104 American Fisheries Society 



Mr. Leach: It will be an interesting experiment to try this with a 

 three-inch pipe. If it works well with pipe from two to three inches, we 

 could use a very low head of water at the intake, with a larger opening, and 

 it might prevent the fish from jumping and also aerate the water. 



Model of a Riffle Pond, for Rearing Small Fingerling Trout. 



DESIGNED BY MR. GEO. A. SEAGLE, 



Wytheville, Va. 



PRESENTED BY MR. G. C. LEACH, 



U. S. Bureau of Fisheries. 



The ponds are constructed entirely of concrete, except outlet 

 pipe and guard-screens, and are from 43^ to 9j/£ feet wide and 

 50 feet long; with water 6 to 10 inches deep at upper end, and 

 20 to 30 inches deep at lower end when pond is filled. These 

 ponds were first built without riffles, but were unsatisfactory, as 

 the fish would crowd around the foot screens and in the corners 

 of the pond. At that time only about 5,000 No. 1 fingerling 

 fish could be kept in one of the small ponds, and it was necessary 

 to take them up for treatment for a slimy affection every ten days 

 or two weeks, which was always attended by some loss of fish. 

 The riffle ponds have been in use two seasons, and have given 

 excellent service; from 30,000 to 35,000 are carried successfully 

 where only 5,000 were carried before the ponds were changed. In 

 several instances the fish were placed in the riffle ponds before they 

 had been fed, and they were reared to No. 2 fingerlings with only 

 one change, and that was for the purpose of assorting the fish 

 as to size. 



The riffles were designed to furnish a means to exercise the 

 fish, which is very essential to keep the young fish in a thrifty 

 condition. To exercise the fish it is only necessary to draw out 

 the first paddle, which will reduce the water to the desired depth, 

 and the fish will scatter out to all the compartments. When they 

 are properly constructed, and are working well, the water should 

 be about 1% inches deep above the riffle, and % to % in. deep at 

 the foot of the riffle above. This is easily governed by placing the 

 riffles at the proper distance apart, according to the drop in the 

 bottom of the pond, which should not be very great, say about 

 one inch in four feet. From 25 to 40 gallons of water per minute 



