Alosa aestivalisHerring(Also: River herring)

Geographic Range

The blueback herring (Alosa aestivalis) ranges from Prince Edward Island in the northwest Atlantic south to the mouth of the St. John's River in Florida.

There are landlocked populations, but the furthest inland the bluback herring exists is Lake Champlain and the Mohawk river, New York.


The blueback is anadromous and develops in freshwater, then migrates to marine, and then migrates back to freshwater to spawn.

Physical Description

The blueback herring is slender like the alewife (Alosa pseudoharengus) and several papers that exist only for identification purposes between these two species (MacLellan 1981). The blueback herring has a smaller eye, its otolith has more hooked shape than the alewife's L-shaped otolith, and the lining of the viscera is black instead of silver (this is the most distinguishing characteristic). However, if you do not want to sacrifice the fish just to identify it: the dorsal surface of blueback herrings have a blue color, and they have 41 to 51 gill rakers. Also characteristic of bluebacks are one dark spot on the shoulder. The American shad (Alosa sapidissima) often has 4-5 spots in the same location.

Blueback herrings grow to a maximum of 15 inches, but are more commonly around one foot long. Smith (1985) notes that most adults are 10 to 12 inches long in the Hudson River, NY.

In general Clupeids, or the herring, shad, and menhaden (among others) family, are silvery with a sharp ventral keel. This keel has given them the common name of "sawbellies," which is an adaption for optimal schooling movement and organization. They have forked caudal fins and the anal fin is usually longer than the dorsal fin. Their body shape is teardrop, but more elongate than faster moving fishes such as the tunas. The maximum depth of the fishes' body is just anterior to the dorsal fin.

  • Range mass
    400 (high) g
    14.10 (high) oz


Blueback herring, like many other clupeids are anadromous fish, meaning they spawn and spend larval development in freshwater, and then they migrate out to spend most of their lives in marine waters. Landlocked populations will make spawning runs up rivers and streams, but spend most of their life in the pelagic zone of lakes. Many fish can make extensive spawning runs. In New York, the species can reach the Mohawk river, more than 150 kilometers from the Atlantic Ocean. Ian Blackburn and Karin Limburg, researchers at the SUNY college of environmental science and forestry, are trying to determine whether some of these individuals found here are migratory or residents of the Mohawk River.

Spawing runs can get large and begin in mid to late April (as soon as the water is 4-9 degrees Celcius) and last until mid-August. The blueback herring is also known as the summer herring since most of the large spawning runs occur from mid-may to mid-july. (This is another environmentally friendly way to separate alewives and bluebacks: the spawning runs are spatially and temporally separated from each other). Spawning occurs in separate runs in groups through the season, but the fish can be inhibited by high temperatures (27 deg C). Bluebacks prefer spawning habitat with swift water and a hard bottom, and fish from ages 3-7 normally spawn.

During courtship, the female is often pursued by several males--all of which will swim as a group in circles. Males nudge the vent region of the female with their snouts, most likely to stimulate the female to release her gametes. All together, they make a dive towards the bottom, stop short, face the current and release their gametes. The eggs need 50 hours of incubation at 72 deg F to develop.

  • Average age at sexual or reproductive maturity (female)
    Sex: female
    1460 days
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    1277 days


  • Average lifespan
    Status: captivity
    8 years


See above for spawning behavior.

Communication and Perception

Food Habits

Blueback herring are planktivores and eat anything the size of larval fish to zooplankters. Blueback herring also consume small fishes and shrimps. (Froese and Pauly, 2001)

Economic Importance for Humans: Positive

The blueback herring is has been the subject of fisheries. It is more commonly known with come other clupeids as river herring, which includes the alewife. Very general "river herring" labels may include other bait fish such as the American shad and menhaden (Brevoortia tyrannus), or bunker.

Other Comments

Blueback herring (Alosa aestivalis) is also known as summer herring and is known collectively with alewives and other clupeids as river herring. You may find bluebacks in bait stores sold as river herring, sawbellies, or even bunker.

Bluebacks are known as alose d'ete in France (literally, shads of the summer), blueback glut herring or shad herring in United Kingdom vernacular, and sinisilli in Finnish vernacular.


Claire Dennis (author), SUNY College of Environmental Science and Forestry, Kimberly Schulz (editor), SUNY College of Environmental Science and Forestry.


Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

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


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.


uses touch to communicate


Froese, R., D. Pauly, eds.. 2001. "FishBase: Alosa aestivalis" (On-line). Accessed 8 March 2001 at

Loesch, J., W. Lund. 1977. A contribution to the life history of the blueback herring (Alosa aestivalis). Transactions of the American Fisheries society, 106 (6): 583-589.

MacLellan, P., G. Newsome, P. Dill. 1981. Discrimination by external features between alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis). Canadian Journal of Fisheries and Aquatic Sciences, 38 (5): 544-546.

Smith, C. 1985. The Inland Fishes of New York State. Albany: NYS DEC.