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 The data below may be out of date.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

Herring Runs at Streams with Upstream Planned Fishway Projects

CTDEEP Inland Fisheries Division/ US FWS CT River Coordinator's Office

Alewife – Fish Counter
Queach Brook Mill Brook Greeneville Fishlift (Shetucket River)
2002 10,048 2,288
2003   4,198    335
2004   1,682    329
2005   1,790    592
2006     3,123   9,093 2,412
2007     1,318         99 2,422
2008     2,684       698    535
2009     3,477           9    186
2010   50,668   1,239    156
2011     4,476   9,080    248
2012        610 17,057    267
2013        563   9,137    713
2014     1,395   1,543    787
2015        538      134    502
2016     1,514      406 1,456
2017     3,308   8,522    735
– indicates no counting done.
Shad – Fish Counter
Greeneville Fishlift (Shetucket River)
2002 3,056
2003 4,573
2004 2,005
2005 1,767
2006 1,981
2007 2,453
2008 1,966
2009 1,927
2010 2,461
2011    992
2012 3,132
2013 3,800
2014 2,248
2015  1,919
2016  2,669
2017  1,910


River herring is a collective term for the alewife, Alosa pseudoharengus, and blueback herring, Alosa aestivalis, two anadromous fish species that are related to the American shad. Anadromous fish migrate from the ocean to rivers to spawn.  The coastal range of the alewife extends from northeastern Newfoundland to South Carolina, while that of the blueback herring extends from Nova Scotia to Florida. Both species undertake upriver spawning migrations during spring.  The American shad, Alosa sapidissima, is the largest of the herring family, and is a favorite Connecticut River sportfish. It also undertakes upriver spawning migration during spring. The historic range of American shad was from the St. Lawrence River to Florida. Shad are still distributed throughout their historic range but shad are most abundant in east coast rivers between Connecticut and North Carolina.


River herring and shad are important to our freshwater, marine and estuarine ecosystems because adult herring and their young provide food for a variety of predators including freshwater gamefish, marine gamefish, osprey, bald eagle, harbor seals, porpoise, egrets, kingfishers, and river otter. Historically, river herring runs into Connecticut rivers and streams numbered into the millions; however, runs have been declining steadily in recent decades. To help restore river herring populations and other anadromous fish, CTDEEP has built fishways at dams, removed dams, and widened culverts to allow fish to bypass barriers to find habitat upstream to spawn.


This group of streams has one fishway where fish are counted.  The amount of available habitat upstream of the fishway is expected to increase due to future fish passage projects (e.g. there are upstream dams that will have fishways in the future).  Because of this, the number of fish returning in the future will likely increase regardless of survival at sea.  These numbers can be used as an index of how restoration is progressing for each watershed over time.

All alewife counts were lower in 2014, indicating lower survival at sea.

Show/Hide Table

CT Fish Pass Map 2010

Juvenile American Shad. Photo by Richard Howard/Long Island Sound Fish Trawl Survey.

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