The alewife (Alosa pseudoharengus) is an anadromous species of herring found in North America. It is one of the “typical” North American shads, attributed to the subgenus Pomolobus of the genus Alosa.
Alewives reach a maximum length of about 40 centimeters (16 in), but have an average length of about 25 centimeters (10 inches). The front of the body is deep and larger than other fish found in the same waters, and its common name is said to come from comparison with a corpulent female tavernkeeper (“ale-wife”).
In Atlantic Canada it is known as the gaspereau. In southwestern Nova Scotia, it is called a kiack (or kyack). The word “gaspereau” comes from the Acadian French word “gasparot”, first mentioned by Nicolas Denys. William Francis Ganong, New Brunswick biologist and historian, wrote:
Gaspereau, or Gasparot. Name of a common salt-water fish of Acadia (also called Alewife), first used, so far as I can find, by Denys in 1672. Nowhere can I find any clue to its origin. It seems not to be Indian.
Acadians named two rivers after the fish, the Gaspereau River in Nova Scotia and the Gaspereaux River in New Brunswick.
In the Southeast US, when sold and used as bait, the fish is often referred to as “LY”. There are anadromous and landlocked forms. The landlocked form is also called a sawbelly or mooneye (although this latter name is more commonly applied to Hiodon spp.).
Adult alewives are preferred bait for the spring lobster fishery in Maine. It is also used for human consumption, usually smoked. It is caught (during its spawning migration upstream) using large dip nets to scoop the fish out of shallow, constricted areas on its migratory streams and rivers.
Alewives are perhaps best known for their invasion of the Great Lakes by using the Welland Canal to bypass Niagara Falls. Alewives colonized the Great Lakes and became abundant mostly in Lake Huron and Lake Michigan. They reached their peak abundance by the 1950s and 1980s. Alewives grew in number unchecked because of the lack of a top predator in the lakes (lake trout were essentially wiped out around the same time by overfishing and the invasion of the sea lamprey). For a time, alewives, which often exhibit seasonal die-offs, washed up in windrows on the shorelines of the Great Lakes. Their control was the impetus for the introduction of various Pacific salmon species (first coho, and later the Chinook salmon) to act as predators on them. This caused the development of a salmon/alewife fish community, popular with many sport anglers. Alewives, however, have been implicated in the decline of many native Great Lakes species through competition and predation. The species is a common predator of numerous native and non-native zooplankton taxa (Bythotrephes longimanus, Leptodiaptomus ashlandi, Leptodiaptomus minutus, Leptodiaptomus sicilis, Leptodora kindtii)
Alewife populations have seen big declines throughout much of their range. Several threats have most likely contributed to their decline, including loss of habitat due to decreased access to spawning areas from the construction of dams and other impediments to migration, habitat degradation, fishing, and increased predation due to recovering striped bass populations.
In response to the declining trend for alewife, the states of Massachusetts, Rhode Island, Connecticut, Virginia, and North Carolina have instituted moratoriums on taking and possession.
The alewife is a US National Marine Fisheries Service Species of Concern. Species of Concern are those species about which the National Oceanic and Atmospheric Administration, National Marine Fisheries Service, has some concerns regarding status and threats, but for which insufficient information is available to indicate a need to list the species under the US Endangered Species Act.