630 BULLETIN OF THE BUREAU OF FISHERIES. 
known, as was demonstrated by Mr. J. J. Stranahan by a very careful experi- 
ment in the fall of 1897, that the life of an unfertilized whitefish egg, if left in 
the water, is less than 4 minutes, while more than 50 per cent of them perish in 
14 minutes, and the life germ contained in the milt of the male fish may be fairly 
supposed to live no longer under the same conditions, it will readily be seen 
that the percentage of eggs fertilized under natural conditions must of a neces- 
sity be very small. In fact, it is estimated by those fish culturists who have had 
most to do with the propagation of whitefish that not more than 1 per cent of 
the eggs are fertilized when deposited under natural conditions. At this rate 
let us see how many fertile eggs each pair of whitefish will produce each season. 
It is estimated that the average number of eggs produced annually by each 
female whitefish is 35,000. The greatest number the writer has ever known to 
be secured from one fish was 150,000, from a fish weighing 11 pounds, giving 
13,636 eggs to the pound of fish. This would be equivalent to a little more 
than 37,000 eggs from a fish weighing 234 pounds, and as the average weight of 
the spawning whitefish is from 21% to 3 pounds it will be seen that 35,000 eggs to 
the fish should be nearly correct. Then if each pair of whitefish produce 35,000 
eggs, and but 1 per cent of them are fertilized, 350 fertile eggs to the pair is all 
that can be expected to commence with. As the period of incubation for 
whitefish eggs is from 128 to 150 days, and as these fertile eggs must lie on the 
lake bottom all this time, in danger of destruction by being smothered in mud 
and filth as previously shown, and exposed to the still greater danger of being 
eaten by all kinds of aquatic animals that feed at the lake bottom, it is quite 
evident that but few of these 350 fertile eggs will survive to reach the fry stage. 
It is evident, moreover, that nature never intended there should be such a 
large increase in numbers as would result from anything like a perfect fertiliza- 
tion, for in that case the lake in a short time would be so densely inhabited that 
the waters could not produce sufficient food for all; neither would there be room 
in the lake for them if they came to maturity. It is therefore safe to suppose 
that naturally the number increases but little if it more than overbalances the 
loss, and reasoning from the known to the unknown we are sure that this is true. 
The number of young produced each year by those fishes, of which there 
is a large family, that carry their young through the period of incubation and 
produce them alive, ranges, so far as the writer has been able to learn, from 
1 to 22, giving an average of 11 young to each pair of fish; and as these fishes 
are very numerous where found, it appears that this rate of increase in the fry 
state is sufficient to more than overcome the losses under natural conditions. 
Thus by analogy we have the proof that an increase of 11 young from each 
pair of fish of any kind, including whitefish, is more than enough to overbalance 
the natural losses. 
