The e¡ect of feeding graded levels of vitamin E (E 0 , E 20 , E 40 , E 60 , E 100 , E 140 , E 180 , E 220 , E 260 ) in nine case-in^gelatin-based isonitrogenous (450 g kg À 1 crude protein) and isoenergetic (17.97 kJ g À 1 gross energy) experimental diets was evaluated in ¢ngerling Channa punctatus for 12 weeks. Growth, nutritional and haematological parameters were studied. Hepatic lipid peroxidation as thiobarbituric acid-reactive substances (TBARS) was also assayed. The maximum absolute weight gain (AWG g/¢sh, 55), best feed conversion ratio (FCR, 1.32), protein retention e⁄ciency (PRE, 40%) and energy retention e⁄ciency (ERE, 76%) were achieved in ¢sh fed on a diet supplemented with 140 mg vitamin E kg À 1 diet (E 140 ). A consistent decline in the hepatic TBARS concentration and an improvement in haematocrit (Hct) and haemoglobin (Hb) were displayed in ¢sh fed on diets with increasing concentrations of vitamin E up to 140 mg kg À 1 (E 0^E140 ), beyond which (E 180^E260 ) a reverse trend in these parameters was evident. Based on the broken-line regression and exponential analyses of AWG, FCR, PRE, ERE, Hb and Hct data, diets for ¢ngerling C. punctatus should contain vitamin E in the range of 140^169 mg kg À 1 to maintain satisfactory ¢sh performance.

A 12-week feeding trial was conducted to estimate the dietary copper requirement of fingerling Channa punctatus. Six caseinÀgelatin-based test diets (450 g kg À1 crude protein; 18.81 kJ g À1 gross energy) with graded levels of copper as copper sulphate (3.7, 4.7, 5.7, 6.7, 7.7 and 8.7 mg copper equivalent kg À1 diet) were formulated and fed to triplicate groups of fish (7.25 AE 0.81 cm; 5.21 AE 0.27 g) near to satiation. Fish fed diet with 6.7 mg kg À1 copper had highest absolute weight gain (AWG; 51.63 g fish À1 ), protein efficiency ratio (PER; 1.42 g fish À1 ), protein gain (PG; 8.34 g fish À1 ), haemoglobin (Hb; 9.68 g dL À1 ), haematocrit (Hct; 31.18%) and RBCs (3.24 9 10 6 9 mm À3 ). Feed conversion ratio (FCR) was found to be best (1.57) at above level of dietary copper. Whole body copper concentration was found to increase with the increasing levels of dietary copper. Hepatic thiobarbituric acid-reactive substances concentration was found to decrease with increasing dietary concentrations of copper up to 6.7 mg kg À1 beyond which a reverse trend in this parameter was noted. Broken-line regression analysis of AWG, FCR and PG concentrations against varying levels of dietary copper yielded the requirement in the range of 6.66-6.78 mg kg À1 . Data generated during this study would be useful in formulating copperbalanced commercial feeds for the intensive culture of this fish.

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Morphometric, meristic and DNA riboprinting analyses of Tilapia species and their hybrids inhabiting the River Nile were examined. Morphometric data showed striking similarities and overlapping among Tilapia species, making it impossible to differentiate these species. Meristic characteristics revealed that Tilapia species could be identified into four major groups (Oreochromis niloticus, O. aureus, Sarotherodon galilaeus and Tilapia zillii). The lateral line scales differed significantly between the four Tilapia species, while the number of fin rays in the dorsal and anal fins differed significantly, differentiating three species (but not between O. niloticus and O. aureus). Restriction fragment length polymorphisms (RFLPs) of nuclear small sub‐unit ribosomal RNA (18S srRNA) gene were used to differentiate the species. Polymerase chain reaction‐restriction fragment length polymorphisms data provided a unique pattern for each species with a specific restriction enzyme. Two hybrids of Tilapia designated H1 and H2 were detected. The endonucleases SacII and ApaI differentiated H1 and H2. This research revealed a monophylogenetic relationship among all the studied Tilapia species.

The present study was intended to test the protective upshot of calcium carbonate against the gifted toxicity of arsenic to the Nile cat-fish (Clarias gariepinus). Enhanced hepatosomatic index (HSI) and reduced gonadosomatic index (GSI) and intestinal index (ISI) as well as some of the tested blood parameters were recorded for fishes down to arsenic spotlight. The plasma levels of aspartate aminotransferase (AST, EC 2.6.1.1), alanine aminotransferase (ALT, EC 2.6.1.2), total bilirubin, direct bilirubin, total lipids, glucose and total protein were significantly increased in fishes exposed to arsenic. Likewise, the activities of AST, ALT and lactate dehydrogenase (LDH, EC 1.1.1.27), in the liver and muscle were radically increased, whereas the total protein and glycogen contents in these organs were significantly abridged following arsenic exposure, this may be an indication of energy expenditure attributable to arsenic toxicity. The histological examinations of the liver and gills renowned arsenic induced degenerative changes of these organs. Furthermore, the addition of calcium carbonate as a liming agent induces reversibility of most of these arsenic-induced changes, especially those of fishes subjected to 1/20 LC 50 of arsenic. Consequently, calcium carbonate could be feasible to be used for the fortification of C. gariepinus in opposition to arsenic toxicity.

Capture fisheries is the utilization of the usable aquatic organisms by the public with or without permissions (El-Sayed, 2006). Aquaculture is the farming of marine and freshwater organisms under controlled conditions. It is a highly growing food production sector (Ahmed and Thompson, 2019). Its global production of fish in 2018 was approximately 179 million tons (FAO, 2020). Farmed Fish are a chief source of food for poor people (Stead, 2019). It is a cheap form of animal protein (Nölle et al., 2020). Due to overfishing, fisheries stock worldwide is largely exploited. As the aquaculture become the main source to cope the fish demand, there is an awareness to increase its productivity with the increase of human population (Tidwell and Allan, 2001; Gephart et al., 2020). Tilapia is regarded as the second most farmed fish all-over the world ARTICLE INFO

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he present study inspects the effect of phenol as one of environmental xenobiotic compound on the histology and histocemistry of liver, gills and spleen of Oreochromis aureus (O.aureus) juveniles. Fish were subjected to three sub-lethal concentrations of phenol (20%, 40% and 80% of LC 50) for seven days. The liver, gills and spleen were studied from the histopathological and histochemical point of sight. Histopathological changes viz degeneration, necrosis, severe hemorrhage pynknosis and distinct cellular proliferation in the prescribed organs of fishes exposed to phenol were observed. Further, detachment of gill epithelium (GE), marked proliferation of gill epithelium (Hyperplasia, H) with distinct shortening of lamellae were recorded. Even though, complete fusion of gill lamellae, enhanced connective tissue disposition and blood permeation were also induced due to phenol exposure. Furthermore, histochemical annotations affirmed reduction of carbohydrate store due to oxidative stress caused by phenol publicity. Marked rise of gills mucoplysaccharides which impedes fish respiration were reported. DNA was also amplified in tested organs after phenol exposure, signifying carcinogenesis of phenol.