85 



in the water b}^ means of a zinc vessel placed abont 

 twenty centimetres from the bottom. The general 

 principles of rearing fr}^ shonld be followed rigoronsly. 

 In feeding them one should not seek for variations or 

 for imaginary improvements. It should be our aim to 

 grow the alevins rapidly and give them the richest and 

 most easily assimilated food. 



For more than ten j^ears I have employed for this 

 purpose the spleen of beef, calf, or horse, the price of 

 which is low and its preparation very simple, because 

 it is given raw and its nutritive properties are very 

 great. This substance has been emploj^ed for food of 

 the 3'oungest salmon at the Aquarium of the Trocadero 

 almost exclusivel}^ since 1883, and many fish culturists 

 have followed our example. Blood is also an excellent 

 and cheap food. It should be slightly cooked in hot 

 water. One ma}' ignore all other forms of nourish- 

 ment, particularly daphnia and the prepared foods 

 which are so extensively advertised. 



What number of alevins can be reared per hectare? 

 Exj^erience has shown me that if the couditions are 

 favorable one may raise without danger in a hectare of 

 water, with an average depth of one and one half 

 metres, two hundred kilograms of Salmonidte at least. 

 If, then, the fish culturist follows my advice by raising 

 California salmon to the weight of two hundred grams, 

 he will place one thousand alevins in a hectare. If he 

 desires to raise fish of a larger size he must use fewer 

 per hectare. Here are, in this respect, the approxi- 

 mate numbers : 



1000 salmon of 200 grams per hectare. 

 500 ' ' 400 " " " 



200 " I kilogram " " 



125 " 1J2 " " " 



These numbers are the results of numerous experi- 

 ments which I have made upon this point, and I have 

 taken pains to give the minimum, which may often be 

 surpassed under favorable conditions. 



