Humpback and blue whale photographic identification: Report of research in 1996

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Citation

Calambokidis, J., T. Chandler, K. Rasmussen, G.H. Steiger, L. Schlender, D. Ellifrit, and J.L. Quan. 1997. Humpback and blue whale photographic identification: Report of research in 1996. Final report to Monterey Bay, Channel Islands, and Olympic Coast National Marine Sanctuaries, Southwest Fisheries Science Center, and University of California at Santa Cruz. Cascadia Research, 218? W Fourth Ave., Olympia, WA 98501. 40pp.

Introduction

This report summarizes the research effort and methods used in 1996 and the preliminary findings from this research including the number of individual whales identified, resightings, and movements of some of these animals. While data obtained in 1996 will also be incorporated into the longer term objectives of the research effort, these overall findings will only be briefly reviewed here.

Cascadia Research conducted photographic identification boat surveys for humpback and blue whales off the coast of Washington and California. In total there were 159 vessel days of survey effort including Cascadia vessels, NOAA ships (days when photographs were taken) and deployed inflatables, and collaborators (Table 1). For 128 of these surveys we had detailed information on effort and these involved 761 hours and covered about 6,709 nmi of search effort (not including the effort for opportunistic identifications ships during SWFSC cruises). In addition to effort from NOAA ships and Cascadia vessels identifications were also made from whale watch boats, other opportunistic platforms, and by scientific collaborators (primarily Nancy Black, Jeff Jacobsen, and Eric Martin). Major areas of emphasis included northern Washington, Monterey Bay to Bodega Bay, and the southern California Bight. Identifications were obtained as a part of Southwest Fisheries Science Center cruises off California, Oregon, and Washington, as well as off Pioneer Seamount near the location of the ATOC sound source.

Humpback whales were identified on 617 occasions in 1996 representing 362 unique individuals. This is the second highest number of individuals we have identified in any year and brings the total number of individuals identified since 1986 to 908. A total of 157 humpback whales were seen more than once in 1996 representing 410 separate sightings. Although many of these were short term and short distance movements, there were also a number of longer intervals. The longest period over which an animal was sighted was over six months. A higher than expected proportion of humpback whales seen in 1996 had not been previously identified in our research. Research in 1996 and early 1997 has provided new information on the migratory connection of humpback whales feeding off California, Oregon, and Washington and those that winter off Costa Rica. Of 27 whales identified during the winter off Costa Rica through February 1997, 22 matched with whales identified off California (two of the five not matching were poor quality photos). This match rate (81%) is remarkably higher than other wintering to feeding areas, and suggests that whales wintering off Costa Rica are almost exclusively from California.

Blue whales were identified on 296 occasions in 1996 representing 184 unique individuals. This total is slightly less than the number of identifications made in the previous two years but still provides a good sample for future mark-recapture calculations. The total number of individuals in the blue whale catalog is now 1,090. Of the 184 blue whales identified in 1996, exactly half (50%) had been identified in a previous year (part of Cascadia’s catalog). All identifications of blue whales were made south of the California/Oregon border, as has been the case in past years. A total of 62 individual blue whales were seen multiple times in 1996 (from 2 to 10 times). Documented movements included numerous short-term resightings in the same area as well as some long-distance movements.