592 EEPOET OF COMMISSIONER OF FISH AND FISHERIES. 



But in open water, where the fish must live on what they find in it in the 

 form of insects, moUusks, Crustacea, and larger or smaller fishes of other 

 commoner, chiefly vegetable-eating kinds, probably a considerably 

 greater surface room and likewise cubic space should be allotted to each 

 one. Since a natural lake, wherein fish can live in our country in win- 

 ter, must have a considerably greater depth than the basins indicated, if 

 one estimate according to the bottom alone, there will arise a much 

 larger space for each fish ; but this increase cannot be taken into con- 

 sideration except in so far that the commoner fishes, which live in 

 schools near the surface of the water, will thereby get the necessary 

 space. Since I take it for granted that the young are preserved in the 

 greatest possible degree from enemies in the first year only, as long as 

 this can be done without considerable expense for building si^ecial breed- 

 ing ponds, also that one has not the opportunity of procuring other 

 kinds of reservoirs for young fishes than such as will freeze to the bot- 

 tom in winter, young fishes must be liberated in the water late in the 

 autumn when the cold commences — they are then only about one-half year 

 old as developed fish. Because of the small size at this age, I think 

 that the deaths in the first year become considerably more numerous 

 than experience has shown them to be under more solicitous care, and 

 that likewise the loss from year to year will become much greater than 

 experience has shown it to be with proper care in ponds. I assume, 

 therefore, that of 1,000 young about one-half year old, which are liberated 

 in the water one autumn, the next autumn only 700 one and a half 

 year old fish will live, and of these the following year 550 two and a 

 half year old fish ; moreover, of these the following year there will be 

 450 three and a half years old, while the next year will be found only 400 

 grown fish over four years old, which thus in the fifth year become the 

 profit of culture. These grown fish I will on the average estimate at a 

 weight only one kilogram, though, according to experience, the average 

 will reach a considerably greater weight. 



Experience has sufticiently shown that among the fishes, as in other 

 classes of animals, individuals differ greatly with regard to the rapidity 

 of growth. But this cannot be taken into consideration ; one will natu- 

 rally catch and sell the fish which have reached the proper size, 1 kilogram 

 and upwards, or whatever other size and weight he may find most profit- 

 able, without the slightest regard to what age the individuals may have ; 

 it is essential that one can calculate with certainty the chosen size 

 reached by the corresi)onding ages of the number of fish calculated. 

 If this size is reached earlier or by a greater number of fish, the profit 

 will become so much the greater. The thing is, not to calculate the prob- 

 able profit too high, also the business more profitable than it is likely to 

 become, and this is perhaps done here as well with regard to the sale 

 from year to year, which probably is placed at too high a figure, as with 

 regard to the increase in size and weight of the fishes surviving, which 



