878 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



of a larger class of creatures, and represent therefore the productiveness 

 of food of the pond, on which, in its turn, the carp depends for its 

 sustenance. Too much humus or dissolved peat is injurious. Water 

 which runs through bog-meadows or oak woods is not of much use, be- 

 cause it contains too much humic acid and tannin; these impart a moldy 

 taste to the fish. A too considerable amount of gypsiferous earth, car- 

 bonate of lime, or sulphate of lime is injurious also. Should any min- 

 eral-springs fall into a pond they must be turned off. The most favora- 

 ble water will always be that which comes from rivers and brooks. 

 Ponds might be constructed which would fill themselves with rainwater 

 during the winter or at any other time, but such water takes a moldy 

 taste easily, which it will communicate to the fishes, as does the water 

 from bogs also. 



In Europe, experience has shown that water coming from fertile fields 

 and meadows, carrying with it particles of offal from villages, is best 

 adapted for carp-culture. 



Spring-water direct from the ground is not favorable, and ought to 

 be conducted for at least a few hundred yards through wide, shallow 

 ditches, in order to receive more nourishing components from the air as 

 well as the earth, and above all to be warmed to some extent by the 

 sun and warm air. 



A tract of land, such as above described, merits the preference as a 

 site for a pond, if in other particulars the ground is favorable and has 

 not too great a fall. If this were the case, very high and strong dams 

 would be required for the collection of water. Such dams cost large 

 sums if ccnsiiucted of good water-proof material. 



A low undulating country, with only slight elevations or hills, where 

 the small valleys are easily closed up by dams for tbe purpose of form- 

 ing reservoirs, is favorable, the construction of these dams involving 

 comparatively trifling expense. 



3. — The construction of the ponds. 



Ponds must not be too deep, as the water will be colder and will har- 

 bor fewer insects, larvae, and worms, which form part of the carp's food; 

 besides, this fish does not grow quickly in cold water. A depth of 3 feet 

 in the center of tbe pond is sufficient ; toward the outlet-sluice it may be 

 from G to 8 feet deep, but only for an area of from 200 — 1,000 square 

 feet, in the depths of this "collector" the fishes seek their resting- 

 place for the winter, and also in summer, when the water is too warm 

 near the edge. The outer part of the pond should not be deeper than 

 one foot for the distance of about 70 or 100 feet, so that the water 

 there may be warmed more thoroughly by tbe sun. 



Toward the center of the pond, and in accordance with its size, a cav- 

 ity of from 20 to 50 feet in length and 2 feet deeper than the rest of 

 the ground should be dug. This will serve the fishes for a resting-place 



