from year to year, if comparable coverage of the fishery is to be maintained. If 

 comparable coverage proves impossible, then at least the degree to which coverage 

 has changed must be measured accurately and recorded. In Lake Opeongo, the 

 fishery has been changing during the past few years and we are facing the prob- 

 lem of measuring the change. Guides, who have provided information traditionally 

 for so many years, are now used less, and many anglers are campers whose 

 experience in fishing is casual and whose fishing hours are mixed with boating 

 hours, cannot be counted upon to supply reliable data. 



Because of the background of knowledge about Lake Opeongo and neigh- 

 bouring waters in the Park, a number of our own research units and other 

 research agencies used facilities of the laboratory in 1964. These included: Lake 

 Trout unit, Brook Trout unit, Smallmouth Bass unit, Limnology unit, Parasitology 

 unit, Inventory (Productivity) unit, Selective Breeding (Splake) unit, Ontario 

 Research Foundation, University of Toronto, University of British Columbia, 

 University of Texas. 



LAKE TROUT 



The success of plantings of lake trout from normal hatchery stocks in Lake 

 Opeongo and we suspect, in similar lakes, has been nil. Any of the traditional, 

 additional protection techniques used to improve survival have also failed. Water 

 quality is being tested to see whether this is the factor responsible for failure in 

 Lake Opeongo in contrast to success in other waters; e.g. South Bay and Lake 

 Manitou. Lake trout eggs, taken from trout inhabiting both hard water and soft 

 water lakes, have been hatched and reared in both hard water and soft water 

 hatcheries and are being planted in Lake Opeongo. Each lot of fish has been 

 kept separate and has been marked differently. The first such planting was made 

 in Opeongo in 1963 and the second planting, consisting of a total of 59,000 

 yearlings was made in May of 1964. The creel census, in the coming five or six 

 years will provide the assessment of survival of the various lots. 



The study of the importance, in terms of lake trout management, of the 

 plankton feeding versus the fish feeding habit in lake trout was continued in 1964. 

 These feeding habits are now known to affect the rate of growth, the size and age 

 at maturity, the general condition (weight per unit length), and the number of 

 eggs per pound of female. There are also consequent differences in the kinds of 

 angling which are produced, in the year class fluctuations and in the age and size 

 at both maturity and at vulnerability to the angler. Such differences are important 

 to management and are being measured precisely. 



BROOK TROUT 



Studies of natural brook trout populations are under way to determine, as has 

 been done for lake trout, the natural variation in year class strength which occurs 

 in such typical lakes as Redrock and Dickson. Yields to the angler under different 

 controlled fishing intensities is being measured. It is interesting to note that in 

 Redrock Lake in 1964 when the total catch was 530 trout, 50% of these were 

 caught in the first four days of the angling season. The survival of hatchery reared 

 and planted brook trout in such native brook trout lakes has been very low. 

 Predation by native lake trout and brook trout is now recognized as an important 

 factor in the mortality of planted fish. 



Fifteen lakes, representing a cross section of brook trout lakes in northern 

 Ontario, were selected for stocking rate studies shortly after the establishment of 

 this research unit. The first experimental plantings were made in 1962, and 



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