I am on a discovery kick, locating and surveying ponds in the metro area that might hold fish such as bass and perch. I have come across quite a few that have tons of polywogs and a lot of crayfish, yet I see little vegetation and no signs of obvious fish activity. Because I'm surveying so many ponds, I don't have time to fish all of them for several hours to see if they have fish in them. What other factors would lead you to believe that a pond/lake would be productive or do I just have to bite the bullet and throw in a line? Many lakes look dead to me (such as the Wash Park ponds in Denver), yet I'm told there are fish in them. I know very little about successful pond ecology, despite having been a biology major in college.