ANNUAL REPORT, 1937-38 23 



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WATER LEVELS 



During the past three years, marked improvement has been shown in regar<? 

 to the control of water levels. Biologically, proper control is of the greatest im- 

 portance, especially when we consider that bass, maskinonge, pike, sunfish, minnows, 

 and many other species spawn in shallow water, and that their immature stages, 

 or adult stages, or both, live in comparatively shallow water. The fall spawning 

 fish such as lake trout, herring, and whitefish run into comparatively shallow 

 water and spawn on suitable shoals or grounds. The spawning depth of water 

 for these fall spawners is much greater than that required by black bass, which 

 is about two feet, or by minnows, which is only a few inches. The withdrawal of 

 water from these shallows is menacing to the eggs of the spawning fish, this 

 depending on the spawning depth and the drop in water level, but quite apart from 

 this, the withdrawal of water from the shallows destroys myriad forms of life, for 

 example, those of sedentary habit, those temporarily attached, the algae which 

 harbour minute life, shellfish, and insects, and aquatic plants of various kinds. 



REMOVAL OF COARSE FISH 



Between December 20th and January 16th hoop nets were operated for the 

 removal of ling from the following waters: 



(a) In Leeds County, — 



Charleston, Grippen, Wolfe, and Otter Lakes. 



(b) In Lanark County, — 



Tay River and Otty Lake. 



The total number of ling removed from these waters was 6,520; the average 

 weight of the ling was 7 pounds, and the total weight of ling removed was in the 

 neighbourhood of 45,640 pounds or 22.8 tons. 



Similar operations were conducted on Lake Manitou, Manitoulin Island. During 

 the whitefish spawntaking operations in the lake 4068 pounds of ling were taken in 

 pound nets. The average weight of each ling was approximately six pounds. Night 

 lines were used experimentally without satisfactory results. 



During the latter part of February and in March of 19 38, hoop nets and 

 gill nets were operated and 2270 pounds of ling taken. Each of these averaged 

 four pounds in weight. 



BIOLOGICAL SURVEYS 



Pollution surveys were conducted on the Rainy River, Maitland River, 

 (Goderich), and the Niagara River. 



Fish planting surveys were carried out on the Holland River, Bradford, 

 and Waterworks Pond at Richmond Hill. 



Extensive surveys were conducted in connection with suitable sites for black 

 bass rearing ponds on Manitoulin Island, Muskoka District, and Peterborough 

 County. Surveys were also conducted in the Timiskaming District in regard to a 

 suitable site for a trout rearing station. 



With the exceptions noted above, all the work of a biological nature was con- 

 centrated on the fish cultural activities carried on in our hatcheries and rearing 

 stations. 



The Ontario Fisheries Research Laboratory of the Department of Biology, 

 University of Toronto, conducted field investigations, coupled with laboratory studies 

 on a number of waters in Algonquin Park during the season 1937-38, and the 

 following is a concise account of this important work: 



"One of the principal functions of this laboratory is to examine the conditions in 

 game fish producing lakes and streams. Information obtained in this way gives 

 a better understanding of how rapidly fish grow and how a good supply can be 

 maintained. During 1937-38 the work was carried on in the lakes and streams 

 of Algonquin Park. 



