102 NEW YORK ZOOLOGICAL SOCIETY. 
that from brooks. Its value for pond supply will be improved, if 
it can be led some distance as a rivulet. 
Fish-life in small ponds with limited water supply will suffer 
from heavy ice in winter. The ice should be broken daily, and 
masses of brush and branches placed partly in the water will aid 
in keeping air holes open, especially if they are moved by the 
wind. 
Extent and Depth of Ponds.—The extent and depth of ponds 
made by damming streams, will be governed somewhat by the 
nature of the situation available. 
A pond of an acre or more in extent, and with eight or ten feet 
of water in the deepest part, will, if properly managed, give ex- 
cellent results. It may be necessary to make it less than one- 
quarter of an acre in extent, but a small pond should have an 
extreme depth of not less than six feet, although it is quite pos- 
sible with a strong water supply to raise fishes in very small and 
shallow ponds. This, however, means active cultivation, with 
daily feeding of the fishes, numerous ponds to permit of sorting, 
and all the details of a fish-cultural establishment. As a matter- 
of-fact, nearly all of the extensive fish-breeding carried on by 
the National and State fish commissions has been done in ponds 
of rectangular shape, averaging perhaps less than 100 feet in 
length and 25 feet in width, having depths of only three or four 
feet. Such ponds are worked in series, as nursery and rearing 
ponds, and there are generally two or more ponds of large size 
in which fishes of different growths can be held. 
The following extract from the report of the fish commissioner 
of Indiana for 1903-04, is worth inserting in this connection: 
“Mr. Carl H. Thompson, of Warren, Indiana, has a fish pond 
60 x 120 feet in surface dimensions, and from four to six feet 
deep. In May, 1895, he placed in this pond four pairs of small- 
mouthed black bass. Fifteen months later he seined the pond and 
took therefrom, by actual count, 1,017 black bass averaging one 
pound each. In addition to the above he took between six and 
seven hundred yellow perch, weighing, according to his statement, 
‘not less than 250 pounds.’ This makes the production of the 
pond amount to 1,267 pounds for a period of fifteen months.” 
The whole subject of fish-culture of this character—carried on 
in small excavated ponds, wiil be found, discussed at length, in 
the “Manual of Fish Culture,” referred to later. 
Ponds to be used for black bass and in fact most other fishes, 
ought to be several acres in extent and quite deep. In general, 
