Optimization of off-bottom spat collectors for restoration and production of the European flat oyster (Ostrea edulis) in Dutch coastal waters

Efficient spat collection is essential to both the successful restoration and cultivation of the European flat oyster (Ostrea edulis). The results of four different experiments investigating larval abundance, and the use of seven different types of suspended spat collectors in seven locations in the SW Netherlands were compared. These different types included Chinese hats, Vexar mesh, PVC tubes, and four types of bivalve shells. Larval abundance, and timing of peaks in abundance for both O. edulis and the non-indigenous Pacific oyster (Crassostrea gigas) varied between locations and years. The most successful spat collectors were sacks of bivalve shells. In general, most spat were observed on collectors deployed 1-2 weeks after the peak in larval abundance was detected. Fouling was heavy and may have prevented larval settlement on collectors deployed too early. Suspended sacks of bivalve shells show great promise as O. edulis spat collectors intended for reef restoration purposes but may need further development for cultivation application.