The geographic stock structure of female and immature sperm whales in the South Pacific

Individual Physeter macrocephalus photo-identified during a survey of the South Pacific in 1992-93 were matched to existing identifications collected off the Galapagos Islands since 1985 and off Ecuador/northern Peru in 1991. None of these females and immatures identified in the earlier studies were found in the W South Pacific or in the E Pacific south of 10°S. However, some animals seen previously off the Galapagos Islands were found off Ecuador/N Peru north of 10°S. It therefore seems unlikely that the female and immature sperm whales in the South Pacific undergo trans-oceanic movements but rather that their movement is limited to c1000km. No large mature males seen in this study (all from the W South Pacific) were matched to any individual identified previously off the Galapagoes Islands or off Ecuador/N Peru. The mature males observed in these two regions may be from separate breeding stocks. -from Authors