Can one tell the difference between coho and pinks without looking in their mouths?

Yes, Humpies have really small scales,that come off on everything,and they also have large oval spots on their entire tail.

The spots on the back and tail are much thicker on a pink. Plus, the scales are smaller.

Yes.

In saltwater it can be a little more difficult.

Pinks will have much smaller scales, and large oval spots covering both lobes of the tail. They may be hard to see so look carefully.

Once both species start to mature and enter the river, the differance is pretty obvious.

Pinks have really small scales with oblong spots on the tail. There backs have a blue tint.

Silvers have small spots on the back, average size scales, and silver pigment in the tail. Very few spots on the tail.

Good advice all!

I'll stray from the subject matter a bit and point out that coho's have more teeth but the pinks, despite their lack of teeth, are not snaggers.

Thanks all!! I must have caught silvers today then.

Aside from all the visual hints here, like Plunker says you can tell the difference with your eyes closed. Rake a bare finger down the jaw of a coho (outward, towards the nose) and you'll chew your finger up pretty nicely.

The humpy males start to get that "hump" just behind their head as well.

Coho also have a silver shine to their tail while pinks have little or non.

Cool, what river did you find them in?

the river starts with the letter p and ends the same

Pinks are slimey, slimey, slimey. Coho aren't.