- Scientific name: Alosa sapidissima
- Species of Greatest Conservation Need (MA State Wildlife Action Plan)
Description
American shad (Alosa sapidissima)
The American shad is the largest member of the herring family found in Massachusetts waters, commonly reaching a length of 46-61 cm (18-24 in). It has more gill rakers (59-75) than all of the other herrings except the gizzard shad. American shad are anadromous and classified as fluvial specialists while in freshwater. They are tolerant of warm waters as adults will remain in freshwaters until July and juveniles spend their first summer in freshwater only entering the sea in late fall as river temperatures decline.
Life cycle and behavior
The species is anadromous, ascending coastal rivers to spawn in spring, and often migrating long distances up major rivers such as the Connecticut and Merrimack. After spawning, adult American shad migrate back to marine environments. The young form large schools and feed in freshwater until they grow to about four inches, then migrate to the sea and enter saltwater before winter. Adult American shad eat a wide variety of zooplankton, shrimp, and small fishes. In freshwater, the adults eat little and only occasionally feed on small prey. The young-of-the-year feed on small midwater copepods, ostracods, and insects while in freshwater. American shad first spawn at the age of four or five years, and adults may live to 10 years of age.
Population status
The Connecticut and Merrimack River American shad populations are considered under restoration due to habitat degradation, limited access to historic spawning and rearing areas, and abundance lower than the management plan target. However, the populations are considered stable enough to allow for limited recreational fisheries.
The status of other Massachusetts populations in the Palmer, Taunton, Jones, Indian Head and South Rivers in the North River watershed, Neponset River, and Charles River is uncertain—no fisheries are permitted.
Distribution and abundance
Native to the Atlantic coast of North America from maritime Canada to Florida. Historically in Massachusetts, the American shad entered most coastal streams. Damming, dredging, pollution, and other alterations of Massachusetts waters caused large declines in the mid-1800s, when American shad were eliminated from the Massachusetts portions of the Connecticut, Blackstone, and Charles rivers. Since the mid-1950s, with new or improved fishways and fish lifts, shad numbers have increased dramatically, especially in the Connecticut and Merrimack rivers. The population in the CT River has had a notable shift to fewer repeat spawners, Prior to the 1980s, approximately 40% were repeat spawners, which is a management concern for population resilience.
Habitat
Adult American shad are found in shallow marine waters along the continental shelf where they co-occur with river herring, Atlantic herring, and Atlantic mackerel. American shad spawn in a wide range of lotic environments connected to the ocean.
Healthy habitats are vital for supporting native wildlife and plants. Explore habitats and learn about conservation and restoration in Massachusetts.
Threats
Like other anadromous fish, American shad populations have been reduced by multiple factors such as overfishing, inadequate fish passage at dams, predation, pollution, water withdrawals, channelization of rivers, changing ocean conditions, and climate change.
Climate change will be a problem going forward as diadromous fish are amongst the functional groups with the highest overall vulnerability to climate change based on a recent marine and migratory fish vulnerability assessment (Hare et al. 2016). Marine habitats are affected as ocean temperature over the last decade in the U.S. Northeast Shelf and surrounding Northwest Atlantic waters have warmed faster than the global average (Pershing et al. 2015). New projections also suggest that this region will warm two to three times faster than the global average from a predicted northward shift in the Gulf Stream (Saba et al. 2016). Freshwater habitats will be affected by a high rate of sea-level rise, as well as increases in annual precipitation and river flow, magnitude of extreme precipitation events, and magnitude and frequency of floods (Hare et al. 2016).
Conservation
Recreational and commercial harvest of river herring was prohibited in Massachusetts in 2006 out of concern over their status, and as of January 2012, all directed harvest of river herring in all Atlantic Coast state waters is prohibited unless states have approved sustainable fisheries management plans (FMP) under ASMFC’s Amendment 2 to the Shad and River Herring FMP.
Research needs
- Information on the consequences of climate change
- Improvements to fish passage design/operation
- Greater monitoring of offshore fisheries for bycatch
References
This species description was adapted, with permission, from:
Karsten E. Hartel, David B. Halliwell, and Alan E. Launer. 2002. Inland Fishes of Massachusetts. Massachusetts Audubon Society, Lincoln, Massachusetts
NMFS. 2019. Status Review Report: Alewife (Alosa pseudoharengus) and Blueback Herring (Alosa aestivalis). Final Report to the National Marine Fisheries Service, Office of Protected Resources. 160 pp.
Hare, J. A., W.E. Morrison, M.W. Nelson, M.M. Stachura, E.J. Teeters, R.B. Griffis, M.A. Alexander... and A.S. Chute. 2016. A vulnerability assessment of fish and invertebrates to climate change on the Northeast US Continental Shelf. PloS one, 11(2), e0146756.
Pershing, A. J., M.A. Alexander, C.M. Hernandez, L.A. Kerr, A. Le Bris, K.E. Mills, ... and G.D. Sherwood. 2015. Slow adaptation in the face of rapid warming leads to collapse of the Gulf of Maine cod fishery. Science, 350(6262), 809-812.
Saba, V. S., S.M. Griffies, W.G. Anderson, M. Winton, M.A. Alexander, T.L. Delworth, ... and
R. Zhang. 2016. Enhanced warming of the Northwest Atlantic Ocean under climate change. Journal of Geophysical Research: Oceans, 121(1), 118-132.
Contact
| Date published: | April 10, 2025 |
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