One of the classic signs of imminent problems for a fishery is the proliferation of an undersized catch. For some time Irish periwinkle wholesalers have found a shortage of the medium- to large-sized periwinkles (more than 16 millimetres in size) required by the continental market. Lack of regulation has increased the risk of over-harvesting and there is concern for the stability of coastal populations.
Before the problem can be solved, there is a need to find out more about the biology and ecology of the edible periwinkle, according to Dr Gavin Burnell, of the Department of Zoology and Animal Ecology, in NUI Cork. He and research assistants, Ms Susan Coughlan and Ms Orla McLean, are currently carrying out a shore survey to determine the potential sustainable development of the periwinkle.
There is currently a dearth of research on the management of the species. "We have to define the resource and know exactly what we are dealing with before we can fully examine the viability of its development," says Dr Burnell. They are embarking on a project, funded by the Marine Institute, to find out more about the distribution of the species. In a separate project, which began in January, Dr Burnell is working with Kilkenny-based animal feeds producer, Red Mills, to develop an artificial diet or diet supplement which will bringthe periwinkle up to market size.
The periwinkle is principally a seaweed eater or macroalgivore, and although it is recognised that aquaculture is the only route for its development, the variable abundance and quality of native seaweeds and the high cost of artificial feed has up to now been prohibitive.
"The trick is to find a diet that is not too expensive. There is a problem finding a palatable, cost effective diet which will be stable in water for up to one week. Pilotscale trials will be carried out in association with commercial mariculture operations," he said.
Commercial hatcheries are already in operation for sea urchins and abalone. With all three species being principally seaweed eaters, it means they could theoretically use a vegetable protein source which would be cheaper and more environmentally friendly than the fishmeals fed to farmed marine fish.
"At this stage we have not got as far as breeding periwinkles in a hatchery but NUI Galway have successfully raised periwinkles in a hatchery and don't think it is too difficult."
Although perwinkles are the least commercial of the farmed fisheries, their value lies in their numbers. An estimated 5,000 to 7,000 tonnes are harvested each year in Ireland, North and South, and they are sold at about £600 a tonne.
"We want to understand more about their reproductive biology," says Dr Burnell. His research team has done some research on the periwinkle's life cycle.
They lay eggs which float away. The eggs develop in plankton. This is followed by a larval stage during which larvae drift in sea water before they metamorphose into baby periwinkle.
They then recolonise on the rocky shore and are found in the middle region of the shore between low and high tide. They are also found in rock pools where it is sheltered and the water is shallow.
Although picking is uncontrolled at present, Dr Burnell is optimistic that the fishery can be managed effectively. "The scientists in NUI Cork and NUI Galway are working with the wholesalers and pickers to understand the dynamics of the fishery, and to arrive at a mutually agreeable management plan for its sustainable exploitation."