In 2010 the ostreid herpes (OsHV-1) virus caused up to 90 percent mortality in the wild spat which Pacific oyster farmers rely upon to restock their aquaculture farms. The crisis led to job losses, factory closures and saw an overall drop in production of 50 to 60 percent, with some individual farmers hit significantly harder.
Cawthron Institute was already collaborating with industry on a small-scale Pacific oyster selective breeding programme that had been underway for 10 years. This became much bigger and more urgent because, with not many oysters around, researchers needed to not only secure the good quality traits that programme had been focused on, but include survival as well.
With government assistance the research programme was rearranged to provide help to oyster producers in their crisis. Within six months of becoming aware of the virus, and working with industry, Cawthron set up new trials and re-focused its breeding strategy towards breeding for virus resistance. It had some government research money in place and could do a breeding run straight away.
Research and farm trials over the past three years have indicated oyster herpes resilience. A combination of genetic improvement through breeding, and improved farm husbandry – such as by growing oysters to a larger size and age before exposure to the virus – makes a big difference in terms of oyster survivorship and a return to viable production.
Cawthron's shellfish team believes that new breeding strategies will help achieve genetic gains in a relatively short time. Oyster families have been identified with a very high survival rate when exposed to the oyster virus at juvenile stage.
Cawthron Institute Cultured Shellfish Programme Leader Nick King said these resilient families will be bred with oysters from the pre-existing breeding programmes that had been selected for desirable attributes. The resulting seed is sent to farmers to see how it performs under challenge from the virus. Now the best of these are coming back to the hatchery so that they can be commercialized.
"When the virus hit we all worked together to address this problem," said King. "We could not have got this far without the huge support we have received from our industry partners, in particular Pacific Marine Farms – a subsidiary of Aotearoa Fisheries Limited, and Te Matuku Bay Oysters, who managed the bulk of the on-farm trials. It is truly a joint effort."
Pacific Marine Farms produces about one-quarter of the oyster spat used by farmers around the country.
Video and news story courtesy of Rural Delivery and Showdown Productions.
