American Fisheries Societi/. 55 



water and ^\^hen it approaches 50 degrees Fahrenheit, we shut of? 

 the supply and keep it shut off until the water warms up. Since 

 the ponds are well stocked with water plants the fish do not 

 suffer from lack of oxygen when the water is shut off. Indeed, 

 if the water did not leak out of the ponds T douht if it would be 

 necessary to introduce any running water into them during the 

 lu'eeding season. 



The second (Jl/ficulli/ irifli our irater supjiJij has l)een from 

 sediment brought down Ijy the brook after heavy rains Avhich 

 has sometimes accumulated over the nests so thick as to smother 

 the eggs and drive away the 25iii"eiit fish. This difhculty also we 

 now get over by shutting off the water supply whenever the 

 water is much roiled. 



The only difficulty with shutting off the sujiply is that the 

 level of the water must be kept fairly constant. If it lowers 

 more than about 6 inches, the fish leave their nests and the eggs 

 die. For the purpose of maintaining a constant water level it 

 would ])robal)ly be best to have the ponds made with clay l)ot- 

 toms. The difficulties arising from roily water of variable tem- 

 perature are, however, local and would probably not be usually 

 encountered. 



6. I have still to speak of the Itandling of the fri/ after ttiei/ 

 rise from the nest and of rearirnj tliem to tin(/erlinf/s. 



The fry of the small mouth have the halnt of scatttering 

 into a large swarm when they leave the nest, and it is conse- 

 quently difficult to seine them when Avanted. I have therefore 

 adojited the practice of setting over each nest, just before the 

 fry rise from the bottom, a cylindrical screen of cheese cloth 

 su])ported on a frame of jjand iron. I first remove the wooden 

 nest frame. The screen keeps the fry together. They thrive and 

 grow within it and may be left there until one desires to ship 

 them. The old fish stays outside and watches the screen. The 

 fry feed on the Crustacea inside the screen. When this supply is 

 gone other Crustacea may be taken from the ])ond with a tow net 

 and placed inside the screen. We remove the fry from these 

 screens directly to the shipping cans as wanted. 



In order to raise fingerlings. I lower the water in one of the 

 l)onds, seine the old fish out of the kettle, and transfer them to 



