What freshwater species is in the most concern for extinction?

there are lots of threatened fish but as far as gamefish go, probably the white sturgeon in pacific coast rivers. a lot of them die below dams because of excessive nitrogen levels and the fish ladders put there for salmonids aren't suitable pageways. they can't reach their spawning grounds. they keep changing the limits every year to give them a chance but they are quite vulnerable to poachers. there used to be 20 footers in the columbia. now a 6 footer is considered big. actually, a 6 footer doesn't have all that much meat on it for a 6' fish. they are fairly slender.