That looks like a juvenile king

Malachilawrence: I did notice its dark gums, but it also had the distinctive slash under its throat. you can see it in the photo but it was even more noticeable in person.

That's a king. Trout don't have forked tails or black gums.

I agree with the others. That's definitely not a trout. Cutthroats have spots on their bodies from top to bottom. This one has silvery sides with no spots. The black mouth gives it away too. The slash on its throat looks like a wound, probably from a fish hook. It's in the wrong spot and is the wrong shape and color for a cutthroat.

Ya that is a Chinook possible small Blackmouth.

Definitely a juvenile chinook

Ok, I fold. It does seem to check all the chinook boxes. No need to keep piling on. =] I'm happy to know that there are still kings moving through the lake. He swam off like a bullet.

This is actually a great learning opportunity. If you are fishing lake Washington or Lake Sammamish and pick up a trout like fish with anything other than white gums, you're dealing with a salmon. The numbers of native chinook and especially coho spawning in the system are on the rise and this little fella is a great example of their efforts.

looks like a lingcod to me.

A chinook of that size is likely a resident of the lake. I would assume Lake Washington has a resident population of both Chinook and Coho as well as Sockeye (kokanee).

I am a fishery science major at UW and from the photo it appears that it is indeed a juvenile chinook. There are a small percentage of juveniles that will rear in the lake for 1-2 years before migrating out to saltwater. There is an even smaller percentage that spend their entire life in the lake. Please know the regs and return these salmon to the water safely as the Lake Washington chinook fishery is one of the most fragile in our state and one that causes implications on fishing seasons throughout Puget Sound.