A new satellite tagging technology has proven that it can help resolve the mysteries of tuna migration at a time when management strategies for these remarkable and commercially valuable fish are in dispute and their breeding population is in sharp decline.
The microprocessor tags, deployed in 1996 and 1997 by scientists from Stanford University, the Monterey Bay Aquarium and the National Marine Fisheries Service, revealed that tunas tagged off Cape Hatteras, N.C., were able to move as far as 1,670 nautical miles in 90 days -- and that some fish crossed the line separating eastern and western management zones for the bluefin fishery.
"The results of our work indicate that pop up technology works, and that survivorship is high. The fact that the bluefin spread out in 90 days across the western Atlantic and into the western margins of the eastern Atlantic management zone indicates these fish are on the move," said Dr. Barbara Block of the Tuna Research and Conservation Center (TRCC), a collaborative effort between Stanford University and the Monterey Bay Aquarium.
The findings appear in the Aug. 4 issue of the Proceedings of the National Academy of Sciences.
The new tags, called satellite pop-up tags, pop free of the fish at a preprogrammed time, float to the surface and beam their accumulated data via satellite to scientists in the lab, revealing where the fish moved and what ocean temperatures they favored.
Giant bluefin tuna, which can fetch as much as $80,000 apiece in the Tokyo
seafood market, currently are managed as two separate Atlantic stocks with
limited mixing between the western and eastern Atlantic. Using this management
strategy, breeding stocks in the western Atlantic have declined by more than 80
percent over the past 22 years, and eastern Atlantic bluefin of similar ages
have fallen by 50 percent during the same period. Western Atlantic tuna are
managed under a strict annual quota; eastern Atlantic bluefin have been managed
Contact: Ken Peterson