Status of blue whales off Isla de Chiloe, Chile, during 2007 field season

Authors

Bárbara Galletti Vernazzani
Carole A. Carlson
Elsa Cabrera
Robert L. Brownell Jr., NOAAFollow

Date of this Version

6-2007

Comments

Paper SC/59/SH1 presented to the International Whaling Commission Scientific Committee, June 2007, Anchorage, Alaska, USA.

Abstract

Since 2004, a collaborative research program of the Alfaguara Project on blue whales off Isla de Chiloe, Chile, has produce important new information on present day conservation status of this population. This paper presents preliminary findings from 2007 and compares such data with that reported in previous years. Land-based monitoring in 2007 resulted in 36 days of observations with 262.85 h of land-based effort. The maximum number of individuals sighted from land ranged from 2 to 44, with an average of 18.14 individuals per day (SD=12.00 ; CI95% =14.08 - 22.20). Preliminary results on fifteen of seventeen photo-identification surveys conducted in 2007 resulted in the documentation of 123 blue whale groups comprising 156 individuals. The number of whales encountered does not include animals resighted on same day. Individual photo-identification of left and right side respectively, resulted in 80 individual blue whales, including seven between years and sixteen within year recaptures; and 74 individual blue whales, including nine between years and fourteen within year recaptures. The combined photo-identification catalogue (2004-2007) is comprised of 143 individual blue whales (left-side) and 137 (right-side). A photo-identification recapture from different areas provides evidence that the blue whale feeding ground off southern Chile is extensive and dynamic. A recapture analysis of 2005 and 2006 whales shows an overall return rate of 10.8% (left side) and 11.4% (right side) highlighting the northwestern Isla de Chiloe as an important long-term feeding area for this population. Of the 80 individuals recorded this season, 56.8% (n=42) were recorded to be “skinny”, including 5.4% (n=4) with ribs clearly visible. The 2007 proportions of skinny whales are the highest documented to date. It is unknown if these skinny whales represents any potential threat to this population. Therefore, it is essential that long-term photo-identification research continue to monitor this condition.