5-Year Study to Set Limits on Dolphin Kills for Tuna Fishermen

Starting today and for the next four months, Rennie Holt and his scientific observers will be crisscrossing the eastern tropical Pacific Ocean, their eyes glued to high-powered binoculars from dawn to dusk, looking for dolphins.

And during the next four years, the same crew will retrace the same route in their count of dolphins to establish whether there are fewer dolphins as a result of the nets used by fishermen to catch tuna.

Whatever the scientists from the federal Southwest Fisheries Center in La Jolla learn will help the U.S. Congress determine whether to adjust present annual limits on dolphin kills by American tuna fishermen. The accuracy of data used to set the quotas has been a source of controversy among environmentalists, government scientists and the fishermen since they were first posted in 1972.

The quotas resulted from environmentalists’ outcry and subsequent congressional action to try to protect what appeared to be the dolphins’ dwindling numbers.

The numbers right now “aren’t really very believable,” said Holt, chief scientist for the five-year counting survey. Present data, he said, is based on old surveys and information from fishermen going back to the 1960s and earlier.

Last month, officials of Southwest Fisheries Center warned fishermen that they could kill more than the 1986 quota of 20,500 dolphins allowed as early as late August if they are not more careful with their nets. The fishermen frequently locate tuna schools by spotting dolphins, which often swim above the tuna. When nets are spread around the dolphins to capture the tuna, some of the mammals become entangled and, unable to surface to breathe, die.

In an attempt to end the feud over numbers, 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 the dolphins.

“It’s a 6-million-square-mile area from Baja south to Peru and west almost to Hawaii,” Holt said. “We’re going to try and cover a representative area in a systematic manner.”

“Are dolphins an endangered species? No,” said Doug DeMaster, acting chief of the fisheries division that monitors the effects of commercial fishing on marine mammals. “But are their numbers in decline? We can’t say if adverse (tuna) fleet activity has affected the dolphins or not. That is what the study will answer.”

DeMaster did say that today’s fishermen, using a new net design, are far more careful than two decades ago when hundreds of thousands of dolphins used to be killed each year during tuna catches.

The survey involves two ships from the National Oceanic and Atmospheric Administration, the federal parent agency of the fisheries center. The two ships will spend 30 days at a stretch at sea, the longest time feasible given the need to replenish and restock, and for the crew to regain their land legs.

“The four-month period and its timing (July to November) are based on logistics and the fact that the period is historically that of calm weather (which allows for easier spotting),” Holt said.

The researchers cannot expect to come up with a precise dolphin-by-dolphin total, of course, any more than population counters come up with a person-by-person count in years other than the national census once a decade. But they hope statistical analysis, together with the new spotting methods, will allow a far more accurate count.

“We will look for dolphins on predetermined track lines--based on historical data--which allow us to move through areas of both high density and low density,” DeMaster said.

Added Holt: “If you just went to Shea Stadium (in New York) on game day, for example, you’d come up with a high population estimate for the whole city. If you went there when there’s no game, your estimate might be very low.

“But the name of the game for fishermen is to find those areas of high density and stay there.” For that reason, information from federal dolphin spotters who are stationed on tuna seiners from time to time is considered biased. The federal monitors perform spot checks on compliance by tuna fishermen with the federal dolphin laws.

The key to the survey’s accuracy rests with two 25-power computer-connected Fuji binoculars mounted on each side of the vessels, each of which has a six-mile range. Two teams of three highly-trained observers spend the day in two-hour segments searching the horizon for indications of dolphin schools. Those clues can include certain birds which follow dolphins, such as sooty terns or brown-footed boobies, or splashes during calm weather that indicate dolphins are present.

Both the number of schools--the density--and the numbers within each school are critical for the survey. When a school is spotted, Holt said, the ship will move in close to estimate the number of individual dolphins more accurately. (A helicopter will be added to one of the vessels next year for additional accuracy.) “The number of schools could remain constant over the five-year period but the number within the schools might be declining,” Holt said in explaining why both figures must be estimated.

Computer analysis, primarily through connecting the binoculars sightings to data processors, will help researchers better estimate the size of schools in relation to the path of the ships. The analytical base was worked out over several years in cooperation with Navy researchers, who want to track accurately surface ships and submarines from a moving vessel.

Once the five-year trend is established, the U.S. could approach Latin American nations fishing the eastern Pacific about an international program to protect the dolphins, Izadore Barrett, director of Southwest Fisheries Center, said.