Efforts to conserve threatened marine creatures such as sharks and turtles should concentrate on so-called hotspots of biodiversity, according to a new scientific study.
By Richard Black
BBC science correspondent
Researchers from Germany and Canada discovered that certain areas of the ocean seem to teem with many different species and that these locations should be developed as marine reserves.
Under pressure tuna would benefit from "fish parks"
The scientists' modelling shows that preventing fishing in these "parks" would be the most efficient way of enhancing the survival prospects of those fish and other marine animals now threatened with extinction.
The team, led by Dr Boris Worm from the Institute for Marine Science in Kiel, publishes its findings in the journal Proceedings Of The National Academy Of Sciences (PNAS).
It is well known that on land, some places are far richer in species than others; a couple of examples are tropical rainforests and savannah watering-holes. Many of these areas have now been turned into protected parks.
But Dr Worm and colleagues have shown this concentration of life to be true also of the oceans. Although scientists have long suspected this to be the case, the new study is said to be one of the first to put some hard data to the idea.
"This is like the watering-holes in the Serengeti, where you have lions and leopards and gazelles and wildebeest and all species congregating at a relatively small spot," Dr Worm said.
"We've looked for these spots in the open ocean," he told BBC News Online.
And they found them. By using records compiled over many years by scientific observers on long-line fishing boats, Dr Worm's team discovered that there are places in the ocean that really are the marine equivalents of the Serengeti, rich in species like tuna, swordfish, shark and billfishes.
Many of these organisms are under threat of extinction - some of the large predatory species have seen their numbers decline by 90% in living memory.
The hotspots tend to lie in regions where the tropical and temperate oceans meet, and coincide with features like reefs and underwater mounts where there is also a diversity of plankton and smaller fish.
"We see the ocean as a seemingly uniform, monotonous landscape which is just plain water," Dr Worm said.
"We find out more and more that this is not true. The ocean has structure; this structure is imposed by differences in temperature, in salinity, in different hydrographic features."
Dr Worm's team has run computer models showing that locating marine reserves in hotspots would be a highly efficient way of preserving the spectacular predators of the open ocean.
"If you preserve the wrong area, if you close it off from fishing - fishermen go elsewhere and then they may go to an area which has high diversity and where they cause increased harm.
"If you protect the right areas, you do conservation most efficiently."