5 IMPOUNDING WATER TO CONTROL BREEDING OF MOSQUITOES. 17 
TABLE 8.—List of fishes taken in 12 collections in the impounded area, Bayou 
| Walnut, Mound, La., 1916-17, by F. M. Barnes, U. S. Bureau of Fisheries. 
| 
Number | Number 
Species. Common name. of collec- | of speci- 
tions. mens. 
SERIES ee Top minrety. si ease nee canes sa ces = 7 | 163 
Lepomis cyanellus...-...............----+..- Green. SUIMIGG 4 245. ard de anu caus o4-5- 7 95 
Pepontauniilis. 222422282002 os. Suniish 5 eee Ja eet ee ae 6 89 
Me POETS PANGS =24— eos ee se Blug-palisenrshs. = eee 1 | 1 
Lo ES Sisk 0 es Sunfish 55 Sse Sees Sa eS 1 1 
MeEPORNIS SyIMMELFICUS® 22. -.,0.=.-+2-. +. -5- Be: (i apne ee ee ee ae ee 1 1 
MEBOMISHHEPAIONSE SS soo see ook 8 Secs es Cogers i tee Gace spree Peete.» 1 1 
Sieooexis AWNUIALIS..- 11-2... 2-2... Crapplesse ne es ao ee tee eee 5 103 
Hoemoxisisparoides- =.) - S025. 27 Slee ike rek Calico Dass teeter AP et cE 3 25 
AMEITHIS HEMUIOSIS.. 2... 5.250 5 oe one oe Common Hnllhead .* . o3---5...-5¢-+.- 5 43 
Dorosoma cepedianum. ...-...--.........-. Hickory shadsten?. tet cod bebe lee 5 15 
Notemigonus crysoleucas.-.............---- Roach. shiner: es ee ees Pee 3 151 
qenrenodeans Sayers? 634i ser Soo bi a. Pirate perou. ~-.5). tee oe Se 2 | 3 
leropterus salmoides: =< .~.=-.255.-tse.-5- Large-mouth black bass. ..-.......---- 2 2 
Micropterus dolomieu. --............-..---- ietne pe eee oe oe ce, oe ee 1 | 3 
] 12 
| 
| 
| 
j 
In the comparison of the numbers of the top minnows found per 
collection in the natural bayou and in all other classes of surface 
water it was seen that for all classes of water there was an average of 
63 Gambusia per collection and for the natural bayou 25 specimens 
per collection. From the figures in Table 8 we find an average of 
14 specimens of Gambusia for the 12 collections made in the im- 
pounded water. Just as the comparison of the numbers of these 
fish in the natural bayou and in all other classes of water is influenced 
by the fact that some of the collections in the latter case were made 
in locations where the fishes were highly concentrated, so in the 
impounded water, as compared with the natural bayou, we must con- 
sider the effect of great dilution in the former. It is sufficient for 
the practical results of the work to note that the Gambusia survived 
in important numbers the effects of the impounding, and that the 
_ presence of the game fishes in the area serves the purpose of keeping 
_ the top minnows along the margins where they are useful in the 
marginal control of mosquito breeding. 
FACTORS PREVENTING MOSQUITO BREEDING IN THE IMPOUNDED 
WATER. 
The nonbreeding of Anopheles in the impounded water is due to a 
number of factors which have not as yet been definitely measured. 
In general, as has been stated, the important difference between the 
impounded section of the bayou and the natural bayou is just the 
difference between lakelike conditions which do not favor the de- 
_ velopment of Anopheles and swamplike conditions which do favor 
~ such development. The factors which are considered to operate 
against mosquito development are the greater freedom for action 
- on the part of the predators, the fish and the aquatic insects; wave 
- action; depth, which influences temperature of the water; absence 
110446°—22 2 
