Alosa pseudoharengusAnadromous alewives(Also: Bigeye herring; Clipped roefish; Corned alewives; Freshwater herring)

Geographic Range

Alosa pseudoharengus (Wilson, 1811) is an anadromous species, native to the Atlantic Ocean and the lakes and streams that drain to it from Newfoundland to North Carolina (Scott and Crossman, 1998). This includes the Gulf of St. Lawrence, the outer coast of Nova Scotia, the Bay of Fundy, and the Gulf of Maine (Scott and Scott, 1988). It is also present, although non-native, in all of the Great Lakes (USA), and many lakes in northern New York. In the Great Lakes, A. pseudoharengus was first caught in Lake Erie in 1931 off the coast of Nanticoke, Ontario, Canada. Populations then moved slowly upstream to the upper great lakes (Scott and Crossman, 1998). It was discovered in Lake Huron in 1933, Lake Erie in 1940, Lake Michigan in 1949, and Lake Superior in 1954 (Scott and Crossman, 1998). It is now abundant in Lake Huron and dominant in Lake Michigan. Alewives cannot dominate Lake Superior due to cold water and predation by lake trout (Salvelinus namaycush), nor can they dominate Lake Erie because the lake is too shallow to provide suitable overwintering grounds for large numbers of fish (Scott and Crossman, 1998). Several theories exist on how alewives could have become established in the Great Lakes. Scott and Crossman suggest that alewives may have been accidentally included in a batch of American shad (Alosa sapidissima) that were used to stock Lake Ontario. The alewives also could have migrated from Lakes Seneca and Cayuga in New York to the Great Lakes through the St. Lawrence River. A third argument for the current distribution is that alewives were native to Lake Ontario in small numbers but went unnoticed until the population explosion in 1873 (Daniels, 2001). Daniels (2001) argues against both the theory of introduction with stocked American shad and dispersal through canals. He argues against the canal introduction because the alewife floater, Anodonta implicata, is not found in the upper portions of canals or in Lake Ontario. Anodonta implicata is a mussel and a parasite of alewives (Daniels, 2001). (Daniels, 2001; Scott and Crossman, 1998; Scott and Scott, 1988)


For anadromous populations, much is known about their freshwater spawning habits, but little is known about movements within the ocean. Alewives spend most of their time in coastal waters and most are caught in water 56-100 m deep at about 4°C (Scott and Scott, 1988). Light sensitive, they tend to be in deeper waters during daylight hours. They also follow diel movements of zooplankton in the water column (Scott and Scott, 1988). Adults can withstand temperatures up to 25°C and young of the year can live in waters up to 30°C (Scott and Scott, 1988).

Freshwater populations spend most of their time in the deep waters of the lakes but come to the shallows and tributary streams in the spring to spawn (Trautman, 1957). The fish go to the deepest parts of the lakes to overwinter. (Scott and Scott, 1988; Trautman, 1957)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams
  • coastal
  • Range depth
    56 to 100 m
    183.73 to 328.08 ft

Physical Description

Alosa pseudoharengus has an overall silvery color with a grayish green back. A black spot at the eye level is directly behind the head. Adults have longitudinal lines that run along the scale lines above the midline of the body. Small specimens have a violet sheen on the sides while anadromous adults have a golden cast on their heads and upper parts. The scales are deciduous and the lateral line is not well-developed (Scott and Crossman, 1998). Coloration is generally similar to that of the skipjack herring, Alosa chrysochloris. Scales on the midline of the belly form scutes, creating a serrated surface (Trautman, 1957). Females are bigger than males and generally live longer. The body is strongly laterally compressed and relatively deep. The head is broadly triangular. Eyes are large and have well-developed adipose eyelids. The front of the jaw is thick and extends past the lower jaw when the mouth is closed. The maxillary extends to below the middle of the eye. A few small teeth are present on the premaxillary and mandible (Scott and Crossman, 1998). There are more than 30 gill rakers on the lower angle of the first gill arch (Trautman, 1957). The singular dorsal fin usually has 13-14 rays but may have 12-16. The caudal fin is forked. The anal fin is short and wide with 15-19 rays (usually 17-18). The pelvic fins are rather small and contain 10 rays. The pectoral fins are low on the sides and usually have 16 rays but may have as few as 14 (Scott and Crossman, 1998). There are a few physiological differences between anadromous and land-locked individuals. Anadromous specimens tend to be longer, ranging from 255 to 355 mm while land-locked species average 150 mm in length. Land-locked fish mature faster than anadromous ones (Daniels, 2001). (Daniels, 2001; Scott and Crossman, 1998; Trautman, 1957)

