THE GERMAN CARP IN THE UNITED STATES. 625 



ditches which arc deeper, and these finally lead into a still deeper pit 

 (the "fish pit''), which is situated at the place of outlet, usually near 

 the dam. When it is desired to drain the pond, the water is drawn 

 off gradually, the fish work down into the ditches, which completely 

 drain the pond, and so they all come finally into the fish pit, whence 

 they can be taken with nets. In a properly constructed pond it is 

 possible to draw all the water from the pit, and thus completely drain 

 the pond. It is common on many farms to have a curious " rotation 

 of crops;" the fish ponds are drained and turned to agricultural pur- 

 poses for a season or two, when by closing the outlet gates and allow- 

 ing the water to fill them again they are reconverted into ponds, and 

 pisciculture is resumed. Such a proceeding is said to have a salutary 

 effect upon both industries. 



TEMPORARY PONDS AND PENS. 



Although there are very few, if any, carp-cultural establishments 

 in this country conducted on the principles of those that have just 

 been described, there is, nevertheless, an increasing number of ponds 

 being constructed and used for the temporary retention of the fish. 

 This is true especially in the Lake Erie district. These inclosures 

 vary all the way from the simplest pens, not calculated to hold more 

 than one-half ton to a ton of carp, to extensive ponds covering large 

 areas and constructed and maintained at a considerable expense. 



These temporary inclosures may again be divided into two classes: 

 (1) Those in which the level of the water is not under control, but 

 Varies with the changing level of the surrounding waters; and (*3) those 

 in which the water level in the ponds can be artificially maintained at 

 any desired height. 



Under the first class the simplest kind is that already mentioned 

 (p. 612) as being used when it is desired to retain the fish only a very 

 short time — a few days to a week or so at most. These are the ordi- 

 narv live-cars or crates — large boxes constructed of rough boards with 

 cracks between, which allow the access of plenty of fresh water. When 

 the fish have been placed in these, the covers are fastened down and 

 the cars towed out to where the water is deep and certain to be fresh- 

 well out in a stream, if possible. The cars are weighted with heavy 

 stones, so that they float with their tops just at the surface of the 

 water. Fish kept in cars are seldom fed, unless it is necessary to keep 

 them much longer than is usually the case. When the} 7 are taken out, 

 dip nets are employed. 



A common method of constructing inclosures which will accommo- 

 date a larger number of fish, and in which they may be kept indefi- 

 nitely, is to build out into a stream, or from the shore of a bay or 

 lake where the conditions are suitable, a sort of rough picket fence 

 around three sides of an area, the shore usually forming the fourth 



F. C 1904—40 



