20 



Conservation Department 



The number of i)ouncls of fish a unit of stream length will pro- 

 duce depends ui)on the average width of the stream, the amount 

 of food it contains and the number and condition of pools. 



The average width of one mile of stream is a rough measure of 

 the area covered by that length of stream and within certain 

 limits, the larger the area, the greater the production. Hence a 

 stream, say 10 feet wide, should be able to produce approximately 

 twice as much as one 5 feet wide, because the area is twice as great. 

 Consequently in order to keep np the stock, twice as many fish 

 must be planted in the larger as in the smaller stream. 



Likewise ■streams differ greatly in nutritive richness and the 

 greater the amount of food the greater will be the production of 

 fish per unit area. It is not possible to determine quickly all 

 degrees of food richness but with a little experience it is a compara- 

 tively easy matter to place streams into three classes : — very rich, 

 average richness and those poor in food. The very rich stream 

 according to our calculations would be expected to produce on the 

 average three times as much fish flesh as one poor in food and 

 consequently would receive three times as many fingerlings. In 

 this connection one should consult the paper presented in this 

 volume by Dr. Paul R. Needham.* 



In much the same manner the streams are placed into three 

 categories with respect to pool conditions : — highest, average and 

 ])Oorest. 



Finally values are given for all possible combinations of these 

 three factors, as shown in Table 1. 



Table 1. — Planting Table for Trout Streams: Number of 3-Inch Fingerlings 



PER Mile 



WIDTH FEET 



1 

 2 



3 

 4 

 o 



r> 



7 



8 



9 



10 



C3 



36 

 72 

 108 

 142 

 180 

 216 

 252 

 284 

 324 

 360 



The lablc I'dVi-s to iJ-inch fingerlings only. 



To find the number of 1, 12, 4, or (i-inch fish, iHiilti|)ly l)y one of 

 the following factors: — - 



8ize ill inch(^s 1 '2 :; 4 (> 



Factoi- 12 1.7 1 O.?.") ().(i 



This is based upon an cxpccled morlalily as follows: 



Si/c 1 L> ;{ 4 i; 



Mortality . . D.V/o (i.V,;, 40% 20% 0% 



See i)age 220. 



