626 REPORT OF THE COMMISSIONER OF FISHERIES. 
boundary (fig. 2, pl. 1).¢ This fence consists of rough boards driven 
into the mud a short distance apart, and supported at intervals by strong 
stakes driven firmly into the bottom. It is necessary to have the top 
of the fence several feet higher than the highest water, to prevent the 
fish from leaping out. A woven-wire netting 2 to 3 feet highis often 
added to the top of the fence for this purpose; it is not practicable to 
use the wire netting under the water, as the fish would become badly 
bruised in attempting to get through it, or by dashing into it without 
seeing it. The pens may be of any size, from small ones, which will 
accommodate only one or two hundred fish, to those covering an extent 
of some2cr3acres. Larger ones than this are probably not practicable 
on account of the difficulty that would ensue in attempting to get the 
fish out of them; obviously the water can not be drawn off and the pen 
drained, so the only way of taking the fish is with a seine. This is 
done by setting the seine around the perimeter of the area, close to 
the fence, and then hauling it to one corner of the inclosure, where the 
fish can be gathered into the bag of the seine (fig. 2, pl. 1). 
As a rule there is not enough natural food in these pens for the 
sustenance of the fish, and in order to keep them from falling away 
greatly in weight it is necessary to supply them with food. The 
necessity of removing the fish with a seine makes it impracticable to 
build the pens where there is plenty of vegetation to supply the fish 
with natural food, since much vegetation would interfere greatly with 
the seining. 
Pens should be built in ‘places sheltered as much as possible from 
storms, for the high waves are apt to break down the fence and allow 
the fish to escape. Unusually high water and severe storms caused 
great damage in this way in Sandusky Bay and vicinity in the summer 
of 1902, one pen, in which there were said to be 40 tons of carp at the 
time, being broken down in places so that all the fish were lost. 
Portions of marsh which have comparatively narrow openings lead- 
ing into them are sometimes converted into ponds by throwing 
embankments, or more often building board stockades, across the 
narrow places. Such ponds usually have the advantage of containing 
plenty of natural food, but trouble usually arises when it comes time 
to take the fish out, as the places are not adapted to the use of a seine. 
In some cases the embankatent or fence, with a cor venient gateway, 
is constructed early in the spring and the gateway is left open until 
a large number of fish have entered the shallow water of the inclosure 
for the purpose of spawning, after which the gateway is closed and 
the fish are entrapped, to be seined out at leisure. At one or two 
places great areas of marsh were cut off in this way and the fish were 
prevented om returning to the larger open waters; but this was of 
aA photograph of a carp pen similar to this is shown in the Illinois fish commissioner's cane for 
1900-1902. 
