624 REPORT OF THE COMMISSIONER OF FISHERIES. 
effects o1 it after passing, together with the large estate of a rich monastery of the 
same name, in the year 1670, into possession of the Princes of Schwarzenberg, their 
present owners. The extent which carp-culture has reached on these princely 
domains will be seen from the circumstance that their artificial ponds comprise an 
area of no less than 20,000 acres. The proceeds amount to about 500,000 pounds of 
carp per annum. The ponds of the Princes of Schwarzenberg are probably the most 
extensive of the kind on the globe. They are usually situated in some undulating 
iowland country, where small valleys have been closed in by gigantic dams for the 
purpose of forming reservoirs. Similar establishments, though not equally exten- 
sive, are found in the provinces of Silesia and Brandenburg; as, for instance, near 
Breslau and Cottbus, in Peitz and Pleitz, which 1 visited last year. In Hesse-Cassel, 
Hanover, Oldenburg, Mecklenburg, and Holstein there are also many nundreds of 
ponds, none of them covering more than a few acres, but almost every large farm 
possessing at least one of them. 
The well-appointed carp-cultural establishment has at least three 
kinds of ponds, each adapted for a particular phase of the industry. 
These ponds are usually made by throwing dams across small valleys, 
and by the aid of dikes, and are commonly fed by smail streams flow- 
ing into them, by springs, or they may depend entirely upon the 
rains to keep them filled. These last are often spoken of as ‘*‘sky- 
ponds,” and are much more uncertain than the others. The ponds 
fed by streams are ordinarily protected from flooding by freshets by 
leading the main channel of the stream around them, so that the 
amount of water which fiows into the pond can be regulated at will. 
The classes of ponds are: 
1. Spawning ponds. Shallow ponds in which the water is easily 
warmed by the sun, and suitable for the spawning fish. 
2. Raising ponds. Ponds, usually of medium size, to which the fry 
are transferred and where they are retained, isolated from the larger 
fish, until they are a year or two old. 
3. Stock ponds. Large ponds in which the fish are kept until they 
have reached a marketable size; this is usually considered to be when 
they have reached a weight of 24 to 24 pounds. One reason that the 
young fish are reared for a time in the raising ponds is that in the 
stock ponds with the older carp are often kept a number of predaceous 
fish, such as perch, pike, etc., which are supposed to keep the carp in 
better condition by preventing them from becoming too lazy and seden- 
tary. These fish would destroy the carp fry if the latter were put 
into the stock ponds while still small. The predaceous fish also forma 
secondary source of income. 
Since the stock ponds are not always favorable for the wintering of 
the fish there are sometimes ponds especially adapted for this, and 
these are known as— 
4. Winter ponds. These should be in sheltered localities, if possible, 
and should have a depth of at least 6 to 8 feet. 
All the above classes of ponds are constructed upon the same general 
principle. Ditches from the various parts of the pond lead into other 
