The dredge oyster or Bluff oyster,Tiostrea chilensis, known in Chile as ostra chilena, is a species of marine bivalve mollusc in the family Ostreidae.
This species is native to Chile and New Zealand.
Also, a self-sustaining population in the Menai Strait was accidentally introduced from the Fisheries Laboratory, Conwy, in 1965 or 1966 (sources disagree).
This bivalve is found from low tide to depths of up to 35 m.
Its length is up to 105 mm, width up to 70 mm, and inflation up to 33 mm.
In New Zealand, they are a prized delicacy, and harvested from March to August from the Foveaux Strait oyster fishery, which centres on the town of Bluff (hence the local name). From the early 1980s, the fishery went into serious decline, due to the outbreak of an oyster parasite, Bonamia exitiosa, with the disease killing an estimated billion oysters between 2000 and 2003. The population has been recovering since 2003, with fishermen voluntarily limiting the catch to half the allowable to aid the revival.