That is why salmon bury their eggs. Any eggs that are not buried get eaten by just about everything, including juvenile salmon. So the chance of survival for these eggs is just about zero if they're not underground. Suckers don't dig up salmon eggs to eat them. They just eat whatever is rolling along the bottom of the river.

I'm not sure what they are referring to when they say that suckers compete with salmonids in lakes and ponds. For the most part, salmonids don't inhabit lakes and ponds. They live in rivers and streams. They would certainly inhabit large lakes, but even then, competition is difficult to imagine. Most salmonids are pelagic (i.e., they inhabit the open water areas of a lake) while suckers are benthic (they inhabit the bottom of the lake). Not sure where the competition would occur, or if it does, how significant it might be.