Coho Salmon

Coho salmon in ocean coloration
Photo: Washington Department of Fish and Wildllife

(Oncorhynchus kisutch)

Other names: Silver Salmon

Coho salmon typically weigh between 8-12 pounds and measure, on average, 24-30 inches long. Smaller coho, ranging in length from 12-20 inches, may be seen spawning with larger fish. These smaller male coho are referred to as “jacks” and return to spawn after only one year in the ocean. Other species of salmon also have precocious jacks that comprise small segments of annual spawning populations. Coho salmon closely resemble chinook salmon in ocean and spawning coloration. Distinguishing characteristics for coho salmon include spots on the upper lobe of the caudal fin (not on the bottom lobe), white instead of black gum coloration, and an overall smaller size. Coho are typically not quite as “beefy” in appearance compared with chinook. They are often targeted by recreational anglers but are typically not as highly esteemed as chinook salmon.

 

Figure 5. Distinguishing features of coho salmon: no spots on the lower lobe of the tail (left) and a lack of black coloration (white gums) at the base of the teeth (right).
Photo: Washington Department of Fish and Wildlife

Abundance, distribution, and natural history

A total of 322 records exist for this species in the park but only 30% provide spawning fish abundance estimates. Coho salmon are documented in 56 streams and tributaries (spawning adults in only 26) but they’re likely in almost every stream from short, small creeks one can literally step across to large complex systems like the Dundas/Seclusion and Alsek River. The fish enter rivers from August through October with peak abundance occurring in September. Few records exist beyond October, although fish are still present in streams, because little research or recreational fishing typically occurs at this time of year.

 

A Male coho salmon in spawning coloration.
Photo: Washington Department of Fish and Wildlife

Conservation measures and concerns

Coho salmon throughout Alaska and within the park are generally not a conservation concern because of their widespread spawning distribution and relatively undisturbed habitat. Spawning populations in small creeks and headwater streams may be very small, numbering in the tens or hundreds of individuals. These small populations could be susceptible to overharvest by recreational anglers or extinction due to geologic forces (e.g., glacial advances, landslides, etc.) affecting spawning habitat or habitat access. Development and logging on or adjacent to small streams in the Pacific Northwest has also threatened spawning runs. Protection of small, seemingly inconsequential watersheds and “ditches” is key to preserving species diversity.

 

Relative (averaged across records) coho salmon run timing. Values in parenthesis indicate number of records for each month (total n = 96).