New Zealand's NIWA scientists have discovered a rare, deep-sea fish last seen more than 60 years ago. Five of the hadal snail fish were caught in a trap 7,000 metres deep in the Kermadec Trench during the scientists' special research assignment between NIWA and the University of Aberdeen in Scotland.

The hadal snail fish is the second fish that has been caught alive. According to reports, it was only caught once many years ago. The deep-sea creatures are being examined at NIWA's laboratories in Wellington.

According to marine ecologist Dr Ashley Rowden, catching the snail fish took a lot of skill. He said it was tricky to set a trap in the deep sea. Baited traps were deployed to lure the snail fish. Scientists also sent cameras to capture images and take videos of other deep-sea fish and other organisms in the trench.

University of Aberdeen's Dr Alan Jamieson said that the researchers wanted to use the special trip to analyse the biochemistry of fish and other organisms living in deepest parts of the ocean. Scientists noted the presence of a compound known as trimethylamine oxide (TMAO) in fish. This compound indicated how deep they dwelled in water.

The snail fish caught in Kermadec at 7,000m had the highest levels of TMAO ever recorded. When combined with earlier data, scientists determined that a bony fish can survive in 8,200 metres under the sea.

Scientists have agreed that fish cannot survive in the deepest part of the ocean which falls between 8,200 to 11,000 metres.

The findings of the research study were published in the Proceedings of the National Academy of Sciences journal.

Most of deep-sea fish remain untouched by fishermen

Meanwhile, scientists have discovered that 95 per cent of the world's fish remain untouched by fishermen. According to Australian researchers, most of the fish in the sea especially those that live in the deep have never been fished.

Mesopelagic fish or fish that thrive between 100 and 1000m below the surface make up most of the fish biomass in the world. Researchers have found that the secret to their survival is staying away from fishing nets.

Since mesopelagic fish remain untouched they may play a significant role in the flow of oxygen and carbon in the ocean.