NZ scientist completes marine life census

Census of marine life

SEA CENSUS: A selection of images from the Census of Marine Life. Clockwise from top left: Dragonfish, deep water octopus, queen angelfish, deep sea jellyfish.

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New Zealand waters have more than 4100 undescribed fish species, according to a major new study.

The Census of Marine Life estimates there are more than 230,000 species in our oceans, including more than 4100 undescribed species in New Zealand's specimen collections.

Scientists have combined information collected over centuries with data obtained during the decade-long census to create a roll call of species in 25 biologically representative regions, from the Antarctic through temperate and tropical seas to the Arctic.

They have found the number of known, named species, contained in the 25 areas ranged from 2600 to 33,000 and averaged about 10,750, which fall into a dozen groups.

Lead author of the 10-year study Mark Costello of the Leigh Marine Laboratory, University of Auckland, is also sounding an alarm about the findings.

"In every region, they've got the same story of a major collapse of what were usually very abundant fish stocks or crabs or crustaceans that are now only 5-10 per cent of what they used to be," said Dr Costello.

"These are largely due to over-harvesting and poor management of those fisheries. That's probably the biggest and most consistent threat to marine biodiversity around the world."

On average, about one-fifth of all species were crustaceans which, with mollusks and fish, make up half of all known species on average across the regions.

"This inventory was urgently needed for two reasons," says Dr Costello.

"First, dwindling expertise in taxonomy impairs society's ability to discover and describe new species. And secondly, marine species have suffered major declines - in some cases 90 per cent losses - due to human activities and may be heading for extinction, as happened to many species on land."

The number of unique "endemic" species seen nowhere else on Earth provides another measure of biodiversity.

The relatively isolated regions Australia, New Zealand, Antarctica or South Africa have the most endemic species.

Endemics comprise about half of New Zealand and Antarctic marine species and a quarter of those in Australian and South Africa.

The proportion of species not yet described is estimated at 39 to 58 per cent in Antarctica, 38 per cent for South Africa, 70 per cent for Japan, 75 per cent  for the Mediterranean deep-sea, and more than 80 percent for Australia.

New Zealand has more than 4100 undescribed species in its specimen collections, which would comprise 25 per cent of the country's known marine species.

However this is a minimum estimate because many species have not been collected and then distinguished in collections, the census says.

Australian and Japanese waters, which each feature almost 33,000 forms of life that have earned the status of "species" are by far the most biodiverse.

The oceans off China, the Mediterranean Sea and the Gulf of Mexico round out the top five areas most diverse in known species.

The authors note that their work constitutes a roll call of marine plant and animal species - either present or absent in 25 regions. It does not indicate the abundance, or biomass they represent.

- © Fairfax NZ News