Coho Salmon Oncorhynchus kisutch

Juvenile Coho fry spend their first winter in small streams and marshes before migrating into the North Pacific

Few animals on the Pacific Coast of Canada symbolize the interdependence of natural ecosystems and people like salmon. Historically, these silver-sided fish have been the principal food for many First Nations peoples and significant in their spirituality. Early 19th century towns were often fish canneries. Even today, smoked salmon is one of Canada's internationally known exports.

The six species of Pacific salmon - Chum, Pink, Chinook, Coho, Sockeye and Steelhead - have a similar life cycle: hatching from eggs laid in the gravel of freshwater lakes, rivers and streams, heading out to the ocean to mature, then returning as adults to lay (spawn) or fertilize eggs and die. Of the five species (not Sockeye) that use the Little Campbell River, upon which A Rocha Canada's study site is centered, Coho Salmon have so far been the focus of A Rocha's work.

While other species spawn in larger lakes and rivers, returning adult Coho head up into the headwaters of streams to the cold, narrow tributaries that penetrate our mountainous temperate rainforests. Here in the fall, female Coho spawn eggs into gravel beds while males fight to fertilize them. In early spring, the eggs hatch into alevin that remain in the gravel, feeding from their yolk sac. Coho eventually emerge as fry to spend a whole year in freshwater, eating insects and overwintering in marshes and backwaters that fill only in heavy rains. Smolting, a kind of puberty for salmon, precedes their migration to the ocean. Upon reaching the Pacific, smolts will often linger close to the estuary using eelgrass for cover, before heading out to pursue larger prey.

Measuring fry - A live Coho fry is out of the water momentarily to be measured and recorded

Coho Salmon are vulnerable to human activity. Urbanization, hydroelectric development and logging have often overlapped with natural Coho streams, blocking them with dams or culverts, covering gravel habitat with silt or pavement. Even in the ocean, the Coho's tendency to remain near the estuary leaves it vulnerable to coastal pollution. There are also effects we don't fully understand: marine survival rates have dropped significantly in recent years, perhaps an effect of changing climate.

A Rocha Canada has been working to protect and restore Coho Salmon habitat. In North Vancouver, we have been monitoring Coho through spawner and fry surveys. In the less urbanized Little Campbell, we are working to restore habitat as well. A recent project removed a collapsed culvert from a tributary, opening up significant overwintering habitat. The salmon need us too - it's time to give back.

Patrick Lilley
Originally in A Rocha International News
Issue 33, January 2004