The blue bastard fish, long rumoured to exist among Australian fisherman, has formally been identified as a new species.

Queensland Museum ichthyologist Jeff Johnson named the fish plectorhinchus caeruleonothus — the Latin translation of blue bastard. "Caeruleo is blue and nothus is bastard," Johnson told Mashable Australia.

North Australian locals and fly fisherman had given the creature the colloquial name because of its hue and the difficulty of catching it, but many thought it was simply a painted sweetlips fish and not something new. "The water is relatively murky [up there] with quite a few crocodiles," Johnson said. "That's one of the reasons why it hasn't been noticed in the past."

Photos of the fish, now recognised as a unique species of sweetlips, were sent to Johnson last year by Weipa fisherman Ben Bright. "I suspected that there was a new species of sweetlips around," Johnson said. "I saw Bright's photos and immediately recognised it as something new ... The dorsal spines were 12, and the painted sweetlips has nine or 10."

Bright sent the museum a few he had caught, and after geneticist Jessica Worthington Wilmer analysed the DNA sequence codes of comparative specimens, it was determined to be something distinctive.

Blue bastard is a salty name for a fish, but Johnson said it's now been published and formally recognised. "Fisherman have been calling it this name for twenty odd years, so I thought what better name to use?" he said. "It's quite an affectionate term, because the fisherman have to do quite a bit of fishing before they find one."

In fact, the reviewers of Johnson's scientific paper in the zoological journal Zootaxa apparently thought it was a great idea and quintessentially Australian. "They were quite cool with it," Johnson added.

Two Blue Bastards "kissing."

Besides its unique name and physical features, the fish also has some unusual habits. Rival males often lock jaws in combat. "The fisherman call it kissing, but it's anything but," Johnson said. "They'll come to the surface and struggle away for minutes at a time ... it's a behaviour that's unique to this species among sweetlips." Johnson suspects it's not a fight to the death, but just a territorial response.

The fish, found mostly in tropical waters north of Australia, can grow up to one metre (3.28 feet) in length and turns blue as it ages.

The blue bastard won't end up on your dinner table, however. It's mostly nabbed by sport fisherman who catch and release it, and the fish probably doesn't taste too good. "A lot of members of that family are only fair sort of eating. I suspect this one will be along the same lines," Johnson said.

The blue bastard isn't likely to be the last new species Johnson and his team find. In Australian waters alone, there are about 30 new species of fish described every year, he said.