Northwest Fishing Reports

The chinook is blue-green or purple on the back and top of the head with silvery sides and white ventral surfaces. It has black spots on its tail and the upper half of its body. Its mouth is often dark purple. Adult fish range in size from 33 to 36 in (840 to 910 mm) but may be up to 58 inches (1,500 mm) in length; they average 10 to 50 pounds (4.5 to 23 kg) but may reach 130 pounds (59 kg). The current sport-caught World Record is 97.25 pounds (44 kg) and was caught in May 1985 by Les Anderson in the Kenai River (Kenai, Alaska). The commercial catch world record is 126 pounds (57 kg) caught near Rivers Inlet British Columbia in the late 70's.

http://en.wikipedia.org/wiki/Chinook_salmon

also look for a black stripe running from tip to tip of the tail and a pungent fishy smell