|Japanse oesterbanken op droogvallende platen in de Nederlandse kustwateren in 2013: bestand en arealen|
Brummelhuis, E.B.M.; van Asch, M.; van den Ende, D.; Troost, K.; van Zweeden, C. (2013). Japanse oesterbanken op droogvallende platen in de Nederlandse kustwateren in 2013: bestand en arealen. IMARES Wageningen Report, C210/13. IMARES Wageningen UR: IJmuiden.
Part of: IMARES Wageningen Report. Wageningen UR. IMARES: IJmuiden, more
Coastal zone; Population dynamics; Crassostrea gigas (Thunberg, 1793) [WoRMS]; ANE, Netherlands [Marine Regions]; Marine
|Authors|| || Top |
- Brummelhuis, E.B.M., more
- van Asch, M.
- van den Ende, D.
Research Institute IMARES, part of Wageningen-UR, was commissioned by the Ministry of Economic affairs to estimate the surface area of Pacific oyster (Crassostrea gigas) beds in the littoral part of the Wadden Sea, Oosterschelde and Westerschelde estuaries in 2013. It is one of the shellfish inventories that are carried out annually by IMARES in collaboration with the fishing industry and the ministry. The surveys are designed to substantiate the policy for the shellfish fisheries and are an important source of information for further ecosystem and impact studies. An estimate was made of the total stock size in the littoral. In addition, in 2013 an estimate of Pacific oysters on the dike slopes around the Oosterschelde estuary was made.Surface areaMapping of oyster beds mainly takes place on foot during low tide; the position of the beds is logged with GPS equipment. Within the time available as many beds as possible are visited. The area of not visited beds is estimated from data of earlier years. Prior to the surveys in the Wadden Sea and Oosterschelde estuary an inspection flight was made. Newly appeared, disappeared or changed beds were compared with last year’s information and locations where much has changed were visited on foot with priority. In the Oosterschelde and Westerschelde estuaries also aerial photographs were used to localize beds.For the Wadden Sea the area of oyster beds in 2013 is estimated at 1121 hectares. Of these, 681 ha were measured in the field and 440 ha were reconstructed in GIS. The reconstructed beds were measured in previous years during the littoral mussel / oyster beds survey, and the contours of the most recent years are taken as provisional reconstruction in 2013. Of the total area, 243 ha consisted mainly of Pacific oysters. The remaining 878 ha are characterized as mixed mussel / oyster beds.For the Oosterschelde estuary the area of Pacific oyster beds is estimated at 779 ha. Of this, 582 ha were reconstructed and 40 ha are seen on aerial photographs. At least 392 hectares can be characterized as mixed mussel / oyster beds. BiomassThe biomass in the surveyed beds is quantified based on a stratified grid. In the Wadden Sea 311 stations are sampled at oyster/mussel beds and in the Oosterschelde estuary, 197 stations are sampled. No stations were sampled in the Westerschelde estuary.In the Wadden Sea the total fresh weight on the littoral beds is estimated at 42.8 million kg. In the Oosterschelde estuary the total fresh weight on the littoral beds is estimated at 29.6 million kg. In the Westerschelde estuary the total fresh weight on the littoral beds estimated at less than 1 million kg. Many oysters grow on dike slopes and stone deposit. For the Oosterschelde the biomass on the dikes is estimated at 3-10 % of the total littoral biomass.