170 DOMESTICATED TROUT. 



that they can take their choice, and not be obliged to 

 stay in the sun because there is no shade. 



Their place of confinement must not be too much 

 crowded. Be very careful to guard against this, and 

 do it in season. It is very injurious to keep young 

 trout too close together. They will not grow as well. 

 The water breathed over so many times becomes vi- 

 tiated ; the foul matter thrown off by the fish in- 

 creases the evil ; and in time disease will break out 

 among them, and rage all the worse because of the 

 very thing that caused it, namely, the overcrowding. 



Anything which combines all the points above men- 

 tioned will answer for a nursery for the young fry, wheth- 

 er it is a pond, or trough, or rearing box, or what not. 



I recommend the use of a rearing box, because it 

 does embrace these points. Anything else that does 

 will answer as well, but it will be a rearing box still, 

 either on a large scale or a small one. It is the com- 

 bination of principles which makes the rearing box, 

 and not its name, or form, or material. It should be 

 added here, that is a good plan to keep water plants* 

 in the nurseries of young fish. I will not say that it 

 is indispensable, but I think it is very important in- 

 deed. 



Trout consume oxygen, and return carbon. Water- 

 plants consume carbon, and return oxygen. By put- 

 ting plants and fish together, therefore, we avail our- 

 selves of one of nature's great universal agencies in 

 balancing vital forces against each other, and main- 



* For list of water plants suitable for trout ponds, see Appen- 

 dix III. p. 275. 



