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FISHERY BULLETIN OF FISH AND WILDLIFE SERVICE 



salmon, 11 square yards; and blueback salmon, 

 8 square yards. 



SUMMARY 



1. Observations were made on a large number 

 of chinook, silver, chum, and blueback salmon 

 redds in the Columbia River watershed, and 850 

 redds were measured. 



2. Normally, the female salmon constructs the 

 redd, the male taking no part in this activity. 



3. The redd is formed or excavated by the 

 female turning on her side and making violent 

 flexions of the body and tail. The boiling currents 

 set up by this action disturb the gravel of the 

 stream bed which is carried a short distance 

 downstream to form the tailspill. 



4. A typical redd is an excavation in the stream 

 bottom, oval in shape, the greatest diameter being 

 lengthwise with the current, and with a tailspill 

 at the downstream end. The center of the redd 

 is referred to as the pot, and it is here that the 

 bulk of the eggs is deposited. 



5. Current velocities at spawning areas varied 

 from less than 1 foot a second to 3.5 feet a second. 

 Redds made in fast water were invariably long 

 and narrow; those in quiet water had a broad 

 oval shape. 



6. The current in the pot of the redd flows 

 slightly upstream, which favors safe deposition 

 of the eggs in the gravel and is conducive to 

 complete fertilization by the milt of the male 

 salmon. 



7. As the spawning progresses, the redd in a 

 sense moves upstream by continued excavation of 

 the upstream edge and filling in of the tailspill 



area. 



8. In general, salmon chose areas of stream bed 



composed of gravel less than 6 inches in greatest 



diameter, with the size of the redd inversely pro- 

 portioned to the size of gravel. Firmly cemented 

 gravel was avoided, though where there was some 

 cementation, the size of the redd was inversely 

 proportioned to the amount of cementation. 



9. Percolation of water through the gravel 

 appears to be a requisite of the redd site. 



10. In general, salmon prefer areas of stream 

 bottom relatively free of mud or silt for redd- 

 making purposes. Silvers (0. kisutch) were the 

 only salmon of the four species which constructed 

 redds in areas of stream bottom containing up to 

 10 percent mud. 



11. Average redd size for the various salmon is 

 as follows: Summer and fall chinook, 6.1 square 

 yards; spring chinook, 3.9 square yards; silver, 

 3.4 square yards; chum, 2.7 square yards, and 

 blueback, 2.1 square yards. 



12. Few redds of any species were made side 

 by side. For the most part, nests were either up 

 or down stream from each other so that they 

 woidd form diagonal rows across the stream. 



13. The tendency of female salmon to prevent 

 other females from getting too close resulted in 

 interredd space approximately three times the 

 size of the redd. 



14. By dividing the area suitable for spawning 

 in a given stream by four times the average redd 

 area, a conservative estimate will be obtained of 

 the number of salmon that may satisfactorily 

 spawn in the stream. 



LITERATURE CITED 



Fish, Frederic F., and Mitchell G. Hanavan. 



1948. A report upon the Grand Coulee fish-maintenance 

 project 1939-1947. U. S. Fish and Wildlife Service, 

 Special Sci. Rept. No. 55. 



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