Chinook Salmon

Oncorhynchus tshawytscha

Native Trout Fly Fishing

A Puget Sound resident chinook salmon caught at night using a glow in the dark fly

Introduction

Chinook or king salmon are the largest of the Pacific salmon and can attain weights in excess of 100 pounds, with the largest confirmed fish weighing in at 127lbs. Most adult fish are much smaller than this though, and the average size is between 10 and 25 pounds and 28" and 40" in long (Behnke 2002). Due to their size, life history patterns and somewhat due to over-harvest Chinook are also the least abundant species of Pacific salmon.

Life History Information

Chinook salmon exhibit a wide variety of life history strategies and while the overwhelming majority of these fish are anadromous they have adapted to make the most of their environment. Much of this diversity occurs with how Chinook utilize their spawning habitat. Most Chinook salmon spawn during the fall, with the bulk of the spawning activity occurring between September and November (Behnke 2002). Spring spawning runs are also fairly common across the native range of Chinook salmon and these fish generally arrive during April and June and than spawn during late summer or early fall. These differences in run timings are largely due to the type of habitat that is used by the spring and fall run fish. Spring Chinook tend to spawn near the headwaters of streams in areas that are inaccessible except during the high flows of spring run-off. The fall Chinook on the other hand generally utilize the lower reach of rivers as spawning and rearing habitat, allowing them arrive during the lower flow periods that typically occur during late summer and early fall. One river of note for Chinook salmon is the Sacramento which has four distinct spawning runs corresponding with each season; winter, spring, summer and fall. While Chinook salmon are considered a fall spawning fish, the winter run fish from the Sacramento River generally arrive in January and February and spawn during May. This population represents the only native population of chinook known to spawn during the spring (Behnke 2002). Once Chinook reach the inner estuary of their spawning stream they stop feeding, a behavior which is common to all Pacific salmon. Some populations of Chinook spawn very far from the ocean, and have been noted to spawn between 1000 and 2000 river miles upstream ocean in the Columbia and Yukon River systems. Chinook salmon tend to utilized larger streams and rivers for spawning habitat and are even known to spawn in the main stem of the Columbia River.

Chinook salmon populations are usually broken up into stream type and ocean type fish depending on the age at which they migrate to sea. Stream type fish generally reside in their natal stream for anywhere from one to three years. While ocean type fish migrate to sea within their first year and are more common in the southern part of the Chinook's native range where there is a higher growth rate. In the Columbia River system these two forms correlate with the fall and spring spawning runs as well. The fall Chinook of the Columbia River and the spring Chinook of the lower Columbia belong to the ocean type lineage while the spring run fish of the mid and upper Columbia and Snake River systems belong to the stream type lineage (Utter et al. 1995). Teel et al. (2000) showed that these two life history types are genetically distinct, and it is thought that they arose from geographic isolation during the Pleistocene glaciations.

Although rare, Chinook salmon also have a stream resident life history pattern where the parr (juvenile fish) stay in the stream until adulthood instead of migrating to sea. Once the smolts enter the saltwater, they often spend some time feeding in the estuaries (generally in the spring). While some Chinook salmon remain in estuarine waters near their home river most travel further out to sea. The general trend for Chinook salmon is to travel northward from their home stream while remaining in coastal waters (Quinn 2005). This is just a general trend though, and catch records from fishing on the high seas indicate that a large number of Chinook salmon do travel out to offshore waters as well. In the Puget Sound, there is an estuarine life history form known as "blackmouth," which matures in the waters of the sound instead of traveling further out to sea. Chinook in the saltwater show a low tolerance to light, and are generally found in deeper water than the other four species of salmon. In the ocean their diet is largely made up of other fish (60 - 70%) but they also feed on crustaceans, which make up the remaining 30 - 40% of their diet. Most Chinook return to spawn at two to five years of age, with some returning at up to eight years old.

