Mud crab fattening in ponds

摘要

Two independent experiments on mud crab (Scylla serrata, Portunidae) fattening were conducted simultaneously in 150 m~2 ponds for 30 days: Expt. I - monosex male (286 +- 1.2 g) vs. monosex female (267 +- 0.9 g) stocked at 0.5 centre dot m~(-2), andExpt. II - monosex male (338 +- 3.1 g) or female (338 +- 2.8 g) vs. mixed sex (338 +- 3.4 g) stocked at 0.25 centre dot m~(-2). The crabs were fed daily a mixed diet of 75 percent brown mussel flesh and 25 percent fish bycatch at 10 percent of the crab biomass. Intermolt full male crabs weighing >= 400 g and rood females >= 350 g were partially harvested from the ponds after 20 days of culture using lift net and current method. Results of partial harvest from all treatments in both experiments showed atotal yield of 51-55 percent of the total initial number of stocked crabs (450 crabs in Expt. I, and 338 crabs in Expt. II). From this partial harvest, crabs in Expt. I attained a mean final body weight of 496 g, a specific growth rate (SGR) of 2.75 percent in males and 432 g, SGR of 2.4 percent in females. Expt. II gave a mean final body weight of 520 g (males), 484 g (females), and 517 g (mixed sex) and SGR of 1.1, 0.73 and 0.81, respectively. Results of total harvest showed that the overall mean final body weight (372 +- 4.5 g) of monosex male crabs in Expt. I was significantly higher (P < 0.05) than monosex females. However, specific growth rate, carapace length and width, survival, and production were not significantly different (P > 0.05) betweenmonosex males and females. On the other hand, growth and production of monosex crabs in Expt. II was net significantly different (P > 0.05) from mixed sex crabs. However survival of monosex crabs (100 percent) was significantly higher (P < 0.05) than mixed sex crabs (87 +- 1.88 percent).