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Environmental groups insist that the kill rate is higher than even the Fisheries Service's estimate. For their part, the tuna fishermen dispute both Greenpeace's and the NMFS's kill estimates, claiming that Fisheries Service observers, who are assigned to only some of the 29 boats in the fleet, have incorrectly extrapolated their data. The fishermen are also irked by the fact that the foreign tuna fleet, which has no legal quota, will most certainly ignore any forthcoming NMFS restrictions. These ships, say the fishermen, may have already killed more than 20,000 dolphins in 1986. On only one point is there agreement: observers must be placed on all U.S. tuna ships as soon as possible to establish a true count.

The squabble comes at a time when the U.S. tuna fleet has made substantial progress in reducing dolphin deaths. Tuna fishermen say that between 98% and 99% of the animals captured in nets are released unharmed, and the tuna-boat association has instituted the "Golden Porpoise Award" for the skipper with the fewest dolphin kills in a season.

The most effective way of freeing trapped dolphins from a net that is full and cinched shut at the bottom is for the ship laying the net to run in reverse, dragging the net and its finny contents into an elongated shape (see diagram). Crewmen in rubber rafts then drive the surface-swimming dolphins toward one end, and as the ship pulls the net, the dolphins spill out, leaving the tuna behind. Despite these efforts, an average of eight dolphins die during each netting, often at night, when freeing them is more difficult.

Dolphins, which are among the more intelligent mammals, seem to have recognized the tuna-fishing threat. As recently as 15 years ago, says Veteran Tuna Skipper Harold Medina, they could be rounded up easily with a couple of skiffs propelled by small outboards. Sometimes they would even play in the mother ship's bow wave. Now, in areas where dolphins have been heavily fished, they are much more difficult to corral, forcing the fishermen to resort to more and higher-powered chase boats. Mexican fishermen call these recently sophisticated dolphins the "untouchables," because they disappear at the first sight of a fishing boat. The discerning mammals are apparently able to tell the difference between fishing vessels and other craft, because they still approach small sailboats or motor cruisers. Still, marine biologists complain that it is increasingly difficult to study dolphins and take population counts. The oceanographic vessels evidently look too much like tuna boats.

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