thumb|226x226px|School of alewife

The alewife or river herring (Alosa pseudoharengus; : alewives) 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. As an adult it is a marine species found in the northern West Atlantic Ocean, moving into estuaries before swimming upstream to breed in freshwater habitats, but some populations live entirely in fresh water. It is best known for its invasion of the Great Lakes by using the Welland Canal to bypass Niagara Falls. Here, its population surged, peaking between the 1950s and 1980s to the detriment of many native species of fish. In an effort to control it biologically, Pacific salmon were introduced, only partially successfully. As a marine fish, the alewife is a US National Marine Fisheries Service "Species of Concern".

Description

Alewife reach a maximum standard length (SL) of about , but have a typical SL of about . to greyish green dorsum. A humeral spot is often present. The peritoneum is light-colored with spots Additionally, the eye is larger than that of A. aestivalis; or, alternatively, from the word aloofe, possibly of Native American origin, that was used to describe this fish in the seventeenth and eighteenth centuries.

In southwestern Nova Scotia, alewife are referred to as kiacks (or kyacks). In Atlantic Canada it is known as the gaspereau, from the Acadian French word gasparot, first mentioned by Nicolas Denys. William Francis Ganong, New Brunswick biologist and historian, wrote:

<blockquote>

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.

</blockquote>

Acadians named three rivers after the fish, the Gaspereau River in Nova Scotia, as well as the Gaspereau River near Grand Lake and Gaspereau River near Northumberland Strait that are both in New Brunswick.

Both anadromous and landlocked forms occur. The landlocked form is also called a sawbelly or mooneye (although this latter name is more commonly applied to Hiodon spp.) Adult alewife are caught during their spring spawning migration upstream by being scooped out of shallow, constricted areas using large dip nets. They are the preferred bait for the spring lobster fishery in Maine, and are eaten by humans, usually smoked.

In the North American Great Lakes

Alewife are known for their invasion of the Great Lakes by using the Welland Canal to bypass Niagara Falls. Although the United States Department of Agriculture suggests they may be native to Lake Ontario, alewife colonized the other Great Lakes and became abundant mostly in Lake Huron and Lake Michigan. It appears that they had spread from Lake Erie to other Great Lakes by the Detroit River and Lake St. Clair.

For a time, alewife, which often exhibit seasonal die-offs, washed up in windrows on the shorelines of the Great Lakes. Various species of Pacific salmon (first coho, and later the Chinook salmon) were introduced as predators. Though marginally successful, this led to the development of a salmon/alewife fishery popular with many sport anglers.

In spite of such biological control methods, alewife remain implicated in the decline of many native Great Lakes species. It is also a common predator of numerous native and non-native zooplankton taxa (e.g. Bythotrephes longimanus, Leptodiaptomus ashlandi, Limnocalanus spp., Leptodiaptomus minutus, Leptodiaptomus sicilis, and Leptodora kindtii). Wells (1970) found that increases in population of alewife in the Great Lakes between 1954 and 1966 were associated with population declines in certain larger species of zooplankton, while an alewife die-off in 1967 was temporally related to population rebound in most of those species.

The alewife is a US National Marine Fisheries Service Species of Concern, 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.

References

Further reading

  • Fisheries and Oceans Canada: Alewife
  • Virginia Marine Resources Commission
  • The Man with the Salmon Plan
  • Species Profile- Alewife (Alosa pseudoharengus), National Invasive Species Information Center, United States National Agricultural Library. Lists general information and resources for Alewife.
  • Fish Win: Maine About-Face Lets Alewives Return to Canada Border River