The success on pre-mating molt of immature female mud crab (Scylla tranquebarica) reared at different depth in concrete tank

Abstract

Cannibalism is one of the obstacles event in the mud crab breeding program. Placement of the prospective broods communally in a container waiting for coupling and mating to occur naturally often leads to fights each other that cause limb defects and even death. Fail in providing optimal environmental conditions in a controlled container also often results in prolonged period of premating-molt and spawning. This study aims to prepare female mud crab broods separately from males placed at different depth in the water column to see the success of premating-molt and mating process. The early inter-molt phase of immature female crabs that heading premating-molt stage were randomly selected from crab sellers in the local market with the following initial data: CW 100 ± 3.4 mm, CL 65.6 ± 2.5 mm, and BW 154.2 ± 16.6 g. Each of 30 available crabs was inserted in separate crab-box after then 10 crab-box placed at each different depth of 0, 70 and 140 cm respectively in an outdoor concrete tank. At the same time, three male broodstock weighing >350g were placed individually in a 0.5 ton fiberglass tank in the hatchery building. The newly molted female in crab-box were immediately transferred to the male tank to mate. The response to growth, molting time, molting frequency, success of mating and spawning to the depth treatment were recorded during the study. The results showed that the rearing of crabs at different depths did not show any significant differences (P>0.05) in growth and molting time, but the molting frequency and survival rate at 70 cm depth were better than other depth treatment.