Since I dont live in an area that supports dollies I dont catch them. If I do have the pleasure of catching a Dollie when I do fish rivers that support them I always release them.
The only fish I release into to the brush when I catch then are squawfish(nothern pikeminnow for the politcally correct) and smallmouth bass. Smallmouth are a non native species. Icatch a few in the South Santiam while fishing for summer steelhead. As for whitefsh, They are benificial to salmonoids. The smolts of slmon and steelhead feed on the eggs and fry of whitefish. Whitefish and suckers mainly feed on aquatic insects. They do feed on loose salmon and steelhead eggs when the oppurtunity arises. Steelhead and resisdent trout, Rainbows and cutthroats also feed on eggs and fry of salmon and steelhead. Do you see people killing trout because they are eggs eaters? No you dont.
Every fish has its place in a river system. What would happen to one species if another species is removed from the system. I dont think anyone has an answer for that. Im sure the result would not be very good the remaining species. Just think about that next time a pesty dollie, whitefish or sucker grabs your offering.