54 DEPARTMENT OF GAME AND FISHERIES No. 9 



of an unpurified preparation of nucleoprotein (from calf thymus) to the dried 

 skim milk diet. The resultant growth was of the same order as that caused 

 by a diet consisting wholly of raw liver, a result obtained with none of the other 

 experimental diets. This points to the possible importance of phosphorus to 

 the growth of fish. Fish eggs are noteworthy in their content of nucleoprotein, 

 and this also would suggest the importance of this complex phosphate-containing 

 protein to fish. 



It seems probable from this work that salmon egg meal and dried skim 

 milk may prove of value as ingredients of hatchery diets. Further work seems 

 indicated on the conditions causing disappearance of Factor H from raw liver, 

 its distribution in other food materials, and on the value of nucleoprotein and 

 phosphorus in fish nutrition. 



(c) An Investigation of the Most Suitable Natural Environment for 

 Lake Trout Fingerlings (Continued from 1930) 



Work on the experiments involved in this investigation was commenced 

 in 1930 by J. H. Fox, Science Master, Windsor Collegiate Institute, under the 

 supervision of the Biologist and Director of the Branch. The work was continued 

 in 1931 by J. H. Fox' and H. J. Perkin. 



The experiments were carried out ofif Port Bowmanville, Lake Ontario, and 

 the following abstracts taken from Mr. Fox's report explain the methods followed 

 and the results of the problem: 



"Lake trout fingerlings were placed in cages constructed of galvanized 

 iron with No. 20 galvanized iron wire mesh, eight to an inch, on the top and 

 bottom. The wire riveted to the frame-work. A galvanized iron shield extended 

 two inches below the bottom of each cage. The cages were of two sizes, the 

 large ones being 18 inches long, 15 inches wide and 10 inches deep; and the 

 smaller ones 15 inches long, 12 inches wide and 8 inches deep. They were 

 allowed to rest upon the bottom, excepting in the open water experiments, 

 being anchored at one end and attached to a buoy at the other. These cages 

 were placed in various positions in Lake Ontario opposite Port Bowmanville 

 and examined once a week to determine the rate of mortality and general 

 condition of the enclosed fish. At each examination live specimens were removed 

 for stomach analysis. At the same time water samples for analysis were taken 

 in the vicinity of each cage. Plankton collections and temperature records were 

 also taken at the time of each examination. Bottom dredges were made from 

 time to time. 



Plankton collections were made with a vertical closing net consisting of an 

 upper truncated cone of heavy cotton and a lower straining cone of No. 20 

 silk bolting cloth, about 6,000 meshes to the square centimetre with openings 

 of 0.001 to 0.003 square millimetres. The lower end of the straining cone bore a 

 cylindrical metal bucket, the lower end of which was covered with No. 20 silk 

 bolting cloth. A vertical haul was made near each cage at the time of examination. 

 The length of the haul was ten metres except where the water was too shallow. 

 It began as close to the bottom as the apparatus would permit and proceeded 

 at the approximate rate of one-half metre per second. 



A Negretti-Zambra reversing thermometer was used for the temperature 

 records. Bottom samples were obtained with an Ekman dredge and washed 

 through screens in the usual manner. 



The hydrogen ion content of the water was determined by the colorimetric 

 method immediately after the sample was taken. Other water samples were 



