74 REPORT OP COMMISSIONER OF FISH AND FISHERIES. 



A guard-rack made of thin, narrow slats is arranged on an incline of 

 about 45°, as shown at C. If the water is to be used again in ponds 

 below, a receiver is built nnderneatli the bottom of the pond at the 

 lower end, between the foot of the guard-rack and the dam-boards, 

 and the floor of the pond immediately over the receiver is cut away and 

 fitted with a grating. This allows matter to fall through the receiver 

 and from there it is washed through the sluiceway, which taps the 

 receiver by drawing the gate shown at D. The sluiceway, E, is 

 covered and leads off to a general waste-ditch. 



The pond is provided with a spawning-race about a foot deep, 4 feet 

 wide, and 25 feet long, placed at the upper end of the pond, as shown 

 at H. Three division boards (shown at F), about 12 feet long and of 

 suitable width to come within 1 or 2 inches of the surface of the water 

 when the pond is filled, are firmly fixed at the bottom. The object of 

 these boards is to form four avenues leading to the raceway, so that 

 one or two pugnacious fish can not command the approach and keep 

 back spawning fish inclined to enter. There is a dam across the race- 

 way about 4 inches high (shown at G) for the purpose of bringing the 

 water to that depth in the lower end, so that when the trout enter they 

 will find sufficient water in which to swim freely, and not be inclined 

 through fear to return to the pond. 



The water in the pond is of sufficient depth to bring its surface 

 within 6 inches of the top of the dam in the raceway, which will give 

 the fish, in entering the raceway, a Jump of 7 inches, allowing 1 inch 

 for the depth of water on the dam in the raceway. This distance has 

 been found more satisfactory than any other, and spawning fish alone 

 will go up. If a jump of less than 7 inches is given, other fish can 

 enter the raceway without much exertion, and will ascend and disturb 

 the breeding fish, 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 gov- 

 erned by the temperature of the water, size and shape of the pond, 

 size of the fish to be supported, the amount of shade, etc. 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 degrees and all other conditions are favorable. While 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 maintain an even 

 temperature in the pond the earth is banked against the sides and 

 ends, covering the framework shown on plate 25, and the embankments 

 are made broad enough on top to admit of a good footway around the 

 ponds. 



Such a pond as this can accommodate from 1,000 to 1,500 breeding 

 fish. Fish must not be overcrowded, and in estimating the capacity of 



