The Atlantic Silverside (Menidia menidia) is found in the shallows of the Hudson River estuary and other tidal rivers and creeks in southeastern New York, and Long Island from the spring to the fall. They move out away from the shorelines and enter deeper water in the Chesapeake Bay during the winter.
The Atlantic Silverside is a small fish, approximately 3 to 6 inches in length. The upper sides are translucent green-yellow, gradually turning iridescent white on the sides to pale white on the underside. A metallic-silver stripe, bordered by a thin, dark line, runs along the length of the fish. The lateral line is composed of tubes passing through the lateral line scales. The posterior end of the dorsal fin is in front of the posterior end of the anal fin and the tail is forked. The eggs are small and transparent yellow-green in color with tiny filaments. These filaments help the eggs adhere to aquatic vegetation located along shorelines and to each other.
Atlantic Silversides are short-lived, generally dying in the winter after they spawn, although several two-year-old fish have been caught. Spawning generally occurs during the day at high tide and is centered around the lunar cycle, roughly starting during the first new or full moon phase of the spring. Between 5 and 20 spawning events can occur throughout the season, every 15 days or so, with individual females releasing up to 5,000 eggs total. Incubation time depends on water temperature, with eggs laid in higher temperatures hatching earlier than those laid in cooler temperatures.
Atlantic Silversides feed in schools during the ebb tide on plankton composed of various amphipods, copepods, isopods, and insects. They are quick swimmers and to avoid predators, they form large schools and flee when approached. They will often hide in bay grass.