Every spring, adult herring congregate in huge numbers to spawn along the coastal shores. Between February and April, depending on location, the females lay their sticky eggs on seaweed, sea grass, or rough rocks. On average, each female lays 20,000 eggs. The males spread their sperm, turning large swaths of the ocean into a characteristic turquoise blue color. Depending on the intensity and size of the spawning population, spawning activity lasts 2 to 4 days. Due to their long incubation period at relatively shallow depths, herring eggs are susceptible to a variety of physical and biological dynamics such as wave action and predation. As a result egg mortality is very high. However eggs can even still develop if they temporarily fall dry (–> see video).


A spawn event can stretch over many kilometers of shoreline. Approximately 5,285 km (or 18 %) of British Columbia's extensive 29,500 km coastline have been classified as herring spawning habitat. Of this, an estimated 300 to 600 kilometres, or about 1.8 % of BC's total shoreline length, is intensively utilized by herring spawners in a typical season. Unlike salmon, herring do not die after spawning, and they spawn every year.

Freshly laid herring eggs on bladder kelp in the intertidal.   Photo: Mark Wunsch



Monday, October 7, 2013