Alewife

Common Name(s): Alewife, sawbelly, river herring

 

Scientific name: Alosa pseudoharengus

 

Classification: Alewives are members of the herring family. Close relatives include shad and blueback herring, which are often collectively referred to as “river herring”. 

 

Did you know? Alewives and blueback herring look nearly identical, although there are ways to distinguish which is which. Alewives are the more common of the two species in Maine. 

 

Range:  Alewives are distributed from the Gulf of St. Lawrence and northern Nova Scotia south to North Carolina. In Maine, alewives historically occurred in all major and minor coastal watersheds, and today are also found in landlocked lakes where stocking has occurred. Their range and abundance has shrunk considerably over time, and were historically more abundant and widely distributed in river systems along the east coast. Additionally, with climate change, there is potential for their range to shift further north. 

 

Identification: Alewives have slender bodies, normally growing to 10 – 11 inches in length and weighing in at about half a pound. However, older repeat spawners can be as large as 14 inches and weigh a pound or more. Alewives are predominantly silver, with a grayish green back. They have a forked tail, and a single black spot just behind the head at eye level. The common name "sawbelly" originates from the very distinctive overlapping scales along the belly that creates a saw-like keel. 

 

Life history: Maine alewives have two distinct life history strategies. Sea-run alewives are anadromous, spending most of their lives at sea before returning to Maine’s inland waters to spawn. Landlocked alewives complete their entire life cycle in freshwater and were first stocked in Maine lakes in 1966. 

 

Anadromous alewives spend the majority of their lives in saltwater and seasonally return to freshwater to spawn. While in the ocean, alewives travel in large schools, swimming along the coast foraging on plankton. In the spring, usually between late April and early June, they run up coastal streams and rivers toward ponds and lakes where they spawn. As a rule, alewives spawn in slack water – ponds and lakes or the quiet backwaters of rivers and streams. In general, these fish also make their way back to the same ponds where they hatched, though there is some variation.

 

The temperature range for spawning is about 55-60℉. Each female produces 60,000-100,000 eggs, depending upon the size of the individual fish. Shortly after spawning, surviving adults make their way downstream. Early spawners can often be seen migrating seaward and passing later run spawners still migrating upriver. Eggs will hatch between 3 and 6 days later, depending on water temperature. Young generally migrate to the ocean from mid July through early November, when they are between 1.25 and 6 inches in length. This wide range depends on the length of time they remain in the freshwater environment, which is related to the availability of food and the total numbers of young produced in a particular watershed. Once out of the river, they may use estuary habitats for extended periods before migrating in the open ocean.

 

Ecological importance: River herring are considered “keystone species” in freshwater and marine systems, connecting communities and ecosystems upriver with ecosystems and food webs in the ocean. Being part of the “river herring” group, alewives are a vital component of freshwater, estuarine, and marine environments in Maine. They are prey for important recreational and commercial species, such as cod, haddock, and striped bass. They also provide an important prey alternative to endangered Atlantic Salmon, for predators like fish-eating birds and seals. Alewives provide cover for juvenile Atlantic salmon migrating downriver, young salmon in the estuaries and open ocean, and even upstream migrating adult salmon. Alewives tie our ocean, rivers and lakes together, providing vital nutrients and forage needed to make healthy watersheds. Across fresh and saltwater habitats, everything eats alewives, including other fish, birds, reptiles, and both marine and terrestrial mammals.

 

Cultural importance: Before European settlers arrived in Maine, river herring were plentiful in the rivers and ponds, and provided a bountiful source of food for people and wildlife for thousands of years. The Passamaquoddy at Sipayik describe river herring as “the fish that feeds all”. Historical accounts describe spring herring runs as being so large one could “walk on the backs of the fish” to cross rivers. A number of Maine’s river names include Native references to alewives. The Mattamiscontis Stream, a tributary to the Penobscot River, derives its name from the Penobscot word for alewife (“madames”). Mattamiscontis thus can be translated as “plenty of alewives.”

 

Alewives were also important for early settlers and their communities. The spring runs would bring people together to catch and process large volumes of fish each year, and provide a way for communities to catch up with one another after winter. Today, alewives are still the most abundant, and arguably the most well known, sea-run fish in Maine. Each spring, hundreds of thousands of alewives make their way upstream to spawning grounds, and are celebrated by festivals along the coast. The Saturday before Memorial Day of each year is even designated as Maine Alewife Day, celebrating the rich fishing traditions of coastal Maine communities. 