Genetically speaking, both Chinook and coho are more closely related to trout than the other North American species of Pacific salmon. While Chinook have never been documented to survive to spawn more than once in the wild, under hatchery conditions stream resident male Chinook parr have been shown to have the ability to spawn up to three times (Unwin et al. 1999). Although hybridization with other species of salmon is rare, Chinook have been documented to hybridize with both coho and pink salmon most likely due to hatchery stock influences. This hybridization appears to occur on a more regular basis in the Great Lakes where both Chinook and pink salmon were introduced and produce a hybrid fish commonly called pinook salmon.

Status

Currently Chinook populations are depressed throughout much of their native range. Of the 17 recognized evolutionarily significant units (ESU) of Chinook salmon in Washington, Oregon, Idaho and California, two are listed as endangered, and seven are listed as threatened (NOAA, 2007). The causes of the decline of Chinook salmon can be traced back mainly to the four H's. In the Columbia River system, hydroelectric dams have severally limited the abundance of Chinook salmon. The Grand Coulee dam alone in eastern Washington which was built without a fish ladder cut off access to over 1,000 miles of spawning and rearing habitat. To reach the uppermost spawning grounds in the Columbia River system, Chinook must travel over nine dams. A study done on hatchery Chinook smolts in the Snake and Columbia River systems showed that there is about a 6% to 11% mortality rate at each dam (Muir et al. 2001). Some of the causes of this mortality include damage from contact with the turbines, delayed migration timing due to the slack water behind the dams, and increased predation. When you add in the damaged done to Chinook populations by habitat destruction, hatchery fish, and over harvest, it is easy to see why so many populations are in trouble.

Description

Chinook salmon have irregular shaped and sized black spots, which are generally concentrated above the lateral line, and across their dorsal and caudal (tail) fins. Juvenile Chinook salmon rearing in freshwater, tend to have olive to greenish-brown backs and silvery sides with nine to eleven oval parr marks. During the smolting process, the parr marks begin to fade and the Chinook become more silvery in preparation for their marine journey. This increase in the silver coloration results from the deposition of guanine in the skin of the fish and is thought to provide better camouflage in the marine environment (Haner et al. 1995). Like all species of Pacific salmon, this bright silver coloration predominates throughout the marine portion of Chinook salmon's lifecycle. A distinguishing feature between Chinook and coho salmon is that Chinook have a black coloration on their gums, which has earned them the name "blackmouth." Coho on the other hand have more of a gray to white color on their gums. When they reach the freshwater to spawn the silvery sides of Chinook change to a reddish brown or maroon color on their sides and males develop a kype.

Fly Fishing Information

Although Chinook salmon can be readily taken on the fly under the right conditions, they are not considered to be nearly as fly friendly as coho, pink or chum salmon. Chinook are very sensitive to light and as such they tend to hold in deeper water while in marine waters, far from shore thus being out of the range of beach anglers most of the time. In the Puget Sound, Chinook with the resident life history pattern can be caught from shore with the right tactics. For those anglers to don't mind missing some sleep, these fish can often be found near shore during low light conditions and will aggressively attack flies. When targeting Chinook at night, glow in the dark or black baitfish and squid patterns can draw some aggressive takes. In rivers these fish generally like to hold in deep pools and are best targeted will sink tip lines and a wide array of flies. While Chinook in rivers can be quite "lock-jawed" at times certain colors will often trigger them to hit flies, with popular colors being black, pink and orange.

Smolt Stage

Click on images to view a larger picture

 

Estuarine Resident

Native Trout Fly Fishing

A chinook salmon caught in the waters of the Puget Sound

Native Trout Fly Fishing

A chinook caught during the winter of 2006 at night

Native Trout Fly Fishing

A chinook salmon caught on a glow in the dark fly at night

Native Trout Fly Fishing

A Puget Sound chinook salmon caught off of the mouth of a creek at night

 

 

Spawning Stage

 

Native Range

Native Trout Fly Fishing

A map of the native range of Chinook salmon in North America. Data Sources: Behnke (2002) and Augerot et al. (2005).