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 m ulberry e xtract (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 identify ing 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 enter s 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 t otal 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 u nidentified factors dominate the cause of mortality (± 57.47%). Other factors are fungal attack (±17.65%), morphological disorder (±9.28%), and cannibalism (±14.93%).
Highlights
Portunus pelagicus L. is one of the commercial crabs traded widely around the world
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 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
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
Summary
Portunus pelagicus L. is one of the commercial crabs traded widely around the world. In Indonesia, the crab species is under intensive development to meet the increasing overseas market demand. The increasing amount of crab fishing caused decrease in natural populations, in both quantity and quality. FAO (2011) in World Bank (2012) mentioned that in 2008, Indonesia contributed 20 % of the world blue swimming crab production and ranked second of the biggest producer after China. Along with the increase of human needs and pressure on the marine biological resources environment, the live stock of crabs in Indonesia is continually decreasing by 20 30% each year (Mahesa, 2010). Other methods to increase crab the supply of crab raw material is highly needed, for example through culture
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