Photos of the Long Island Sound

Research & Monitoring

Status & Trends

LISS Ecosystem Targets and Supporting Indicators

Index of Anadromous Fish Runs

( Click labels in legend to hide data and adjust scale )
Alewife – Fish Counter
Mianus River Bride Brook* Latimers
2002
2003 117,150
2004   81,350
2005      1,198   68,757
2006      6,515 129,114  1,654
2007    81,854   66,975     903
2008    80,906   76,108   2,556
2009    22,979   74,839 no data
2010    93,077 164,149   2,560
2011    66,521 196,996   2,679
2012  119,335 287,003  22,154
2013    69,074 363,224  33,065
2014    49,081 265,969  17,003
2015     4,313 218,076    4,926
2016 11,940 148,596 4,226
2017 19,242 386,325 5,675
2018 32,961 395,026 16,210
– indicates no counting done.*Bride Brook run was enumerated by hand counting 2003 and 2004
Blueback Herring – Fish Counter
CT River Mianus River Bride Brook Latimers
1967 356
1968   –
1969   –
1970 188
1971 302
1972 188
1973 302
1974 504
1975 1,600
1976 4,785
1977 32,492
1978 40,765
1979 39,895
1980 197,950
1981 419,734
1982 586,808
1983 454,247
1984 482,954
1985 632,255
1986 517,521
1987 358,607
1988 343,361
1989 286,537
1990 392,157
1991 412,344
1992 312,863
1993 103,465
1994  31,843
1995 112,124
1996 55,011
1997 63,945
1998 11,146
1999   2,699
2000 10,587
2001 10,602
2002 1,939 not present not present
2003  1,392
2004     151
2005     534   3,386
2006       21   1,402
2007       75 12,463
2008       84 13,309
2009       39   9,563
2010       76   7,028
2011     138  25,753
2012       39  13,212
2013     976  27,810
2014     647  29,424
2015       87           0
2016    137 3,455
2017    875 4,807
2018 1,060 8,202
‘ – ‘  no counting done.
American Shad
CT River
1967 19,484
1968 24,693
1969 45,349
1970 65,751
1971 52,719
1972 25,572
1973 25,104
1974 53,147
1975 110,000
1976 346,725
1977 202,997
1978 145,136
1979 255,753
1980 376,066
1981 377,124
1982 294,842
1983 528,185
1984 496,884
1985 487,158
1986 352,122
1987 276,835
1988 294,158
1989 354,180
1990 363,725
1991 523,153
1992 721,764
1993 340,431
1994 181,038
1995 190,295
1996 276,289
1997 299,448
1998 315,810
1999 193,780
2000 225,042
2001 273,206
2002 374,534
2003 286,814
2004 191,555
2005 116,511
2006 154,745
2007 158,807
2008 153,109
2009 160,649
2010 164,439
2011 244,177
2012 490,431
2013 392,967
2014 370,506
2015  412,656
2016 385,930
2017 536,670
2018

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 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 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 over 80,000 annually. This is one of the strongest alewife runs in Connecticut and other species like gizzard shad, 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 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 three years, the run size has increased annually. The 2013 run of alewives was the largest on record and it now appears that the pipe replacement  has resulted in the increase.

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 fishlifts 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 fishlift 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.

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

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