The island was declared a
nature reserve in 1969 managed by the Department of Park and Wildlife; its reserve number is 27614. The island is also registered as a national estate. The island is 103 hectares (250 acres) in area, 3 kilometres in length, and 600 metres at its widest part. The closest island is Michaelmas Island, located 1.5 kilometres north of Breaksea Island.