Quick Dips

Monsters from the Deep?

MAF Fisheries biologist Alan Hart found a variety of strange deep-water fish in a recent survey by MAF Fisheries research ship Tangaroa. Some 30 unusual fish were pulled up from 2,000 metres.

"The strange fish were caught in what is believed to be the first fishing trawl to go as deep as 2,000 metres in New Zealand waters," said Hart, who led the survey. "It took one and a half hours for the trawl -- using 3,400 metres of wire -- to reach the bottom."

The 10-minute trawl was carried out to test floats and net monitoring equipment during a recent survey of juvenile orange roughy, north-east of the Chatham Islands.

Although on the seabed for only a short time, the trawl picked up a range of rare and unusual fish, including pineapple rattails, halosaurs, sabre-tooths, a gulper eel, angler fish and octopus.

Most displayed the features common to deepsea species -- inky black or brilliant red colouring and large eyes. Black colouration provides ideal camouflage in the dark depths. Fish and crustaceans that move up in the water column, however, tend to be red in colour, as red is the first wavelength of light lost in water, making red objects appear black.

The large eyes enable the fish to gather what little light there is --  most of it generated by other fish. All were relatively small, with the largest, the halosaur, about 60 centimetres long. Tangaroa is the first New Zealand research ship capable of trawling to 2,000 metres. With 4,000 metres of wire onboard, she has the capability to trawl as deep as 2,700 metres.

"Up until now, we've only been able to sample to depths of 1,500 metres, using chartered commercial vessels," said Hart.

"The ability to trawl so deep is important, as it will enable scientists to measure the depth range of deepsea species, such as orange roughy and smooth oreos. This information will help us more accurately estimate the size of deepsea stocks, which is essential for advising on safe catch levels."

The deepsea catch is now being formally identified and preserved by the natural history unit of the National Museum, a regular recipient of unusual marine organisms caught by MAF Fisheries researchers.