Schooling silver fish hunt copepods in jump-length grids
Herring—oily forage fish of temperate northern seas—move in vast schools that once underwrote European fisheries and early fisheries science. Juveniles even space themselves a copepod's escape-jump apart so that endless relays of open mouths finally catch prey no lone fish could seize.
Clupea, the type genus of family Clupeidae, holds the Atlantic herring of the North Atlantic and the Pacific herring of the North Pacific—together the core of a catch in which Atlantic fish alone exceed half of all herring landings. Related clupeids and lookalikes share the "herring" name from the Arabian Sea to South American coasts; the word may echo Old High German heri, a host or multitude. Silvery bodies carry one soft dorsal fin, no lateral line, and a protruding lower jaw. Baltic herring run only 14–18 cm; Atlantic herring can reach about 46 cm and 700 g; Pacific about 38 cm.
Some Atlantic stock spawns every month of the year on rock, gravel, or algae; females lay roughly 20,000–40,000 sticky eggs (about 30,000 average). Eggs need wave turbulence; thick mucus layers smother them. Incubation lasts about forty days at 3 °C, fifteen at 7 °C, eleven at 10 °C, and fails above 19 °C. Larvae hatch 5–6 mm long and nearly transparent, looking herring-like near 40 mm, reaching about 10 cm at one year and first spawning at three. By day they linger deep; at night they filter plankton at the surface. When copepods pack densely, schools switch to ram filter-feeding, aligning in grids matched to the prey's roughly fixed jump length—after about eighty jumps a copepod tires, and the next herring snaps it up.
Higher predators from cod and tuna to rorqual whales that lunge through bait balls depend on them; humans have eaten herring since at least 3000 BC, calling them "silver darlings" or "silver of the sea," rich in EPA, DHA, and vitamin D.
The multitude in the name is also a hunting machine.
Source: Herring
