Growth

M. rosenbergii larvae hatch at about 1.9 mm, grow in size to 7.7 mm by stage XI, and then decrease slightly as PL (Uno & Kwon 1969). Generally, growth is measured by the evolution of larval stages. Ismael et al. (2001) examined the growth of M. rosenbergii larvae in artificial and natural sea-water. There is a decrease in larval dry biomass in stage II, probably due to the yolk consumption, but after that the biomass increases exponentially with developmental stages or days. More precocious larvae reach the PL stage in 20 and 26 days in natural and artificial brackishwater, respectively. Advancement from one larval stage to the next takes about 2 days until larval stage VII. Under good growing conditions, the first PL appear on day 19 to 22 (Aquacop 1983). Valenti et al. (1998) presented a table containing the typical number of larval stages represented on a daily basis for recirculation systems in Brazil. Malecha (1983) graphically presented similar data from semi-flow-through systems (greenwater). The picture is similar until day 15, when development accelerates and becomes more synchronised in recirculation systems. Three to six larval stages may be present in the tank at the same time; however, maintaining three or less helps to minimise cannibalism. The larval rearing period for closed systems using natural brackishwater generally varies from 30 to 35 days at the optimum temperature (28-30°C) (Aquacop 1983; Ong 1983; Mallasen & Valenti 1998a; Carvalho & Mathias 1998; Valenti & Moraes-Riodades 2004; Valenti & Tidwell 2006), but can be less than 25 days (Ra'anan & Cohen 1982).

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