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NOAA scientists leave on 4-month dolphin census.


Two research vessels belonging to the National Oceanic and Atmospheric Administration (NOAA) left the San Diego, Calif, harbor on 29 July 1989 to begin another 4-month census of porpoise populations in the eastern tropical Pacific (ETP) Ocean. Scientists aboard the NOAA ships David Starr Jordan and McArthur will be busy 12 hours a day counting dolphins over 5 million square miles of sea, conducting research on dolphin populations, and providing facts that will help resolve issues relating to the incidental take of these marine mammals by the ETP yellowfin tuna fleet.

"Comparison of counts made on this cruise with counts made on other cruises using the same methods, will enable us to determine if dolphin stocks are declining and therefore in need of more protection than now exists under current regulations, " says Program Leader Doug DeMaster, of NOAA's Southwest Fisheries Center in La Jolla, California. A 1984 amendment to the Marine Mammal Protection Act gave NOAA the responsibility of monitoring the relative abundance of dolphin stocks in the eastern tropical Pacific.

Because of the vast area to explore, the ships were to crisscross the ocean along different track lines, from off Baja California, Mexico, south to Peru and west to the Hawaiian Islands. The cruise is organized into four legs and will last from 29 July to 7 December with various stops throughout the Pacific.

Every scientific operation and procedure on the cruise has been carefully preplanned and will be scrupulously followed to maintain the consistency of the data that are gathered. Trained observers will be searching through special 25 X 150 binoculars for signs of dolphins, identifying species and estimating the numbers in each school. A helicopter launched from the Jordan will be used to Photograph dolphin schools from the air, to calibrate the observers' estimates of schoolsize. Scientific data on the physical and biological environment will also be collected, to see how environmental factors affect the distribution of dolphins in the sea.

Other "piggyback" research projects will be carried out to get maximum use of precious research vessel time. Information will be gathered on the genetic makeup and vocalization patterns of the different dolphin stocks; on the diet of sea turtles; and on the distribution of flying fish. The scientific party will also be monitoring populations of seabirds, sea turtles, and sea snakes along the cruise track lines.

Although scientists are impatient for the results of the dolphin monitoring program, reliable estimates of population trends will not be available until 1991. This is because rates of change in these sporadically distributed dolphin populations must be measured over a period of at least 5 years. This is the fourth in a series of six planned cruises, so final results await completion of this and two more cruises.

Certain species of dolphin associate closely with schools of yellowfin tuna, and sometimes become trapped and drown in nets set for tuna, despite fishermen's efforts to free them. Last year, 19,712 dolphins were accidentally killed in the ETP by yellowfin tuna fishermen from the United States. Under Federal law, U. S. fishermen are limited to the incidental take of 20,500 of the mammals annually. Foreign fleets that export tuna to the U. S. are now required by U. S. law to conform to similar restrictions in the mortality rates of dolphin in their catches.

The Southwest Fisheries Center in La Jolla will continue monitoring the status of dolphin populations in the ETP as well as coastal marine mammals of California, producing the most scientifically sound data possible to determine changes in population levels of these valuable living resources. The Center is a regional component of NOAA's National Marine Fisheries Service, under the U.S. Department of Commerce.
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Title Annotation:United States National Oceanic and Atmospheric Association
Publication:Marine Fisheries Review
Date:Sep 22, 1989
Previous Article:NMFS-UH workshop eyes Pacific fisheries data.
Next Article:Cooperative research eyes driftnet impacts.

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