The river condition most apt to 

 influence day-night movement of salmonids 

 is turbidity, because light penetration of 

 the water is affected. The chinook fln- 

 gerlings in 1952 and 1953 were abundant 

 enou^t to fonn eight groups for statistical 

 analysis, and the yearlings seven groups, 

 thus permitting the fitting of regression 

 lines by the method of least squares and 

 computing coefficients of correlation be- 

 tween several factors, as shown in figure 

 13. The other species were not tested 

 because some of the periods had few fish. 

 Secchi-disk readings and percent night 

 migrants were lowest in 1952. The corre- 

 lation coefficients for fingerlings (O.65I; 

 P>0.20) and yearlings (0.663; P>0.30) 

 were not significant at the five percent 

 level. 



It is realized that the lack of data 

 precludes the acceptance of any of these 

 values £18 facts, but comparison of the P- 

 values siiggests that within the limits 

 encountered in this report the percentage 

 of night -migrant chinook salmon is more 

 highly correlated with turbidity than with 

 days elapsed from start of sampling. 



SUMMARY AND CONCLUSIONS 



1. Inclined-plane fingerling traps, 



located in the fingerling bypasses of 

 Bonneville Dam, were used to collect 

 all of the data in this report. 



05 10 1.5 20 25 



SECCHI DISK READING (FEET) 

 CHINOOK FINGERLINGS 



3.0 



0.5 1.0 1.5 2 2,5 



SECCHI DISK READING (FEET) 

 CHINOOK YEARLINGS 



3.0 



Pl«uj« 13. --Perc4at of nl^t-al^rant cMnook flD^rlla^ ODd yvarlln^ 

 plotted afialjut Gacehl-dlmk rsadlnga (1952 and 1933). LljM* 

 ■Jtoim are th* leaat-aqu&n flt«. 



Hourly sampling in 1952 and 1953 indi- 

 cates that chinook salmon and steelhead 

 trout increase their rate of downstream 

 migration during the hours at dawn and 

 dusk. Additional data are needed for 

 blueback and silver SEilmon. 



Although the correlation coefficients 

 were not significant, the data suggest 

 that the relative numbers of chinook 

 salmon which migrate at night are more 

 closely associated with varying tur- 

 bidity of the river than with time of 

 year (or advance of the migration 

 period). 



Data collected at Bonneville Dam indi- 

 cate that, although in most years 

 downstream-migrant salmonids tend to 

 migrate predominantly at night, some 

 years may have more day migrants. 



5. A knowledge of the proportion of down- 

 stream migrants sampled by the finger- 

 lings bypasses would increase the value 

 of the data In this report. 



LITERATUBE CITED 



Bamaby, J. T. 



1950. Fluctuations in abundance of red 

 salmon, Oncorhynchus nerka (Wal- 

 baum), of the Karluk River, Alaska. 

 U. S. Dept. Interior, Fish. Bull. 

 Fish and Wildlife Service., vol. 

 50, pp. 237-295. 



10 



