North Atlantic herring schools have been measured up to 4 cubic kilometres (0.96 cu mi) in size, containing an estimated four billion fish.

Gill rakers in their mouths filter incoming water, trapping any zooplankton and phytoplankton.

The Baltic herring has a specific name in many local languages (Swedish strömming, Finnish silakka, Estonian räim, silk, Livonian siļk, Russian салака, Polish śledź bałtycki, Latvian reņģes, Lithuanian strimelė) and is popularly and in cuisine considered distinct from herring.

Cooling in the mid-16th century related to the Little Ice Age, combined with this overfishing, led to a dramatic loss of productivity in the population of autumn-spawning herring that rendered it nearly extinct.

Once fertilized the 1 to 1.4 mm diameter eggs sink to the sea bed where their sticky surface adheres to gravel or weed.

[6] Herrings are most seen in the North Atlantic Ocean, from the coast of South Carolina until Greenland, and from the Baltic Sea until Novaya Zemlya.

Conversely, they are a central prey item or forage fish for higher trophic levels.

The reasons for this success are still enigmatic; one speculation attributes their dominance to the huge, extremely fast cruising schools they inhabit.

Orca, cod, dolphins, porpoises, sharks, rockfish, seabirds, whales, squid, sea lions, seals, tuna, salmon, and fishermen are among the predators of these fishes.

Herring schools keep a certain distance from a moving scuba diver or a cruising predator like a killer whale, forming a vacuole which looks like a doughnut from a spotter plane.

Many hypotheses have been put forward to explain the function of schooling, such as predator confusion, reduced risk of being found, better orientation, and synchronized hunting.

Schools of herring can on calm days sometimes be detected at the surface from more than a mile away by the little waves they form, or from a few meters at night when they trigger bioluminescence in surrounding plankton ("firing").

[12] Because of their feeding habits, cruising desire, collective behavior and fragility they survive in very few aquaria worldwide despite their abundance in the ocean.