Alosa braschnikowi Alosa braschnikowi Alosa braschnikowi, the Caspian marine shad or Brazhnikov's shad, is one of the clupeid fish species endemic to the Caspian Sea. This is a relatively large shad, typically 30 cm and up to 50 cm length. It also has a more "herring-like" body shape than other Caspian shad species, being a slender and elongate fish. It has well developed teeth in both jaws. "Alosa braschnikowi" feeds on small fishes but also on crustaceans and occasionally other invertebrates. It performs migrations within the Caspian Sea, but does not enter rivers. Several subspecies have been described, with different breeding habits
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