102 REPORT OF THE SECRETARY OF COMMERCE 



waters under the jurisdiction of the State of Michigan for the 

 6-year period. 



In addition to the statistical studies reports dealing with the life 

 history and racial affinities of the several species of pike-perches 

 have been completed. The remainder of the investigative program 

 includes the preparation of seven reports covering major investiga- 

 tions completed in the field during the i^ast several years. 



POLLUTION INVESTIGATIONS 



The growing menace of pollution in the fresh waters of the United 

 States by erosion and by municipal and industrial wastes has been 

 accepted by many as inevitable because the basic facts — chemical, 

 phj'sical, and biological — concerning stream pollution generally have 

 not been available. The menace is spreading not only throughout the 

 various river systems but into the impounded waters as well, and 

 threatens at various points the waters of the public domain and of 

 the national playgrounds. Consequently remedial and corrective 

 measures compatible with the interest of fisheries and with economic 

 necessities have not been easy to define. 



To meet this situation the Bureau of Fisheries has been conduct- 

 ing for some time investigations to ascertain (1) the natural condi- 

 tions favorable for fish and other aquatic life in unpolluted waters, so 

 that a polluted stream can be defined with fairness to all concerned; 

 (2) the specific effects on fish and other aquatic life, and on the 

 aquatic environment itself, of the various types of effluents which are 

 being released into the fresh waters of the United States. 



Much effort has been given to devising suitable tests that could be 

 applied practically in the field in order to determine the extent 

 of stream pollution. A set of water standards has been defined based 

 upon the results of thousands of tests and analyses made in all of the 

 major river systems of the United States. From these studies it has 

 been possible to make definite recommendations for practical reme- 

 dial measures in various cases of stream pollution ; and a comprehen- 

 sive report embodying the findings of this investigation has been 

 completed for early publication. 



AQUICULTURAL INVESTIGATIONS 



Researches in the field of aquiculture, or water farming, as ap- 

 plied to food and game fish in interior waters are intended to in- 

 crease the efficiency of hatchery practices by stopping the loss from 

 hatchery diseases; by greater economy in operation through the de- 

 velopment of less expensive and more effective diets ; by the rearing 

 of fish to larger sizes so that they are better able to survive after 

 planting; by the selective breeding of superior stocks of fishes with 

 more rapid growth, greater egg production, and increased resistance 

 to disease; by environmental control to improve the productive ca- 

 pacity of streams and lakes; and by the development of a more effec- 

 tive policy of stocking to assure the best distribution of the hatchery 

 products in waters where the highest survival can be expected and 

 the planting of fish in proper numbers and in proper localities to 

 assure' the greatest supply. In previous years research has been di- 

 rected primarily toward proper hatchery technique and combating 



