Southern Roughy
Southern Roughy are often confused with a much more common fish in Sydney, the Bullseye. Both are a similar shape and colour and both like hiding in the dark under ledges and in caves.
You can tell the difference in two ways: 1) the Southern Roughy has a distinctive black and white stripe behind its gills and 2) when captured the Southern Roughy releases a highly toxic substance through pores in its skin.
Needless to say we definitely recommend identifying them by looking rather than licking.