MANUAL OF FISH-CULTURE. 35 



WATER FOR A SALMON HATCHERY. 



The first requisite for a salmon hatcberj' is an ample supply of suit- 

 able water, on a site where it can be brought completely under control 

 and the proper tall secured. In this matter there is quite a range of 

 choice. The very best is the water from a stream fed by a clean lake of 

 considerable depth, taken a short distance below the outlet of the lake, 

 with an intervening rapid. Craig Pond may be taken as an example of 

 such a lake. It has an area of 231 acres, an extreme depth of 69 feet, 

 and a depth of 25 feet within 500 feet of the outlet. The depth directly 

 iutlueuces the temperature and, other things being equal, a deep lake 

 will afford water more uniform in temperature than a shallow one — cooler 

 in summer and warmer, though never too warm, in winter. Such water 

 is commonly quite even in volume and temperature, and comparatively 

 pure. It is cold in winter and warms up slowly in spring, assuring a 

 slow, normal development of the eggs, which is more conducive to 

 health and vigor than a quicker development. The passage down a 

 rapid will further improve this water by charging it highly with air. 



After this, the water of a brook is to be chosen that is fed largely by 

 springs, so as to insure constancy in the supply and some moderation 

 of the temperature on warm days, but it is better to have the water 

 flow a long distance in an open channel before using, and, if possible, 

 over a rough and descending bed, that it may be well aerated, and in 

 cold weather somewhat cooled down from the temperature with which 

 it springs from the ground. 



Thirdly, choose pure spring water; but in all cases where this is 

 necessary provide a cooling and aerating pond, that the original warmth 

 of the water may be subdued by the cold of the air before it reaches 

 the hatching-troughs, and that it may absorb more or less air by its 

 wide surface. 



Lastly, choose ordinary river or brook water, as clean as possible. 

 The latter are considered inferior to spring water by reason of their 

 liability to floods, drought, muddiness, and foulness of other sorts, and 

 in cold climates to anchor ice. Between these diflereut sorts there is 

 of course an infinite number of gradations. If lake water can not be 

 obtained it would be of some advantage to have a supply of both 

 spring water and brook water, depending for ordinary use on the brook 

 water or a mixture of the two, and on the spring water for emergencies, 

 such as the freezing, drying, or excessive heating of the brook, floods 

 with accompanying muddiness, etc. Avoid water coming from boggy 

 and stagnant ponds and marshes; for though excellent water, capable 

 of bringing out the most vigorous of fish, may sometimes be had in 

 such places, yet when not supplied by springs it is dependent for its 

 freshness and good qualities upon rainfalls, and if these fail, as they 

 are liable to, the water may become foul and unfit. It must be borne 

 m mind that these remarks about the selection of water for fish-cultural 

 purposes apply only to the culture of Atlantic or landlocked salmon, 

 in a climate like that of the State of Maine. 



