Leeches are common to a lot of OP waters, including lakes (Ozette) and rivers (Wishkah, Satsop and others). See them sometimes on late coho in the Grays Harbor streams, seems to me mostly on dark fish that have been in the river for a while. Good reason to release them without bringing them into the boat. Leeches are an annelid worm, and while they are heinous little bloodsuckers, they are eaten by fish -- leech patterns are very effective flies for trout on eastside lakes.