SAN DIEGO (AP) _ A five-year study on dolphins now under way in the Pacific Ocean is aimed at determining whether quotas are needed to protect the water mammals from the American tuna industry.

Congress first imposed quotas on U.S. tuna fishermen in 1972, when studies indicated that the number of dolphins being captured along with tuna was causing a dramatic drop in the dolphin population.

But Rennie Holt, chief scientist for the new counting survey, said that data is based on information dating back to the 1960s and earlier.

Holt and a team from the federal Southwest Fisheries Center in La Jolla will be using state-of-the-art counting equipment in the study, which will take them back and forth across the eastern tropical Pacific. Their findings will be used by Congress to determine whether present limits on dolphin kills should be changed.

Dolphins are caught by tuna fisherman because the fisherman use them to locate tuna schools. The dolphins often swim above the tuna and are caught in nets that are dropped to capture the tuna. They become entangled in the nets and die.

Last month, officials of the Southwest Fisheries Center warned fishermen that they could exceed the 1986 annual quota of 20,500 dolphin kills as early as late August if they are not more careful.

The scientists plan to spend 12-hour days using computer-enhanced spotting systems and a statistical theory designed by the U.S. Navy for deep-sea tracking to locate schools of dolphins and estimate the numbers within each.

Holt said the area to be covered is 6 million square miles from Baja California south to Peru and west almost to Hawaii. The survey involves two ships from the National Oceanic and Atmospheric Administration, the parent agency of the fisheries center. The two ships will spend 30 days at a stretch at sea.

Researchers hope that statistical analysis and the new spotting methods will allow a far more accurate determination of the dolphin population.