The DNR and Marine Police you talk about are different agencies. The Maryland Natural Resourses Police (MNRP) has both an inland and marine side. The MNRP enforces fish and game laws in the State of Maryland. Maryland did a Marine Police about 20 or more years ago, but was changed to this system. The DNR most of you talk of is the Maryland Park Service as in Park Rangers. The Park Rangers patrol the State Parks, but also enforces fish and game law inside the parks. I guess it is hard to understand, since both are in the DNR department.
Freqs: 39.22 MNRP mostly marine side
151.205 statewide repeater mostly inland, but I think the boats are going to this freq
soon.
There is about four 37 MHZ freqs listed to the MNRP I don't have much knowledge on these, but think most are used on eastern shore.
The parks uses seven freqs in the 151mhz area
151.145 (used in Balt Co.), 151.310, 151.355, 151.250, 151.325, 151.415 (mostly used in Balt Co.), 151.460 mhz.
These park freqs change with the regions and parks. Also used one or two repeaters 159.450 activity in central MD and 159.425 I think this the right freq, but I haven't heard any traffic on.