Species: Balaenoptera physalus
Encyclopedia of Puget Sound

A large dark gray to brownish black baleen whale; narrow V-shaped rostrum has a prominent median ridge; dorsal fin is angled strongly rearward, located about one-third the body length forward from the fluke notch, and is followed by a distinct dorsal ridge that extends to the tail; throat has numerous longitudinal grooves; many individuals have a whitish chevron on each side of the back above the flippers; right lower lip and right front baleen are whitish, left lower lip is dark and remainder of baleen is streaked with yellowish white and bluish gray; flippers are fairly long and narrow; baleen is up to 72 cm long; two nostrils; grows to about 26.8 m, females reaching larger sizes than males (Leatherwood and Reeves 1983).
Articles:
Fin whales are the second-largest species of animal on the planet. Their occasional presence in the Salish Sea is notable because they are rare and listed as Endangered federally and in Washington State. Sightings today are considered most likely to occur in the Strait of Juan de Fuca, which is closest to their migration route on the outer coast.

The reasons for the surprise visits are unknown, but changes in environmental conditions here or elsewhere are one possibility.

A 2013 article in the journal Animal Conservation compares the effects of increasing anthropogenic noise to habitat loss for endangered fin, humpback and killer whales in the Salish Sea.

Classification
Mammalia
Cetacea
Balaenopteridae
Balaenoptera
NatureServe
Classification
Ecology and Life History
A large dark gray to brownish black baleen whale; narrow V-shaped rostrum has a prominent median ridge; dorsal fin is angled strongly rearward, located about one-third the body length forward from the fluke notch, and is followed by a distinct dorsal ridge that extends to the tail; throat has numerous longitudinal grooves; many individuals have a whitish chevron on each side of the back above the flippers; right lower lip and right front baleen are whitish, left lower lip is dark and remainder of baleen is streaked with yellowish white and bluish gray; flippers are fairly long and narrow; baleen is up to 72 cm long; two nostrils; grows to about 26.8 m, females reaching larger sizes than males (Leatherwood and Reeves 1983).