Table 8. — Unspawned female spring and summer 

 Chinook salmon in streams above Rock Island 

 Dam, 1957-60 



Table 9. --Egg retention in spawned female 

 spring and summer chinook salmon in streams 

 above Rock Island Dam in 1960''^ 



^ In addition to the 97 spawned fish, three 

 unspawned females were observed, one of which 

 probably died from spear wounds noted on the 

 carcass. 



During 1960, a count was made of the num. 

 ber of eggs retained in those fish that had 

 spawned (table 9). Egg retention was re- 

 markably low. Very little difference was 

 noticed in comparing egg retention of spring 

 and summer chinook salmon. 



Sockeye Salmon 



The two most important runs of sockeye 

 salmon remaining in the Columbia River 

 system spawn in the Wenatchee and Okanogan 

 River systems (figs. 7 and 8). In the Okanogan 

 River, nnost spawning occurred above the town 

 of Oliver, British Columbia, although sub- 

 stantial spawning occurred near and below 

 the town. In 1957-58, the construction of 13 

 vertical-drop structures by the Canadian 

 Government as a flood control project re- 

 sulted in spawning area changes. As a result, 

 nearly all of the spawning has been concen- 

 trated above the 1 3th drop structure with 

 only a scattering of spawners observed be- 

 tween the structures. Aerial surveys of the 

 river in 1959 showed some spawning between 

 all structures but one; in I960 spawning redds 

 were observed in only one section. 



In the Wenatchee River system, most sock- 

 eye salmon spawn in the White River above 

 Lake Wenatchee; the Little Wenatchee River 

 is a second major spawning area. Spawners 

 have been noted for some years in the 

 Wenatchee River at the outlet of the lake 

 and in the vicinity of the town of Leavenworth. 

 A few have been observed spawning in Nason 

 Creek. 



Scattered sockeye salnnon spawners are 

 found in the Entiat, Methow, and Similkameen 

 Rivers; some are found also at the Entiat 

 and Winthrop National Fish Hatcheries. 



SUMMARY 



Important runs of chinook salmon, sockeye 

 salmon, and steelhead pass Rock Island Dam 

 on the Columbia River bound for spawning 

 areas in main tributaries between Rock Island 

 and Chief Joseph Danns. 



Most spring chinook salnnon passing Rock 

 Island Dam in 1954 to 1960 continued past 

 Rocky Reach damsite and the Wells damsite 

 to spawn in the Methow River system. Most 

 summer chinook salmon passing Rock Island 

 spawned in the Wenatchee River; fall chinook 

 salmon passing Rock Island probably spawned 

 in the main Columbia River, mainly above 

 Rocky Reach damsite. Sockeye salmonpassing 

 Rock Island Dann spawned in both the Wenatchee 

 and Okanogan River systems. The majority 

 of sockeye salmon counted at Rock Island was 

 estimated to have passed Rocky Reach dam- 

 site bound for the Okanogan River spawning 

 areas in 6 of the 7 years of investigations. 



Most steelhead arrived at the upper Columbia 

 River areas during the fall. Silver salmon 

 were comparatively few in number. 



Spawning surveys showed the Chewack River 

 in the headwaters of the Methow River systenn 

 to be the most important spring chinook 

 salmon stream. The Wenatchee River is the 

 most innportant summer chinook salmon 

 stream. 



Length frequency distribution of chinook 

 salmon measured on spawning grounds indi- 

 cates a wide length distribution of all age 

 groups in all tributaries each year. Large 

 spring chinook salmon of both sexes were 

 noticeably absent from the Chewack River 

 samples obtained in 1957. 



Few unspawned fennale chinook salmon were 

 observed on the spawning grounds; of 898 

 females examined, only 15 (1.7 percent) were 



17 



