582 



Yearboo\ of Agriculture 1949 



from the land and 90 percent by the 

 water itself. Riffles are the larders of 

 streams. To stones in any normal riffle 

 cling a myriad of immature insects of 

 all sizes, shapes, and varieties. 



Stream larders are usually well- 

 stocked with food of many kinds. Trout 

 waters draining granitic or rocky basins 

 and lacking in dissolved mineral food- 

 stuffs are usually those poorest in foods. 

 Strongly alkaline waters that drain rich 

 soils, either forested or farmed, are the 

 richest in foods. The maintenance of 

 the soil cover through good watershed 

 management improves the capacity of 

 streams to produce fish. 



The dominant stream foods eaten by 

 trout are the immature forms of in- 

 sects such as Mayflies, stone flies, cad- 

 disflies, aquatic trueflies, beetles. The 

 immature stages of dragonflies and 

 damsel flies frequently bulk large in 

 the diet of trout, as also do crayfish, 

 hellgrammites, small snails and clams, 

 and small fish. 



THE STOCKING of hatchery-reared 

 fish is conducted on a large scale by 

 the State conservation agencies, the 

 Fish and Wildlife Service of the De- 

 partment of the Interior, and the De- 

 partment of Agriculture. Many mil- 

 lions of fish, principally trout, are 

 annually transported in tank trucks 

 and widely distributed in both streams 

 and lakes. Back-country streams and 

 lakes remote from roads are planted 

 from pack strings of horses and mules 

 that carry small cans of fish long dis- 

 tances by trails. Today, except in the 

 most remote districts, few lakes remain 

 barren of fish life. Without hatcheries, 

 it would have been impossible to estab- 

 lish fish in many lakes and streams that 

 were originally barren of fish life. 



Although the establishment of trout 

 populations in barren waters has pro- 

 vided much excellent sport, planting 

 hatchery fish in the streams where fish 

 were already abundant has not pro- 

 duced results commensurate with costs 

 of the process. Indeed, only in recent 

 years have we found out that in our 

 best trout streams, nature does better 



work of stocking than man does. Since 

 it was discovered in the sixteenth cen- 

 tury that eggs of fish could be pressed 

 by hand from fish, fertilized, and 

 reared artificially, it has been assumed 

 that hatcheries were the answer. No 

 critical analysis of the survival of hatch- 

 ery-reared fish was made until after the 

 First World War. Investigations at 

 that time caused an almost complete 

 reversal of opinion with respect to fish 

 hatcheries: During more than a cen- 

 tury, millions of dollars had been spent 

 on hatchery programs without question 

 or test of their value. 



It used to be commonly believed 

 that there was virtually a total loss of 

 the eggs naturally spawned by trout in 

 streams. Several investigators have 

 since proved that the opposite is true. 

 A. S. Hazzard discovered that approx- 

 imately 80 percent of eastern brook 

 eggs survived through hatching in 

 streams near Ithaca, N. Y., and D. F. 

 Hobbs, working in New Zealand on 

 introduced trout and salmon, found an 

 average mortality to hatching of only 

 8.7 percent. He also found the effi- 

 ciency of fertilization to be more than 

 99 percent. All the observations indi- 

 cate a high survival of eggs and fish to 

 the time they leave the gravel nests in 

 the stream beds; after that, the losses 

 may be heavy because of floods, pred- 

 ators, and other conditions. 



Creel-counts on the survival of 2- 

 to 3 -inch fingerlings planted in streams 

 have indicated extremely low survivals 

 to anglers of usually less than 3 per- 

 cent, the average being about 1 per- 

 cent. Of yearling 6-inch, legal-size 

 fish planted during open fishing sea- 

 sons, 70 to 80 percent have survived to 

 be caught. Even with fish of that size, 

 average survivals are usually less than 

 25 percent in streams. In lakes, much 

 better survivals have been obtained 

 with legal-size fish. South Twin Lake 

 in the Deschutes National Forest in 

 Oregon regularly returns around 60 to 

 65 percent of 6- to 8-inch fish planted 

 in it. 



Research in fisheries has demon- 

 strated that the planting of large fish 



