Coho Salmon

Introduction: Coho salmon are also known as silver salmon, for their bright silver color while at sea. These fish average between 6 and 9 pounds and 24 to 28 inches in length, and are the second least abundant species of Pacific salmon behind Chinook (Behnke 2002). Coho are the third largest species of Pacific salmon, with the world record fish weighing in at 33lbs.

Life History Information: While Chinook salmon populations have four distinct spawning runs, coho tend to be strictly fall spawners. As a general rule, coho spawning runs occur from September into November, but in some streams spawning may occur as late as February (Behnke 2002). For the most part coho only spawn in streams within 100 to 200 miles of the saltwater, although some travel much further. One example of this is the coho populations of the Yakima River system in Washington, which travel 400 or more miles from the ocean to reach their spawning grounds. The majority of Coho salmon spawning occurs in smaller sized streams and tributaries of rivers, instead of the in the main river channel like Chinook.
Coho usually hatch between March and April, and generally will spend one year in their natal stream before migrating out to sea. However in some populations juveniles may head out to sea the spring after they hatch or remain in their natal stream for two years. Coho smolts usually head out to the saltwater in April and May at a length of between 4 and 5 inches. Most coho head out further out to sea after feeding in estuarine waters for a short time, but some may stay to spend their entire lives in these estuarine waters. This life history pattern is quite common wild fish in the Puget Sound, although the majority of these "resident" fish are of hatchery origin. The hatchery "resident" coho fishery is maintained by holding the young coho in net pens longer than usual, causing a large portion of them to remain in the Puget Sound. The Puget Sound resident coho will often make a mini migration north into the Strait of Juan de Fuca, but do not general grow as large as their ocean going counterparts. Ocean going coho generally feed in the coastal waters off of the continental shelf, and have a tendency to travel north of their natal streams. While at sea coho feed mostly on euphausids, squid and fish and feed the second highest on the food chain after Chinook salmon (Quinn 2005). Generally speaking coho and Chinook travel slower than other salmon on their migration from their feeding grounds to their natal stream, often feeding heavily along the way. Most coho return to spawn after two years at sea (3-4 years of age), although some males; referred to as "Jacks" are known to return after a single summer of feeding in marine waters.

Status: As with the other species of Pacific salmon, coho populations have severely declined across their native range since the arrival of European Americans on the west coast. Today out of the seven ESU populations of coho that have been identified by NOAA in Washington, Oregon and California, one is currently listed as endangered, and two are listed as threatened (NOAA 2007). Like the other species of salmon, there is a slough of factors that are contributing to the decline of coho populations (4 H's) with two of the major ones being habitat destruction and hatchery fish. The use artificial propagation has been a long standing problem in fisheries management. This is a major problem facing coho and other salmon populations and dates back to when the original brood stocks of hatchery salmon were established. At that time local adaptations were not taken into account and hatchery stocks were often mixed and/ or brought in from out of state. When these hatchery fish return and spawn with native fish it leads to a loss of genetic adaptations to the local environment. Another problem with hatchery fish has to do with competition with native fish. When the hatchery fish are released, they are generally larger than the native fish making them better competitors for food and territory (Lichatowich 1999). Beyond this due the fact that the hatchery fish are raised in confined areas (raceways and holding ponds) with many other fish, they tend to be bolder also giving the a competitive edge. Logging and urbanization have been especially harmful to coho due to the habitat destruction associated with them. The loss of riparian vegetation from logging leads to warmer water temperatures and lower summer time flows, which can be lethal for juvenile salmon. Due to the loss of forested lands and increase in paved land in areas with urbanization and logging, the effects and magnitude flooding and run off events are greatly increased. This in turn leads to in increase in scour and erosion causing more silt to enter the streams. This increase in siltation can be lethal to incubating salmon eggs by cutting off their air supply. These are just a couple of the issues in the long list of problems facing coho salmon, and salmon in general for that matter making it no big surprise that coho stocks around the Pacific Northwest are depressed.

Description: Coho salmon tend to be somewhat similar to Chinook in appearance, but do have a few distinguishing traits. The first way to tell these fish apart is that Chinook have black gums where as coho salmon have gray gums. Also Chinook salmon have spots across their entire tail, but coho just have spots on just the upper half. The coloration juvenile coho is generally olive to greenish-brown with silvery sides, and the anal fin tends to be more curved than in other species of Pacific salmon. Coho typically display small irregular shaped spots above the lateral line and while in the saltwater these fish have a bright silver coloration, with bluish-green to greenish-brown backs. As spawning approaches, coho become dull greenish-brown to rosy or maroon color. Like other species of salmon the morphology of male coho tends to be more extreme than that of the females. When spawning approaches the males obtain small hump in front of their dorsal fin, as well as a pronounced kype, which has led to the nickname of "hook nose" for late season male coho.

Fly Fishing Information: Coho salmon have long been very popular with fly fisherman, due to their willingness to hit flies and their hard fighting nature. When coho are intercepted in the ocean or in waters some distance from their natal streams, they will often hit flies with reckless abandon. However once coho reach their home estuary they can become very difficult to catch due to the fact that they stop feeding once they reach freshwater. In Washington it is not unusual to find good numbers of coho off of estuaries that refuse any offering an angler throws at them. However at other times these "lock jawed" fish in the Puget Sound will take flies very willingly. One life history form of coho that provides a particular appeal for fly fisherman in the Puget Sound region is known as the "resident coho". These fish can be caught from shore during any time of the year in the Puget Sound although fishing tends to be best during the winter and spring. Resident coho usually are not very large, averaging around 12" - 16", with some larger fish around making them great fish to target with a six weight rod. When adult ocean going coho arrive in the rivers, they are generally best targeted with a 7 or 8 weight rod and are usually receptive of flies in pink, orange, and chartreuse with a bit of flash.