36 TROUT CULTURE. 



have a current of oxygen-bearing water passing all 

 round it, which cannot be the case when all the eggs 

 are left in heaps. 



Eggs are a favourite prey of a number of enemies. 

 Some fishes prefer them to any other sort of food, 

 and rats or mice will eat them greedily if they get a 

 chance. Care should therefore be taken to keep the 

 troughs closely covered if peril be apprehended from 

 the latter source. 



