BULLETIN OF THE UNITED STATES FISH COMMISSION. 157 



The lirst year he iisotl about 12 acres of land [4 tonder; and 1 tondo— 

 about 3 acres] for carp ponds. From sixteen female and ten male carp, 

 wbicli be obtained from Denmark, be raised one bundred thousand car[K 

 sufficient to stock an area of about 1,200 acres. In tbe north of Ger- 

 many, Denmark, and the south of Sweden, carp are ready to si)awn in 

 the third or i'ourtb year, and weigh at that time from 2 to 4 pounds. 

 Each female contains about one hundred thousand eggs, but of course 

 not all of these become young fish. 



The ponds for the young fry are not made very large, about from 1 acre 

 to a few acres in extent. They should have very flat banks, and have 

 shallow water throughout, from 1 to a few feet deep; if the water is 

 deeper it is heated too slowly, the carp spawn too late in the season, the 

 eggs are liatched very slowly, and the development of the young fish 

 does not progress fast enough. The fish do not only become thinner and 

 more slender during the first summer, but even later their growth will 

 be retarded, fu Germany the opinion is held that carp do not like to 

 spawn until the water has a temperature of 17.5° C. [about 63^ F.], and 

 some i)eople even maintain that the temperature of the water should be 

 from 22.50 to 25° C. [about 75° F.]. 



iSTear Gustafsberg the spawning season has often set in during the 

 last half of May, and the young carp have been hatched in as short a 

 time as six days ; but when the weather was cold it has taken ten or more 

 days. A warm spring and a mild autumn are of the greatest importance 

 for carp culture. Mr. AVendt states that carp do not grow at all when 

 the temperature of the water fixlls below 9° C. [about 48^ F.] , while their 

 growth progresses in proportion as the warmth increases. The period 

 of growth is, even in Germany, limited to five months, and it has been 

 calculated that in May it is 13 per cent of the growth of the entire sum- 

 mer, in June 31 per cent, in July 34, in August 18, and in September 4 

 per cent. If the spring is warm, the growth is not only comparatively 

 greater in May, but also greater throughout the entire year, as the young 

 fry can then during the summer far better derive all the possible benefit 

 from their food. Attempts have therefore been made in Germany, and 

 Avith considerable success, to cause carp to spawn earlier than usual by 

 heating the water, so that they spawn as early as March. One spring 

 Mr. Weudt placed glass frames over a portion of his pond which con- 

 tained young fry, but this experiment was not successful. 



The ponds for the young fry (as it is advisable to have several of them), 

 as well as the ponds for the growing fish, should be kei)t dry previous 

 to the time when carp are to be placed in them. This method has sev- 

 eral advantages. Thus, the water gets w\arm sooner in a pond which 

 has lain dry. Von dem Borne observed that while the temperature in 

 such ponds was, in the middle of May, 20° C. [08° F.], it was in others 

 where the water had stood for some time, only 17.5° C. [03° F.]. The 

 consequence was a full mouth's diflerence in the si^awning time, and 

 moreover the young fry in the first-mentioned i)onds were much more 



