HABITS AND CULTURE OF THE BLACK BASS. 
43 
fish. This remained unexplained till the ponds were drawn down after the spawning 
season, when it appeared that although the fish had been sorted, the number of 
male fish was considerably in excess of the number of females, and these excess 
males, banding together, went about breaking up the nests of their more fortunate 
brothers. It is now the practice when setting the nests to seine out the stock fish and 
sort them, putting about 40 males to 60 females, thus removing the second source 
of fighting. 
During the present season from 493 adult fish we had produced 430,000 fry up 
to May 26, and we believe that we can do as well every year. 
Up to the present year there have been two sources of loss incident to the water 
supply. The supply is a spring-fed brook, which runs over an open country before 
it reaches us. The water in this brook becomes quite warm on a hot, sunny day and 
cools off at night. The temperature thus falls at night sometimes as much as 13° F. 
and becomes as low as 46° F. This is disastrous, since when the temperature gets 
below 50° F. the adult fish desert the nests and the eggs or young fry are killed by 
the sediment. By watching the temperature of the water and, when it approaches 
50° F., shutting off the supply until the water warms up, this difficulty is obviated. 
Since the ponds are well stocked with water plants the fish do not suffer from lack 
of oxygen when the water is shut off. Indeed, if the water did not leak out of the 
ponds, I doubt if it would be necessary to introduce any running water into them 
during the breeding season. 
The second difficulty with the water supply is from sediment brought down by 
the brook after heavy rains. This sometimes accumulates over the nests so thick 
as to smother the eggs and drive away the parent fish. By shutting off the water 
supply whenever the water is much roiled this trouble is avoided. 
The water supply, however, must be kept fairly constant. If the level lowers 
more than about 6 inches the fish leave their nests and the eggs die. For the purpose 
of maintaining a constant water level it would probably be best to have the ponds 
made with clay bottoms. The difficulties arising from roily water of variable tem- 
perature are, however, local, and would probably not be usually encountered. 
Handling the fry after they rise from the nest. — The small-mouthed fry have 
the habit of scattering into a large swarm when they leave the nest and it is con- 
sequently difficult to seine them when wanted. It is therefore desirable, just before 
the fry rise from the bottom, to set over each nest a cylindrical screen of cheese- 
cloth supported on a frame of band iron, first removing the wooden nest frame. 
The screen keeps the fry together. They thrive and grow within it and may be left 
there until one desires to ship them. The old fish stays outside and watches the 
screen. When this supply is gone other Crustacea may be taken from the pond 
with a tow net and placed inside the screen. The fry are removed from these 
screens directly to the shipping cans, as wanted. 
Raising the fingerlings.- — The water in one of the ponds is lowered, the old fish 
seined out of the kettle and transferred to another pond; the pond is then refilled, 
and the fry, now about one-half to three-fourths of an inch long, are put in. The 
water in the pond is thick with Daphnia and other Crustacea, and these do not get 
out when the water is drawn off. The fry feed on them and the supply is usually 
sufficient; but if it gives out, a fresh supply may be gathered from another pond and 
placed in the nursery pond. As the young bass grow they eat not only the Daphnia 
but young Corixa, and doubtless other aquatic animals. 
