Paralleling the decrease of available spawning and rearing areas for 

 the bluebacks has been the decline of the commercial catches of blueback 

 salmon. This is illusorated in figure 2 and shows early catches of 1 mil- 

 lion povjids to be common, mth occasiona"". takes exceeding h million poiinds 

 (Craig and Hacker ipliO , po I98) „ 'AH.de fluctuations occurred in the com- 

 mercial fishery but a distinct downward trend persisted until a low of only 

 8_„500 pounds was taken in 19hS'> 



PRESENT STATUS OF BLUEBACK RUNS 



Since the Grand Coulee Fish Salvage Project of 1939~ll3, the blueback 

 runs have shown evidence of recoveryo This may be a result of special 

 effort in connection with the salvage program (Fish and Hanavan 19^8, p«^), 

 or may be merely a natural fluctuation such as those which occurred before 

 the Grand Coulee Dam was built „ 



In their spawning migration blueback salmon must pass over Bonneville 

 and Rock Island Dams (figure 3) where counting stations are maintained. The 

 counts of salmon over the two. dams on the migration route to the spawning 

 grounds help considerably in an. analysis of the runs,. Information obtained 

 from the States of Oregon and Washington on daily deliveries of blueback 

 salmon to canneries enables us to complete the picture of the trends of 

 abundance of the species o 



An example of the runs analysis derived from the available information 

 is seen in table 1. Inspection of the Rock Island Dam precentage of escape- 

 ment (item 13) reveals considerable fluctuation from year to year. This is 

 probably due to three factors? (1) low water conditions and resulting higher 

 temperatures causing mortality2/j (2) natural mortality of fish infected with 

 disease or otherwise in a weakened condition^ and (3) straying into other 

 streams o The percentage of fish at Rock Island Dam does appear to be in- 

 creasing, however, as shown in table 1, 



Item 11 in table 1 gives fishing intensity which is calculated by 

 dividing the total commercial deliveries by the total estimated run. It 

 can be seen that there is a wide variation in fishing intensity, which 

 ranges from 13o^ to 89,3 percento The 19^8 and 19U9 rates of fishing in- 

 tensity were low due to & closure of commercial fishing during the major 

 part of the blueback nigra tion^ the purpose of the closure being to obtain a 

 larger spawning escapement so as to increase future runs of fish. 



2/ The extremely small percentage of bluebacks reaching Rock Island in 19hl 

 was caused by extreme low water conditions aggravated by a water shortage as 

 a result of the filling of Grand Coulee Reservoiro Low water caused lethal 

 temperatures and provided poor passage over artificial and natural barriers 

 in the river (Fish and Hanavan I9U8, p. ^1) » 



