A 70-day feeding trial was conducted to evaluate the effects of dietary supplementation of selenium nanoparticles (Se-NPs) on physiological and biochemical aspects of juvenile mahseer (Tor putitora) fish. Maintaining a 40% protein level, 2 different experimental diets supplemented with 0% Se-NPs and 0.68 Se-NPs mg kg -1 were fed to triplicate groups of fish. The experiment was conducted in a semistatic condition consisting of 6 fiber tanks. The fish were first acclimatized, and then 30 fish per tank were randomly put into each fiber tank. At the end of the feeding trial, samples were collected from the fish and analyzed. Results obtained showed that the diet supplemented with Se-NPs significantly increased (P < 0.05) physiological aspects like red blood cell count, hemoglobin level, hematocrit values, and lysozyme activity as compared to the basal diet. Similarly, biochemical parameters including serum growth hormone levels, tissue total protein content, and glutathione peroxidase activity in liver and muscle tissues of T. putitora also significantly (P < 0.05) increased. Thus, dietary Se-NP supplementation at the rate of 0.68 mg kg -1 diet has very beneficial effects on the physiobiochemical health aspects of juvenile T. putitora.

In the present review, the ongoing researches about selenium research in fish nutrition have been comprehensively discussed. Selenium research is getting popularity in fish nutrition as it is required for the normal growth and proper physiological and biochemical functions in fish. Its deficiency or surplus amounts create severe problems in fish. It is available as inorganic form, organic form, and nano form. In fish, most of the previous research is about the selenium requirements for fish by using only one selenium source mainly the inorganic one. Selenium shows maximum biological activity and bioavailability when it is supplied in proper form. However, to differentiate the more bioavailable and less toxic form of selenium, sufficient information is needed about the comparative bioavailability of different selenium forms in different fish species. In fish, important data about the new forms of selenoproteins is still scarce. Therefore, it is necessary to focus on the determination and elucidation of the new selenoproteins in fish through the utilization of recent approaches of molecular biology and proteomics. The adaptation of these new approaches will replace the old fashioned methodologies regarding the selenium research in fish nutrition. Moreover, the use of molecular biology and proteomics-based new approaches in combination with selenium research will help in optimizing the area of fish nutrition and will improve the feed intake, growth performance, and more importantly the flesh quality which has a promising importance in the consumer market.

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For the production and commercialization of ornamental fish species, it is indispensable to collect biometric data that facilitate the selection of animals for trade and genetic improvement of the stock. However, during the handling process, fish receive more stress if proper anesthetics are not used. Thus, application of appropriate anesthetics is an important tool for minimizing stress in animals. The objective of this study was to determine the effective concentrations of benzocaine, eugenol, and menthol for achieving anesthesia in Freshwater Angelfish Pterophyllum scalare and to develop induction and recovery response curves for different concentrations of these anesthetics. In total, 75 fish were exposed to five concentrations of the three anesthetics in a completely randomized design: benzocaine at 60, 85, 110, 135, and 160 mg/L; eugenol at 40, 80, 120, 160, and 200 mg/L; and menthol at 50, 75, 150, 200, and 250 mg/L. Each concentration (5 fish/concentration) consisted of five replicates, with each replicate represented by a single fish. The results indicated that the tested substances met the criteria of anesthetic efficiency. The effective concentrations of benzocaine, eugenol, and menthol for the anesthesia of Freshwater Angelfish were identified as 89.25, 90.6, and 92.1 mg/L, respectively.

In the present study, juvenile (live body weight, 54.3 ± 8.2 g), preadult (live body weight, 822.5 ± 33.9 g), and adult (live body weight, 1,562.8 ± 41.8 g) pacu, Piaractus mesopotamicus, were used to estimate their dietary essential amino acid (EAA) requirements using the whole‐body amino acid (AA) pattern. The results showed that whole‐body moisture, crude protein, total lipid, and ash contents expressed on a wet weight basis (%) were significantly different among the studied growth phases. No significant differences were observed in the dietary EAA requirements estimated for the three growth phases of pacu. These dietary EAA requirements were found to be different than those previously estimated for the same fish through its muscle AA pattern. Based on whole‐body EAA to total EAA ratios {A/E ratios; [(each EAA/total EAA) × 1,000]}, EAA requirements were estimated to be histidine (0.42%), arginine (1.36%), threonine (0.82%), valine (0.90%), methionine (0.45%), isoleucine (0.83%), leucine (1.29%), phenylalanine (0.74%), lysine (1.64%), and tryptophan (0.14%) for pacu. These estimated requirements may serve as a reference line in the formulation of practical and experimental diets until dose–response‐based optimum EAA requirements are available for pacu.

A 70 days feeding trial was conducted to evaluate the effects of graded level of L-ascorby-2-polyphosphate (APP) on growth performance and hematological indices of juvenile mahseer Tor putitora. Four different 40% protein experimental diets supplemented with APP at the rate of 0, 100, 200 and 300 mg APP kg-1 diet were fed to triplicate group of fish. The APP supplementation showed their effect in a dose dependent manner. Significantly (P < 0.05) improved growth performance i.e. weight gain (WG%), feed conversion efficiency (FCE%), specific growth rate (SGR%) and hepatosomatic index (HSI%) was observed with APP 300 , followed by APP 200 and then APP 100 enriched diet. The growth hormone (GH) level of fish also increased with increase in concentration of APP in the diet and showed a positive relationship with WG%. Moreover, the hematological parameters like red blood cell count, hemoglobin and hematocrit values also followed the same trend in response to graded levels of dietary APP supplementation, significantly (P < 0.05) higher values with APP 300 enriched diet followed by APP 200 diet while comparatively low, but significantly higher (P < 0.05) values as compared to control group of fish were obtained in response to APP 100 supplemented diets. The results of this study indicate the dose dependent beneficial effects of APP on growth performance and hematological indices of T. putitora.

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