In this study, heritability was estimated for growth-related traits of giant freshwater prawn (Macrobrachium rosenbergii) before and after morphological sexual differentiation. Estimation was made on data from16 fullsib and eight half-sib families. The variance estimation was performed using a univariate mixed linear animal model and variance components were analysed following an animal model using restricted maximum likelihood procedure using average information algorithm. Heritability estimates (h 2 ) varied considerably with ages. At 2 months old, h 2 for carapace length (CL; 0.35 AE 0.15) and body weight (BW; 0.26 AE 0.13) were higher than those estimated at 5 months old, based on mixed sex data. However, when data were sorted by sex, h 2 calculated from data of females were higher than those of males for CL (0.26 AE 0.16 vs. 0.10 AE 0.06), BW (0.28 AE 0.17 vs. 0.12 AE 0.08), body length (0.40 AE 0.17 vs. 0.11 AE 0.07), total length (0.47 AE 0.18 vs. 0.11 AE 0.07) and claw length (0.29 AE 0.16 vs. 0.03 AE 0.04). The same trend was observed for traits at 6 months old in both bulk and individual rearing.

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Tilapia is a popular fish for consumers and aquaculture in every part of Thailand. This study was conducted to determine the level of mineral supplementation in the diet for the growth of red tilapia fingerlings, which gave the lower fish production cost. The fingerlings with an initial average weight of 3.1 ± 0.48 g and a length of 2.5±0.24 cm were raised in 3 m3 concrete tank with 1.5 m3 of water volume at 20 fish/m2 stocking density. Fish were fed with pellets diet (28 % crude protein), which contained different levels of mineral supplements (0 (control), 20 and 40 g/Kg) in triplicate replications. The experiment was conducted within 80 days. The results showed that fish fed with diet3 had better average daily weight gain (ADG) and food conversion ratio (FCR) than diet2 and diet1 significantly (P<0.05). The ADG and FCR of fish fed with diet3 showed 0.70 ± 0.02, 1.72 ± 0.02 respectively, but there was a non-significant difference in survival rate from all treatments (P>0.05), and the fish production cost of diet 3 is lower than those in diet1 and diet2. Thus, this experiment concluded that minerals supplementation at the level 40 g/kg diet were suitable for tilapia aquaculture.