These figures show the number of days per month the Southern Resident Community of orcas were detected in Puget Sound south of Port Townsend and east of Deception Pass, Whidbey Island (Osborne, 1999; Osborne et al, 2001). Sighting days were included in the plot only if there were two or more sightings in the same location, or the observer was a researcher or otherwise experienced observer.

The yellow bars represent the number of days the whales were detected on a particular month and year, and the black line shows the average (or mean) number of days that would be expected. Whenever the yellow bars are above the black line it means the whales were detected more often than expected. Whenever the yellow bars fall below the black line it means the whales were not detected as often as would be expected.

This archive is a compilation of all available sightings called into the Museum's WHALE HOTLINE (800-562-8832), the B.C. Whale Hotline (800-665-5939) maintained by the Marine Mammal Research Group in Victoria, reported over Sea Coast Expeditions' pager network, printed in the Orca Network listserve, or reported directly to the Museum by individual researchers and experienced observers.

Of interest in this figure are: 1) the historical shift in how often the orcas are detected in Puget Sound, 2) the oddity of the Dyes Inlet incident in 1996, and 3) the recent trend for the orcas to spend much more time in Puget Sound than they used to (except in the summer).

References:

Osborne, R.W., J. M. Olson, and R.E. Tallmon, 2001. "Southern Resident Killer Whale Habitat Use at Different Time Scales Using Sighting and Photo-Identification Records." Abstract of a paper presented to the 14th Biennial Conference on the Biology of Marine Mammals, Vancouver, B.C.

Osborne, R.W., 1999. "A Historical Ecology of Salish Sea 'Resident' Killer Whales (Orcinus orca): with Implications for Management." Doctoral Dissertation, Department of Geography, University of Victoria, B.C., 262 p.