Humpback and blue whale photographic identification research off California, Oregon, and Washington in 1998

Publications >> Humpback and blue whale photographic identification research off California, Oregon, and Washington in 1998

Citation

Calambokidis, J., T. Chandler, K. Rasmussen, G.H. Steiger, and L. Schlender. 1999. Humpback and blue whale photographic identification research off California, Oregon, and Washington in 1998Final report to Southwest Fisheries Science Center, Olympic Coast National Marine Sanctuaries, and University of California at Santa Cruz. Cascadia Research, 218½ W Fourth Ave., Olympia, WA 98501. 35pp.

Executive summary

This report provides an update on the results of humpback and blue whale research based on the field work conducted in 1998. It summarizes the photo-identification results and examines distribution, abundance and population trends, and reproduction and mortality for humpback and blue whales. Surveys were conducted by Cascadia Research and a number of collaborators as a part of several studies. Cascadia personnel conducted 83 vessel days of survey effort between 4 May and 8 Dec 1998 covering most of the California coast and northern Washington. An addition, effort was conducted by collaborators who provided identification photographs to us.

Surveys were primarily conducted using two 5.3m rigid-hull inflatable boats (RHIBs). Individual identification photographs were obtained of humpback and blue whales using methods that have been employed in past research with these species. During survey effort by Cascadia personnel, 433 sightings of 1,027 humpback whales and 322 sightings of 437 blue whales were made off California and 23 sightings of 40 humpback whales were made off Washington. Combined with additional effort by a number of collaborating researchers these sightings resulted in 888 successful identifications of humpback whales representing 423 different individuals and 400 identifications of blue whales representing 228 individuals. This represents the largest sample of humpback whale identifications and one of the largest for blue whales we have obtained since our research began in 1986.

Humpback and blue whale identifications were obtained from a number of different areas and months and these indicated extensive movements among most regions. Humpback whales off northern Washington were an exception and animals from this region show a low matching rate with California and appear to be part of a separate feeding aggregation that begins north of about 47°30’N.

New estimates of humpback whale abundance were obtained using several mark-recapture models. These provide a new estimate of 905 humpback whales for California-Washington. This feeding aggregation has shown a highly significant annual increase since 1988 averaging about 8% per year. The annual survival rate during this period has averaged 95%.

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