Most of the catfish in the Willamette and Multnomah Channel (MC) are bullhead. I catch them on accident fishing for sturgeon or walleye. They are usually really fat. Once a year or so I catch a channel cat in the river. They are always healthy and fat too but there just do not seem to be that many of them around. I do not know of any place around here where channel cats are prevalent. I think that sturgeon mostly hold that spot in the food chain and outcompete the channel cats. Plus, the pikieminnows also would be a competitor for smaller cats.
Also, I am in agreement with Billl. I would not eat a resident fish out of the MC. It is downstream from the Portland harbor superfund cleanup site. Check page 16 of the ODFW regulations under health advisories.