ARTIFICIAL. PROPAGATION OF TROUT. 11 



It is best to select a site for a hatching establishment in time of 

 extreme drought, and if there is then an ample supply of pure sweet 

 water the first requisite is fulfilled. It is also well to visit the place 

 in time of flood, and during severe winter weather if in a cool cli- 

 mate, to learn what dangers must be guarded against. The volume 

 of water necessary will depend upon its temperature, character as 

 to aeration, the facilities existing for its aeration and repeated use, 

 and the capacity of the proposed establishment. With water of 

 the highest quality, low temperature, and adequate facilities for 

 aeration, possibly 3 to 5 gallons per minute, or even less, will be 

 sufficient for the incubation of 100,000 eggs. As the temperature 

 rises or the facilities for aeration are curtailed a largfer volume will 

 be necessary. In the case of spring water having a temperature 

 ranging between 48 and 52° F., aerated only by exposure in a pool 

 and with no facilities in the hatching house for aeration, the amount 

 necessary to incubate eggs in a trough of any given dimensions will 

 be from 5 to 8 gallons per minute. As the number of eggs in a 

 trough will vary from 40,000 to 50,000, or even more, no set rule 

 can be applied. The proposition is different with relation to fry. 

 A hatching trough 14 to 16 feet long and holding from 25,000 to 

 40,000 fry will require 6 to 8 gallons of water per minute. On the 

 basis of 100,000 fish it may be figured that the following amounts of 

 water will be required : 



Gallons. 



Fry up to feeding stage 30 



Fingerlings, 1 to 4 months old 50 



Fingerlings, 4 to 6 months old 100 



Fingerlings, 6 to 12 months old 200 



These amounts are ample and probably even half as much would 

 suffice if it were necessary to economize in the use of water. 



If the water supply is drawn from a small brook or spring, it is 

 necessary to measure the volume approximately, which is easily 

 done. With a wide board 1 inch thick and having a smooth l-incli 

 hole bored through the middle, a tight dam is made across the 

 stream so that all the water will have to flow through the hole in 

 order to escape. If the water above the board rises just to the top of 

 the hole, it indicates a volume of 2.3 gallons per minute. A rise of one 

 half inch above the top of the hole indicates a volume of 3.5 gallons 

 per minute; a rise of 2 inches, 5 gallons per minute; 13 inches, 12 

 gallons per minute. If two 1-inch holes are bored twice the volume 

 will be indicated in each case, of course. The quantity of water 

 flowing through holes of different sizes is in proportion to the 

 squares of their diameters. Thus, a 2-inch hole permits the passage 

 of four times as much water as a 1-inch hole. A tube whose length 

 is three times its diameter will allow 29 per cent more water to 

 pass than a hole of the same diameter through a thin plate or board. 



THE HATCHERY SITE. 



^Yhen a satisfactory supply of water has been found, a site that 

 affords facilities for creating a head of water to provide the requi- 

 site fall into and through the troughs, security against inundation 

 and severe freezing, and for general safety and*^ accessibility must be 

 selected for the hatchery. The extent of fall from the source of the 

 water supply to the hatching house can hardly be too great. The 



