Blueback Herring (Alosa aestivalis)
The blueback herring and alewife are of similar shape and general appearance, and distinguishing between them is difficult. Bluebacks tend to have a smaller eye than alewives, with the eye diameter usually smaller than the snout length. As their name implies, these fish often have dark blue backs.
The blueback herring is a common fish on Long Island and in the Hudson and lower Mohawk rivers.
An anadromous fish, the blueback herring spends the greater part of its life in salt water and returns to fresh water to spawn. It usually spawns later in the spring than the alewife, when water temperatures are a bit warmer. During spawning, many eggs are deposited over the stream bottom where they stick to gravel, stones, logs, or other objects. A few surviving, spent fish move back to the sea after spawning. Young fish usually move to sea when about l month old and 1 1/2 to 2 inches long.
Bluebacks feed on plankton, various small floating animals, small fish fry, and fish eggs.
Distribution of blueback herring in NY state. Dark dots represent where actual samples of blueback herring were taken. White dots represent historic distributions.
An image of the blueback herring is also available for download.