I dove the Fleetwing in Door county in October. The bottom was literally carpeted with Gobies. I think they are eating the zebra mussels. There are alot of empties(zebra's) and I observed the gobies sucking up the schells and spitting them out. If they are eating the zebras that would explain thier population explosion, the empty shells and the degrading viz we seemed to have this year. I think the gobies will be around for awhile, but like the zebra's they will outstrip thier food supply and nature will find an equalibrium.
As a diver, settle down on the lake bottom and remain as still as possible. After a few minutes the gobies will resume thier activities as if you aren't there. Some will gather around and watch the large bubble emitting object in thier midst. There will be a few who will stake out an area the size of a pie plate and defend it. Great fun to watch. I spent an hour more then once at the deep section of the Fleetwing just watching them interact with each other.
Getting back to the original question. There's not enough fish in a single gobies to make it worth the effeort to spear. At best, if you could net a few hundred and clean them like smelt, deep fry those little suckers in a beer batter, you might have something. With a little luck the salmon, bass, northern pike or perhaps muskies may decide that gobies taste good. That would trim thier numbers pretty fast. In the end, only Ma nature knows for sure.
Jim