Action: Deter birds from landing on shellfish culture gear by suspending oyster bags under water
A replicated and controlled study from Canada found that significantly fewer birds roosted on oyster bags suspended 6 cm below the water, compared with non-submerged bags. Birds roosted on bags suspended 3 cm below the water as frequently as control bags.
Oyster bags are mesh bags, attached to floats and anchored on the seabed into which young ‘seed’ oysters are placed. They then grow and are harvested when large enough. Oyster cages are similar, but are made of rigid wire mesh.
Supporting evidence from individual studies
A replicated and controlled experiment in summer and autumn 2006 and 2007 in oyster Crassostrea virginica farms off the coast of New Brunswick, Canada (Comeau et al. 2009), found that suspending oyster bags 6 cm under the water significantly reduced the number of birds roosting on them (1 bird/100 bags on submerged bags vs. 37 on controls). However, suspending bags 3 cm below the water did not significantly reduce the number of birds roosting (15 birds roosting/100 bags).