142 FISH FARMING : 



CHAPTER XIII. 

 CAEE OF ALEVINS AND YOUNG FRY. 



The alevins may be left in the trays until hatching is 

 quite completed; the use of the trays may then be dispensed 

 with, the alevins being tipped into the box itself and the 

 trays thoroughly cleansed, dried, and varnished, and put 

 away for another season. But, before the fish are trans- 

 ferred from the trays to the boxes, the equipment of the latter 

 has to be looked to, and this is the next matter for consider- 

 ation. 



In Fig. 34 it will be noticed that the slanting board c 

 is used while incubation is going forward. First remove 

 this board so that the 'water falls into the box direct from the 

 spout of the box above. Next have ready a screen, which is 

 to be placed in position at the lower end of the box; it 

 should slant, as should all other similar screens used in fish- 

 culture, at a decided angle, and should be covered with No. 9 

 perforated zinc. Be careful about the size of the perforation. 

 With No. 9 you are quite safe, for if the alevins are forced 

 against the screen, and any of their delicate umbilical sacs 

 are drawn into a smaller perforation than No. 9, the alevin 

 will be unable to extricate itself from its disagreeable posi- 

 tion, and will most surely die. The screen should slant from 

 the bottom to the top in the direction of the current, i.e., 

 towards the outlet spout. The bottom of the screen should 

 be in such a position as to leave the outlet plug G quite clear : 

 about one foot from the end of the box is a convenient dis- 

 tance. The screen must fit absolutely accurately to the sides 

 and bottom of the box; the slightest crevice will prove a 



