36 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



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

 extreme drought, and if it then has an ample sui^ply of pure, sweet 

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

 in time of flood and, if in a cold climate, in severe winter weather, to 

 learn the daugers to be guarded against on those scores. The volume 

 of water necessary will depend mainly on the i^roposed capacity of the 

 establishment, the temperature of the water, its character as to aeration 

 and the facilities existing for the aeration and repeated use of the water. 

 With water of the highest quality and low temperature, and with unlim- 

 ited facilities for aeration, possibly a gallon a minute, or even less, can 

 be made to answer for the incubation of 100,000 eggs of salmon. As 

 the temperature rises or the facilities for aeration are curtailed a larger 

 volume becomes necessary. In case of spring water, cooled only to 

 40° and aerated only by exposure to air in a pool of about a square rod 

 surface, with no facilities in the house for aeration, and with the eggs 

 and fry crowded in the troughs at the rate of 4,000 per square foot, 

 4 gallons a minute is the least that can be allowed, while 6, 8, or 10 

 gallons per minute are better. While the minimum is, as stated above, 

 possibly less than a gallon a minute, it is not advisable to trust to 

 less than 3 gallons per minute for each 100,000 eggs under the most 

 favorable circumstances. 



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

 sary to measure the volume approximately, which is easily done, in the 

 following manner: With a wide board 1 inch thick, having a smooth 

 inch 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. If the 

 water on the upper side rises just to the top of the hole, it indicates a 

 volume of 2.3 gallons per minute; a rise of half an inch above the top 

 of the hole indicates a volume of 3.5 gallons per minute; 2 inches rise, 5 

 gallons per minute ; 3 inches, 6 gallons per minute ; inches, 8 gallons per 

 minute ; 13 inches, 12 gallons per minute. If two 1-inch holes are bored, 

 the same will, of course, indicate twice the volume. The volume 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 as a 1-inch hole. A cylindrical 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. 



SITE. 



After a satisfactory supply of water is found a site for the hatching- 

 house must be selected that affords facilities for creating a head of 

 water to provide for the requisite fall into and through the troughs, 

 security against inundation, security against too much freezing if in a 

 cold climate, and, finally, general safety and accessibility. The fall 

 required in the hatching-house can hardly be too great. The minimum 

 is as low as 3 inches, but only under the most favorable circumstances 



