Pink Salmon (Oncorhynchus gorbuscha) are the most numerous of the Pacific salmon species. Often referred to as “Humpy” because of the pronounced physical change they undergo before spawning, they are also the smallest, typically averaging between three and five pounds. These fish constitute an important component of Washington’s ecosystem, and their periodic mass return to natal freshwater streams offers a major event for observers and anglers throughout the Puget Sound region.
The Biennial Run Cycle
The Pink Salmon run adheres to a two-year life cycle, which dictates that significant returns only occur during odd-numbered years. Every pink salmon completes its entire life cycle in exactly two years, returning to the river of its birth to spawn and then die. This predictable two-year pattern has resulted in the evolution of two separate genetic lines: an odd-year line and an even-year line, which are reproductively isolated.
In Washington State, the odd-year population is overwhelmingly dominant, while the even-year population is often negligible or non-existent. This means a massive run of pink salmon is reliably expected in odd years (such as 2023 and 2025), while intervening even years see very few fish returning.
Peak Timing and Migration Routes
The Pink Salmon migration into Washington waters begins in late summer, reaching its peak density in August. The vanguard of the run is typically observed entering the Strait of Juan de Fuca in late July. The highest concentration of fish, known as the primetime fishery, generally occurs from the second week of August through the first week of September.
Prominent migration routes lead to rivers such as the Skagit, Snohomish, Puyallup, Green, and Nisqually. Pink Salmon generally spawn in rivers closer to tidewater than other salmon species, often migrating less than 30 miles from the river mouth. The timing of their final push into freshwater is often influenced by rainfall, as an increase in river flow in early September encourages them to leave the saltwater and race upstream.
Identifying Pink Salmon in Their Spawning Phase
In their spawning phase, males undergo the most pronounced change, developing a large, fleshy, humped back just in front of the dorsal fin. This feature gives them the nickname “Humpy” and is accompanied by a change in their jaw structure, which becomes sharply hooked.
Both sexes transition to a duller pattern of pale grey on the back with a yellowish-white belly. Males often exhibit sides blotched with brownish-green or reddish patches, while females undergo a similar but less intense color change and do not develop the large dorsal hump. Throughout these transformations, the large, dark, oval spots scattered across their back and entire tail fin remain a consistent, distinguishing characteristic.