Triploid oyster mortality is reduced to 5 pc. (Photo: Edison Barbieri, pesca.sp.gov.br)
Triploid oysters, a solution to summer mortality
Wednesday, February 08, 2012, 04:40 (GMT + 9)
In the state of Santa Catarina triploid oysters (with three sets of chromosomes) are being introduced to reduce problems that occur in the summer when the sea temperature increases, up to 30 degrees Celsius, causing mortality of many molluscs.
The Federal University of Santa Catarina has started oyster farming 20 years ago, after observing the good adaptability of this mollusc to Santa Catarina’s sea conditions.
The State’s marine farms account for almost all domestic production of oysters. The last harvest reached 2,000 tonnes, equivalent to about 24 million of specimens.
According to experts, the bays of Florianopolis are some of the best places in the world to produce oysters because the water is rich in nutrients and does not exceed an average of 18-22 degrees Celsius, an ideal temperature to ensure the growth of the mollusc.
These features allow a short production cycle, six to seven months, while in other countries such as China, France and Chile, it takes four years.
Fábio Brognoli, president of the Federation of Aquaculture of Santa Catarina (FEAq) explains that when sea water temperature rises, oysters enter a reproductive process, which makes them loose a loss of energy.
"This also increases the mortality rate of the specimens, with a survival of only 40 per cent of those in the water", he added.
The so-called summer mortality is a major puzzle for producers, who loose 6 out of 10 cultivated oysters.
According to experts, the solution lies in biotechnology, Globo Rural reported.
A company from Florianopolis specialized in aquaculture was authorized by the Ministry of Fisheries to import and use Chilean oysters sperm to produce a more resistant variety.
Fertilization in the lab generates triploid oysters, which are much more resistant to warm water, highlights aquaculture specialist Vinícius Volpato.
"Mortality, amounting to an average of 50 per cent in Santa Catarina, falls to 5 per cent, enabling production in the states of the Northeast of Brazil. They produce much more meat and are sterile. Being sterile and not reproducing themselves, they do not become an invasive species", the expert highlighted.
Santa Catarina's lab already produces 10 million oyster seed, 25 per cent of what local producers need.
"It's a sector bet. People want to reconcile the survival rate, quality of meat and differentiated growth rate we have in relation to the world”, Brognoli emphasized.
By Analia Murias