An acoustic link between blue whales in the eastern tropical Pacific and the northeast Pacific

Blue whale calls in the eastern North Pacific Ocean consist of a two-part c all often termed the A-B call. This call has been described for regions off shore of Oregon, Washington, and California, USA and the Sea of Cortez, Mex ico (reviewed in Rivers 1997). Data collected from moored hydrophones in th e eastern tropical Pacific (ETP) indicate that the A-B pattern is common in this region as well. There is consistency in this call type throughout the eastern North Pacific and throughout the year. This acoustic evidence indi cates continuity between blue whales in the ETP and those found west of Nor th America. The acoustic data suggest that the population of blue whales ge nerally referred to as the "California/Mexico'' stock might better be terme d the "northeast Pacific" stock of blue whales.