Using Antarctic blue whale photo-ID data from the SOWER cruises: Capture-recapture estimates of abundance

Abstract

Photographs of Antarctic blue whales were collected as part of the IWC’s SOWER cruises from 1987/88 to 2008/09. Photo‐ID data from 15 cruises were used in a pilot study that conducted capture‐recapture analysis to produce estimates of super‐population abundance for the circumpolar Antarctic from 1992/93 to 2008/09 and for IWC Management Area III from 2004/05 to 2006/07. The circumpolar estimates are 3,178 (95% CI 534 to 24,239) Antarctic blue whales (left‐side photographs) and 1,109 (95% CI 451 to 3,215) (right‐side photographs) for the years 1991/92 to 2008/09. Estimates of super‐population abundance for Area III are 1,318 (95% CI 515 to 3,716) (left‐side photographs) and 939 (95% CI 421 to 2,323) (right‐side photographs). The SOWER photo‐ID database provides a starting point for improved estimates of population trends in the future as photographs of new individuals and additional recaptures of Antarctic blue whales are obtained.