Ecosystem Targets and Supporting Indicators

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.

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Alewife - Fish Counter
Mianus RiverBride Brook*Latimers
2002---
2003-117,150-
2004-81,350-
20051,19868,757-
20066,515129,1141,654
200781,85466,975903
200880,90676,1082,556
200922,97974,839no data
201093,077164,1492,560
201166,521196,9962,679
2012119,335287,00322,154
201369,074363,22433,065
201449,081265,96917,003
20154,313218,0764,926
201611,940148,5964,226
201719,242386,3255,675
201832,961395,02616,210
20196,030296,70326,390
- indicates no counting done.*Bride Brook run was enumerated by hand counting 2003 and 2004.
Blueback Herring - Fish Counter
CT RiverMianus RiverBride BrookLatimers
1967356---
1968----
1969----
1970188---
1971302---
1972188---
1973302---
1974504---
19751,600---
19764,785---
197732,492---
197840,765---
197939,895---
1980197,950---
1981419,734---
1982586,808---
1983454,247---
1984482,954---
1985632,255---
1986517,521---
1987358,607---
1988343,361---
1989286,537---
1990392,157---
1991412,344---
1992312,863---
1993103,465---
199431,843---
1995112,124---
199655,011---
199763,945---
199811,146---
19992,699---
200010,587---
200110,602---
20021,939-not presentnot present
20031,392-not presentnot present
2004151-not presentnot present
20055343,386not presentnot present
2006211,402not presentnot present
20077512,463not presentnot present
20088413,309not presentnot present
2009399,563not presentnot present
2010767,028not presentnot present
201113825,753not presentnot present
20123913,212not presentnot present
201397627,810not presentnot present
201464729,424not presentnot present
2015870not presentnot present
20161373,455
20178754,807
20181,0608,202
20195,11321,916
- no counting done.
American Shad
CT River
196719,484
196824,693
196945,349
197065,751
197152,719
197225,572
197325,104
197453,147
1975110,000
1976346,725
1977202,997
1978145,136
1979255,753
1980376,066
1981377,124
1982294,842
1983528,185
1984496,884
1985487,158
1986352,122
1987276,835
1988294,158
1989354,180
1990363,725
1991523,153
1992721,764
1993340,431
1994181,038
1995190,295
1996276,289
1997299,448
1998315,810
1999193,780
2000225,042
2001273,206
2002374,534
2003286,814
2004191,555
2005116,511
2006154,745
2007158,807
2008153,109
2009160,649
2010164,439
2011244,177
2012490,431
2013392,967
2014370,506
2015412,656
2016385,930
2017536,670
2018281,232
2019

WHAT ARE THESE SPECIES?

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.

WHAT DOES THIS INDICATE?

This group of streams has one fishway where fish are counted.  The amount of available habitat upstream of the fishway is not expected to increase due to future fish passage projects (e.g. no more upstream dams or all upstream dams are currently passable).  Because of this, the number of fish returning year-after-year will likely be due to changes in survival at sea rather than major changes in freshwater.  These numbers can be used as an index for how the species are doing at sea or in general.

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.

STATUS

Mianus Pond Fishway – This fishway was built by the Town of Greenwich in the mid-1990s and is located at the head of the tide on the Mianus River. It provides access to the large Mianus Pond and a short distance of free-flowing stream prior to reaching the next dam. When it first opened, only hundreds of Alewives moved upstream. After years of being able to spawn in the pond, the Alewives now number in the tens of thousands annually. This is one of the strongest Alewife runs in Connecticut and other species like Gizzard Shad, Sea-run Trout, and Blueback Herring also use the fishway. The data on Blueback Herring is relatively recent but it is believed to be increasing. The Town operates an electronic fish counter and an underwater camera to obtain these data.  There are also two eel passes at this dam to help American Eels get upstream. The Town provides tours upon request.

Bride Brook – This stream flows out of Brides Lake and enters Long Island Sound about a mile downstream at Rocky Neck State Park.  The lake is a natural coastal pond where the Alewives spawn.  The CTDEEP operates an electronic fish counter and a trap at the head of the brook where it flows out of the lake. The trap is on property that is part of a state prison and is closed to the public.  This run has been the subject of research in the 1960s and again in the 2000s, some of which is ongoing.  The run is one of the best in the state and the trap is used to capture fish for transplanting into other streams to accelerate the pace of restoration.  A project during 2010 at Rocky Neck State Park replaced rusting, inadequate pipes with a new open channel.  During the subsequent years, the run size has increased, likely due to the fact that more fish can enter the brook due to the new channel.  This site remains the strongest run of Alewives in Connecticut.

Latimers Brook – This fishway is one of the oldest in Connecticut and was originally built to trap returning sea-run trout. Small numbers of Alewives were transferred from Brides Brook in the 1980s and 1990s and the fishway was modified and a small but stable run of Alewife was created. A trap was installed to help biologists capture returning trout and this trap is also used to count returning Alewives, which are then released upstream of the fishway.

Connecticut River – The counts of returning diadromous fish are obtained at the first dam on the river at Holyoke, MA. The dam is 33 feet high (hydroelectric project) and there are two multi-million dollar fish lifts operated by the City of Holyoke. The fish are counted visually by staff of the Massachusetts Division of Wildlife using a window in the side of the fish lift exit flume. There are four additional dams with fishways located on the Connecticut River upstream of the Holyoke Dam as well as others on upstream tributaries. More fishways and dam removals are planned as well as improvements to existing fishways. Therefore, the number of fish returning each year is a function of successful reproduction and survival in the river years earlier as well as survival rates in the ocean.

Run sizes continue to vary from year-to-year and from site-to-site.  The Connecticut River counts of Blueback Herring extend back far enough to show the drastic decline after the mid-1980s and show that despite occasional increases in numbers in 2018, the run size is still way below what it used to be.  The counts at Mianus, Bride and Latimers Brook do not go back far enough to document those ‘better times’ and when those counts increase in a year, the term ‘good year’ must be used advisedly. In the fall of 2018, the New England Fisheries Management Council closed some nearshore fisheries of Atlantic Herring, which had been incidentally catching river herring when they were in the ocean.  It is hoped that this action may result in some improved runs to Long Island Sound tributaries.

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