38 DOMESTICATED TROUT. 



SCREENS. 



Screens hold a very responsible position in trout 

 culture. 



All that separates your thousands of fish from the 

 outer world, where they would be lost to you, is the 

 twentieth-of-an-inch barrier of wire-screen. As far as 

 their voluntary escape is concerned, the wire-screens 

 stand in the place of gates, locks, bolts, and bars. It 

 is obvious how responsible their office is. 



All screens should be of copper or galvanized iron. 

 Copper is best for fine-mesh screens, galvanized iron 

 for large meshes. 



Wooden slats answer very well for grown-up trout. 



In using slats it should be remembered that a fish, 

 by turning on its side, will go through a surprisingly 

 narrow aperture, if it is long enough. A square mesh 

 of iron will hold fish securely, when slats would need 

 to be only half the width of the mesh apart. 



The wire netting should be fastened on to firm 

 frames, and the frames should fit tight in their place, 

 especially at the bottom. 



Thousands of fish have been lost by neglecting this 

 simple precaution. 



There should be eighteen threads to the inch for 

 the very smallest fry, four threads to the inch for year- 

 lings, and two to the inch for two-year-olds. 



For placing the screens for the young fry, see p. 59. 



If leaves or other debris coming down the stream 

 make trouble by clogging the outlet screen, you can 

 protect it by building out a board frame, say a 



