If a round goby...the law requires it killed upon sight plain and simple (against the law to posses live). If a round goby it would be the nastiest invasive in the USA.
Again, location will rule out goby or not. Mouth just seems wrong for goby but not very large for sculpin IMO either.
First impression I got was round goby, but the head shape is a little off. Would def help if you could give location and maybe snap a pic from directly overhead. Maybe one from under too since gobies have a unique pectoral fin structure.