ANNUAL REPORT, 1941-42 21 



Large- Mouthed Black Bass: 



The distribution of large-mouthed black bass fingerlings was 5,500 in 1940 and 

 17,700 in 1941. 



It should be stated that only two small ponds were used for this work. 



Yellow Perch: 



The number of perch eggs collected in the vicinity of the Kingsville hatchery, 

 Lake Erie, is subject to wide fluctuations each year. Although much lower than some 

 previous collections, the 1941 take was 143 per cent, greater than the take of 1940. 



Maskinonge: 



The distribution of maskinonge fry was 10 per cent, less than that of the pre- 

 ceding year. In addition, 1,494 fingerlings were planted. 



In the culture of maskinonge, provided the temperature gradient is rising with 

 no sudden or serious drops, a good yield of eggs should be obtained and a good hatch 

 of fry result. Since the establishment of a maskinonge hatchery at Deer Lake, Peter- 

 borough County, much better results have been obtained, as the temperature of the 

 water is more constant during the developing and hatching period. 



After feeding starts, the chief obstacles which have not been surmounted, entirely, 

 are cannibalism, inadequate food supply and predators. Cannibalism has been over- 

 come to some extent at least by encouraging the development of vegetation in the pond; 

 this helps to protect the fish from one another. The supply of adequate amounts of 

 natural food, since maskinonge fry will not take artificial food, is another means of 

 reducing cannibalism. As is well known, maskinonge are voracious feeders and large 

 amounts of natural food varying in size from minute water fleas and insects to minnows 

 must be provided. Minnows are taken by the maskinonge before the latter are two 

 inches in length. The pond is fertilized to stimulate the growth of aquatic life and 

 vegetation, thereby increasing the food supply, and facilities are available for raising 

 minnows. It was found, however, that these facilities were not sufficient, and it was 

 necessary to harvest minnows from adjacent waters. One difficulty in supplying min- 

 nows is that they are not always available early enough to keep pace with the require- 

 ments of the maskinonge. The forage minnow which was used, although very satis- 

 factory from some standpoints, is too late in spawning to be of use in the early feeding 

 of the young maskinonge. In order to overcome this difficulty the silvery minnow, an 

 early spawner, is now being cultured. 



Aquatic vegetation in a pond acts as a refuge for valuable insects as well as for 

 predatory insects. During the year under discussion large numbers of nymphs of the 

 large water bug, and also a smaller variety of water bug, developed in the pond. These 

 bugs are so constructed that they are difficult to observe among the aquatic vege- 

 tation as they have considerable protective resemblance to the neighbouring vegetation 

 and to the environment, generally. They are predaceous and have mouth parts adapted 

 for piercing and sucking, and they attack not only small fry but sizable fingerlings. 

 The nymphs are air breathers and, as it is necessary for them to come to the surface 

 of the water to breathe, in order to exterminate them the surface of the water was 

 covered with a thin film of gasoline (kerosene or coal oil is equally effective). When 

 the larvae were exposed to this treatment for an hour they were destroyed. 



CLOSED WATERS 



One of the practical methods of conserving the breeding stock of fish is to close 

 natural water areas to all fishing permanently, or for different periods of time, and in 

 these areas the fish thrive without interference and spread to other parts of the same 



