Fish
Blueback Herring
Alosa aestivalis · also called blueback herrings
Each spring, countless blueback herring surge out of the Atlantic and into coastal rivers to spawn, their bluish-green backs flashing beneath the surface in numbers that once sustained major fisheries and still draw in predators from every direction.
Overview
The blueback herring, Alosa aestivalis, is a migratory fish native to Atlantic coastal waters of North America, entering coastal rivers each spring to spawn. Its mass spring spawning migration, importance as prey for numerous larger predators, and significant population declines tied to dam construction and overfishing make it one of the more ecologically significant and conservation-relevant fish along the Atlantic seaboard.
A migration that feeds an entire coastline
The blueback herring’s spring rush into freshwater rivers does more than continue the species itself, providing a critical seasonal food pulse for fish, birds, and marine mammals all along its migratory route.
Status
Near Threatened, having declined significantly across much of its range due to dam construction, overfishing, and habitat degradation.
Blueback Herring: common questions
Why does the blueback herring migrate into rivers?
This species migrates from the ocean into freshwater rivers in large numbers each spring specifically to spawn, a journey that historically supported significant commercial and recreational fisheries and still provides an important seasonal food source for a wide range of predators along the migration route.
Why has the blueback herring declined?
This species has experienced significant population declines driven by dam construction that blocks access to historical spawning rivers, along with overfishing and habitat degradation, pressures that together have reduced the species' ability to complete its spawning migration successfully across much of its range.
What eats the blueback herring?
This species serves as an important food source for a wide range of predators, including larger fish such as striped bass, various seabirds, and marine mammals, making its spring migration into rivers a significant seasonal food event for numerous other species along the way.
Is the blueback herring related to other herring species?
Yes, this species is closely related to several other migratory herring species with broadly similar life histories, including the alewife, and together these related species are often referred to collectively as river herring due to their shared pattern of migrating from the ocean into rivers to spawn.