Hugo de Jonge tasted the first Zeeland oysters of the new season on Thursday, September 26. The acting commissioner of the king in Zeeland sampled the shellfish during the festive season opening. Eva Hartog, a researcher from the Aquaculture in Delta Areas research group, played an important role at the well-attended event.
The research group conducts a lot of studies for oyster farmers, who must do everything they can to collect enough oyster larvae and help them survive. The Japanese oyster drill, for example, is a formidable enemy. Oyster farming is therefore challenging and varies by area. For example, in the Grevelingenmeer – which accounts for a quarter of the production area – there is no more oyster spat due to the changing water quality.
Lime-coated roof tiles
Oyster farming begins with capturing this oyster spat (the eggs or larvae) on hard, calcium-rich material. For years, lime-coated roof tiles were used for this. Now, mussel shells are being reused. On oyster farming plots in the Oosterschelde and Grevelingenmeer, beds with mussel shells are created to capture oyster spat. Since the arrival of the Japanese oyster drill, mortality rates have increased, and production is under pressure.
Alternative methods
The Aquaculture in Delta Areas research group of HZ University of Applied Sciences, together with the field, is testing systems to combat the snail.
These systems give oyster spat a chance to attach higher up in the water column to hard, calcium-rich material. Tests with socks filled with mussel shells and vertical rods with lime-coated discs have shown promising results during tests in France. The predatory snail cannot reach them. “The alternative methods of capture that we are currently testing show encouraging results. By working off-bottom, there is less mortality from oyster drills. Higher in the water column, better food is also available for the oysters,” says Eva Hartog.
This new method does require investments from the farmers, and the regulations need to be adjusted.
In the Netherlands, two types of oysters are cultivated: flat Zeeland oysters and hollow Zeeland oysters, also known as creuses. The production areas are in the Oosterschelde and the Grevelingenmeer. The production of flat oysters is between 1.5 and 2 million pieces, while the production of creuses is between 15 and 20 million pieces.