PRACTICAL CARP CULTURE. 33 



hatching pond much the smallest, the stock pond next in size and the 

 market pond largest of all. 



THE HATCHING POND. Its average depth should not exceed eighteen 

 inches, less will do. Considerable of its area, about the margin, the water 

 should be from nothing to six inches deep, and over this area the flat, 

 long, soft leaved manna grass, known to botanists as Glyceria fluitans, 

 which grows readily and rapidly and is common in the United States, 

 should be planted. German authors credit the carp with a weakness for 

 depositing their eggs on this particular plant. If these authors have as- 

 signed any reason for the preference of this plant by the carp, we have 

 not yet seen it. There is a cause for everything, and we believe the cause 

 for this is that these plants grow close together, almost covering the bot- 

 tom of the pond their strap like leaves coming straight up to the top of the 

 water and then floating. At the time of spawning the female pursued by 

 the male rushes through the thick mass of leaves, the resistance to her 

 passage compresses her body and requires greater exertion on her part to 

 force the passage, both of which give her aid in ejecting the eggs, which 

 are caught by the leaves as she passes, and as the male follows the same 

 causes contribute to the more liberal ejectment of the milt. A greater 

 per cent, of eggs are thus kept from sinking, and are fertilized by the 

 male than would be possible with almost any other water plant. 



The bottom of the hatching pond must be constructed on the same 

 general plan laid down in chapter IV. ; that is, it must have collector, 

 collector ditches, etc., the main ditch being wide, long and deep enough , 

 to afford a resting place for the fish in either exceeding hot or cold 

 weather, as the young fry pass their first summer and winter in this pond. 

 The collectors in all ponds should be cleaned every year In hatching 

 ponds, owing to the small size of the fish when they are taken from 

 the pond, that the collector should be clean is indispensable. A bed of 

 gravel in the collector, or a rough board floor nailed to mudsills thor- 

 oughly anchored to stakes driven deep and firm, will greatly facilitate the 

 cleaning, as well as the taking out of the fish. The pond must be pro- 

 vided with outlet drains and overflows, and must be protected with side 

 ditches from freshets or inundations. A fundamental requirement of 

 successful carp culture is an unchanging water level. If this is spe- 

 cifically true anywhere in the domain of carp culture it is in the hatch- 

 ing pond, and particularly during the period of spawning and hatching. 

 A change in the water level after the eggs are deposited and before they 

 are hatched is sure to do damage. If the water level is raised it either 

 washes the eggs from their hold on the vegetation of the pond, in which 

 case they sink and are lost, or it covers them with such a depth of water 

 as to change the temperature and chill them, which will delay if it does 

 not prevent their hatching. To lower the water level is still more disas- 

 trous, as it leaves the best lodged eggs, those nearest the surface of the 

 water, high and dry and subject to the direct action of the sun's rays, 

 which speedily dries out and spoils them. For weeks after hatching a 

 change of the water level would be disastrous to the young fish, in its 

 effect on their feeding ground and on the vegetation of the pond. The 



