Abundance of blue whales off Chile from the 1997/98 SOWER survey

The 1997/98 SOWER survey in Chile searched the region from 18°30′S to 38°S. Although the primary intention of the surveys was to maximize blue whale encounters, survey coverage was sufficient to estimate abundance using line transect methods. The baseline abundance estimate, excluding transit legs, was 452 (CV = 0.56, 95% CI: 160–1300). This abundance estimate is negatively biased because inshore regions including Chiloé Island and the Gulf of Corcovado, where blue whales are now known to aggregate, were outside the survey area. If it is conservatively assumed that the baseline estimate applied to the entire population, then the population was at a minimum of 7–23% of pre-exploitation levels in 1997