpio). The present study aimed to identify the critical thermosensitive period and the effect of temperature on sex differentiation in common carp, C. carpio. Our results demonstrated the lower and upper limits of the lethal maximum temperature (LTmax) of C. carpio juveniles (42 dph) were 37.2 and 39.7 °C, respectively in the present study condition. The confidence limit of the median lethal time (LT50) of the juveniles was 38.87 °C. To determine the thermosensitivity of sex differentiation, the larvae were exposed to a high temperature (36 °C) for 7-day durations, starting from hatching until 69 dph. The period of critical thermosensitivity for sex differentiation towards the male phenotype was 7 to 13 dph. The sex proportions and thermosensitivity of sex differentiation illustrated high inter-familial variability of sex ratio skewed towards male phenotype ranged from 69 to 100% in the 10 full-sib families exposed to 36 °C. Exposure of juveniles to the high temperatures (34 °C and 36 °C) significantly altered the sex ratios and produced 63 to 82 % male phenotype even during the transition of sex differentiation. This study demonstrates that sex differentiation in common carp is seriously influenced by the environmental process. Also, it explores a temperature-induced method of skewing sex ratio towards the male phenotype irrespective of morphological gonad differentiation in common carp.

The golden mahseer (Tor putitora) is an important and high valued sport and food fish of national and international importance. Therefore for promotion of golden mahseer, proper mineral supplementation in early developmental stages is very important. The present study evaluated the effects of dietary zinc on growth, survivaland physiological response of Tor putitora fry. One thousand eight hundred fry (avg.wt 54.35±3.09 mg) were randomly distributed into 6 treatment groups with triplicates each. Six iso-nitrogenous (40±0.02% to 41.44±0.01% crude protein) semi-purified diets were prepared with graded levels of dietary zinc. Zinc sulphate was added as the dietary zinc source to the basal diet. The results indicated that specific growth rate (SGR) was of value 2.52 ±0.23 gm of T. putitora fry which increased with dietary zinc levels up to a concentration of 40 mg Zn Kg-1 in diet. The zinc dependent metabolic enzymes and antioxidant enzymes was also observed to be highest in groups supplemented with 40 mg zinc/kg feed. The overall results of the present study suggest the efficacy of dietary zinc on growth, survival and physiological response of golden mahseer fry in order to garner the possibility of establishing the species to commercial aquaculture.

Aquaponics is the combined culture of fish and plants in recirculating aquaculture systems, considered to be an innovative, eco-friendly and sustainable technology. The present study on bio-integration of Common carp and Mint in aquaponic system was aimed at determining the optimum hydraulic loading rate (HLR) for the aquaponic system. Three treatments having different HLRs viz., T1 (3 m day−1), T2 (6 m day−1) and T3 (12 m day−1) were compared and their effect on fish growth, survival, mint growth, yield and various water quality parameters were observed to find the most efficient HLR for Common carp and Mint in aquaponic system. Different HLRs showed significant effect on fish growth in terms of length and weight gain, survival, specific growth rate (SGR). Higher growth rate was observed in treatment T2 (6 m day−1) as compared to other treatments and control having different HLRs. Mint growth rate at the end of both the harvests showed significant variation and got affected by different HLRs with better results obtained in treatment T2 (6 m day−1). Overall water quality parameters, nutrient removal and biofilter performance were better at HLR 6 m day−1 i.e., treatment T2. Hence, HLR of 6 m day−1 can be recommended for culturing Common carp and Mint in aquaponic system.

