72 Proceedings oi^ Niispth Annual Meeting 



The work of the bureau on impounding water was done in a 

 section of Bayou Walnut, which quarters the southwest portion 

 of Hecla plantation. This bayou runs a very irregular course, 

 the distance from the point of origin to its junction with a larger 

 stream being in an air line only seven and one-half miles. How- 

 ever, the bayou travels in its course a total distance of thirty-one 

 and one-half miles. The section of Bayou Walnut in its course 

 through Hecla plantation is shown on Map I. The average fall 

 of the bayou in this section is six-tenths of a foot to the mile. 



During 19 14, in the survey relating to Anopheles breeding in a 

 bayou, it was observed that under natural conditions there was 

 practically no breeding in certain restricted sections of the bayou 

 where open water occurred, where the bed was free of vegetation, 

 and the margins clean. On the other hand, breeding was found 

 in those portions of the bayou where the margins were grass- 

 grown or supported a growth of overhanging trees and vines ; 

 where the water surface was covered with the resulting vegetable 

 debris or ''floatage" ; where the water was shallow enough to 

 permit the growth of aquatic vegetation in the bed of the stream; 

 where the channel was blocked by brush, trees, logs and stumps ; 

 or where the bed was partially dry, thus permitting isolated pools, 

 and water in the hoof -prints of animals and in mud-cracks, which 

 were maintained by summer rains. The more typical conditions 

 of a natural bayou are shown in figures i to 4. 



The collections of Anopheles larvae in the general survey work 

 during the years 19 14 and 191 5 indicated general breeding 

 throughout the course of the bayou under natural conditions, 

 including the portion of the stream which was later cleared and 

 in which the water was impounded. 



The distance covered in the impounding experiment was i ,600 

 yards, nearly a mile. The plants collected from this section of 

 the bayou, before clearing and impounding the water, are listed 

 in Table I. The plant determinations were .made by the bureau 

 of plant industry of this department. 



A survey of the fish of this region was made by the U. S. 

 Bureau of Fisheries in co-operation with this work. This survey 

 was intended to cover the distribution of the top-minnow, Gam- 

 btuia affinis, in this region; the possible presence of other fish 

 useful in mosquito destruction; the presence or absence of fish 

 valuable as food in the deeper and permanent areas of water; 

 the survival of Gambusia in the impounded area in Bayou Wal- 

 nut; and the possibiHty of establishing in the impounded area fish 

 that would be of value for food to the tenants on the plantation. 

 This work was accomplished by Mr. F. M. Barnes, of the U. S. 

 Bureau of Fisheries, during 19 16 and the early part of 191 7. 



