[25] UTILIZING WATER BY FISH-CULTURE. 1125 



there is not a sufficient area of raisiug-poiids for the fish i)roduced iu 

 the spawning-ponds, the ponds will be overstocked, there will be con- 

 sequently a lack of food, and the fish will not grow as well as in ponds 

 which are not so crowded, and where they find ample food. The pond- 

 farmer will have to ascertain by experiments the productivity of his 

 different ponds, and should know what quantity of fish every are of his 

 ponds can produce, under normal circumstances. It is, therefore, ab- 

 solutely necessary to have a thorough system of books, recording every 

 fact relative to the ponds. In the method generally employed it has 

 been found that the following distribution of a given pond area is best 

 suited for the purpose : 4 per cent, should be taken for spawning-ponds, 

 12 per cent, for raising-ponds of the* first class, 18 per cent, for raising- 

 ponds of the second class, 60 per cent, for ponds for older fish, and 6 

 per cent, for winter-ponds. The matter is entirely different if Dubisch's 

 method is followed, when a much larger quantity of young fish are 

 raised. In that case one should count to a 0.1 hectare spawning-pond, 

 3 hectares raising-ponds of the first class, 71 hectares raising-ponds 

 of the second class, and for the fish obtained during the first year (one 

 summer's fish) in the following year 137 hectares raising-ponds, and 

 during the third year 333 hectares raising-ponds. To correspond with 

 these ponds, the number of winter-ponds should also be gradually in- 

 creased. 



10. The different races of carp. 



Among the common carp, whicb have regular scales, there are oc- 

 casionally found, both in ponds and in open waters, fish which have 

 either no scales (leather carp) or only a few very large scales, which 

 generally extend in a row on each side from head to tail (mirror carp). 

 Both these varieties are specially raised in some places, and are con- 

 sidered to grow faster and have a more delicate flavor than the ordinary 

 carp : but no comparative experiments have been made relative to this 

 question, and all the conditions being equal, there will be but little 

 difference between these varieties. If the people in some locality show 

 a special liking for one or the other of these varieties, pond-farmers will 

 of course have some regard to it. Young fry and spawning fish of the 

 different varieties can easily be obtained in many places. 



Of late years the so-called " blue carp " has become a great favorite. 

 This fisli comes originally from Bavaria ; when out of the water its color 

 is a grayi^ blue, and in the water a beautiful dark blue, whilst as a 

 general rule the back of the carp has a darkish-brown, and its side a 

 leather or bronze color. It is said that the blue carp needs warmer 

 water than other carp, spawns later in the season, and when it has 

 reached a more advanced age is quieter and more inclined to seek its 

 food. Among the blue carp there are also found leather and mirror 

 carp. On the whole the blue carp are still confined to a few localities, 