  • Sexual Dimorphism
  • female larger
  • Average mass
    110 g
    3.88 oz
  • Range length
    100 to 355 mm
    3.94 to 13.98 in


Fertilized eggs are about 0.9 mm in diameter. Three to five days after hatching, the larvae begin to feed. They slowly transform into juvenile fish and remain in fresh water until the fall. While in freshwater, young-of-the-year grow 1.5 to 5 inches (3.8 to 12.5 cm). Little is known about sub-adult life-history traits. (Maine Department of Marine Resources, 2004; Scott and Crossman, 1998; U.S. Department of Agriculture, 2004)


All alewives spawn in the spring. The young swim to sea in anadromous populations or to deeper water in lake populations in the fall (Grosvenor, 1965). For anadromous populations, the temperature of the river water determines the timing of spawning migrations upstream, so spawning happens first in lower latitudes. Spawning generally starts in April in the south and lasts until the end of May in upper latitudes (Scott and Crossman, 1998).

In all populations, females reach the spawning grounds first (Scott and Crossman, 1998) and older fish are the first to spawn (Grosvenor, 1965). The oldest fish recorded at spawning sites were 9-10 years old (Grosvenor, 1965). Spawning occurs in groups of 3 or in pairs (Scott and Crossman, 1998). (Grosvenor, 1965; Scott and Crossman, 1998)

Females broadcast their eggs simultaneously with males broadcasting sperm (U.S. Department of Agriculture, 2004). Although the eggs are adhesive at first and may stick to plants or rocks, they loose their adhesive qualities after a few hours and settle to the substrate (Scott and Scott, 1988). Alewives deposit their eggs over any type of substrate (U.S. Department of Agriculture, 2004). The number of eggs per female may be 10,000 to 12,000 (Scott and Crossman, 1998) or 48,000-360,000 (Scott and Scott, 1988).

In anadromous populations, adult alewives spend most of their lives at sea but spawn in streams above the influence of the tide. Although they cannot jump obstacles such as dams, they surmount rapids and fish runs migrating farther upstream than the closely related American shad (Scott and Crossman, 1998). Anadromous fish reach maturity at 3 years for males and 4 years for females (Scott and Crossman, 1998).

Land-locked populations mature at 2 years for males and 3 years for females. These fish move close to shallow beaches or up streams to spawn. They move on-shore at night and off-shore during the day. Adults leave the shallows immediately after spawning and have moved to deep water by late August (Scott and Crossman, 1998). Eggs hatch in 6 days at a mean water temperature of 60°F (15.6°C) and in 3 days at 72°F (22.2°C) (Scott and Crossman, 1998). Their maximum hatching success occurs at 20.8°C (Grosvenor, 1965). (Grosvenor, 1965; Scott and Crossman, 1998; Scott and Scott, 1988; U.S. Department of Agriculture, 2004)

  • Breeding interval
    Alewives breed yearly.
  • Breeding season
    Spawning occurs during the spring.
  • Range number of offspring
    10,000 to 360,000
  • Range time to hatching
    3 to 6 days
  • Range age at sexual or reproductive maturity (female)
    3 to 4 years
  • Range age at sexual or reproductive maturity (male)
    2 to 3 years

Alewives do not have any parental investment in their young beyond spawning. The adults leave immediately after spawning in the spring and the young move to the open water in the fall.

