6 MISC. PUB. 528, U. S. DEPT. OF AGRICULTURE 
water bugs, water beetles, moths, and true flies. The larvae of these 
Insects are the staple food of insectivorous fish. In Alabama the 
three most important foods of the bluegill bream are the larvae and 
pupae of midges, the nymphs of dragonflies, and the larvae of 
caddisflies (6). 
Carnivorous fish will eat fish smaller than themselves, whether of 
another species or of their own. Cannibalism under hatchery condi- 
tions is often decried by fish culturists, but it is a normal and essential 
feature of balanced fish populations in lakes or other bodies of water 
(24). The fish upon which a carnivorous species preys are known 
as forage fish. If a carnivorous fish is to grow to a size large enough - 
for human use, there must be an adequate supply of forage fish for 
it to feed upon. It was formerly thought that special forage species, 
such as the golden shiner, should be available, but the forage species 
should be one that, when it becomes too large to be eaten by carniv- 
orous fish, will be acceptable as a pan fish. A large golden shiner is 
worthless since bass cannot eat it and men will not, but a large blue- 
gill is a fine pan fish. 
Insofar as managed farm ponds are concerned, the rooted aquatic 
plants—cattails, waterlilies, and such—are detrimental and should 
be removed as already stated. The nutrients which they contain are 
not available to phytoplankton until the plants decay. The leaves 
and stems of most rooted aquatic plants die in the autumn, decay in 
the winter, and grow in the summer. Fish grow comparatively little 
in the winter and during this period are not able to benefit from the 
nutrients released by the decaying vegetation (14, 24). Thus these 
plants tie up nutrients during the summer, release them upon decay 
in the winter, and retake them the following summer. Aquatic plants 
grow so luxuriantly in warm climates, smali ponds, and shallow 
waters that they often fill a pond, make fishing difficult, cause a 
mosquito hazard, and provide too much protection to small fish. If 
the forage fish are protected, the carnivorous fish are unable to cap- 
ture them and the pond will become overpopulated with small fish. 
Filamentous algae are also undesirable since they harbor mosquitoes 
and interfere with fishing. 
FISH POPULATIONS 
A successful fishpond must produce fish of the kinds and sizes that 
are acceptable for sport and food. Carp, suckers, and golden shiners 
are among the kinds known as rough and forage fish. They may be 
produced in large quantities, but in many places are not considered 
highly as game or food. The sport and pan fish, such as large- 
mouth bass, bluegill, and crappie, are lower in productivity. 
Rough, pan, and game fish have progressively longer food chains, 
and their differences in productivity are probably due to the differ- 
ences in food (26). In fertilized ponds in the Southeast, the annual 
production for plankton feeders, such as golden shiners, was 750 to 
1,100 pounds per acre; for insect feeders, such as bluegill and bullhead, 
it was 500 to 600 pounds per acre; and for carnivorous fish, such as 
large-mouth bass and white crappie, it was 150 to 200 pounds per 
acre (24). One cannot obtain as large a crop of bass and bluegill 
as one can of carp, and in making comparisons of pond productivity, 
it is necessary to consider the kinds of fish being produced. 
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