562 U. S. BUREAU OF FISHERIES 



The rescue work is supplemented by the propagation of fish in 

 semicontroUed ponds adjacent to some of the substations, and a 

 large rearing pond adjoining the La Crosse station is also utilized. 

 Three ponds over which full control is exercised by the bureau are 

 now in use and there are six others within the boundaries of the 

 refuge which may be operated in favorable seasons under the same 

 conditions as ordinary hatchery ponds. In addition to its other 

 activities the La Crosse station does an important work in trout 

 propagation. It is the chief source for trout for stocking waters in 

 Minnesota and Wisconsin, and during the fiscal year 1932 it produced 

 nearly a million brook, rainbow, and Loch Leven trout for distribu- 

 tion in those States, a considerable proportion being assigned for 

 cooperative nursery work. These cooperative establishments, num- 

 bering 42 in Wisconsin and 12 in Minnesota, required a considerable 

 amount of attention from the La Crosse personnel in their supervi- 

 sion and guidance. An effort is being made to extend this cooperative 

 work to include the rearing of bass and other warm-water fishes. 



With regard to operations pertaining strictly to the Upper Mis- 

 sissippi Wild Life and Fish Refuge, the first half of the fiscal year, 

 comprising the summer and fall of 1931, covered the final activities 

 of the division of scientific inquiry in making biological investigations 

 in that area. The principal accomplishments were (1) continuation 

 of a scientific investigation of slough bottoms, (2) the chemical con- 

 trol of weeds, (3) seminatural propagation of fish in selected slough 

 areas. After an inspection in the fall of 1931 it was decided that 

 this particular phase of the work had reached its maximum useful- 

 ness, and that main attention thereafter should be given to propaga- 

 tion activities. During a high stage of the river in the spring of 

 1932 many of the sloughs which had been the scene of previous ex- 

 periments were flooded, illustrating the wisdom of discontinuing that 

 phase of the work. The funds made available by this change were 

 utilized for the development of rearing ponds in many favorable 

 places, and by such means additional pond space to the extent of 

 over 30 acres was made available for the work. Even in these com- 

 paratively high elevations the operations were hampered by high- 

 water stages dm-ing the spring. 



FISH-CULTURAL NOTES 



POND-CLEANING PUMPS 



The division of fish culture is conducting experiments for the purpose 

 of developing a satisfactory pond-cleaning pump for the removal by 

 suction of loose debris and filth from trout ponds and raceways. 

 There are on the market a number of so-called trash pumps and porta- 

 ble, gasoline-operated, centrifugal pumps which are designed to pass 

 solid material of fairly large dimensions. Fish-cultural agencies have 

 for a number of years been giving thought to equipment of this kind, 

 really applying the vacuum-cleaner principle in water. While the 

 equipment tried out by the bureau thus far has not been fully satis- 

 factory, the results of the experiments have been sufficiently encourag- 

 ing to warrant further study of the problem in cooperation -svith 

 pump manufacturers. 



