Table Ij is a summary of the information showing the estimate by stream 

 sur^reyors of the total number of square yards of suitable spavining gravels 

 available for each section in the V/enatchee systemj the number of bluebacks 

 which can be accommodated ^ and the n'jmber of spaxmers in each section in 

 19li7, ipiiSs 19h9o and 1951. It can be seen that a total of 129^,000 bluebacks 

 could spawn in the area without crowding if they distributed themselves in 

 proportion to area available.. However, it will be observed in table k that 

 some stream sections support nearly maximum populations while others remain 

 only partially usedo Altogether there is about seventy percent more suitable 

 spawning area available than was used during the largest spaiiming concentra- 

 tion in 19ii8„ 



THE OKMOGAN SURVEYS 



The Okanogan River system constitutes the second of the two major 

 spawning and rearing areas for blueback salmon. In this system is Lake 

 OsyocSj which extends north to south wj.th approximately h miles in Canada 

 and h miles in the United States^ and the Okanogan River vrbdch flows through 

 Lake Osoyoos. Tne major spaiming takes place in a 20-mile stretch of the 

 river above the lake (figure 8). The upper limit of spawning is the Oliver 

 diversion dam^ about 6 feet in height. There are no fish-passage facilities 

 there. 



Approximately the same procedure was used for counting the spawners 

 in the Okanogan as vjas used in the Wenatchee area. Table 5 is a summary of 

 Okanogan counts, Uni"ort-inately_, flooding conditions in 19U8 made it impos= 

 sible to make counts in most of the river area in that year. The best that 

 could be done was to compare the areas tallied with those of 19ii7 and make 

 an estimate of the remainder. 



Using the average counts and appljrlng the factor 5 as before provides 

 estimates of lS,125 bluebacks in the Okanogan in 19li7, 35,875 in 19U8s 310 

 in 19ii9 and 12^2U0 in 1951, The 19ii9 light run in this section is easily 

 explained in view of the predominance of a h-year cycle in bluebacks. In 

 the Grand Coulee fish-transportation program no 19U1 adult blueback or brood 

 of that year were planted in Lake Osoyoos and only hi fish (possibly made up 

 of 3-year and 5-year fish) were seen there in 19ii5o The 19li9 run resulted 

 from this 19u5 stock. 



Referring to spax-ming- gravel requirements^ table 6 gives the number of 

 square yards avai.lable compared id.th the number of spawners during each of 

 the h years. Note that this spawning area could accornmodateraany more fish 

 than our raaxim,uro estimate of 19l;8o That was also the general conclusion 

 derived from direct observation of the spawning beds. 



16 



