AKTIFICIAL PROPAGATION OF TROUT. 39 



of less than 7 inches is provided, other fish can enter the raceway 

 without much exertion and will ascend and disturb the breeding 

 tish, which, when spawning, should be kept strictly by themselves. 



There is no rule regarding the supply of water that applies to a 

 spawning pond at all times and in all places. It is necessarily 

 governed by the temperature of the water, size and shape of the 

 pond, size of the fish to be supported, the amount of shade, and other 

 factors. For a pond such as has been described, where water is 

 plentiful, at least 200 gallons per minute should be provided, with 

 not less than 75 gallons per minute as a minimum, even where the 

 temperature is from 50 to 55° and all other conditions are favorable. 

 "\"Miile the former amount is not absolutely necessary for the support 

 of the fish, it insures the pond being kept clean and the fish are more 

 inclined to enter the raceway at spawning time. In order to main- 

 tain an even temperature of water, earth is banked against the sides 

 and ends of the pond, the embankments being made broad enough on 

 top to permit ample footway around the ponds. Such a pond can 

 accommodate from 800 to 1,000 breeding fish. Fish must not be 

 crowded, and in estimating the capacity of a pond several factors 

 must be considered, such as the size of the fish, volume and tempera- 

 ture of water, and shade. In stocking the spawning pond a good 

 proportion is two females to one male. The brood stock must bo 

 selected carefully each year, and only sound and perfect fish retained. 



All pond bottoms should be cleaned frequently to prevent the accu- 

 mulation of undesirable matter. A method recently devised permits 

 the cleaning of ponds without subjecting the fish to the usual more 

 or less protracted period of turbid water while the cleaning is in 

 progress. About 10 feet from the intake end of the pond a cemeiic 

 bulkhead about 18 inches high extends into the pond from either 

 side, leaving an opening in the center 4 feet wide. Each open end of 

 this bulkhead is provided with slots in which boards may be inserted 

 to complete the dam as required. In cleaning the water level is 

 reduced and the section of the pond above the bulkhead thoroughly 

 cleaned. The fish are then driven, by means of a seine, through the 

 opening to the cleaned section and dam boards are inserted as 

 described. The outlet valve is then opened and the remaining por- 

 tion of the pond cleaned. 



TAKING THE SPAWN. 



Tlie spawning season varies with the locality and the temperature 

 of the water. It is usually from two to four weeks later in streams 

 than in ponds where the fish are confined in spring water. At Wythe- 

 ville the spawning fish may be found in the ponds any time after Oc- 

 tober 1 ; the season is well started by October 20, and generally closes 

 about January 25, the height of the season being between Novem- 

 ber 1 and December 15. At the Neosho (Mo.) station the season 

 usually begins about November 1 and extends to the 1st of March ; 

 at Manchester, Iowa, it occurs between November 15 and March 15. 

 In California the season extends from February to May; in Mon- 

 tana from April 15 to June 1 ; and in Colorado from May to July. 



The natural nests of these fish are made on gravelly bottoms and 

 are round or elongated depressions about the size of a dinner plate. 



