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‘Green water’ enhances prawn farming

SORSOGON CITY—The Bureau of Fisheries and Aquatic Resources (BFAR) has intensified its dispersal of saline tilapia in Sorsogon to prevent shrimp disease in the province’s aquaculture farms.

Saline tilapia produces green water, a bio-control agent in prawn culture. In the system, tilapia is grown in net cages and the green water it produces helps control the growth of luminous bacteria that is bad for the development of shrimps and prawns.

Green water is the latest in biotechnology developed by the National Institute of Molecular Biology and Biotechnology (NIMBB) and the Institute of Aquaculture of the College of Fisheries and Ocean Sciences (AI-CFOS) of the University of the Philippines in the Visayas.

Dr. Jesse Ronquillo and Prof. Valeriano Corre Jr. of the NIMBB and AI-CFOS developed this technology starting in 1999 to help prevent and control the spread of aquaculture diseases like vibrio or luminous bacteria.

An outbreak of the disease in 1993 resulted in high mortality rates among cultured shrimps and prawn that various grow-out farms in the Visayas were closed.

Several methods like chlorination, vaccines and antibiotics were applied but failed to control the outbreak.

Chlorination has long been used a means of reducing pathogens in water but was proven to have short-term effect—a rapid repopulation of seawater occurred upon dechlorination.

Vaccines, on the other hand, were not available for most aquaculture diseases and antibiotics were controversial due to its effects on humans.

Modifications in management techniques, like the use of semi-intensive farming method and modular ponds, were even suggested to address the problem but were proven rather expensive and laborious untakings.

The completion of the Ronquillo-Corre green-water project in 2002 has enhanced shrimp production and been hailed as an aquaculture-friendly technology, according to Gil Ramos, provincial chief of the field office of the BFAR here.

The green-water project is a technique that basically involves the use of phytoplankton such as chlorella that turns the water green.

Ramos said saline tilapia is a producer of green water that the BFAR has been distributing fingerlings of the specie to aquaculture-farm operators to help them enhance their productivity.

Among the methods of combating aquaculture diseases, green-water technology has been the most effective and functional, as it inhibits pathogen growth, improves water quality and helps stimulate the immune system of species being cultured, he said.

Its use as a bio-control agent is simply an inexpensive means of improving the country’s shrimp-farming industry. The Department of Agriculture’s Bureau of Agricultural Research has funded its research and development and is now promoting its use, Ramos said.

Written by Danny O. Calleja

Source: Business Mirror