  • Parental Investment
  • no parental involvement
  • pre-fertilization
    • provisioning
    • protecting
      • female


Young alewives have a very high mortality rate. Less than 1% survive to migrate into the sea (U.S. Department of Agriculture, 2004). Annual mortality for adult alewives is on the order of 70% per year. Most die during or shortly after the spawning season (U.S. Department of Agriculture, 2004). Few land-locked alewives live longer than 5 years (Smith, 1970). (Smith, 1970; U.S. Department of Agriculture, 2004)

  • Range lifespan
    Status: wild
    10 (high) years
  • Typical lifespan
    Status: wild
    5 (high) hours


There is little published research on their social behavior except for spawning behaviors and feeding patterns. They migrate up streams or to shallow waters to spawn (Madenjian, Holuszko, and Desorcie, 2003). They are vertical daily migrators, following plankton populations (Scott and Scott, 1988). (Madenjian, et al., 2003; Scott and Scott, 1988)

Home Range

Alewives are not territorial.

Communication and Perception

We don't know much about how alewives might communicate. Their large eyes probably help them find other alewives, their prey, and stay alert for predators.

Food Habits

Little is known about the feeding habits of anadromous alewives (Scott and Scott, 1988). Adult land-locked fish eat mostly zooplankton, especially larger varieties such as copepods, cladocerans, mysids, and ostracods (Scott and Crossman, 1998). When they grow larger than 11.9 cm, they feed mostly on the benthic amphipod Pontoporeia (Scott and Scott, 1988). Some spawning adults eat small fish or fish eggs when in shallow waters (Scott and Crossman, 1998). Larval alewives eat mainly cladocerans and copepods. (Scott and Crossman, 1998; Scott and Scott, 1988)

  • Animal Foods
  • fish
  • eggs
  • aquatic crustaceans
  • zooplankton


Alewives are considered a forage fish and have many predators. In freshwater, their main predators are burbot (Lota lota), lake trout (Salvelinus namaycush), eels (Anguillidae), bass (Micropterus), walleye (Sander vitreus), and whitefish (Scott and Crossman, 1998). Introduced predators include chinook and coho salmon. Little is known about the predators of anadromous alewives but their hatchlings have a high mortality rate. As few as one out of 80,000 will reach the sea (Scott and Scott, 1988). (Scott and Crossman, 1998; Scott and Scott, 1988)

Ecosystem Roles

Alosa pseudoharengus is now the most abundant planktivore in Lake Ontario and it is the main prey of salmonoids stocked into the great lakes (Klumb, Rudstam, and Mills, 2003). Its presence in the Great Lakes has caused the decline of many fish species due to competition.

There have been few studies published on alewife parasites (Scott and Scott, 1988). Anadromous populations host more species of parasites than land-locked populations. Alewives caught off the Atlantic coast were found to host the following parasites: acanthocephalans, cestodes, trematodes, copepods, and nematodes (Scott and Crossman, 1998). Parasites are rare in land-locked populations (Scott and Scott, 1988), but one important freshwater alewife parasite, the alewife floater, Anodona implicata, has been used to research the historical range of the alewife. Anodonta implicata is a mussel which is native to the tidal Hudson river and Delaware Rivers in New York (Daniels, 2001). (Daniels, 2001; Klumb, et al., 2003; Scott and Crossman, 1998; Scott and Scott, 1988)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

Alewives represent an important commercial fishery in the Atlantic Ocean. They are packaged fresh, smoked, salted, or pickled for human consumption and are often sold as “river herring.” Fishermen use weirs, traps, gill nets, and dip nets for alewives, which they consider one of the easiest fish to catch (Scott and Scott, 1988). Alewives have other uses, including pet food, lobster and snow crab bait, and processing into fishmeal and fish oil (Scott and Scott, 1988). The North American Fisheries Organization statistical bulletin includes alewives in the "other fish" category so no catch data are available (Scott and Scott, 1988). Alewives have not seriously been exploited as a fishery in the Great Lakes since these are small and too bony to eat. However, recently there has been a trend to use them for pet food and fish meal (Scott and Crossman, 1998). (Scott and Crossman, 1998; Scott and Scott, 1988)

  • Positive Impacts
  • food
  • body parts are source of valuable material

Economic Importance for Humans: Negative

Alewives have been considered a nuisance in the Great Lakes since their population explosion in 1873. Live fish tend to clog industrial intake pipelines and are “particularly obnoxious during periods of mass die-offs” because they can cause health hazards from the large numbers of dead fish in the spring (Scott and Crossman, 1998). Control measures, such as the introduction of coho salmon, Oncorhynchus kisutch, however, provide important sport fisheries for Lake Michigan (Scott and Crossman, 1998).

