SPAIN - Over the last few years, the production of the Pacific oyster (Crassostrea gigas) in the Ebro Delta has undergone considerable losses due to a herpes virus that has caused high rates of mortality. Now the IRTA (a research institute owned by the Government of Catalonia) has produced oyster seeds free of the virus.
The oysters produced in the Ebro Delta come from oyster seeds imported from France. These seeds are naturally obtained and frequently carry the herpes virus.
The oysters are later affected with the appearance of stress factors such as temperature changes in spring and autumn or changes in the salinity, leading to high rates of mortality that can reach up to 80 per cent.
Thus, IRTA's efforts have focused on achieving herpes virus-free seeds and at the same time avoiding relying on French Pacific oyster seeds, often with the virus.
Using breeding specimens from the Delta which are highly tolerant to the virus and adapted to the environment, IRTA has obtained Pacific oyster seeds without the virus, as announced by Dr Dolores Furones, director of the Sant Carles de la Ràpita IRTA center.
“In IRTA we select Pacific oyster breeders that are adapted to the conditions of the Delta, induce spawning in the center to obtain Pacific oyster larvae, and feed these larvae with phytoplankton until they have an appropriate size to grow in the bays of the Ebro Delta,” added Dr Furones.
A greater survival of the seeds is expected in collaboration with the sector and a better management of the oyster farming, which will allow production to increase and thus the economic performance.
For 2014 IRTA envisions producing five million specimens and double this number by 2015. The goal is to produce seeds for the whole Delta and even to export it.
“After several years of research at the Sant Carles de la Ràpita IRTA, we have managed to produce Pacific oyster seeds without the herpes virus and to start a native production of this species. This will allow selecting more tolerant specimens, adapted to the environmental conditions of the Delta. All this has been done hand in hand with the Delta´s bivalve molluscan seafood sector,” pointed out Dr Furones.
TheFishSite News Desk