24 DEPARTMENT OF GAME AND FISHERIES No. 9 (1944) 



L'nder natural conditions beavers frequently build dams in trout streams and in stream 

 improvement, dams and deflecting weirs are constructed to form deep pools of quiet water. 

 Such dams or deflecting weirs create changes in streams which have a marked influence upon 

 the insect fauna. The nature of this change is important insofar as it results in the production 

 01 different species and numbers of aquatic insects as compared to those present before such 

 •iaras are built. It has been learned that the aquatic vegetation which often appears as the 

 result of such dams definitely increases the number of insects, and further work is being 

 carried out to determine whether the aquatic insects produced in this way are available to and 

 constitute the food selected by the trout and to what extent the other conditions resulting 

 from the dams are favourable or unfavourable to trout production. 



Examination of the fish of the Park waters shows that some of them cany fish parasites 

 and although none of' these parasites are injurious to man they may be quite harmful to 

 the fish. Much of the information from these studies is of value in the local fish culture 

 work, as it has been learned that: the same species of fish in different lakes carry parasites of 

 different kinds and degree of harmfulness which is a warning against indiscriminate transfer 

 of fish from one lake to another. There is a relation between the fish parasites and the food, 

 so that in a large lake fish in one area may be parasitized, while those in another area may be 

 free of that particular parasite, which suggests a possible approach to parasite control. Lakes 

 containing small-mouthed black bass had several species of fish infested with larval cysts of 

 the cestode, Protcocephahis ambloplitis, while fish from lakes that do not contain small- 

 ruouthed black bass do not carry this cestode." 



ACKNOWLEDGEMENTS 



In closing this report I desire to express my appreciation of the excellent spirit of 

 co-operation which has been displayed throughout the year by^the Ontario Federation of 

 Anglers and Hunters and its various constituent Game and Fish Protective Associations, 

 und by the officials and members of the Northern Ontario Tourist Trade Association, as well 

 as others who are interested in the services rendered by this department on behalf of hunters, 

 anglers and trappers. Such contacts cannot but be of inestimable value and assistance to us 

 in the performance of duties required in connection with the proper administration and conduct 

 of the Department. 



Regarding the work of the staff. May I state lliat nienibeis of the Departmental 

 Service generally have been very conscientious in carrying out their duties and courteous in 

 their contacts with the public in their efforts to produce the best results. 



All of which is respectfully submitted. 



I am. Sir, 



Your obedient servant, 



D. J. TAYLOR, 



Deputy Minister of Game and Fisheries. 



I 



