102 



FISHERY BULLETIN OF FISH AND WILDLIFE SERVICE 



CHINOOK SALMON 



The chinook salmon is native to the Pacific 

 coast from California to Alaska. Some runs ex- 

 tend from Bering Strait to the southern Siberian 

 coast. By transplantation of fertilized eggs, runs 

 have been established in the St. Lawrence River 

 and in certain parts of New Zealand. The 

 Columbia River supports the largest population of 

 the species. 



In the Columbia River, most of the chinook 

 salmon migrate upstream from March through 

 September. The migration is divided into three 

 more or less distinct classes, and the fish are 

 referred to as spring-run, summer-run, and fall-run 

 chinooks, according to the time they leave the 

 ocean and start on their upstream journey. The 

 smaller spring chinooks, which average about 15 

 pounds in weight, ascend the Columbia River 

 system for considerable distances and spawn in 

 headwaters from mid-July to mid-September. 

 The larger summer chinooks do not go as far 

 upstream as the spring chinooks, and the time of 

 spawning is later, from September to mid-No- 

 vember. The fall chinooks spawn chiefly in the 

 lower Columbia River tributaries and in the main 

 stems of the Columbia and Snake Rivers at about 

 the same time as the summer chinooks, and the 

 two classes are comparable in size. The summer 

 chinooks have an average weight of about 30 

 pounds, and the fall chinooks average 20 to 25 

 pounds. 



The following three sections describe and com- 

 pare the size and other characteristics of the 

 redds made by spring, summer, and fall chinook 

 salmon, in several tributaries of the Columbia 

 River. 



SPRING CHINOOK 



Investigation of spring chinook salmon redds 

 was made in the Ohanapecosh River, a tributary 

 of the Cowlitz River (which is a lower-Columbia 

 tributary), and in Nason Creek, a tributary of 

 the Wenatchee River. The Ohanapecosh has a 

 natural run of spring chinook salmon, whereas the 

 Nason was one of the streams into which fish were 

 transplanted during the Grand Coulee fish- 

 maintenance project. 



The average redd size and gravel composition 

 of these two streams may be compared in figure 5o, 

 circles A and B. The Ohanapecosh, a mountain 

 stream, contained a high proportion of large 



rubble about the size of a football. Because of the 

 large-gravel component, the Ohanapecosh redds 

 were considerably smaller (2.9 square yards) than 

 Nason Creek redds (4.9 square yards). The 

 Ohanapecosh redds contained an average of 59 

 percent medium and small gravel, whereas the 

 Nason Creek redds averaged 86 percent medium 

 and small. 



Spawning times, stream depths at the redds, 

 depths of redds, and water velocities and tempera- 

 tures for the spring-chinook redds in the two 

 streams are given in the table. 



SUMMER CHINOOK 



The spawning of summer chinook salmon was 

 studied in the Entiat River, the Wenatchee River, 

 and the White River tributary of Wenatchee Lake. 

 These are streams selected as foster rivers for some 

 thousands of the chinook salmon blocked by Grand 

 Coulee Dam. The spawning redds measured were 

 made by the transplanted salmon, trapped at 

 Rock Island Dam near Wenatchee, Wash., in July, 

 August, September, and October. Because of the 

 similarity of summer-run to fall-run chinook sal- 

 mon in all but time of migration, I have combined 

 the measurements of the summer-chinook redds 

 with those of fall-chinook redds in the size fre- 

 quency graph, figure 7. 



For the 41 redds measured in the Entiat, the 

 average size was 7.8 square yards. A comparison 

 of the Entiat average, figure 5a, circle C, with the 

 average nest areas for summer and fall chinooks 

 from other streams shows that the Entiat River 

 redds were distinctly larger than those in other 

 streams. The Entiat River contains an abundance 

 of medium and small rubble which facilitated redd 

 construction and resulted in large redds. The 

 degree of cementation was less in the Entiat than 

 in the Kalama River or the Toutle River (where 

 fall-chinook redds were studied) and probably con- 

 tributed to the ease of digging. Subsurface per- 

 colation was greater, and this is a factor that 

 governs the location of redds to a greater extent 

 than is generally recognized. 



It was noted that most spawning took place on 

 gravel through which there was a flow of water. 

 The flow was detected by releasing potassium- 

 permanganate solution in test holes in the stream 

 beds. There were areas in the Entiat River and 

 in nearly all streams examined, apparently unex- 

 celled for redd building and where trial redds were 



