FOR PLEASURE AND PROFIT. 143 



simple means of suicide on the part of the alevins, and one of 

 which they will not fail to avail themselves. The general 

 method adopted to make a perfect fit of the screen (and I 

 know of no better) is to make it so that it slides quite freely 

 into pO'sition, then fasten a strip of new, coarse flannel along 

 the two ends and the bottom, and, when this is done, gently 

 drive the screen into position, and it will be found to be 

 perfectly tight. The flannel should be new, as it fits much 

 closer. When the screen is in position, and the box is 

 cleaned, you may empty the alevins from the trays into the 

 box. Be gentle, and " float out " as many as possible ; should 

 a few stubborn ones still remain in the tray, they may be 

 very carefully washed out by submerging the tray and rock- 

 ing it from side to side. Do not forget that the little fish 

 are quite easily injured jat this delicate stage of growth. 



If, as I pointed out in the previous chapter, perfect cleanli- 

 ness is observed in the boxes, there should occur only a very, 

 very small percentage of loss among the alevins until they 

 reach the stage at which they start to feed, and this occurs, 

 with healthy fish, a few days before the complete absorption 

 of the umbilical sac. Indeed, the alevins require little care 

 other than this important item of cleanliness. It will be 

 found that the little fish " pack " in masses ; this is a good 

 sign, and it should occur when they are in the trays, and 

 also for some two or three weeks after they have been 

 transferred from the trays to the box. As the alevins gain 

 strength, a bigger volume of water may be sent through the 

 boxes, the quantity being gradually increased throughout, 

 say, one month, until the total amount flowing through 

 reaches from four to four and a half gallons per minute, 

 according to the size of the boxes, a four-gallon supply being 

 about ri^ht for the size of box I have described. It will be 



o 



found that the alevins actually scour the bottom of the box; 

 but some sediment will accumulate between the screen and 

 the outlet of the box, and this sediment should, without fail, 

 be removed each morning by means of one of the rubber 

 syphons. The sides of the box should be carefully watched, 



