The current high demand and cost of fish meal (FM) necessities the evaluation of alternative plant protein ingredients in diets of farmed marine fish. A 56‐day feeding trial was performed to study the effects of replacement of FM with soy protein concentrate (SPC) in diets of Acanthopagrus schlegelii. Diets were prepared at levels of 0%, 30%, 47.5%, 65%, 82.5% and 100% SPC, respectively, replacing FM. The results indicated no significant differences (p > .05) in % weight gain (WG) and specific growth rate of fish fed S30% to S82.5% diets compared with the control diet while, further inclusion at 100% significantly depressed growth performance. SPC inclusion and phytase supplementation significantly affected the phosphorous discharge (P‐load) showing lowest value (3.83 ± 0.53 g/kg WG) in S100% compared to control (14.79 ± 0.37 g/kg WG) and in fish fed S30% diet (13.24 ± 0.89 g/kg WG) (p < .05). The results of this study showed that FM could be substituted up to 82.5% by SPC in the diet of Acanthopagrus schlegelii fingerlings (5.53 ± 0.12 g) without any adverse effects. Phytase supplementation SPC based diets could be effective in reducing the phosphorus load in the aquatic culture environment.

The present study aimed to investigate the macroscopic and histological structure of the gastrointestinal tract (GIT) of Larimichthyscrocea (Richardson, 1846). It consists of esophagus, stomach regions, pyloric caeca, intestinal regions, and rectum. Sixteen tubular light yellowish pyloric caeca of similar sizes were observed in all individuals. The digestive wall consists of mucosa, submucosa, muscularis, and adventitia. No major differences appeared in the structure of the tunica, epithelial cell types, connective tissues and musculature glands of L.crocea GIT. The mucosal epithelia in the oesophagus has longitudinal branched folds with frontward and hindmost zones. The gastric tunica mucosa has a characteristic folded structure and can be divided into three regions. The intestinal tunica mucosa is characterized by villi structures and numerous mucus-secreting cells. Mucus-secreting goblet cells were strongly positive to AB at pH 2.5 in the oesophagus (excluding gastro-oesophageal junction) and intestine mucosal regions, which indicates an abundance of carboxylate mucins. The surface epithelia of the gastric mucosa is PAS-positive and AB-negative. SEM examination revealed that cells in the epithelium of the esophagus have an unbroken apical layer and goblet cells. The intestinal coefficient (IC) of L.crocea was 0.80 ± 0.21, consistent with a carnivorous or omnivorous habit. Our study adds the knowledge of the digestive system of L.crocea and might be useful in the management of L.crocea stocks.

Acanthopagrus schlegelii is an autochthonous teleost species concerning the remarkable economic importance and prevalent fish cultivated in China as well as in different nations of South-East Asia. Little is known about the digestive tract (DT) morphology of A. schlegelii. Therefore, anatomical and histomorphological aspects of A. schlegelii DT were examined by light and scanning electron microscope (SEM).Anatomically, DT of A. schlegelii was mainly formed of oesophagus, well-developed stomach and fingers like pyloric caeca (four in number), intestinal regions and rectum. Histomorphologically, oesophagus occurred as a shorter tube-like organ presenting a longitudinal folded mucosa that connects oropharynx cavity to stomach.Stomach was a muscular thick-wall organ that included three regions, thickly longitudinal folds were observed in the first (cardiac) and last (pyloric) regions, whereas the second (fundic) region showed folds in different directions. Long villi were observed within pyloric caeca and anterior intestine. Tunica muscularis appeared narrow in the anterior intestine, whereas thicker in the posterior part of the intestine.Collectively, anatomical and histomorphological aspects of A. schlegelii DT are consistent with the carnivorous habit of this species. These data could be a potential source to modify better methods of nutrition and identify the DT pathogenic conditions in farming of this fish. K E Y W O R D SAcanthopagrus schlegelii, anatomy, digestive system, histomorphology, scanning electron microscope

