Humpback and blue whale photographic identification: Report of research in 1997

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Citation

Calambokidis, J., T. Chandler, K. Rasmussen, G.H. Steiger, and L. Schlender. 1998. Humpback and blue whale photographic identification: Report of research in 1997Final report to Southwest Fisheries Science Center, Olympic Coast National Marine Sanctuaries, University of California at Santa Cruz, and Cornell University. Cascadia Research, 218? W Fourth Ave., Olympia, WA 98501. 41pp.

Summary

Intensive research of humpback and blue whales off California using photographic identification has been conducted annually since 1986 with the primary objectives of examining population size and trends, reproductive rates, and movements of animals. The focus of the 1997 research was to gather data to achieve these overall objectives as well as to address other more specific objectives including studies in the Olympic Coast National Marine Sanctuary, and documentation of whales in the vicinity of two low-frequency sound sources (ATOC and LFA). This report summarizes the research effort and methods used in 1997 and the preliminary findings from this research including the number of individual whales identified, resightings, and movements of some of these animals.

Cascadia personnel conducted 150 vessel days of survey effort between 21 February and 5 November 1997 covering most of the California coast as well as northern Washington. An additional 87 days of survey effort was conducted by collaborators who provided identification photographs to us. During survey effort by Cascadia personnel, 284 sightings of 539 humpback whales and 207 sightings of 313 blue whales were made. Over 100 additional sightings of each species were made by collaborating researchers. These sightings resulted in 402 successful identifications of humpback whales representing 286 different individuals and 326 identifications of blue whales representing 182 individuals. Additional photographs were also taken of more than 50 fin whales primarily in the Southern California Bight, more than 30 "summer resident" gray whales in Washington State, more than 15 sperm whales primarily near Pioneer Seamount, and killer whales off Washington.

More than 80% of the humpback whales identified in 1997 had been seen in previous years. Only limited evidence of interchange was seen between humpback whales identified near the Washington/British Columbia border and those seen off California. The proportion of humpback whale calves seen in 1997 was higher than has been seen in most years and closer to that expected of a healthy increasing population. A higher proportion of calves was seen early in the season compared to late summer and fall. Abundance estimates of humpback whales for 1996-97 are now over 800 and are consistent with an increasing population.

The distribution of blue whales appeared to be different in 1997, with concentrations noted earlier in the season in some areas, such as the Santa Barbara Channel, than had been common in past years. Blue whales were much less common in the Southern California Bight in both inshore and offshore waters in the fall than had expected, resulting in low sighting rates in our fall surveys in these areas. Blue whale movements between a number of regions along the California coast were seen. The most dramatic finding, however, was the movement of one whale (ID# 1110) from off the Queen Charlotte Islands in northern British Columbia on 12 June 1997 (photographed by Randy Burke) to the Santa Barbara Channel on 10 July 1997. This represents a minimum distance of 1,347 nmi covered in a maximum time of 28 d. Both the transit between these locations as well as the direction of movement (south in early summer) were unexpected and suggest a connection between blue whales that summer off California and those that utilize more northern waters.