You will also see this change as you travel from distant rivers and streams, which are fresh, toward the Bay. Besides fish that live here all the time, some ocean dwelling fish, like sad and rick fish, come here to spawn. These are called anadromous fish. Parts of the Bay and nearby stream sections have fresh water but are also influenced by the rise and fall of the tide. This tidal fresh regime contains spawning grounds for white perch and nurseries for rock fish and other species.
Some tidal water contains very little salt.
The amount of salt varies during the year and from year to year depending on rainfall. Because this constant change is stressful to plants, comparatively few species live in this oligohaline regime . Medium salty water comprises most of Maryland s part of the Bay and the lower parts of its tributary rivers and streams. This mesohaline regime supports almost all of the Bay s oyster bars. Many other animals live on the bars and support the ecosystem of the Bay, including blue crabs, snails, mussels, and fish.