DENVER — Scientists gathered here have long puzzled over how baby marine animals survive in the complex swirl of ocean currents off the California and Oregon coastlines.
What portion of these tiny larvae, which are not strong swimmers, get swept away to unknown fates? How many manage to cling to coastal areas and grow up to become fat rockfish or large lobsters? These questions have taken on more urgency with the sharp decline in fish and shellfish, leaving fishermen and government officials wondering how to help bring them back.
A team of marine scientists announced on Saturday that its members have been surprised to learn that far more larvae stay close to home than was previously known.
Oceanographers and biologists for decades have just assumed that microscopic larvae get scattered widely by the cold, unyielding pull of the California Current, which sweeps 1,200 miles down the West Coast. Until recently, they hadn't tried, in any systematic way, to unravel the complexities of coastal currents and dispersal of larvae.
A multi-university team of scientists, presenting findings at the annual meeting of the American Assn. for the Advancement of Science, said it has cracked this "black box" of oceanic secrets. The scientists haven't done that by tracking currents, but by following larvae in some unusual ways.
Most fish and shellfish spend the first few weeks, and sometimes months, in the microscopic larval stage, swimming freely before settling down to the seafloor to continue their development.
Robert R. Warner and other scientists at UC Santa Barbara have discovered that they can chart an animal's wanderings since birth by scrutinizing its ear bones, which act like tiny flight recorders, logging its movements through the sea.
The bones have layers like an onion; each day a new layer incorporates the tell-tale chemical signatures of certain metals associated with various places in the ocean. Warner can tell which larvae were born around the Channel Islands and which were born closer to the coastline. And he can pinpoint where they have been swimming every day since birth.
Stephen R. Palumbi, a Stanford marine biologist, has been mapping neighborhoods of marine animals using their DNA. Palumbi, who has carved out a niche as a genetic detective of the ocean, was startled to discover that barnacles settle in specific areas, using circling currents, or gyres, to keep them close to their parents. Genetics show that they like to stick to their old neighborhoods and stay with their own kind.
