A new satellite-based tagging technology has proven that it can help resolve the mysteries of tuna migration at a time when management technologies 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 60 days-and that some fish crossed the internationally established line separating eastern and western management zones for the bluefin fishery.