River herring – this term combines two species:
Alewife (Alosa pseudoharengus)
Blueback herring (Alosa aestivalis)
Spawning occurs in the spring with alewife slightly earlier than blueback herring. Blueback prefer shallow waters covered in vegetation, Alewife use coastal brackish stream, barrier beach ponds, and mid-river sites to spawn. Eggs are sticky for the first 24 hours. At about ¾ inch, the larvae develop into juveniles. They feed on zooplankton in the river until they are about 3 inches long in the fall, then they migrate to the ocean. Adult average about 8 inches in length and males are smaller than females.
Alewife: Newfoundland to South Carolina, plus landlocked populations in the Finger Lakes, NY and in the Great Lakes
Blueback herring: Nova Scotia to Florida
- Alewife: eggs are green, eyes are large – diameter greater than snout length, peritoneal lining is gray
- Blueback herring: eggs are amber, eye diameter is small - equal or less than snout length, peritoneal lining is dark
- Herring mature at age 3-4 years and may live 7-8 years, spawning multiple times.
- After spawning, alewife die but their bodies help the ecosystem live on - providing nitrogen, carbon and phosphorous nutrients to small streams.
Alewife and Blueback Herring Species Profiles (pdf - 1.03MB)
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