Lake Huron herring, public domain drawing (click for large version and credits)
A herring is a type of small oily fish found in the temperate, shallow waters of the North Atlantic.
Herring is one of various species of fishes of the genus Clupea especially the Atlantic herring (English herring) (Clupea harengus). Herrings move in vast schools (swarm), coming in spring to the shores of Europe and America, where they are caught, salted and smoked in great quantities.
Herrings can also be pickled and served in a sour cream sauce.
A kipper is a split and smoked herring, and a bloater is a whole smoked herring.
A typical Dutch delicacy is raw herring with raw shredded onions.
A rollmop is a cured herring fillet, rolled up and preserved in vinegar which is flavoured with onions and spices.
Figuratively, a red herring is a false lead in a mystery. In this context, red means smoked, and a smoked herring has such a strong smell that it can be used to create a false scent that causes hunting dogs to lose a trail.
Video of feeding herring, catching copepods - scanned with the ecoSCOPE - the fish is ca. 38 mm long