184 MOSQUITO ERADICATION 



purpose of the work and perhaps a notice or two put up at the 

 aquarium, will generally prevent any considerable losses in this 

 way. 



Fish for stocking the aquarium, if it is not already stocked with 

 them, may generally be obtained in abundance from nearby 

 streams or swamps. In this connection, care should be taken not 

 to draw too many from one source, so as to leave such source 

 unprotected against mosquitoes. 



The number of fish that should be placed in the aquarium will 

 vary with the size of the aquarium, the requirements of the fish- 

 control work and the abundance of fish in the vicinity. It should 

 be borne in mind that these fish, particularly Gambusia, multiply 

 with great rapidity, especially if those installed in the aquarium 

 include a number of pregnant females. 



Should the aquarium be small and the number of fish therein 

 very large, it will be necessary to feed the fish. Minced meats 

 or fish, bread, corn-meal and similar substances are considered 

 suitable for this purpose. 



NUMBER OF FISH REQUIRED 



When the aquarium has once been established, the work of 

 distributing the fish among the places where they are needed may 



begin. 



The first question that arises in this connection is : How many 

 fish are necessary in a pond, stream or other breeding-place in 

 order to prevent mosquito production? Hildebrand 1 answers 

 this question as follows : 



"Data upon which a definite answer could be based are extremely 

 difficult to obtain, for there are scarcely two ponds which offer identical 

 conditions. The size of the pond of course must be considered; whether 

 or not it is subject to wave action is of importance; the presence or 

 absence of vegetation is very important; and the presence or absence of 

 enemies of Gambusia (or other larva-eating fish) must not be overlooked. 

 Even then, we can only make a guess, for Anopheline mosquito larvae, 

 at least, breed much more prolifically in some ponds than they do in 

 others for reasons not understood. . . . 



"It has been shown . . . that a small number of minnows freed 

 badly infested pools of mosquito larvae in a short time; also that they 

 destroyed the mosquito larvae in ponds and kept the ponds free of the 



> "Fishes in Relation to Mosquito Control in Ponds," U. S. Bureau of 

 Fisheries, 1919. 



