In an effort to breed blue swimming crab (BSC) to rebuild dwindling stocks in critical areas, PACPI opened its first BSC Hatchery in Tigbauan, Iloilo in 2013. Two years in operation and the aquaculture of crab is still difficult. Survival rate of newly-hatched larvae to crab instar is only about 5% to 10% and even lower in some cases. High mortality rates are normally a result of cannibalism during molting, or the shedding of exoskeleton. Crabs undergo series of molting throughout the larval stages. The longer they are reared, the lower their survival. From 28 days, the team has decided to reduce the rearing period to 21 days or up to the crab instar 4 stage to reduce costs and prevent further mortalities. Despite these efforts, production hit all-time low early 2015 due to reported fluctuations of water salinity and temperature, although bad management cannot be omitted.
In late 2015, PACPI has decided to close the hatchery following failed production targets and the existing pricey rental that ate up a big portion of project funds. The team moved to a private hatchery in Escalante City, Negros Island and collaborated with the Provincial Government of Negros to conduct mass production of BSC juveniles and dispersal activities in the region. The BSC hatchery commenced in April 2016 and 55,836 juveniles were produced on its first month of operation with a 9.3% survival rate. The proceeding months have been favorable, with production reaching the 70,000 mark and survival rate of 10%. September production reported 88,614 juveniles at 14.8% survival, an all-time high. As of this writing, dispersal activities have spanned 8 municipalities (14 sites/barangays) in Northern Negros namely Silay City, Talisay City, E.B. Magalona, Manapla, Victorias City, Cadiz City, Sagay City, and Escalante City.
How did the hatchery come up with such huge volume of seeds?
Aside from good management, several factors can be attributed to the success of the BSC hatchery in Negros.
Healthy broodstock yields good quality eggs. And quality eggs hatch healthy larvae. Believe it or not, only 1 or 2 gravid crabs are “incubated” for their eggs. An intact egg sponge indicates healthy mother crab.
Good water quality. Besides thoroughly-cleaned tanks, water undergo double filtration and UV treatment. In the absence of UV, chlorine treatment can be an alternative.
Use of green water. Green water technology was a breakthrough in aquaculture in the 90s. Green water technology is a technique that uses phytoplankton-rich water obtained from saline tilapia tanks. Aside from providing algal food in the early stages of development of crabs, it is also known to inhibit growth of pathogenic microorganisms.
Optimum water conditions. BSC larvae require high saline water (28-32 ppt) and consistent, high temperature (28-34 C). One or two-unit sudden change in temperature is lethal, and without proper monitoring, this could result in mass mortalities.
Monitoring of fungal and luminous bacteria occurrence at night is also conducted.