An alien-like creature discovered in the Bay of Islands is a frogfish which is a rare find in Northland waters, a fish expert has said.
Ichthyologist Andrew Stewart, collections' manager at Te Papa Museum in Wellington, examined the fish, which was just over 100 millimetres long, and said it was a striped angler, commonly known as a frogfish.
An absence of stripes and an unusual black colour pattern intrigued him, as frogfish usually have stripes.
He has been doing research on fish for more than 33 years but it was the first time he had come across a striped angler without stripes.
"I determined it [the species] based on a special lure on its head which is a highly special fin ray that has flappy lobes which waves around to fool other fish that there's something tasty to eat and when they come close to a frogfish, they are eaten," Mr Stewart said.
He said the creature packs an impressive bite - the fastest of any vertebrate.
Their mouths expand at a speed approaching a .22 rifle bullet, and that is in a medium 800 times denser than air.
The unusual fish was discovered by Aucklander James Beuvink and his girlfriend Claudia Howse while snorkelling in chest-deep waters in Pipi Bay off the Bay of Islands, earlier this month.
They were holidaying on a launch in the Bay of Islands for a week and the discovery was made on the last day of their Northland holiday.
"At first I thought 'what the hell is that'. It was sitting on the sand in only about 1.5 metres of water. I didn't really know whether it was a fish and when we got closer, I saw the eyes and fins moving around a bit," he recalled.
"I then thought maybe it's a stonefish but then thought we don't get stonefish in New Zealand."
Mr Beuvink used a net and scooped up the creature before putting it inside a live bait tank on board the launch.
But the creature did not survive the trip to Opua.
His girlfriend's mother suggested the creature be sent to the Te Papa Museum which they did in a chilled courier bag.
"I thought it was some kind of a fish but others perhaps not familiar with the ocean could have easily thought of it as an alien," Mr Beuvink said.
"My friends who also came up with us to the Bay Of Islands have been diving for 30 years but they've never seen anything like this before."
He said pictures of the bizarre black fish were sent to the museum and staff expressed an interest in examining it.
Museum staff thawed it and began tests yesterday.
Mr Stewart said there were only four species of frogfish in New Zealand waters out of nearly 50 worldwide.
"They come here usually after or before a tropical cyclone and they can be found between North Cape to about the East Cape or Gisborne. You'll never find them south of Gisborne.
"Most specimens come from the north because the water there is as cold as they can tolerate. They can go over 200 metres deep but most are found in very shallow waters."
Mr Stewart said he would make available the latest discovery to fish specialists overseas if they needed to do work on it.
The fish will be transferred into an alcohol solution for storage. The museum has 20 specimen of frogfish from the past 60 years that were discovered from Northland to the Western Bay of Plenty.