14 U. S. BUREAU OF FISHERIES. 



Further indications of the relative ineffectiveness of roach as 

 mosquito killers were found in some of the experiments at Car Pond, 

 N. Y. Here young roach were abundant along with mud minnows 

 and young of the common sunfish as well as other small fishes. The 

 roach and sunfish schooled separately but were found in the same 

 places and frequently were taken in the same seine hauls. When ob- 

 structed shallow waters in which culicine mosquitoes were breeding 

 abundantly were opened up, the roach did not enter them freely as 

 did the sunfishes and mud minnows and the stomachs of the few 

 that were actually taken within these areas yielded no mosquito 

 larvae, while those of mud minnows and sunfishes taken at the same 

 time did. (Compare records under dates of July 12, July 15, etc., 

 p. 16, 44, 45.) 



The roach evidently fail to react strongly toward these conditions 

 and do not push their way into the very shallow plant-grown waters 

 where the mosquitoes breed. In all other respects they seem well 

 qualified for mosquito control. They are widely distributed, abund- 

 ant, unusually prolific, adaptable, and active, and they will eat 

 mosquito larvae but seem to lack the courage and enterprise to go 

 after them. 



While further experiments under other conditions will be neces- 

 sary before a final conclusion is reached, tlie results of this investi- 

 gation to date indicate that the roach has been much overrated as 

 a mosquito destroyer. It has, nevertheless, a definite place and value 

 in pond culture. Where ponds are stocked with bass, pickerel, or 

 other predacious game fishes and it is desired to establish sunfishes 

 for purposes of mosquito control, the simultaneous planting of roach 

 Avould be an advantage. They will furnish abundant and natural 

 food for the larger fishes and thus greatly reduce the destruction of 

 the young sunfishes. For this purpose they are preferable to the 

 species of Notropis, as they are not only more prolific but are less 

 inveterate spawn eaters. I'hat they will eat spawn of sunfishes dur- 

 ing the absence of the owners from the nests has been observed by 

 the author ; but because of their timidity they are more easily held 

 off by the fishes on guard than the bolder minnows and darters which 

 will rush into the nests and often secure some of the tempting spawn 

 whenever the attention of the guard is turned from their immediate 

 direction. The success of the roach in life may be attribyted mainly 

 to its gi-eat fecundity and the adoption of the " safety-first " prin- 

 ciple rather than to the possession of any of the heroic and aggres- 

 sive qualities that characterize the sunfishes. 



Furthermore, in so far as they compete with the young sunfishes 

 for food, especially for Entomostraca and chironomid larvse, they 

 might be expected to drive them to a keener search for other more 

 hidden food, including mosquito larvse. Thus indirectly they might 

 aid the purposes both of mosquito control and of food and game fish 

 production. 



GOLDFISH (Carassius auratus). 



This well-known introduced species is widely naturalized and is 

 frequently mentioned as a mosquito repressor. Indeed, it is a com- 

 mon practice to feed aquarium stock upon mosquito larvae, as has been 

 done at the University of Pennsylvania vivarium. The goldfish is 

 largely a plant eater and scavenger, and all of the stomachs of both 

 young and adults examined by the author contained almost ex- 



