American eels, our only catadromous species, grow in river systems after hatching in the Sargasso Sea. Phytoplankton are the single celled plants upon which primary consumers such as small fish feed. The primary consumers are, in turn, preyed upon by carnivorous species, including many commercially-important fish and shellfish. Estuaries are formed where rivers meet the ocean and salt water is diluted by fresh. The input of nutrients, fresh water, and abundant food combine to provide unique, shallow habitats.
Estuaries provide sanctuary from the harsh action of ocean currents and waves.
These systems are often fringed by salt marshes and tidal flats and may contain valuable beds of subaquatic vegetation such as eelgrass and widgeongrass. As many as forty percent of commercially and recreationally important species of the Northeast depend on estuaries for some part of their life cycle. Salt marshes filter pollutants from streams and rivers protecting fragile estuarine nurseries, and they buffer shorefront property from wave and water damage during storms and floods. Striped bass and bluefish depend on these areas for food, while the prey species, such as killifish and silversides, use the channels and marsh interiors as habitat throughout their lives. Nontidal wetlands provide numerous indirect values to anadromous and estuarine fish resources.