As shrimp farms, particularly the discharge from them, continue to remain a risk to the environment, the Central Institute of Brackishwater Aquaculture (CIBA) in Chennai has fine-tuned a technology that substantially reduces the nitrogenous metabolites like ammonia, nitrite and nitrogen level through in situ bioremediation.
This eco-based approach, leading to high productivity with sustainability, is called ‘bio-floc and periphyton-based technology (BPT).’ It is based on the concept of retention of waste and its conversion to microbial protein as a natural food within the culture system.
On Saturday, the scientists in the breeding centre at Muttukadu successfully demonstrated this culture technology and harvested shrimps –L. Vannamei (Vellai Eraal).
The objective, as the CIBA scientists said, was to reach a situation in which total ammoniac nitrogen would be under control through the ‘heterotrophic microbial system.’
“Besides reducing the nitrogen level, the technology will also reduce input costs and combat diseases such as early mortality syndrome (EMS) in shrimps which has devastated the shrimp aquaculture industry in South East Asia,” said Akshaya Panigrahi, Principal Scientist, who is also the Principal Investigator of the project.
Dr. Parnigrahi said while shrimps reared under non bio-floc reached between 25 and 30 grams in 130 days, they gained between 36 to 40 grams in the same period under bio-floc farming.
For the first time in the country, the institute could demonstrate that even the protein requirement in the feed could be substantially reduced in the bio-floc system still making it equally productive and profitable.
The ‘autotrophic system,’ where plankton controls the entire environment, has several limitations in converting the organic waste.
“For this we have to supply carbohydrates in the form of molasses, wheat flour, rice flour or jaggery. The carbon-nitrogen ratio should be 15:1 to help the heterotrophic bacteria to grow and form floc,” explained Dr. Panigrahi.
C. Gopal, the director of the CIBA said, since bio-floc culture systems had ensured that shrimps consumed protein two times as the bacteria even converted the faeces of the shrimps into protein.
P. Paul Pandian, executive director of the National Fisheries Development Board (NFDB), said they had provided financial assistance under the technological up-gradation project, adding, its objective was to make the technology available to the farmers.
