A 120-day feeding trial was conducted to determine the dietary requirement of phosphorus for Indian major carp, catla (Catla catla) ¢ngerlings. Four hundred and eighty ¢ngerlings (mean body weight: 4.23 AE 0.87 g) were randomly distributed among eight treatment groups with three replicates each. Eight isonitrogenous and isocaloric semi-puri¢ed diets (crude protein: 35% and crude lipid: 8.5%) were formulated with graded levels of phosphorus using KH 2 PO 4 (T 1 : control, 0.1%; T 2 : 0.3%; T 3 : 0.5%; T 4 : 0.7%;T 5 : 0.9%;T 6 : 1.1%; T 7 : 1.3%; T 8 : 1.5%) and fed to the respective groups. Twenty ¢sh were stocked in150 L plastic tanks and fed to apparent satiation twice a day. Speci¢c growth rate (SGR) signi¢cantly (Po0.05) increased with increasing dietary phosphorus concentration from 0.73% to 1.27%, after which there was a slight decline in growth at 1.1% available phosphorus (aP) and remained constant thereafter. The quadratic broken-line model based on growth was Y 5 317.5 À 581(0.64 À x) (0.64 À x); R 2 50.73. Moisture and crude protein contents of whole body were similar among all the treatments. However, the ether extract in T 1 group was signi¢cantly (Po0.05) higher than all the other treatments. The whole-body phosphorus content increased signi¢cantly (Po0.05) with an increase in phosphorus in the diets. The one-slope broken-line model based on whole-body phosphorus concentration was Y 5 4.07 À 1.63 (0.71 À x); R 2 50.48. The one-slope broken-line model for non-fae-cal phosphorus excretion as inorganic phosphorus (Pi) for 24 h revealed a trend of Y 512.67173.96 (x À 0.6); R 2 50.81. Minimum aP requirements based on weight gain (%), whole-body phosphorus content and phosphorus excretion were 0.64%, 0.71% and 0.6%, respectively. Hence, the dietary aP requirement of catla ¢ngerlings ranges from 0.6% to 0.71%.

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With the objective to develop an indoor tank seed rearing system for pearlspot (Etroplus suratensis), effects of three stocking densities in presence or absence of soil base were evaluated on growth, weight variation, survival and body composition in a 60‐day trial. The experiment had a 3 × 2 factorial design with three levels of stocking density (150, 300 and 450 fish m−3) and two levels of soil base (with and without) in triplicates. Pearlspot fry (27.5 ± 0.5 mm/0.39 ± 0.02 g) were stocked in experimental tanks (Length×Breadth×Height: 0.65 × 0.50 × 0.48 m) and fed with a formulated diet containing 29.85% crude protein. Increasing the stocking density from 150 to 450 fish m−3 significantly decreased the growth (average body weight and total length), daily weight gain, specific growth rate and survival (P < 0.001) and increased the feed conversion ratio (P < 0.01). Significantly lower growth and survival were observed in treatment having soil base compared with that of without soil base (P < 0.001). However, coefficients of variation at harvest weight and body composition of fingerlings were independent to stocking density and presence or absence of soil base (P > 0.05). A significant positive interaction effect of stocking density and presence or absence of soil base was observed on average body weight (P < 0.05) and survival (P < 0.001) of pearlspot fingerlings. This study suggests that stocking density of 150 fish m−3 without soil base in tanks would be appropriate for raising pearlspot fingerlings in brackishwater indoor seed rearing system.

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