86 COMMISSION OF CONSERVATION 



have previously referred. If we are to utilize the waters to their 

 fullest limit, we must know more than we generally do of the available 

 food supply of the fish, the breeding habits, the distribution or range 

 of species, the enemies, the diseases ; in short we must understand the 

 cycle of the fish's life from the ovum to death and its correlation to 

 all other subaquatic life occupying the same area of water. The pro- 

 fessional fish culturist is much handicapped by want of data obtained 

 by research, so that he cannot be expected, even if highly trained, to 

 do good work. Surely the farming of livestock on land is a dif3&- 

 cult enough study, if success is to be obtained. How much more, 

 then, is expected of a man who has to farm livestock in an element 

 different to that in which he himself has to live? Research must be 

 carried on to assist fish-culture just as it does to assist agriculture. 

 In view of the vast potential value of our waters, this point cannot be 

 urged too strongly. 



Another point we have to realize is that, under natural conditions, a 

 very small proportion of the ova of certain salmonoids, for instance, 

 is ever impregnated, so we must bear in mind that, when one species 

 is being artificially incubated, the others should also be maintained in 

 the same proportion — ^not primarily in numbers but in proportion to 

 their food supply, their abilities in offence and defence and their 

 adaptability to the surrounding waters. Take as an example one fish 

 only, the whitefish, and see how far artificial incubation affects the 

 conservation of this fish. 



On an average foi' every povmd weight of the female fish there 

 are 13,000 ova in her ova sacs. Therefore, a 2J^ to 3 lb. fish should 

 produce approximately 35,000 ova. Incubation takes place over a 

 period of from 125 to 150 days according to the temperature of the 

 water used. However, under natural conditions the whitefish, unlike, 

 I believe, all other salmonoidse, do not always pair off. Hence there 

 is little chance of universal impregnation of the ova. But let us 

 assume that one per cent of the total ova is fertilized; that would be 

 350 ova per pair. Of these 350 ova many, we expect, would be lost 

 to predatory fish, silt and other causes. From Downing's observa- 

 tions, an average of 11 fish may be expected as the result of natural 

 incubation. Now artificial influences, that is, netting, accounts for the 

 extraction from the waters of all this. Consequently, if the whitefish is 

 to be kept as part of our fauna and further provide occupation for 

 fishermen and food for the people, some stimulation or assistance to 

 nature must be given in the form of fish culture. This is what we 

 are wholly depending on to-day in lake Erie, for instance. In this case, 

 artificial incubation aims to redress the balance that man has disturbed. 