Since they feed mainly on planktonic and benthic organisms, alewives are particularly good at accumulating DDT (dichloro-diphenyl-trichloroethane) in their fatty tissues (Scott and Crossman, 1998). This bioaccumulation can make it dangerous for humans and other high-level predators to eat piscivorous fish, such as salmon, that feed primarily on alewives. (Scott and Crossman, 1998)

Conservation Status

Alewives not listed as an endangered species, but in many places in their natural range, their habitat is threatened by dams along spawning rivers. On the other hand, their introduction into the Great Lakes and other areas resulted in declines in native fish in those areas.

Other Comments

Alosa pseudoharengus was formerly classified as Alosa pseudoharengus. Common names for A. pseudoharengus include alewife, gaspereau, sawbelly, kyak, kiack, river herring, and glut herring.

Alewives have some interesting cultural and historical connections. Alewives are the fish the Native Americans in New England buried with crops as fertilizer (Grosvenor, 1965). The silvery coating on the scales is sometimes used in making costume jewelry and is called pearl essence by the jewelry industry (Grosvenor, 1965). (Grosvenor, 1965)


Vanessa Tobias (author), University of Michigan-Ann Arbor, William Fink (editor, instructor), University of Michigan-Ann Arbor, Renee Sherman Mulcrone (editor).



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map


uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


uses smells or other chemicals to communicate


the nearshore aquatic habitats near a coast, or shoreline.

  1. active during the day, 2. lasting for one day.

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature


uses electric signals to communicate


an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.

external fertilization

fertilization takes place outside the female's body


union of egg and spermatozoan


A substance that provides both nutrients and energy to a living thing.


mainly lives in water that is not salty.


having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

intertidal or littoral

the area of shoreline influenced mainly by the tides, between the highest and lowest reaches of the tide. An aquatic habitat.


referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.


makes seasonal movements between breeding and wintering grounds


having the capacity to move from one place to another.


specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.


active during the night


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.


an animal that mainly eats plankton


the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season


reproduction that includes combining the genetic contribution of two individuals, a male and a female


associates with others of its species; forms social groups.


uses touch to communicate


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


movements of a hard surface that are produced by animals as signals to others


uses sight to communicate


animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)


Daniels, R. 2001. Untested assumptions: the role of canals in the dispersal of sea lamprey, alewife, and other fishes in the eastern United States. Environmental Biology of Fishes, 60: 309-329.

Grosvenor, M. 1965. Wondrous World of Fishes. Washington, DC: National Geographic Society.

Klumb, R., L. Rudstam, E. Mills. 2003. Comparison of Alewife Young-of-the-Year and Adult Respiration and Swimming Speed Bioenergetics Model Parameters: Implications of Extrapolation. Transactions of the American Fisheries Society, 132: 1089-1103.

Madenjian, C., J. Holuszko, T. Desorcie. 2003. Growth and Condition of Alewives in Lake Michigan, 1984-2001. Transactions of the American Fisheries Society, 132: 1104-1116.

Maine Department of Marine Resources, 2004. "Maine Department of Marine Resources" (On-line). Fact Sheet- Anadromous Alewife. Accessed October 27, 2004 at

Scott, W., E. Crossman. 1998. The Freshwater Fishes of Canada. Oakville, Ontario, Canada: Galt House Publications Ldt..

Scott, W., M. Scott. 1988. Atlantic Fishes of Canada. Toronto, Canada: Canadian Bulletin of Fisheries and Aquatic Science (University of Toronto Press).

Smith, S. 1970. Species Interactions of the Alewife in the Great Lakes. Transactions of the American Fisheries Society, 4: 754-764.

Trautman, M. 1957. The Fishes of Ohio. Baltimore, Md.: Ohio State University Press (Waverly Press).

U.S. Department of Agriculture, N. 2004. " A gateway to Federal and State invasive species activities and programs" (On-line). Accessed October 27, 2004 at