Photos of the Long Island Sound

Research & Monitoring


The Long Island Sound Study has launched a new version of the Environmental Indicators section. The data below may be out of date. Please visit and bookmark the new section here to see the most recent data.

Status and Trends: LISS Environmental Indicators


Watershed Population

This indicator uses US Census data to track the population living within the Long Island Sound watershed. View Indicator

Impervious Cover and Stream Health in Long Island Sound Basins

The indicator tracks the expansion of impervious cover (surfaces such as sidewalks and parkling lots) in the watershed. The impervious cover model predicts expected stream quality of a basin based on watershed impervious cover. View Indicator

Eelgrass Abundance

Eelgrass is a rooted underwater grass that grows along the coast, serving as an important habitat for fish and source of food for many migratory birds. It is sensitive to declines in water and sediment quality, so serves as an indicator for overall health of the aquatic environment. View Indicator

Changes in Forest Cover in CT & NY

According to research from the University of Connecticut’s Center for Land Use Education and Research (CLEAR), forested land in the late 20th and early 21st century declined by 6 percent n New York and Connecticut from 1985 to 2006. View Indicator

Piping Plovers

Piping plovers are small shorebirds that nest on the beaches of Long Island Sound. The abundance of breeding pairs reflects availability of beach nesting habitat and management efforts to protect nesting pairs from human intrusion, storm tides and predators. View Indicator

Least Terns

The least tern is the smallest of American terns. They are migratory birds that breed along marine and estuarine shores of the United States. Their abundance indicates the quality of coastal habitat and quantity of forage fish available for food. View Indicator

Shad & Blueback Herring—Long Island Sound

Abundance of American shad and blueback herring, as reported in the Long Island Sound Trawl Survey. View Indicator

Sediment Quality Index

This index indicates the extent and severity of contaminants such as PCBs, hydrocarbons, metals, and pesticides in seafloor sediments throughout Long Island Sound. View Indicator

Game Fish

The abundance of game fish is a reflection of the productivity of Long Island Sound and the effectiveness of coast-wide fishery management plans that seek to stabilize populations while maximizing harvest opportunities. View Indicator

Finfish Biomass Index/Species Richness

Fish biomass indicates the productivity of the Long Island Sound fishery. Species richness measures the diversity of species supported within the Sound's various habitats. View Indicator

Forage Fish – Open Water/NY and CT Coastlines

The forage indices measures the productivity of small fish in the Sound, which is the basis of the food supply for larger fish, including game fish. View Indicator

Index of Anadromous Fish Runs

These counts of river herring and shad in Long Island Sound tributaries indicate the quality of upstream habitat that has been opened up as a result of completed fishway projects. View Indicator

Approved Shellfish Acreage

This measure indicates whether water quality conditions in tidal rivers and coastal waters can support recreational and commercial shellfishing of oysters and clams. View Indicator

Lobster Abundance

Lobster has historically been an important fishery in Long Island Sound but populations have declined in recent years. This indicator is a fisheries-independent estimation of their abundance in the Sound. View Indicator

Horseshoe Crab Abundance

This indicator shows the abundance of Horseshoe Crabs in Connecticut and New York. View Indicator

Beach Closures and Advisories

Beaches are closed when high abundances of pathogens (bacteria or viruses) are detected or when heavy rainfall results in a high risk of increased pathogens. A large number of beach closure days can be an indicator of a problem with pathogen contamination or of an unusually wet year. View Indicator

Water Quality Index

The water quality index is a calculation that combines several water quality measurements to rate overall water quality in Long Island Sound on an annual basis. View Indicator

Western Sound Spring Bloom Chlorophyll a Concentration

Chlorophyll a is the green pigment in plants, and the concentration in surface water is an indicator of the amount of microscopic plants (called phytoplankton). This indicator is intended to characterize the spring phytoplankton bloom conditions in the western Sound each year. View Indicator

Duration of Hypoxia

Hypoxia is a condition that occurs in bodies of water as dissolved oxygen concentrations decrease to levels where organisms become physically stressed and ultimately cannot survive. Duration of hypoxia refers to the number of days in a year during which hypoxia was observed in Long Island Sound. View Indicator

Area of Hypoxia

Hypoxia is a condition that occurs in bodies of water as dissolved oxygen concentrations decrease to levels where organisms become physically stressed and ultimately cannot survive. The area of hypoxia in Long Island Sound refers to the number of square miles in which dissolved oxygen concentrations were less than 3 mg/L over the course of a single year. View Indicator

Land Use Along 300-foot River Corridors in Watershed

The amount of naturally vegetated (e.g. trees, shrubs, wetlands, and grasslands, but not turf grass or agriculture) land in the riparian zone immediately adjacent to a stream or river is an indicator of hte health of the waterbody. View Indicator

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