Table 6. --Results of tests IID through IIG where one observer's estimate of 

 number of fish is compared with another's, HoUis area streams, 1956 



Test IID - Twelvemile Creek, 

 September 1, 1956 



Test UE - Twelvemile Creek, 

 September 11, 1956 



Test IIF - Indian Creek, 

 Septennber 2, 1956 



Section 



Observer 2 

 Pool I Riffle 



Observer 3 



Pool I Riffle 



1 124 74 73 69 



2 5 4 



3 573 1,164 428 918 



Test IIG - Indian Creek, 

 September 10, 1956 



Observer 3 



Pool Riffle 



Observer 4 



Pool f Riffle 



1 144 



2 



3 121 



163 89 26 



76 72 



977 1,198 



Total 



697 



1,243 



501 991 



Total 265 l,2l6 



89 1,296 



was higher when observers estimated num- 

 bers of salmon in pools than when they esti- 

 mated them on riffles. In addition, variation 

 generally increased with increase of mean 

 estinnate. 



Such results indicate that to obtain the best 

 indices of abundance of salmon from foot 

 surveys, pools should be ignored, and num- 

 bers of salmon should be estimated only on 

 riffles. 



Therefore, I suggest that in small streanns 

 a sufficient number of estimates should be 

 made of salmon on riffles to form anabundance 

 curve. If average length of time salmon re- 

 main on riffles is known (this can be deter- 

 mined from small-scale tagging experiments), 

 then total number of salmon can be calculated 

 for the season. 



In larger streams where, for sonne reason, 

 fish cannot be counted on all the riffles, well- 



defined spawning riffles should be chosen at 

 random (in some streams stratification with 

 regard to upstream and intertidal zone or 

 other classifications may be desirable). Sum- 

 mation of estimates for each index riffle fur- 

 nishes an index of abundance for the stream 

 that is comparable from stream to streann 

 and from year to year. 



This type of enumeration decreases variabil- 

 ity because numbers of salmon in pools are 

 not estimated. Second, it allows surveyors (in 

 large streams) to concentrate on a few index 

 riffles rather than attempt to estimate the 

 nunnber of salmon in the entire stream. 

 Finally, it does away with the need to use the 

 peak count as an index. 



Environmental conditions such as light dif- 

 ferences, turbidity, rain dimpling water sur- 

 face, and stream stage can increase variability 

 in estimates. Hence, time of counting should 



