Research on humpback and blue whales off California, Oregon, and Washington in 2002
Calambokidis, J., T. Chandler, L. Schlender, G.H. Steiger, and A. Douglas. 2003. Research on humpback and blue whales off California, Oregon, and Washington in 2002. Final report to Southwest Fisheries Science Center, La Jolla, CA. Cascadia Research, 218½ W Fourth Ave., Olympia, WA 98501. 47pp
Cascadia Research continued a long-term research effort on humpback and blue whales off California, Oregon, and Washington in 2002. The research had a number of components with the overall purpose to examine distribution, abundance, movements, and population dynamics of humpback and blue whales in the eastern North Pacific using photographic identification of individual animals. Also included in the effort in 2002 was monitoring underwater behavior and vocalizations of blue whales as part of a cooperative research effort with Scripps Institution of Oceanography, National Geographic and Office of Naval Research.
Identification photographs were taken from a number of platforms and collaborators. Cascadia Research conducted 89 days of effort totaling 798 hours and 6,352 nmi from small boats. Additional identifications photographs were obtained by: 1) SWFSC scientists during the outbound leg of a cruise headed off California, 2) by the naturalists from the Channel Islands National Marine Sanctuary’s Whale Corps opportunistically as a part of whale-watching trips in the Santa Barbara Channel, 4) by Peggy Stapp and Nancy Black opportunistically from whalewatch boats in Monterey Bay, and 5) as part of some surveys conducted by the Olympic Coast National Marine Sanctuary off northern Washington. In total, suitable identification photographs of blue whales were made on 530 occasions representing 312 unique whales, one of our highest annual totals. Humpback whales were identified on 529 occasions representing 347 unique individuals.
Estimates of humpback whale abundance using a number of mark-recapture models revealed an increase in abundance of humpback whales from the past two years with 2001-2002 estimate of 1,034 (CV=0.11). This is an increase from the previous two estimates (1999-2001) that were under 800. Humpback whale abundance had steadily increased from the early to the late 1990s at a rate of about 9% per year. Some time between 1998 and 1999 there had been a drop of 25% in our estimates of abundance. Because our most recent abundance estimate represents a larger increase from previous years than would possible by population growth alone, it suggests either the drop in the late 1990s may not have been as large as originally estimated or the current estimate may be high due to chance or bias.
We were able to obtain a more accurate updated blue whale abundance estimate incorporating the 2002 data. The pooled sample from 2000 to 2002 of the systematic and coastal samples was adequate to estimate abundance with a similar level of confidence as in past years. Estimates for 2000-2002 for right and left sides were 1,567 (CV=0.32) and 1,953 (CV=0.33), respectively, averaging 1,760. This is slightly lower than estimates from 1991-93 and 1995-97 using similar procedures. While these estimates are not significantly different from those in the early and mid-1990s, they do not suggest that blue whale populations have been increasing over the last decade has was the case with humpback whales.
Tagging efforts in 2002 resulted in successful suction-cup attachment of three types of tags on blue whales (National Geographic’s Crittercam, Bill Burgess’s bio-probe acoustic tag, and WHOI’s dTag). One extended deployment provided more than 15 hours of dive data through the evening and night. Underwater vocalizations by the tagged or adjacent animals were documented on three deployments (one of each tag type).