58 GERTRUDE M. WHITE 



When the Brook Trout grow larger, lose the yolk sac, and 

 become strong enough to escape their enemies by swimming 

 away, they begin to notice moving objects inside and outside 

 of the water. The approach of any object sends them darting 

 about in all directions in search of a hiding place. Just before 

 the trout are old enough to commence eating, they show great 

 interest in every object in the water, and begin to try taking 

 any small object from a bubble or a bit of alga to a piece of 

 meat into their mouths, though they appear to swallow only 

 such as are edible. 



From the consideration of the facts of behavior one is natur- 

 ally led to ask what are the artificial conditions which best 

 suit the needs and instincts of the young trout. In other words, 

 what is the economic importance of the experiments discussed 

 in this paper. One easily concludes from the observation of 

 the natural conditions of Brook Trout and their reactions to 

 current and carbon dioxide, that the first essential is cool run- 

 ning water with plenty of oxygen. The water should be free 

 from algae of a sort which is apt to get into the gills. If a 

 fungus attacks the young trout, the disease spreads rapidly, 

 unless the infected and dead fish are removed, since the fish 

 knock against each other as they swim about. 



The fact that Brook Trout are so strongly negative to light 

 seems to indicate that hatching troughs should be covered, 

 or if the fish are in ponds or streams, that the trout should have 

 natural covers, such as rocks, stones, or water plants, under 

 which to hide. By living beneath these they may often escape 

 predaceous animals which prey upon them. 



Since it requires nearly a week for Brook Trout to learn to 

 eat, they should be carefully watched when they are near the 

 feeding stage, for if they do not learn to take food before the 

 yolk sac is entirely absorbed, they will die of starvation. Shortly 

 before the trout are two months old, they commence to swim 

 to the top frequently and to exhibit curiosity, which indicates 

 that they will soon begin to eat. Meat ground or chopped 

 very fine should then be introduced into the water, so that the 

 fish may take particles of it into their mouths by chance, as 

 they wander about, and thus become accustomed to it before 

 it is necessary for them to eat. 



