Boaters in all three states felt that polluted runoff was more of a threat to lakes and streams than were exotic species. In Wisconsin and Ohio, Industrial pollution, fish contaminants, faulty septic systems, and habitat loss were also more of a concern than exotic species.n order to determine if boaters perceived exotic species as a threat to their lakes and streams, they were asked to rank a variety of possible threats. Only in Minnesota did exotic species rank among the top three concerns.