Fish and Aquatic Conservation

illustration of a Blueback herring

Blueback herring

Alosa aestivalis (Mitchill, 1814)

Cool Facts

A The oldest age reported for blueback herring is 8 years. The heaviest reported weight for blueback herring is 200 g (0.44 lbs.)

SIZE: The common length for blueback herring is 27.5 cm (11 inches) with the maximum reported length being 40 cm (15.7 inches).

RANGE: The range of Blueback herring extends from the lower parts of Cape Breton rivers in Nova Scotia, Canada and south to the St. John’s River in Florida.

HABITAT: Blueback herring spawn in brackish water or fresh water rivers. Their eggs are essentially pelagic in still water. Blueback herring larvae are found in fresh and brackish rivers. Juvenile blueback herring leave fresh and brackish nursery grounds when they are about 5 cm (2 inches) long before they begin to migrate out to sea.

DIET: Blueback herring feed on small fishes, copepods, and small shrimps.

Natural History

Blueback herring are an anadromous species which form schools along the coastline and then begin to approach the shore in late spring to enter freshwater to spawn. Spawning occurs in fast moving, shallow water in the main stem of river tributaries. Juvenile blueback herring normally remain in the same watershed throughout the summer and fall and then migrate to the sea.


Currently, a River Herring Conservation Plan is being developed and implemented for the management of alewife and blueback herring. The two species of herring are more commonly called “River Herring” by the Atlantic States Marine Fisheries Commission (ASMFC) and the National Marine Fisheries Service (NMFS).

NMFS through ASMFC and the U.S. Fish and Wildlife Service also provide funding to the Atlantic Salmon Federation and St Croix International Waterway Commission to continue river herring counts at the Milltown Dam fishway in the St. Croix watershed located in Maine.

Migration Behavior

Blueback herring are are a migratory species. Blueback herring and alewife are more commonly referred to as river herring along the Atlantic coast of the U.S. Blueback herring are born in fresh water and then migrate to the ocean for their adult lives and then return to fresh water to reproduce.