A 60-day feeding trial was performed to test the nutritional value and utilization possibility of palm kernel meal (PKM) as a feed ingredient for juvenile Labeo rohita. Five iso-nitrogenous diets were prepared with various inclusions of PKM which replaced sunflower oil cake and de-oiled rice bran namely, control (without PKM), T1 (50 g/kg PKM), T2 (100 g/kg PKM), T3 (150 g/kg PKM) and T4 (200 g/kg PKM). The experiment was conducted in 350 L fibre reinforced plastic tanks in triplicate and each tank stocked with twenty-five juvenile rohu (7.2 ± 0.01 g) were fed twice daily at 5% of body weight with the experimental diet. The growth performance values showed a higher overall linear trend in T2 and it is significantly different from control as well as T1 groups. Final results showed highest average body weight, specific growth rate, protein efficiency ratio, and apparent net protein utilization in a dose-dependent manner (p < 0.05). Significantly higher amylase, protease, and lipase activities were recorded in T2 treatment (p = 0.003, p = 0.001 and p = 0.002, respectively). Additionally, dietary PKM significantly lowered the aspartate amino transferase, alkaline amino transferase and alkaline phosphatase enzyme activities in a dose-dependent manner (p < 0.05). Significantly higher lactate dehydrogenase, malate dehydrogenase, superoxide dismutase and catalase activities in the liver tissues were recorded in T4 (p = 0.004, p = 0.01 and p = 0.02 and p = 0.001, respectively). Based on the polynomial regression analysis, the PKM inclusion at 26.17–100.11 g/kg can be effectively used in the diet of juvenile L. rohita as a non-conventional growth-promoting feed ingredient without any harmful effects on its growth performance and physiological activities.

Carotenoproteins from four different shrimp shell wastes Penaeus monodon, Parapenaeopsis stylifera, Metapenaeus affinis and Nematopalemon tenuipes were extracted with the aid of papain enzyme and characterized by their protein, amino acid and carotenoid content of the shell wastes and the antioxidant activities like DPPH, FRAP, ABTS radical scavenging activity and reducing power assay of the carotenoprotein. Higher protein content of 9.8 g 100 g−1 and 9.2 g 100 g−1 was recovered from shell waste of Penaeus monodon and Parapenaeopsis stylifera respectively along with highest carotenoid content of 114 ± 0.02 μg g−1 in Parapenaeopsis stylifera followed by 100.6 ± 0.02 μg g−1 from the shell waste of Metapenaeus affinis. Highest antioxidant activity was found in the carotenoprotein extracted from the shell waste of P. stylifera which suggest that the antioxidant activity of carotenoids followed a concentration dependent pattern. The amino acid profile showed that carotenoprotein is a rich source of essential amino acids such as glutamic acid, aspartic acid, lysine and leucine. Among shell wastes, P.stylifera shell waste was calculated to be superior as it contained higher amount of essential amino acids and exhibited higher antioxidant activity in terms of protein, carotenoid as well as radical scavenging and reducing power and it could serve as a supplementary nutritive feed ingredient in animal diets. This would help in utilization of crustacean (shrimp) shell waste for formulating low cost feed for ornamental fish and also encourage shrimp processing industries to utilize of the same in order to control pollution of land and water.

An experiment was conducted to compare the efficiency of biofilm production in natural and artificial substrates and to study their effect on water quality and growth of Etroplus suratensis. Four different substrates were used for biofilm formation: paddy straw (T1), sugarcane bagasse (T2), polyvinylchloride (PVC) pipe (T3) and plastic sheet (T4). The experiment was carried out in mud-bottomed fibre-reinforced plastic tanks (300 L) in triplicates. About 3000 cm2 surface area (600 g) of each substrate was suspended in water supplemented with fertilizers. Only cow dung and urea were applied in control tanks. The tanks were stocked with 25 fishes with average weight of 9.1 ± 0.22 g. The overall mean value of heterotrophic bacteria in substrate was found higher in straw followed by bagasse, plastic and PVC. The dominant genera of bacteria in the substrate were Bacillus, Pseudomonas and Micrococcus in that order of preponderance. The mean phytoplankton and zooplankton density on the substrates were higher in bagasse followed by straw, plastic and PVC. The biofilm developed on the substrate significantly reduced the ammonia nitrogen and nitrite-nitrogen content of water. The growth of fishes was significantly (P