Zigging and Zagging in the Name of Science : Pair of Research Vessels Ready for ’89 Dolphin Count

The courses plotted for the research vessels David Starr Jordan and McArthur seem to be more the meanderings of drunken sailors than routes to be followed by members of a reputable scientific expedition.

Still, early this morning, the two ships will begin a 10,000-mile voyage to nowhere. On Dec. 8, they will return to San Diego, having repeatedly crisscrossed a 5-million-square-mile patch of ocean off the coast of Central and South America.

The 25 scientists and 51 crew members on board the two vessels will stop for provisions and fuel at ports in Mexico, Panama, Colombia, Ecuador, Peru and Clipperton, a tiny dot of an island that sits 1,800 miles west of the Panama Canal. But, after each port, the ships will return to the zigzag course that seems torn from a log compiled by the mythical Flying Dutchman.

Fourth of Six Cruises

The seemingly chaotic course is actually a carefully plotted sea voyage, the fourth of six annual cruises that the National Marine Fisheries Service is conducting to count dolphin populations. The National Oceanic and Atmospheric Administration ships are carrying scientists affiliated with the Southwest Fisheries Center in La Jolla.

The zigs and zags built into the course are designed to give scientists an annual look at dolphin populations close to shore and in the middle of the vast eastern tropical Pacific.

Congress authorized the population counts to help marine biologists determine how many dolphins are being drowned after becoming trapped in nets that commercial fishermen set to catch yellowfin tuna.

Last year, 19,712 dolphins died in the eastern tropical Pacific after being snagged by nets set by U. S. fleets. Federal law confines U. S. fishermen to the “incidental take” of 20,500 dolphins each year. Foreign countries that export tuna to the United States are now required to adopt similar limits.

The research expedition “is a relatively long cruise,” according to Doug DeMaster, a Southwest Fisheries marine biologist who is serving as chief scientist for the expedition. “It’s comparable to the Antarctic cruises, which last from spring to the end of summer.”

Each summer, scientists try to follow a course that is “as identical as possible” to the previous summer’s voyage, DeMaster said. From San Diego, the two research ships will head toward southern Mexico, a three-day trip that “will let everyone get their sea legs,” said DeMaster, who will remain in San Diego during the voyage.

Will Scan for Schools

The ships will then head toward Central and South America. They will work their way to the west, toward the Hawaii. They will then double back and crisscross the eastern tropical Pacific.

Trained observers will use high-powered binoculars to scan the ocean for dolphin schools. Scientists aboard a helicopter to be launched from the Jordan will verify estimates of school sizes gleaned from shipboard observers. Those researchers will also collect physical and biological data that will be used to determine how environmental factors affect the distribution of dolphins in the Pacific.

However, scientists affiliated with the Southwest Marine Fisheries won’t release data gathered during the voyage until after the six-year project is completed. “We just won’t have enough data to say realistically what the populations are,” DeMasters said. “The longer the time period, the better the reliability.”

With the data accumulated during six years of study, changes in population of about 10% per year can be detected, DeMaster said.

Scientists will also use the four-month cruise to study the genetic composition of various kinds of dolphins, as well as their “vocalization patterns.” They will study the diet of sea turtles and the distribution of flying fish, and monitor the population of fish, mammals and birds.

Aleta Hahn will be cruise leader on the Jordan, and Liz Edwards will be the scientific leader on the McArthur.