Sightings and Movements of Blue Whales off Central California 1986-88 from Photo-Identification of Individuals

We summarize research into the relative abundance and movements of blue whales off central California using data from aerial surveys and photo-identification of individuals from vessels. The Gulf of the Farallones region (including north to Bodega Bay) was the primary study area; 1457hrs of vessel surveys and 88hrs of aerial surveys were carried out from July to November 1986-88. Blue whales were seen on 776 occasions (1,315 animals, including duplicates). The relative abundance of blue whales in the Gulf of the Farallones increased over the three years. a total of 179 individual blue whales were photographically identified in the area from 1986 to 1988. Most individuals were identified in 1988 (101) and 1987 (75). Twenty-two (15%) of the identified whales were seen in more than one year and five (3%) were seen in all three years.

Blue whales were also individually identified in other regions of California (principally near Monterey Bay and Point Arena) using photographs taken on an opportunistic basis by the authors and collaborating researchers. In 1987 and 1988, five and three individuals, respectively were seen in both Monterey Bay and the Gulf of the Farallones; all but one traveled from Monterey Bay in August to the Gulf of the Farallones in late August and September. A large number of blue whales were seen north of the Gulf of the Farallones in September or October. Some of the blue whales identified in this study were also seen off Baja California, Mexico; nine animals seen in the Gulf of the Farallones were seen off the west coast of Baja or the Sea of Cortez, Mexico, including three identified in March and April of 1988 off Baja and seen in August or September 1988 in the Gulf of the Farallones or Monterey Bay.

Citation:

Calambokidis, J., G.H. Steiger, J.C. Cubbage, K.C. Balcomb, C. Ewald, S. Kruse, R. Wells, and R. Sears. 1990. Sightings and Movements of Blue Whales off Central California 1986-88 from Photo-Identification of Individuals. Report of the International Whaling Commission (special issue 12): 343-348.