Blueback herring Blueback herring The blueback herring or blueback shad ("Alosa aestivalis") is an anadromous species of herring from the east coast of North America, with a range from Nova Scotia to Florida. Blueback herring form schools and are believed to migrate offshore to overwinter near the bottom. These fish are silvery in color, have a series of scutes (modified, spiny and keeled scales) along their bellies, and are characterized by deep bluish-green backs. They reach a maximum size of approximately and are believed to live up to 8 years. The most distinguishing characteristic of this species is the black to dusky
Coastal fish but ascend rivers to spawn; eels are catadromous, living in rivers and streams, but returning to the sea to breed. Besides the species that migrate through estuaries, there are many other fish that use them as "nursery grounds" for spawning or as places young fish can feed and grow before moving elsewhere. For example, herring and plaice are two commercially important species that use the Thames Estuary for this purpose. Mangrove swamps are associated brackish water habitats. Many, though not all, mangrove swamps fringe estuaries and lagoons where the salinity changes with each tide. Among the most specialised residents of