300 CIVIC BIOLOGY 



Susqiieliamia River, where there was abundance of food, and introducing 

 food fishes (percli, minnows, and crawfisli) and aquatic insects. The 

 starved black bass very soon grew to proi)er form when well fed. 



Food being practically the limiting factor, self-sustaining ponds are 

 said to be capable of producing from 5000 to 6000 pounds of fish per acre.^ 

 This yields a cash value, at 10 cents per pound, of from $500 to |600, 

 " and this with no expenditure for food." Xo figures are available for 

 limits of possible production in well-planted and aerated ponds if the 

 fish are given adequate variety and quantity of food. Estimates might 

 prove more amusing than instructive. For example, in a self-feeding 

 pond of one acre, 3 feet deep, we have 130,680 cubic feet of water. At 

 5000 pounds per acre, we should have 1 pound of fish produced in about 

 26 cubic feet of water. Sui3pose, by proper care and feeding, we could 

 produce 1 pound per cubic foot (7.48 gallons) ? Can anyone so feed and 

 care for a bluegill or a catfish, in a five-gallon aquarium, that it will gain 

 1 pound in a year? 



Successful combinations in aquaria may suggest similar treatment of 

 ponds. That is, can anyone manage and feed a bluegill and a catfish 

 in the same five-gallon aquarium so that each will gain a pound in a 

 year ? Thus we see that by learning the habits and preferred habitats 

 of different fishes we may have all parts of our pond occupied and so in- 

 crease production. The pout will choose the stagnant holes with muddy 

 bottoms ; the perch, the deej)er channel, where there is some current ; 

 the crappies, rock bass, and sunfish, the shelter of stumps and brush and 

 weed patches. The water will be purified if the bottom is well stocked 

 with the best available mussels, and crawfish (if there is no danger from 

 their burrowing) may do the scavenging and turn waste matters into 

 food for the fishes. Frogs and toads, if allowed to breed, may further 

 help in the balance of life ; and, finally, a few pairs of mallards, teal, or 

 wood ducks might fit in, both for ornament and for j)rofit.^ 



1 N. K. Buller, "What an Acre of AVater Will Do," Bulletin No. 10, 

 Pennsylvania Department of Fisheries, 1914, p. 7. 



2 In a project of this kind, like working for a record production of 

 corn, potatoes, or poultry, we open a new field of interesting possibilities. 

 Who can produce the largest and best-balanced and most varied crops from 

 an acre of water ? Water cress, water lilies (of many rare and beautiful 

 kinds), cowslips, gentians, and cardinal flowers, the fishes, frogs, crawfish, 

 possibly fingerlings for distribution, perhaps a ton or so of highest-grade mus- 

 sel shells, and a fine flock of wild ducks for distribution and propagation — 

 will results from such a home-pond project bear out the statement that "an 

 acre of water may be made to produce as much as five acres of land " ? 



