Pacific Herring live in dense schools throughout their lives. Once they reach sexual maturity, they migrate from offshore feeding grounds to shallow intertidal areas to spawn, in late March to early April. Since herring have no physical defenses against their many predators, they rely on sheer numbers to survive.

Females deposit 20,000 to 40,000 clear, sticky eggs on eelgrass, kelp or other marine vegetation. Males release milky sperm, or milt, into the water. Because schooling and spawning occur in very high densities, the milt can create massive, azure colored clouds during spawning time that can be seen from a very long distance. The appearance of large groups of marine birds and/or mammals may also occur during spawning events. Along the shoreline small white/translucent eggs will be coated on intertidal vegitation and rocks.

Ten to 21 days after the eggs are fertilized, 9mm-long herring larvae emerge. In this area, Pacific herring remain in the Strait of Georgia for their first year, then move to the west coast of Vancouver Island at two to three years of age. Due to intense predation by other animals, out of every 10,000 eggs laid, only one herring is estimated to survive to return to spawn. Herring live to a maximum of about 15 years.

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