Fish and Fishermen 243 



ments have proved that this is not so. The catchable fish may 

 cost on the average five to six times as much as the finger- 

 lings, but under heavy fishing ten times as many are caught. 

 This means that a fish in the angler's creel has cost one hun- 

 dred percent more if planted as a fingerling than if planted 

 at catchable size. It must be emphasized that this is under 

 heavy -fishing fressure. Where anglers are few, many of the 

 catchable fish would go unharvested, and the cost per fish 

 caught would increase correspondingly. If such waters must 

 be stocked at all, fingerlings are still the most economical. 



Man now seems to have the hatchery part of his trout 

 problem well in hand. Just as important is the other part: 

 what happens to the fish after they leave the hatchery and to 

 the fish which have never been in a hatchery? Most of man's 

 activities are detrimental. Deforestation, whether for lumber 

 or for other needs of civilization, leads to silting and to 

 higher water temperatures. Dams drown sections of trout 

 streams. The resulting reservoirs may provide fishing if they 

 are stable, but often their levels fluctuate to such an extent 

 that the bottoms, alternately flooded and desiccated, produce 

 very little trout food. Below them, stream flows may be so 

 reduced that the water becomes too warm for trout, or at 

 least so warm that it is invaded by undesirable species which 

 crowd out the trout. Once in a while, to be sure, the reverse 

 is true J the muddy Colorado River has become a clear trout 

 stream for many miles below Boulder Dam because it has 

 dropped its silt load and reduced its temperature in the 

 reservoir above. 



To help trout in natural waters man has thought up some 

 ingenious tricks. He places deflectors in streams to force the 

 current to scour silt accumulations off potential spawning 

 gravels or to dig pools where fish may rest or hide. He 

 builds dams in high mountain valleys to catch the rainfall 

 and release it gradually over long periods into stream chan- 



