Were they Carp or Suckerfish? a lot of people get the two mixed up, hell, some people call anything that feeds on the bottom a carp, like Squawfish.
I bet these are suckerfish people are seeing, almost every place holds Suckers, even some landlocked ponds.
And as far as ''getting rid of the Carp'' I can assure you that any fish Topbloke catches, will be put right back where it came from, Blue Lake seems to be filled mostly with smaller Carp around 8-12lbs. Carp fishermen are just always looking for places that could possibly hold bigger Carp, and Hagg looks like prime water for some 20-30lbers.
Topbloke, how about you try to pull another state record from the same place as the last 25lber (I wouldn't dare mention the name of this lake, probably end up finding them dead on shore), when Scott caught it, it was the only fish he had pulled out of the Lake, so I would imagine theres all sorts of shapes and sizes of carp in there. Yes people, there are state record carp for Oregon, only its a Carp Fishermens Group that qualifies them, not the actual state itself.