The answer is in the salt marsh.
The key is the difference between high and low tides and that the marsh flats, or the mud, which is home to vegetation, mollusks and other creatures is covered by water or uncovered by water during these daily tidal changes.
During the periods of high tide the mud flats are covered by water leaving the tops of the Spartina Grass exposed. Under the surface though, the young shrimp, minnows and crab thrive. All three of these species find nourishment in the nitrates and decaying grasses located here. They also find easy to hide from predators while they are in the grasses.
The bigger predators will cruise along the grass and oyster beds looking for the smaller creatures as the next snack.
Seasoned fishermen understand this behavior and will fish these areas.
This is one reason why the fishing in our area is so good.