The green 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 green bars are above the black line it means the whales were detected more often than expected. Whenever the green 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 is the increase in fall sightings in recent years.
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.