You can only do that if you are the government. They poisoned one lake in order to get rid of the Northern Pike that some idiot put in there. Didn't work and eliminated the towns water supply to boot.
In which case, the problem is that you have too many people voting for salmon and not enough voting for water.
Eventually your neighbors will figure it out, I guess. Hopefully that'll happen before you all are paying $200 a month for drinking water, but when it gets painful enough, people will start wondering exactly how much the stupid salmon is really worth to them. Personally, I'd say "zero", but that's just me...