Phenology Files: August 2021

Coho salmon navigating the Sol Duc River/John Gussman

Coho fry in the Sol Duc River/John Gussman








phenology \ fi-ˈnä-lə-jē \ n 1 : a branch of science dealing with the relations between climate and periodic biological phenomena (such as bird migration or plant flowering) 2: periodic biological phenomena that are correlated with climatic conditions.

Coho Salmon (Oncorhynchus kisutch)

This anadromous fish spawns in fresh water, migrates to the ocean and matures, and then migrates back to its place of birth to spawn and subsequently die. The phenology of of spawning varies, but coho, along with chinook and sockeye salmon, all spawn in late summer to early fall ⁠— right about now.

Coho salmon can spend up to a year as fry in a stream or river before heading out to sea, so quality natal habitat is critical to their survival. Clean, cool water, shade, woody debris, large rocks, and calm side channels are important in enabling fry to hide from predators as well as protect them from being washed downstream during high winter flows.

While coho salmon are found all over the Olympic Peninsula, including the Elwha River, one of the best places to watch their return from the ocean is at the Salmon Cascades Overlook on the Sol Duc River in Olympic National Park. Coho must travel a little over 4 miles up the Quillayute River just to get to the mouth of the almost 80-mile-long Sol Duc. Although not all coho spawn all the way up the Sol Duc River, every bit of quality habitat benefits their success and survival on the last trip they will ever make. It’s an annual event reminds us of the changing seasons and rewards us with one of the most awe-inspiring rituals of nature.