Taurine has been reported as an important nutrient in some fish species, but its efficacy in black sea bream, Acanthopagrus schlegelii has not been determined. Therefore, a study was performed to explore the effects of taurine supplementation on growth performance, serum parameters, and related gene expression in black sea bream juveniles fed all‐plant protein diets. A fishmeal diet (FM) and five all‐plant protein diets with graded taurine levels (T0, T0.25, T0.5, T1, and T2) were formulated. The results showed that all‐plant protein diets could significantly inhibit fish growth, but dietary taurine supplementation could significantly improve weight gain, thermal unit growth coefficient, feed efficiency, and protein retention efficiency when fish are fed with an all‐plant protein diet. No significant differences were observed in moisture, crude protein, and crude lipid content of the whole body and dorsal muscle among all treatments. Dietary taurine supplementation could significantly increase serum total protein and albumin but significantly decrease serum total cholesterol and hepatic total bile acid in all‐plant protein diets. Fish fed the T0 diet showed a significantly lower cholesterol 7α‐hydroxylase (CYP7A1) messenger RNA (mRNA) level than the FM group, but dietary taurine supplementation could significantly improve CYP7A1 mRNA expression.

Effect of stocking density on growth, production and survival of red tilapia (Oreochromis mossambicus × O. niloticus) were conducted in hapa for 60 days at Chilya Thatta. Tilapia fry (4.5±0.02 cm, 2.0±0.01 g) were stocked into hapa (4.5x2.4x1 m). Three treatments with two replicates were used: T 1 -200; T 2 -250 and T 3 -300 fry/hapa. Fry were fed twice a daily with pelleted feed containing 35% protein, 5% of total biomass. After 60 days, the highest growth were determined in T 1 (49.8±0.0 g) while in T 3 lowest growth (29.09±0.0 g) was recorded. Production (9.56, 10.13 and 8.12 kg/m 3 /60days) in T 1 , T 2 and T 3 respectively were significantly different (P<0.05) to each other. Feed conversion ratio of 0.48, 0.48 and 0.49 in T 1 , T 2 and T 3 , respectively not significantly different (P>0.05). Survival was significantly different among treatments (P<0.01). Highest survival (100%) was attained in T 1 with lower stocking density, followed by T 2 (98%) and T 3 (95%). Water quality parameters recorded throughout the study period were found within the ranges for fish culture such as temperature 27.2 to 28.5 °C, dissolved oxygen 5.8 to 6.4 mg/l, pH 6.9 to 7.6, ammonia from 0.45 to 0.51 mg/l, hardness 106 to 110 ppm and nitrite 0.151 to 0.162 mg/l.

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Eight weeks of feeding trial was conducted to investigate the effects of dietary supplementation of microencapsulated sodium butyrate (MSB) on juvenile black sea bream (Acanthopagrus schlegelii). A basal diet was designed with 24% fish meal, and the other four diets were formulated with dietary supplementation of graded levels of MSB at 0.05%, 0.10%, 0.20% and 0.40%, respectively. Triplicate tanks were randomly assigned to each diet with 20 fish having an initial weight of 9.98 ± 0.13 g. The weight gain rate, specific growth rate and feed efficiency ratio of fish fed the MSB 0.2% diet were significantly (p < .05) higher compared to the control group. Proximate compositions of the whole body and dorsal muscle were non‐significantly different among the groups (p > .05). The apparent digestibility coefficients of dry matter, crude protein, and crude lipid were significantly higher in the MSB‐supplemented treatments (p < .05). The contents of total protein, cholesterol and albumin in serum were non‐significantly different in all groups (p > .05). The superoxide dismutase activity, immunoglobulin M content and total antioxidant capacity were significantly (p < .05) higher in the group fed with MSB‐supplemented diets compared with the control group. The villus height and the number of goblet cells per villus in the fore intestine were significantly (p < .05) higher in the group fed with MSB‐supplemented diets. From the present study, we concluded that MSB‐supplemented diet enhances fish growth and its intestinal health.