Wouldn't dream of taking a cent for helping out if I could. Besides being wrong, these acts are getting dangerous and could lead to a serious accident. My family and friends drive these very same roads and could someday become victims of this lunacy, so I'd be very happy for the idiot responsible to be caught.
Any addtional info that you can post about each incident would be a very good thing. The more details the better. Someone in the local rec. / comm. fishing or boating community knows the individual(s) who are doing this. With more information about the particulars, (when, where, how, time, day, etc.) somebody might be able to "connect the dots" and bring this to an end.
Good fishing and stay safe.