The Use of Mulberry (Morus alba) Extract in the Mass Production of Blue Swimming Crab (Portunus pelagicus L.) Larvae to Overcome the Mortality Rate Due to Molting Syndrome

Abstract

One of the problems in blue swimming crab seedling is the high rate of mortality. This study is aimed at analyzing the influence of mulberry extract (ME) on the survival rate of crab larvae which are managed to metamorphose to the next stage and on the rate of larval development, as well as identifying various factors causing mortality in the mass cultured larvae, mainly mortality caused by molting syndrome. There are 4 treatments of different doses of mulberry extract being tested which are: 0 mg/100 g (control), 1 mg/100 g, 2 mg/100 g, and 4 mg/100 g. Mulberry extract is given through feeding since day-8 of the stocking, which is the time when larvae enter zoea 3. The rearing process is done over 19 days in a concrete tank with a volume of 1 ton with the initial number of zoea at ± 350.000. The findings show that mulberry extract has a significant influence on the survival rate, stage growth, and the mortality rate of blue swimming crab larvae due to molting syndrome. The higher the dose of ME in the artificial food, the higher the survival rate and the lower the mortality rate due to molting syndrome. The treatment with 4 mg of mulberry extract/100 mg is the only treatment which successfully enters megaloph and crab stage. Control treatment and the dose of 1 mg/100 g can only reach zoea 3 while the dose of 2 mg/100 g can only reach zoea 4. This study shows that the total mortality rate is still high, but it is found that the main cause is not molting syndrome. Mortality rate due to molting syndrome in the treatment of the dose of 4 mg of mulberry extract is only ± 15.61% of the total larval mortality. The unidentified factors dominate the cause of mortality (± 57.47%). Other factors are fungal attack (±17.65%), morphological disorder (±9.28%), and cannibalism (±14.93%).