Fish & Water - Sounds Wild
Pacific Herring

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Pacific herring

On a spring day in Juneau, I take a shortcut to work and walk the docks of Aurora Harbor. There's an enormous school of fish swimming beside the dock, the harbor is filled with these small fish. I come back a few hours later with my camera and shoot some pictures and video. Thousands of silver fish about three inches long are milling about. A Fish and Game biologist later identifies them as juvenile Pacific herring.

Herring spawn in the spring, in shallow, intertidal and subtidal vegetated areas along the coast. Pacific herring are sexually mature at three or four years of age, and the fish I saw won't be spawning this year, they're juveniles.

Adult herring spawn in massive schools and an entire school can spawn in the course of a few hours. The precise staging of spawning is not understood, but biologists suspect the male initiates the process by release of milt, which has a pheromone that stimulates the female. A single female may lay as many as 20,000 eggs in one spawn, depositing the eggs on seaweed or some other substrate. The behavior seems to be collective, producing an egg density of up to 6,000,000 eggs per square meter.[6] The tiny fertilized eggs, incubate for about 10 days in near shore waters that are about 10 degrees Celsius.

After spawning Pacific herring migrate back to offshore waters to feed. They exhibit a daily vertical migration pattern, remaining near the bottom during the daylight hours and moving to shallow waters to feed at night.