Three distinct forms of this species are recognized. Shells are dirty grey to purple-grey.

Found in mid intertidal on rocks to depths of 120 m on course sand gravel.

Filter feeder.

The strangest thing about these oysters is that they nurse their newly hatched larvae inside the females shell for about a month before release. Called after the port at which the main fisheries for these oysters is based (Bluff). These fisheries began with collecting these animals intertidally at Stewart Island in the 1880's. The entire commercial catch today comes from deep water.
Daily limit per person 50, minimun size 58 mm.

NZ Coastal Marine Invertebrates; Vol 1