138 U.S. BUREAU OF FISHERIES 



of raw sheep plucks 1 part fed at weekly intervals. Thus far, in a 

 period of over 3 months, the growth of the trout fed fresh meat 

 weekly was equal to that obtained by feeding the same dry diet con- 

 taining an equivalent amount of meat fed daily. By weighing the 

 feed every effort was made to allow the same amount of raw meat to 

 both groups. Contrary to the common belief, no untoward effects 

 were noticeable in brook-trout fingerlings fed for 16 weeks on a 

 straight raw-spleen diet. 



Several experiments have not progressed sufficiently at the present 

 time to justify drawing conclusions. Among the incompleted exper- 

 iments are grouped the comparative growth of brook- rainbow- and 

 brown-trout fingerlings on a standard adequate diet, and the possible 

 relationship existing between underfeeding and the resulting slow 

 growth upon the firmness of trout flesh. Experiments are also in 

 progress to determine if the melting point of a fat determines its 

 degree of utilization by fish. 



The use of formalin-preserved meats as substitutes for fresh meat 

 in localities where the latter is not easily available is also under 

 investigation. Fresh ground sheep plucks preserved in 1 percent 

 formaldehyde seem to be as effective as fresh meat in supplementing 

 dry diets. 



LIMNOLOGICAL INVESTIGATIONS IN THE ROCKY MOUNTAIN 

 REGION IN THE INTEREST OF FISH STOCKING 



During the season of 1932 investigations of the waters of this re- 

 gion under the direction of Dr. A. S. Hazzard were continued in the 

 interest of wiser and more economical distribution of the output of 

 Federal hatcheries. Cooperation in this problem was also extended 

 to the States of Montana, Idaho, and Utah, although most of the 

 work was concentrated in the national parks and national forests. 

 The extension of highway travel and the rapid increase in the num- 

 ber of anglers have necessitated radical changes in methods of plant- 

 ing and have demonstrated the necessity for systematic stocking 

 based upon accurate knowledge of conditions for fish life existing in 

 the more accessible lakes and streams. 



Since the Bureau's responsibility for maintaining and improving 

 angling is definitely indicated in the waters of the national parks 

 and national forests, limnological investigations have been concen- 

 trated in these areas. 



SURVEYS IN THE NATIONAL PARKS AND NATIONAL FORESTS 



Grand Teton Park. — A program of biological surveys of the national 

 parks was initiated in 1931 by a study of the lakes and streams of 

 Grand Teton Park, Wyo. In this newly established park little 

 stocking had been done prior to 1931. This, together with increased 

 fishing, resulted in a condition of depletion which called for imme- 

 diate attention. Survey of these waters revealed marked scarcity of 

 suitable spawning grounds which explained the rapid deterioration in 

 angling resulting from heavy fishing and inadequate planting. Rear- 

 ing ponds were constructed here during the summer of 1932 and 

 plantings of good-sized fingerlings were made that season in accord- 

 ance with the findings of the survey relative to suitability for various 

 species and carrying capacity as determined from these studies. It 

 will of course require several years for the results of the stocking 