 

Threats: The main challenges alewives face are obstacles to fish passage, climate change, fishing pressure, and pollution. Over the years, river herring populations have declined due to habitat loss associated with dams, road crossings and other development activities, overfishing as a direct fishery and as bycatch, pollution, and other factors.

 

The hundreds of dams found along Maine’s rivers are remnants of a long and productive history of industry in the state. However, alewives are not jumpers, so artificial barriers like dams and hung culverts, or even natural barriers like beaverdams, can block their migration and prevent the fish from reaching their spawning grounds.

 

In addition to unsustainable fishing in the last century, river herring are currently caught as bycatch in Atlantic herring and mackerel fisheries. There are efforts to limit this bycatch, however, and commercial fishing is collaboratively regulated through federal, state and local groups. Pollution and effects from climate change are additional concerns, because of the species’ reliance on specific water temperatures, consistent river flows, and good water quality. 

 

Restoration efforts: Despite these challenges, river herring are very responsive to restoration efforts, and their populations have started to rebound in recent years. Compared to other species of sea-run fish, alewives are good at using fishways to ascend over dams. Dam removals and construction of fish ladders help the fish complete their spawning migrations, and dozens of projects like these have been completed up and down the coast of Maine in the last few decades. 

 

In addition to restoring habitat connectivity in coastal rivers and streams, the state of Maine participates in trap and transfer programs, where alewives are stocked in watersheds that used to support runs. In the Penobscot River watershed, this program will have successfully recolonized 18 lakes and ponds with river herring by 2025. The state also uses trap and truck programs to maintain historic runs in areas that currently do not have upstream passage, until permanent passage can be achieved.

 

Fishery: Historically, river herring populations reached into hundreds of millions. Returning to coastal rivers every spring, these fish supported some of the oldest fisheries in the United States. Early fishing methods for alewives included weirs, dip nets, seines, drift nets, and set nets. The bulk of the harvest during the 1800s was for human consumption, because they kept exceptionally well in salt or when smoked. The demand for alewives for human consumption declined with the widespread use of refrigeration in the 20th century that made many other fish species available to the market. While some states like Connecticut and Rhode Island have statewide moratoriums on river herring harvest, Maine continues to have both commercial and recreational fisheries. 

 

From 1960 through 1987, the State of Maine recommended a one day closed period per week to allow river herring escapement to spawning grounds, and most municipalities agreed. From 1988–1994 the state required that all municipalities have two closed days or a conservation equivalent to ensure spawning escapement.  In 1995, the state required three closed days or a conservation equivalent. 

 

Today, alewives are harvested commercially both for human consumption and for bait, though the latter is the more common usage. Adult alewives are preferred bait for the spring lobster fishery, when other bait options are limited. There are 35 Maine municipalities that have commercial harvesting rights to alewives on 39 streams and rivers, but the state only allowed 23 municipalities to fish for river herring in 2024. These runs provide revenue to the towns, many of which lease their fishing privileges to independent fishermen. 

 

Towns that have commercial harvests are required to follow specific regulations to insure conservation of the resource. Each run and harvest location is unique, but towns may pick a single location to harvest from each year, and must include a three-day per week escapement period or biological equivalent. The three-day closed period required for commercial fishermen is also required for recreational anglers. Their limit is 25 fish per day and gear is restricted to dip net and hook-and-line, and prohibited from waters where commercial harvest takes place.

 

Sources: 

https://www.fisheries.noaa.gov/species/river-herring

https://www.maine.gov/ifw/fish-wildlife/fisheries/species-information/alewife.html

https://www.maine.gov/dmr/fisheries/sea-run-fisheries/programs-and-projects/river-herring-alewife-fact-sheet

https://www.maine.gov/dmr/fisheries/recreational/anglers-guide/do-you-know-your-catch

https://damariscottamills.org/fish-facts/

https://www.gomriverherringnetwork.org/about-river-herring

https://alewifeharvesters.org/

http://www.downeastfisheriestrail.org/fisheries-then/alewives-and-blueback-herring/

https://asmfc.org/species/shad-river-herring

https://asmfc.org/uploads/file/66f59e40RiverHerringAssessment_PeerReviewReport_2024.pdf