Pacific dives recover novel fish

Marine biologists being filmed for a BBC TV series have confirmed an astonishing 13 new fish species on a single expedition in the Pacific Ocean.

The researchers have a further 15 animals they think may also be new to science but require additional study.

The haul comes from deep dives made across reefs in Micronesia.

The quest to find the novel fish is detailed in the series Pacific Abyss and includes the capture of a long-sought and spectacular damselfish.

The team concentrated its efforts on waters referred to as the twilight zone.

Sited some 60m (200ft) to 150m (500ft) down, this is a transition region between depths that still receive some sunlight during the daytime and waters that are in perpetual darkness.

The twilight zone is rarely explored, being below the activity of normal scuba activity but above the operations of most submersibles.

The scientists had to use sophisticated closed-circuit rebreather gear to avoid decompression problems. Even so, for safety reasons, their dives were strictly time-limited, and each sortie saw a quick scramble to net as many different fish as possible before the required slow ascent to the surface.

The newly described species include several new colourful damselfish in the Chromis genus; at least one new species of basslet (from the Plectranthias genus); an unusual hawkfish and a new species of butterflyfish.

The most spectacular recovery was of the bright blue damselfish found 120m down off Palau. This was described recently in the scientific literature by team-member Dr Richard Pyle, from the Bishop Museum, Honolulu, Hawaii.

The fish has been named Chromis abyssus in honour of the TV series.

The story is a more complicated one, however, because Dr Pyle first saw this fish more than a decade ago. Other researchers, too, had sightings, including one from a small submersible and another from a Remotely Oerated Vehicle (ROV).

It was during the BBC filming, though, that nine specimens were finally captured, allowing for an official scientific submission this year.