Hi Guy's...
The Susky Flat's is fresh water. However, 2 years ago when we had the drought, Trout and drum fish along with 4 lb. bluefish were caught on a regular basis because of the salt moving up so far.
The Susquehanna River is the main water feed for the flats, along with the North East River as a second source. The runoff from Penna empties into the upper Susky then through the Conowingo Dam then to the flats and so on...On a normal basis, the brackish water starts around Pooles Island, which is about 15 miles south of the flats. Give or take a little...Depends on the water flow...
Conditions change but for the most part the above holds true...in a normal year...
Thanks...
Bruce
Cisco651
North East Md.