The Long Island Sound (LIS) is a productive body of water situated between New York and Connecticut, representing one of the largest estuaries in the United States. This environment supports a high level of biodiversity, hosting over 170 different species of fish and countless invertebrates. The LIS supports a marine ecosystem and popular recreational fishing activity. The fish found here reflect the unique blend of ocean and riverine influences that define the Sound’s habitat.
Defining the Long Island Sound’s Environment
The LIS is classified as a complex estuary, a partially enclosed coastal area where freshwater runoff mixes with Atlantic Ocean saltwater. Salinity levels vary across the Sound, typically ranging between 27 and 32 parts per thousand, with lower concentrations near the mouths of major rivers like the Connecticut River. Water temperature is subject to significant seasonal shifts, dropping near freezing in the winter and warming up to 22°C or more in the summer.
The bottom of the Sound is not uniform, featuring diverse substrates that support varied fish communities. These bottom types include fine organic silts, mud, sand, gravel, and extensive rocky reefs. These characteristics determine which species can survive in the LIS throughout the year and which ones rely on seasonal migration. The environment provides distinct zones for both demersal (bottom-dwelling) and pelagic (open-water) species.
Year-Round Residents and Bottom-Dwelling Species
A number of fish species remain within the LIS environment throughout the year, often associated with the sea floor. One well-known bottom-dweller is the Winter Flounder (Pseudopleuronectes americanus), a demersal flatfish. Adult flounder migrate from deeper offshore areas in the autumn to spawn in shallow, inshore bays and estuaries during the winter and early spring. They prefer bottom habitats composed of sand, mud, or gravel, sometimes burying themselves partially in the sediment.
Another prominent resident is the Tautog (Tautoga onitis), commonly called Blackfish, which is sought after by recreational anglers. Tautog are associated with hard, structural habitats like rocky reefs, submerged wrecks, jetties, and mussel beds. They use their powerful, blunt teeth to crush the shells of their prey, mainly crabs, mussels, and clams. Younger tautog often find refuge in eelgrass meadows before moving to the rocky outcrops preferred by adults.
A smaller relative of the Blackfish is the Cunner (Tautogolabrus adspersus), a year-round resident of rocky reef communities. Cunner inhabit inshore waters near the seafloor, utilizing areas with bottom relief such as pilings and rock outcroppings. These fish become inactive and enter a state of winter dormancy (torpor) when water temperatures fall below about 5°C. The Cunner’s smaller size and pointed snout distinguish it from the Tautog.
Seasonal Visitors and Highly Mobile Species
The LIS serves as a temporary, nutrient-rich feeding ground for numerous mobile species that migrate into the Sound during the warmer months. The Striped Bass (Morone saxatilis) is a popular migratory sport fish that arrives in the spring as part of its annual movement north along the Atlantic coast. Many adult bass found in the Sound have recently spawned in the Hudson River before moving eastward. They remain in the Sound until cooling water temperatures trigger their southward migration, typically beginning in the fall.
Bluefish (Pomatomus saltatrix) are another seasonal visitor, arriving in the LIS in the spring to feed and spawn, remaining through the summer and fall. Known for their powerful jaws and razor-sharp teeth, these aggressive predators are often responsible for the chaotic surface feeding known as a “bluefish blitz.” Their migratory patterns are closely linked to the distribution of their primary food source, the Atlantic Menhaden.
The Atlantic Menhaden (Brevoortia tyrannus), often called Bunker, is an oily, schooling fish considered a foundational forage species. Menhaden are filter feeders that strain plankton from the water column, arriving in the Sound in late spring and early summer. Their abundance is a major factor in drawing in predators like Bluefish and Striped Bass, which rely on them for sustenance.
Other species also make seasonal appearances, including Scup (Stenotomus chrysops), often called Porgy, which migrate into the Sound during the warmer months and are a popular recreational target. Weakfish (Cynoscion regalis), a temperate species, can be found in the LIS, with variable abundance in recent years. The timing of these migrations is dictated by the need to find optimal water temperatures and sufficient food resources.