The effects of salinity and added substrates on growth and survival of Metapenaeus monoceros (Decapoda: Penaeidae) post-larvae

This study was carried out to determine the optimal culture salinity and to investigate the effects of added substrate on growth and survival of Metapenaeus monoceros during its nursery culture in two separate experiments. In Experiment 1, at the end of a 50-day culture period, post-larvae (PLs) reared at 5, 10, 20, 30, 35, 40 and 50 ppt displayed 8, 11, 48, 49, 52, 59 and 36% survivals, respectively. Daily growth rates at salinities above 30 ppt (0.266-0.320 mm day-1) were about 5-fold higher than those obtained at salinities below 10 ppt (0.035-0.056 mm day-1) (P < 0.05). Total lengths (TL) at 30, 35, 40 and 50 ppt were 19.09, 18.97, 19.09 and 18.89 mm, respectively (P > 0.05). Mean net weights acquired at 30-40 ppt (63-71 mg) were 7-8 times higher than those at 5 and 10 ppt (8.12-9 mg) (P < 0.05). A rise in salinity resulted in a drastic increase in biomass (over 50-fold) from 0.018 g at 5 ppt to 0.927 g at 40 ppt. Hence, optimum salinity for the nursery culture of M. monoceros PLs appeared to be between 30 and 40 ppt at 28 degrees C. In experiment 2, Group A received no additional substrate while the other two groups had added substrates consisting of wooden frame with vertical (Group B) or horizontal (Group C) plastic mesh. Additional substrate increased habitable surface area approximately 330%. Percentage survivals in Group A, B and C were 71, 70 and 63%, respectively. TL was significantly lower in Group C (15.65 mm) than in either Group A (17.71 mm) or Group B (17.23 mm) (P < 0.05). The PLs in Group A attained a significantly greater mean final weight (62 mg) than those (40-55.14 mg) in both treatments containing artificial substrates. The PLs in Group B and C had 12% and 40% lower biomass than that in Group A. The current results demonstrated that the use of either vertically and horizontally placed substrates do not provide any advantage during the nursery culture of M. monoceros.