10 U. S. BUREAU OF FISHERIES. 



house or cover above it, with a suitable overflow cut through the 

 side of the masonry to provide an outlet for surplus water. The 

 best results are obtained where the supply pipe leading from the 

 spring to the hatchery is placed 2 feet or more below the surface of 

 the spring and is continued underground at as great a depth as pos- 

 sible in order to insure a uniform temperature as it enters the hatch- 

 ery. The most favorable temperature is 48° where the water leaves 

 the ground, though no harm will result if it varies 3 or 4° either 

 way. The entrance to the intake pipe should be covered with a wire 

 screen inside the spring house. 



If lake water is selected, the supply should be taken at a short 

 distance below the outlet of the lake with rapids intervening if pos- 

 sible. The temperature of the water in lakes is influenced by the 

 depth, and a deep lake, as a rule, affords water of more uniform tem- 

 perature than a shallow one. Such water is generally quite even 

 in volume and temperature. It is cold in winter and warms up 

 slowly in the spring, assuring a slow normal development of the eggs, 

 which is more conducive to the health and vigor of the resulting 

 fry than rapid development. 



A water supply obtained from a brook or stream is usually inferior 

 to that from a spring or lake by reason of its susceptibility to floods, 

 turbidity, and droughts, although a brook fed largely by springs may 

 to some extent be free from these objections. In cold climates anchor 

 ice at the intake is a serious cause of annoyance in connection with 

 brook water. If the flow from a spring is not sufficient and lake 

 water is not available, it would be advantageous, if possible, to 

 have a combination of spring and river or brook water. Water from 

 both sources should be brought to the hatchery in such a way as to 

 permit of their use either separately or in combination, so that a 

 temperature between the maximum of the spring and the minimum 

 of exposed water may be maintained during cold weather. Under 

 this arrangement the spring water may be utilized to force early 

 hatching when desirable and the water from the exposed stream used 

 for retarding development. This is a matter of importance in north- 

 ern latitudes where the winters are long and cold and the waters 

 locked with ice until late April or early May, conditions unfav- 

 orable for the distribution of fry. Farther south, where the waters 

 remain open all or nearly all of the year, it is not such an essential 

 factor. 



Between these different sources of supply there is, of course, a 

 great number of gradations. Water from boggy and stagnant 

 ponds or marshes is objectionable, for although water of excellent 

 quality, 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 on rainfall, an unreliable source. 

 Furthermore, bog water, particularly that from sphagnum bogs, is 

 often excessively acid, and therefore deleterious to trout. 



In some localities a meager flow of spring water may be success- 

 fully augmented by artesian wells. The suitability of such water for 

 fish-cultural purposes should be determined in advance of exten- 

 sive preparations, as water from such wells is frequently lacking in 

 certain elements vital to fish life. 



