above Rock Island Dcun, although no 

 spawning ground counts were obtained. 

 Sizes of steelhead rxins passing Rocky 

 Reach were not estimated. 



Silver salmon . --Silver salmon are 

 few in this area at the present time. 

 Total yearly counts of silver Scilmon 

 at Rock Island Daun for 1954-58 have 

 ranged from 40 to 94 fish. These fish 

 p>ass Rock Island Dam during Septem- 

 ber, October, and November. Formerly 

 silver salmon were abundant. Records 

 show that approximately 6 to 7 million 

 silver salmon eggs were taken annually 

 from the Wenatchee River alone during 

 the years 1899 to 1902. From 1910 to 

 1920 the nvimbers of silver salmon eggs 

 taken annually at the Methow River 

 hatcheries ranged from a few thousand 

 to nearly 3 million (Washington State 

 Department of Fisheries, 1899-1920). 

 These silver salmon runs, though of 

 little value now, could p>ossibly be im- 

 proved. 



Rate of travel — Rock Island to Zosel 

 Dam 



The rate of travel for blueback 

 Scilmon between Rock Island Dam and 

 Zosel Dam (figure 1) was determined 

 prior to the building of Rocky Reach 

 Dam in order to ascertaun if delays 

 in migration result from the new dam 

 now under construction. The question 

 of delay and its effect upon migrating 

 salnrion has long been a matter of con- 

 jecture among fishery biologists. The 

 actual effect of a short-term delay or 

 the accumulated effect of several short- 

 term delays to migrating salmon is 

 not known. The most notable example of 

 the effect of a delay in migration has 

 been the blockade at Hell's Gate on 

 the Fraser River. Here, fish that were 

 delayed longer than 14 days did not 

 reach the spawning ground. During these 

 experiments fish captured, tagged, and 

 liberated were often recaptured below 

 the gate and the interval between cap- 

 tures was termed delay (Talbot, 1950). 

 In reference to the Columbia River and 

 many dams now built or contemplated 

 along salmon migration routes, one of 

 the problems is whether dams cause 

 delays over and above the effects of 



pre-existing conditions; and if delays 

 are caused, what might be the cumula- 

 tive effect of many dams. 



Knowing Rocky Reach Dam was to 

 be constructed we decided to determine 

 the rate of travel of salmon through this 

 stretch of river before construction. 

 Then in the future it miay be possible 

 to determine if Rocky Reach Dam de- 

 lays passage of migrating fish. 



In 1957, to determine the rate of 

 travel through this stretch of river, 

 blueback salmon were tagged with var- 

 ious colored tags, were released in 

 the forebay at Rock Island Dsuna, and 

 were observed at Zosel Dam approxi- 

 mately 145 miles upstream on the 

 Okanogan River. The use of combina- 

 tions of colored tags enabled us to 

 identify tagging dates as tagged fish 

 passed an observation point. Zosel Dam, 

 the observation point, is a small wooden 

 structure designed to forni a pool for 

 logging operations at a nearby mill. 

 Observers recorded the daily passage 

 of tagged and untagged fish through the 

 fishways at this dam; however, fish 

 were also able to pass the dam through 

 cracks in the wooden weirs. As few 

 recoveries were made from the 1957 

 experiments, the data from tagging 

 experiments of 1954 and 1955 were used 

 to obtain rates of travel between Rock 

 Island and Zosel Dams. These experi- 

 ments in 1954 and 1955 were similar 

 to the 1957 experiments and were for 

 the purpose of studying the efficiency 

 of the Rock Island Dcim fishways. 



In addition to tagging experiments, 

 peak counts at Rock Island and Zosel 

 Dams were used to determine the rate 

 of travel by computing the difference 

 in time between the peaks in abundance 

 at the two places. 



The data obtained from the blue- 

 back tagging experiments at Rock 

 Island Dam in 1954-55 are presented 

 below. "Days out" represents the time 

 interval between tagging at Rock Island 

 and recovery at Zosel Dam. The day 

 of tagging is treated as zero day. The 

 data from the two seasons were com- 

 bined because the means and variances 



