The yearly Pacific herring spawn on Vancouver Island is one of the most important natural events in the Pacific Northwest. These small but mighty fish are a crucial part of a healthy food web and have immense ecological and cultural significance. Here’s why their spawning event is so important.
What is the herring spawn?
Every spring, millions of mature adults travel from offshore to shallow coastlines to spawn. Females release their eggs into the water column, and males release milt containing sperm to fertilize the eggs. This turns the water a spectacular milky turquoise colour.
The sticky eggs settle onto kelp, eelgrass, and rocks and incubate for 11-40 days. There can be up to 6 million eggs per square meter!
The abundance of herring and their nutrient-rich eggs attract huge amounts of wildlife. Bald eagles, gulls, ducks, seals, and sea lions create a feeding frenzy in spawning areas. Bears and wolves can be spotted on beaches feeding on the herring eggs. Whales like grey whales, humpback whales, and Bigg’s (transient) killer whales can also be spotted.
How often do herring spawn?
Herring have a lifespan of 8-10 years. Unlike salmon, they don’t spawn once in a lifetime… most individuals will spawn 5-7 times in their life. This means that each female can provide the ecosystem upwards of 140,000 eggs in her lifetime!
Why are herring so important to wildlife?
These little silver fish have a big job. When spawning in shallow, coastal areas, this massive flux in energy delivers large amounts of food and nutrients to the ecosystem and its inhabitants. Nearly every coastal species in British Columbia relies on herring for essential nutrients.
Herring and their eggs are food for an immense number of marine animals including salmon, sea birds, eagles, seals, sea lions, and even whales like humpbacks and grey whales. While spawning, they’re also an important food source for terrestrial animals like bears and wolves.
The eggs that succeed in incubation and aren’t eaten, stepped on, or dried out will hatch a tiny herring. These herring will make their way offshore and after around 3 years will join in on the yearly spawn.
It’s believed that the success of the herring spawn affects the reproductive success of coastal wildlife in the Pacific Northwest! Without these tiny, mighty fish and their eggs, the food web would collapse.
Delivering nutrients to terrestrial ecosystems
The herring spawn is an important link for nutrients between marine and terrestrial ecosystems.
The animals feasting on spawning herring and their eggs transport high amounts of nutrients and energy from the ocean to terrestrial and freshwater ecosystems. For example, if a gull eats herring eggs from kelp on a beach, it’s then going to deliver those nutrients to the forest when it poops while flying over!
After the hatching period, dead eggs and casings in shallow waters are subject to waves and tidal movement. This can deliver the eggs to intertidal and coastal ecosystems as they decompose, providing the area high amounts of nutrients.
Herring and their eggs are historically an important food source and hold cultural significance for many coastal Indigenous peoples in the Pacific Northwest. Using sustainable and responsible methods like spawn-on-kelp (SOK), herring are able to spawn naturally and their eggs are not over-harvested.
Threats to herring
These little fish have a big job, and are incredibly important for a healthy marine ecosystem. To learn more about herring and threats they face, visit Hornby Island Conservancy. We’re hoping the future in herring fisheries brings more sustainability.