Population Size and Structure of Melon-Headed Whales (Peponocephala Electra) Around the Main Hawaiian Islands: Evidence of Multiple Populations Based on Photographic Data

摘要

Despite the presence of melon-headed whales in tropical and sub- tropical waters worldwide, little is known about this species. Melon-headed whales frequent offshore waters surrounding the Main Hawaiian Islands where aerial surveys by Mobley and colleagues suggest a relatively small population (154 individuals (CV=0.88)). A 2004 near mass-stranding in Hanalei Bay, Kaua'i occurred when an embayment of 150-200 animals coincided with naval mid- frequency sonar use. To assess population size and movements in Hawai'i, more than 40,000 photos were collected from 47 encounters around the Main Hawaiian Islands between 2002 and 2009, and additional photos were obtained from collaborators from 1986 - 2001. Using only good quality photographs, there were 1,433 unique individuals in the photo-identification catalog, of which 1,046 were distinctive. Of these, 330 (31.5%) were seen on more than one occasion. Re- sighting data combined with social network analyses showed evidence of two distinct populations - a smaller, resident population, seen exclusively off the northwest region of the island of Hawai'i, and a much larger Main Hawaiian Islands population, seen throughout the entire range of the Main Hawaiian Islands.