SEASONAL MOVEMENTS AND FORAGING BEHAVIOR OF NORTHERN RESIDENT KILLER WHALES (ORCINUS-ORCA) IN RELATION TO THE INSHORE DISTRIBUTION OF SALMON (ONCORHYNCHUS SPP) IN BRITISH-COLUMBIA
Lm. Nichol et Dm. Shackleton, SEASONAL MOVEMENTS AND FORAGING BEHAVIOR OF NORTHERN RESIDENT KILLER WHALES (ORCINUS-ORCA) IN RELATION TO THE INSHORE DISTRIBUTION OF SALMON (ONCORHYNCHUS SPP) IN BRITISH-COLUMBIA, Canadian journal of zoology, 74(6), 1996, pp. 983-991
The hypothesis that northern resident killer whales (Orcinus orca) mov
e in response to the seasonal availability of salmon (Oncorhynchus spp
.) was tested using sightings and acoustic recordings of whales and da
ta on the timing and abundance of salmon in Johnstone Strait, off Vanc
ouver Island, between 1984 and 1988, and from King Island, on the cent
ral British Columbia coast, for a 2-month period in 1989. Whales were
most abundant in Johnstone Strait between July and October when salmon
migrate through the strait. Individual whales seen in the strait duri
ng summer were observed around King Island in spring 1989, coinciding
with local sockeye and chinook salmon runs. In Johnstone Strait during
summer 1988, whales foraged along the shore and in areas of strong cu
rrent, where salmon occur in high densities. However, less than half o
f the 16 pods in the northern resident community were present on more
than 15% of summer days (1984-1988). The occurrence of 6 pods (A1, A4,
A5, C1, D1, and H1) in Johnstone Strait during summer was positively
and significantly associated with sockeye and pink salmon abundance, w
hereas pod G1 was positively and significantly associated with chum sa
lmon.,Although we demonstrate an association between certain pods and
certain salmon species, we cannot determine whether this reflects the
true preference of pods or represents differences in the whales' arriv
al times in Johnstone Strait that are related to other factors. Our da
ta suggest that within the northern resident community, pods may have
seasonal ranges.