Herrings are best known for forming large schools. Being in large groups helps the fish swim efficiently and discourages predators (PREH-duh-terz) or other fish that may hunt them for food. Herrings also form smaller, less-organized groups called shoals, particularly during spawning season. Some herrings migrate, or travel, from the ocean to streams and rivers for spawning. Many herrings make daily migrations in the water, staying deep during the day and moving to shallows at night.
Herrings produce large numbers of offspring. Some species spawn once a year, and others spawn several times a year. Most herrings spawn in shoals by releasing large numbers of small eggs that float near the surface. After fertilization (FUR-teh-lih-zay-shun), or being united with a male's sperm, the eggs and larvae drift in the current as they develop. Some herrings produce eggs that sink to the bottom, where they stick to rocks, gravel, or sand until they hatch. After hatching, larvae move to open water.
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