Report of the Department of Lands and Forests for fiscal year ending March 31, 1951 Page US 



Tagging studies also indicated that lake trout movements are largely confined 

 to South Bay. There is evidence that the trout suffered heavily from lamprey predation 

 during the winter, 1949-1950. 



Ontario Fisheries Research Laboratory: Co-operative investigation of the factors 

 concerned in lake productivity have been carried on since 1946 by the Department, 

 the Research Council of Ontario and the University of Toronto, under the direction 

 of Dr. R. R. Langford. A number of the projects have been involved, among which 

 are the artificial fertilization of lakes, the analysis of incoming nutrients, chemical 

 analysis of waters and the addition of lime to highly coloured lake waters. In addition, 

 the Department has carried out a speckled trout investigation under the direction of 

 N. S. Baldwin and an investigation of lake trout under N. V. Martin, as well as the 

 Algonquin Park creel census. 



Lake Improvement Projects: The addition of chemical fertilizers to increase the 

 productivity of lake waters was commenced in 1946 and continued, with minor 

 changes, in 1950. Microscopic plants and animals, as well as forage fish, showed 

 increases in abundance. Oxygen depletion of bottom water as a result of fertilization 

 during 1950 became more acute. The quantities of fertilizer added are being adjusted 

 in an endeavour to correct this undesirable effect. 



The chemical analysis of water entering and leaving the lakes under experiment 

 was continued at the Opeongo laboratory and at the Southern Research Station in 

 order that a "mineral balance sheet" for these lakes may be developed. 



In the course of fertilization it was found that certain important chemical 

 substances in the fertilizers became bound to other substances and were not available 

 to the microscopic plants which are the starting point in the food chain. Hydrated 

 lime was added to one lake in 1950 in order to create an alkaline condition which, it 

 was hoped, would release the important elements to the plants. Another object in 

 adding lime was to decolorize the water to allow a deeper penetration of sunlight into 

 the lake. It was hoped that this would increase the microscopic plant populations at 

 lower levels. In addition, Dolomitic limestone was placed in the beds of inflowing 

 streams to give a more lasting effect. The liming of the lake made the water highly 

 alkaline at first, but this condition moderated and by October the lake was only 

 slightly alkaline. There was a 20' v decrease in the colour of the upper water, with a 

 comparable increase at lower levels. This indicated a "settling out" of the colour. The 

 higher aquatic plants showed a marked increase in response to this change in 

 conditions. 



Algonquin Park Creel Census: For fifteen years the creel census has been following 

 trends in the fishing quality of Algonquin Park lakes. At the same time it has been 

 evaluating such management practices as restocking, lake closure to fishing in alter- 

 nate years, and lake fertilization. The job of studying the effects of water level 

 manipulation on lake trout spawning was assigned to the creel census of 1950. 



The failure of extensive plantings of hatchery-reared speckled trout to improve 

 fishing has been demonstrated by the census. It did show, however, that good results 

 can be obtained when competing fish are first removed by poisoning. 



