Ecosystem Targets and Supporting Indicators

River Miles Restored for Fish Passage

Open 200 additional miles of fish riverine migratory corridors in the Connecticut and New York portions of the watershed by 2035 from a 2014 baseline of 307.76 miles.

View Implementation Actions for River Miles Restored for Fish Passage

Show/Hide Table Data

River Miles Restored for Fish Passage
River Miles per YearCumulative Miles
Opening 200 miles of fish passage
Miles ReconnectedCumulative Miles Reconnected to the TargetPercentage of 2035 Target (200 Additional Miles)
2014 (baseline)000
Percentage of Potentially Passable Rivers Reconnected 1998-2022
YearRiver Miles RestoredCumulative Restored MilesTotal Passable MilesPercentage Passable of Total Potentially Passable Rivers Reconnected
1998 3.13.11096.458.99%
199923.4 26.51119.860.25
2000 11.1437.641130.9460.85

Status and Trends

This target is ahead of schedule. In order to meet the 2035 target, an average of 5.8 stream miles per year from 2015-2034 need to be reconnected to restore 200 stream miles for fish passage to Long Island Sound. The initiative has so far reconnected 129.4 river miles, an average of 12.9 stream miles a year since 2015, and is 64.7  percent of the way toward meeting the target.

When the Fish Passage Initiative began in 1998, a total of 1,858.50 miles of all the rivers and streams in Connecticut were potentially passable. This represents the total river and stream mileage known/thought to have supported anadromous fish at some point in history. In 1998, 58.99% of all rivers and streams in which fish could swim upstream were passable. As of 2022, 82.12% of potentially passable river miles were reconnected. Since 1998, we have restored 432.9 river miles, constituting a 23.13% increase. Data on the rivers, streams, and barriers is consistently being updated. These calculations are subject to addition, removal, and reclassification to best reflect the current state of knowledge.

4.20 new stream miles were reported opened in 2023, due to the Post Office Dam Removal, Whitford Pond Dam Fish Passage, and Strong Pond Dam Removal, CT. Two projects, a fishway and a dam removal, with the potential to open fish passage, were completed in Connecticut in 2021. These projects will not result in opening fish passage to Long Island Sound until barriers at downstream dams are removed. One of these projects, a fishway at the Upper Collinsville Dam in Canton, will open up 32 stream miles  when the barriers are removed.

Trends in populations of diadromous fish that would benefit by reopening of fish migratory corridors are not tracked by the LISS, but the Connecticut Department of Energy and Environmental Protection (CT DEEP) and other partners keep track of population trends through the use of electronic fish counters, video surveillance, volunteers, and other means. LISS has supporting indicators compiled by CT DEEP of spawning runs in Long Island Sound tributaries that track populations in rivers that have completed all fish passage projects and those rivers where projects are still being proposed (see sidebar).

Fish count data also can be found at the Connecticut River Salmon Association website and in the 2016 U.S. Fish and Wildlife Service Connecticut River annual report.


It is difficult to determine trends in stream miles reconnected. The number of miles reconnected from a single fishway or dam removal has nothing to do with the size of the dam, cost of the project, or river where the project is located. Furthermore, past performance of the restoration partners in terms of annual (or averaged) stream miles reconnected has no bearing on miles that will be reconnected in the near or distant future.

In the last decade, there has been spikes in reconnected stream miles in some years and lulls in other years, which can be attributed to funding support. When a large funding source becomes available, the restoration partners focus on engineering and permitting for numerous projects. During these years we see lulls in miles reconnected, but the partners are generally busy with planning for larger-scale and expensive projects. Many of these are completed within a year or two of each other, and that’s when we see these spikes in miles reconnected (2007, 2012-2013, and 2016).

How is This Target Measured?

The LISS Habitat Restoration Coordinators at CT DEEP  and the New York State Department of Environmental Conservation (NYSDEC) track riverine migratory corridor restoration projects that are in progress within the watershed, led by various partners, and report the total stream miles reconnected annually.

This target will be attained by reconnecting, either through dam removal or other fish passage methods, an additional 200 miles of riverine migratory corridors (RMC). The 2014 baseline is 304.56 reconnected riverine migratory corridor miles in Connecticut and 3.2 reconnected riverine migratory corridor miles in New York. For context, there are an estimated 1,850 total riverine migratory corridor miles in Connecticut, more than half of which are dammed or otherwise not passable for fish. The length of New York’s total riverine migratory corridor miles within the Long Island Sound watershed has not been estimated but is much smaller. The Habitat Restoration and Stewardship Work Group track fish passage projects that are in progress within the watershed by various partners and reports the total miles reconnected annually.

[Note: 307.76 miles is currently the 2014 baseline, but is also subject to change as new GIS data for older fish passage projects become available].


Riverine Migratory Corridors, rivers, and streams that connect Long Island Sound to inland habitats that are a necessary part of the life cycle of diadromous fish species must be cleared of obstructions, and kept clear, in order to connect fish with their historic spawning grounds.

Diadromous species of fish are a critically important part of the LIS food web. Adults are eaten in large numbers by birds of prey such as eagles and osprey, while juveniles are a primary source of food, seasonally, to other small fish and smaller coastal birds. Commercially important species such as salmon, bluefish, and striped bass (some of which are anadromous themselves) also depend heavily on smaller anadromous species as a food source, such as alewife, blueback herring, and the catadromous American eel.

Additional Information

The Long Island Sound Study has a database to track and describe every restoration project in the Connecticut and New York portions of the Long Island Sound watershed since 1998.

Diadromous species can be further divided into two primary groups: (1) catadromous, or those which migrate downstream, from inland freshwater systems to spawn in the ocean – the only example in LIS is the American eel (Anguilla rostrata); and (2) anadromous, or those which migrate upstream, from ocean to inland freshwater systems for spawning. Anadromous species in LIS are:

  • alewife (Alosa pseudoharengus)
  • blue-back herring (Alosa aestivalis)
  • sea lamprey (Petromyzon marinus)
  • American shad (Alosa sapidissima)
  • gizzard shad (Dorosoma cepedianum)
  • hickory shad (Alosa mediocris)
  • brown trout (Salmo trutta)
  • eastern brook trout (Salvelinus fontinalis)
  • rainbow smelt (Osmerus mordax)
  • white perch (Morone americana)
  • Atlantic sturgeon (Acipenser oxyrhynchus)
  • Atlantic salmon (Salmo salar)
  • shortnose sturgeon (Acipenser brevirostrum)

Depending upon the species, the riverine migratory corridor may provide the actual spawning habitat, or may simply provide the necessary access to spawning habitat (e.g., a wetland or lake).


Victoria O’Neill, NYSDEC
[email protected]

Harry Yamalis, CT DEEP
[email protected]

Source of Data

CT DEEP, NYSDEC, and Long Island Sound Study Partners


  • The technical explanation on how the target was selected is found in Appendix B of the Comprehensive Conservation and Management Plan.
  • 307.76 miles is currently the 2014 baseline, but is also subject to change as new GIS data for older fish passage projects become available. The 2015 CCMP had listed the 2014 baseline as 317 miles.

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