An Ecological Eye on Oysters - Reducing Stresses and Maximising Benefits
Oysters are a delicacy in demand, but farming them is not without its stresses. ‘Invading’ species can take hold at oyster farms, where they grow rapidly. Conversely, some types of farmed oyster can themselves ‘escape’ and cause problems in the wild.
Dr Tasman Crowe and his group at UCD School of Biology and Environmental Sciences are taking an ecological-eye view of these issues in oyster farming, with the aim of protecting oysters from the environment and of protecting the environment from oysters.
One of the prime targets in their sights is an aquatic animal species called Didemnum, which is well known in some parts of the world for ‘invading’ oyster farms, fouling up equipment with its slimy presence and choking oyster growth.
“In other parts of the world it has caused really big problems and there was major concern when it was found here in Ireland, but so far it has become established in just a few places,” says Dr Crowe. “So In principal we might have an opportunity to reduce its spread at this early stage.”
PhD candidate Martina O’Brien is currently testing protocols of techniques for warding off Didemnum - such as spraying vinegar or turning oyster bags - to see what combination works best for keeping oysters happy and the invasive species out.
“That project is trying to find out whether it is better to do one or the other or both, whether intensive or low doses are better, whether the techniques should be applied simultaneously or not and when during the growing season is the optimum,” explains Dr Crowe. “And this is all derived from ecological theory about how disturbance regimes can have an impact.”
The work will hopefully inform practices in oyster farming in Ireland to help keep Didemnum out, but what about keeping the oysters in?
Already Dr Crowe’s group has made some important discoveries about how to keep the Pacific oyster corralled into farms and not running riot in the wild. “It has become established in the wild in a lot of places in Europe, and when that happens it forms very dense beds and dramatically changes the local ecosystem, often with undesirable effects.”
Dr Crowe’s research has found that Pacific oysters are starting to get a foothold in the wild in Ireland too, and their recommendation is that farmed oysters here should be of a ‘triploid’ variety, a genetic variation that reduces the ability of the animals to reproduce and spread.
But it’s not a clear-cut solution: some markets are not so keen on triploid oysters, and this feeds into Dr Crowe’s wider research on ‘ecosystem services’ or, bluntly, the value of what nature can do for us. That might include fisheries from the marine, new pharmaceuticals from plants, services such as cycles that regulate climate and supply water and the cultural benefits we enjoy.
“The value of nature has become part of the rationale for conservation,” he explains. “So we are trying to better understand benefits from nature and how to value and conserve them.”
Dr Tasman Crowe from the UCD School of Biology and Environmental Science was interviewed by freelance journalist Dr Claire O'Connell.