N. J. Mosquito Extermination Association 75 



A comparison of the Anopheles breeding in the impounded area 

 and in the natural bayou is shown by the collections in the general 

 survey work for the years 19 16 and 191 7. From these collec- 

 tions it is seen that Anopkeies breeding- is confined tO' the section 

 of the bayou below the dam and to the backwater above the im- 

 pounded zone. No specimens were collected in the general survey 

 work in the impounded area proper. The section of the bayou 

 above the impounded area was clear for a distance of about a 

 half mile, and the backwater gave favorable conditions for non- 

 breeding in this distance v/ith the exception of a limited area just 

 above the impounded zone, where a ridge crosses the bed of the 

 bayou and where the aquatic grass, Zizaniopsis miliacea^ per- 

 sisted. The maximum depth where this grass survived was about 

 one foot. Below this point to the dam, a distance of nearly a 

 mile, an average depth of three and one-half feet was maintained, 

 which was sufficient to suppress this grass as well as all other 

 vegetation in the channel of the bayou. Other Anopheles breed- 

 ing found above the impounded zone was some distance above the 

 growth of grass mentioned, among willows and other vegetation 

 characteristic of natural bayou conditions. 



The survey of the fish in the impounded area in Bayou Walnut 

 shows that the top-minnow, Gambusia affinis, finds no difficulty 

 in establishing itself under the conditions of deeper and open 

 water. The fish collections in this water also show that the larger 

 fish of the region, those of value for food, have found their way 

 to the impounded area in some numbers. The most valuable of 

 these are the crappie or 'Vhite perch," Ponioxis annularis; the 

 x:alico bass, Pomoxis sparoides; the large-mouth black bass or 

 "trout," Micropterus salmoides, and the warmouth bass or 

 "goggle-eye," Chaenohryttus gidosus. These game fish are 

 largely predacious, and, of course, take their toll from the Gam- 

 busia, but this feeding of these larger fish upon the little top- 

 minnows must not be view so much in the light of the reduction 

 of the mosquito-eating minnows as from the standpoint that the 

 patrol work which they do serves to keep the little fish in the 

 shallow water along the margins. In the open water of the im- 

 pounded area there is no mosquito breeding, and since the salva- 

 tion of the little fish depends upon their remaining along the 

 margins to escape the larger fish, the value of the larger fish as 

 an indirect aid in the mosquito control is seen. 



There was an average of 14 specimens of Gambusia taken in 

 each collection in the fish survey of the impounded water. In 

 these collections, taken in comparison with the collections from 



