The construction of Waterdunen is currently in progress in Zeeuws-Vlaanderen. Waterdunen is a large nature and recreational area where saline nature is developed on a large scale and opportunities for recreation are created. Zeeuws-Vlaanderen is struggling with socio-economic problems. Project partners Zeeland province, the municipality of Sluis, Molecaten Groep, water board Scheldestromen and the foundation Het Zeeuwse Landschap hope that Waterdunen will give the area a new impulse.
In the project “Aquaculture in Waterdunen: a study into location and planning”, research group Aquaculture in Delta Areas has made concrete recommendations for promising locations and the planning of aquaculture activities: predominantly the cultivation of saline crops and shellfish. The report with recommendations comprises three topics: the cultivation of shellfish (grow-out) in the landscape of creeks, land-based aquaculture (saline crops and shellfish nursery) in the vicinity of Hof Waterdunen and an exploration into a shellfish grow-out in a basin that will be constructed nearby the inlet channel of the planning area Waterdunen. Maps have been drawn of the different topics with search areas for the different species and farming systems. An overview of the most important findings with regard to the design of the area is listed below:
Cultivation of shellfish in the creeks
Off-bottom cultivation methods for oysters and mussels seem to be the most suitable for the Waterdunen/Coastal laboratory concept: mussel rope culture, oysters production in bags on tables, hanging from ropes with the flip-over system or hanging from ropes in baskets are all proven methods of off-bottom cultivation systems. With regard to the food in the system and, related to this, gravity: the water exchange in the back of the creeks will be less because of the low flow. However, the flow is still within range for shellfish. Most likely, the production of shellfish at the back of the creeks system will be less than in parts where the flow and the water exchange is higher. Due to the supply of larvae from the North Sea and the reproduction by cultivated shellfish, the total shellfish stock in the creeks will increase over time, which will have an effect on the capacity of the system for shellfish.
Land-based aquaculture nearby Hof Waterdunen
The soil nearby Hof Waterdunen ranges from clayey silt to clay and is suitable for growing glasswort and sea kale. Sea asters prefer soil that is a bit more sandy. Blending with sand at relevant spots is an option. Smaller test plots could be alternated with larger plots on which commercial crops are cultivated.
Shellfish basins are primarily used to harden off the hatchery (oyster) spat, the so-called nursery phase, before shellfish are cultivated in the creeks to a size that is suitable for consumption. The bottom of the basins is ideally situated at or above 0,65m NAP (groundwater bulge) and consists of thick clay to avoid lateral spread of the water. Saline groundwater could possibly be used to fertilize the algae and to (partially) fill the basins that contain algae.
Shellfish grow-out nearby the inlet channel
The composition (absolute suspended organic matter and part food) of the water flowing into the inlet channel and its variance over the water column, the tides and the growth season of the shellfish is uncertain, according to the best available information. The advice is to wait with the construction of the basin until the monitoring of the incoming water provides more information about the composition. Besides the current uncertainty about the composition of the water, the hydrological model results indicate that if the diameter is wide enough (> 10 metres), enough water will flow through the basin, which will enable the grow-out of oysters/shellfish, with a water flow that mainly falls within the set range (to prevent sedimentation and the the filtration-range of shellfish).
The project started on 1 September 2014 and ended on 1 June 2015. Research group Aquaculture in Delta Areas was the contractor for this project. This project was in part made possible by the financial support from OP Zuid and the Postcode Lottery.