Effect of Artemia feeding schedule and density on the survival and development of larval mud crab Scylla serrata

Abstract

: Two experiments were conducted to determine a suitable feeding schedule and the optimal density of Artemia nauplii on the survival and development of mud crab Scylla serrata larvae. The first experiment consisted of 10 treatments, where rotifers were shifted to Artemia nauplii at the zoea (Z) 1, 2, 3, 4 and 5 stages. Five other treatments were similar to these first five; however, rotifers were continuously added together with Artemia nauplii. The second experiment consisted of five treatments that were carried out to determine the optimal Artemia nauplii density. Four treatments fed different Artemia densities (0.5, 1, 1.5, 4 individuals (ind.)/mL) and in the fifth treatment the density of Artemia nauplii was increased with the developing zoeal stage. The survival rate until the Z5 stage was higher when Artemia were supplied from the Z3 stage (P < 0.05). Mortality caused by cannibalism was observed either when Artemia feeding was delayed or when fed at a low density (0.5 ind./mL). In contrast, feeding Artemia from the early zoeal stage or at a high prey density (4 ind./mL) accelerated metamorphosis and caused the acceleration of morphological characteristics, such as a greater chela length, carapace length and setae bearing pleopods at the Z5 stage. The chela length at the Z5 stage decreased proportionally with the delay of Artemia feeding or a decreasing prey density. The chela to carapace length ratio (ChL/CL ratio,%) could be used as an indicator to predict the success of survival to megalops. A ChL/CL ratio over 45% produced a high percentage of megalopal molting failure. Therefore, to avoid cannibalism or excessive feeding in the larval mud crab, Artemia should be given from the Z3 stage at an optimal level of 1.5 ind./mL or increasing density according to the zoeal stage.