Others use shade cloth, but his can restrict water flow, assisting in silt build-up, although it also keeps out predators. Sprayed oysters have a lower meat temperature than shaded ones. Floods Oyster rafts may suffer damage from flood. Because of this, care is taken in putting the rafts out of main channels and properly anchoring them. Floating debris can damage most oyster growing devices.
Flooding can also cause silting.
In the 1980s, anti-fouling paints polluted several major estuaries in NSW, as well as in France, the USA and Great Britain. This causes shell deformities in the Sydney rock and Pacific oysters. In 1989 anti-fouling paints were banned for use on boats under 25m. This has reduced the pollution from paints and shell deformities have declined. Pollution also comes from sewage and industrial waste put into rivers.