I think they use Cod for most of the year? (which IMO is a better fish for fried fish anyway but that's a different story)
The absolute best fish and chips (well....at least IMHO) is at the Sportsman Pub in Pacific City. Most of the year (just so long as the dories can get out) they serve fresh line caught ling cod. As firm as but much more moist than halibut. And reasonable as hell. But then, Sporty’s is the best kept secret in the PNW......
They only have halibut at specific times during the year now. Usually it's cod. Halibut is WAAAAY better in my opinion. It's just so damn expensive though.