524 A NATIONAL PLAN FOB AMERICAN FORESTRY 



more or less directly the biota, both land and aquatic, of the forest 

 water areas. 



In addition to these physical features, the fishery officers should 

 have a reasonably complete understanding of the biological conditions 

 in the area subject to management, especially the fauna and flora of 

 the waters themselves. This applies especially to a quantitative as 

 well as a qualitative assessment of the organisms present in the water 

 and available from adjacent land areas, which are suitable as food 

 for fishes. 



A further requirement is an assessment of the existing fish popula- 

 tions. The different types of ecological associations among the various 

 species of fish are reasonably well known, and their relation as com- 

 petitors or predators of the more valuable game fishes in most cases 

 is well established; but the numerical relation of the components of 

 the fish fauna, insofar as they can be readily determined, is of prime 

 importance to the fishery administrator, for the aim of fishery man- 

 agement is to produce from a given area the maximum number of 

 food fishes of the most desirable or useful individual sizes. To as- 

 semble this information it is necessary for the fishery biologist to 

 personally survey the waters of each forest area, making detailed 

 observations to determine existing conditions. Such stream and lake 

 surveys are now under way in forest and park areas in the inter- 

 mountain region by the Bureau of Fisheries as mentioned above. 



While conducting these stream surveys, however, it is necessary 

 for the biologist to consider an additional factor, namely, the demands 

 upon the supply by the existing or potential fishery. At present 

 facilities for determining the drain upon the supply are very inade- 

 quate. In national parks the number of tourists visiting the areas 

 in the year can be accurately determined. Park officers and forest 

 rangers can also maintain a general check upon the number of fisher- 

 men in any given watershed. There seems at present to be no 

 practical method, however, of determining the annual take of fish of 

 any species in the public domain. A completed program of fisheries 

 management should include the furnishing of such figures not^only 

 to determine the need for additional production but to provide a 

 more accurate check upon the success of methods devised and applied 

 to increase the yields. 



In addition to conducting extensive physical and biological surveys 

 of streams and lakes in forest areas as a foundation for a rational 

 stocking policy in these waters, more intensive studies of the ecological 

 requirements of the fish to be planted are required. These may be 

 called experimental studies in field ecology, for they contemplate the 

 establishment of areas such as individual stream systems or smaller 

 lakes in which controlled experiments may be conducted bearing 

 upon the various factors of production. In such experimental waters 

 means of augmenting the food supply and the value of various food 

 components may be studied. The effect of competing species upon 

 each other may also be determined, proper levels of stocking intensity 

 can be determined, the migratory and breeding habits of the various 

 species can be investigated, and the general effects of each particular 

 system of management can be assessed. 



Closely associated with experiments in field ecology are laboratory 

 studies for the purpose of improving hatchery technique. Studies in 

 this field conducted by the Bureau of Fisheries during the past several 



