PACIFIC GROVE, Calif., Dec. 9 (UPI) -- Fishing on one side of the Atlantic affects the other side, researchers say, and bluefin tuna populations on both sides have declined precipitously since 1950.
Two Atlantic bluefin populations were studied -- a western population that spawns in the Gulf of Mexico and is primarily fished by North Americans, and an eastern population spawning in the Mediterranean Sea that is fished by European and North African fishers -- a release from The Ocean Foundation said Friday.
Adult bluefin tuna numbers have fallen as much as 83 percent in the western population and 67 percent in eastern population, researchers said.
Tag tracking data show individual bluefin can rapidly move between western and eastern regions but then separate and return to distinct spawning areas, they said.
"Current population models assume that a fish caught in the west Atlantic was born in the west, and a fish caught in the east was born in the east," senior author Murdoch McAllister of the University of British Columbia said. "We now know that upward of 50 percent of bluefin caught in some western fisheries were spawned in the Mediterranean, and incorrect assignment of these fish biases assessments and may compromise recovery efforts of this valuable species."