Blue bastard (Plectorhinchus caeruleonothus) is a species of fish discovered in Australia. The fish is blue when adult. It is found in north Australia and was previously considered as a legend which existed only in fishermen tales. The fish is very difficult to catch. Plectorhinchus caeruleonothus was identified through several features unique to it, such as a distinctive pattern on juveniles and small nostrils. The fish likely evolved its tough ways to survive the many sharks and crocodiles that share its habitat in reef waters off northern Australia.