ARTIFICIAL PEOPAGATIOlSr OF TEOUT. 45 



ated before entering the trough. This arrangement possesses many 

 advantages over the old method, where the screens were vertical, or 

 nearly so, as it permits fish to ascend to the head of the trough and 

 receive the water as it falls from the screen, which is very beneficial. 

 Its use not only keeps the fry clean even in muddy water, but also 

 reduces the loss of fry from suffocation in the early stages, caused 

 by their banking around the vertical screens, and obviates the neces- 

 sity for trough covers to prevent jumping, as trout rarely jump 

 where the horizontal screen has been adopted. 



The horizontal screen and deflector are exceptionally valuable 

 where the water supply is somewhat limited, and when used with the 

 spreaders hereafter described the fish may be held under ideal condi- 

 tions. The bureau's latest troughs have a pocket at the head, fol- 

 lowed by a screen on a frame 6 inches from the upper end. Three- 

 fourths of an inch below this is a dam board made of three-fourth- 

 inch material extending from the top of the trough to within one- 

 half inch of the bottom; a similar screen and dam board is placed 

 in the middle of the trough. This system causes the current of 

 water to pass close to the trough bottom, and a greater number of 

 fish may be held in a trough divided in this way than otherwise. 

 The tin spreaders, however, give the same effect ; some fish-culturists 

 are careless and do not use these until there has been a loss of fish. 

 The young fish like to fight the current of water as it comes under 

 the clam boards or spreaders, and it gives them exercise and good 

 appetites. 



The hatching trays, C (fig. 13), are convenient to handle and ad- 

 just in the troughs when made about twice as long as wide ; that is, 

 28 by 13| inches. The sides of the frame are made of good pine 

 lumber, dressed, \\ by |- inch. The ends are dressed -J by 1 inch 

 and are cut into the sides to form a smooth surface on the bottom 

 for the wire cloth. The wire used on the trays is woven with eight 

 threads to the inch, with a mesh seven-eighths inch long, and should 

 be well galvanized after it is woven in order to prevent rusting at the 

 laps. The inside of the troughs, the egg trays, and all other equip- 

 ment used in the trough are given a coating of asphaltum, thinned 

 with turpentine, prior to use and each successive season thereafter. 

 This acts not only as a preventative of rust and decay, but aids ma- 

 terially in keeping the trough and fittings in a sanitary condition. 



Four hatching trays are placed in each trough and secured by keys 

 or wedges and should be from 1 to 2 inches lower at the end next to 

 the head of the trough, as shown at i>, Z>, Z>, D (fig. 13). When 

 so placed, a tray will hold from 14,000 to 16,000 eggs of average 

 size. Muddy water during the hatching season necessitates the use 

 of a perforated tin tray 32 inches long and 13f inches wide, with per- 

 forations one-tenth of an inch in diameter in the bottom (shown at 

 E^ fig. 13). This rests on feet inside the trough, 1 inch above the 

 bottom. The hatching tray containing the eggs is placed inside and 

 rests on brackets shown at G. As they hatch the fish fall from the 

 hatching tray upon the perforated bottom of the tin tray and by their 

 movements work the sediment through so that they are left on a 

 clean bottom and are in no danger of smothering. The tin trays are 

 useful, also, in counting fish or for holding small lots of different 



