664 U. S. BUREAU OF FISHERIES 



Wabasha, Minn., to the headwaters of Lake Keokuk. A total of 156,697,141 

 fishes were rescued and of this number 155,720,719, or over 99 per cent, were 

 returned to parental waters. The remainder, 976,422, were reserved for distri- 

 bution. 



In former years, in connection with fish rescue operations, the bureau has con- 

 ducted mussel infection work to the extent of an output of billions of commercial 

 larval mussels on the gills of suitable host fishes. However, polluted conditions 

 in the Mississippi River have increased to such an extent that mussel life has been 

 largely exterminated, making it impossible to continue the work to advantage. 



Cooperative trout work in conjunction with the station's trout operations was 

 continued, and during the year 1931 trout establishments to the number of 46 in 

 Wisconsin and 11 in Minnesota were operated. The Wisconsin Conservation 

 Commission assumed control of a number of the trout nurseries previously operated 

 by the bureau that were located where the State could conduct the work to better 

 advantage than the bureau. This change reduced the number of cooperative 

 trout establishments operated by the station. 



Cooperative bass ponds, perhaps because of the large areas required for them, 

 have been more limited in number than the trout establishments. There is much 

 interest in them, however, and the station has no trouble in supplying black bass 

 fry for the ponds. The Minneapolis chapter of the Isaak Walton League is now 

 conducting two ponds, each approximating 20 acres. In these ponds, however, 

 bass are reared from brood stock. The Izaak Walton League at Mason City, 

 Iowa, has also established a successful bass pond of 30 acres. A number of other 

 bass ponds were operated commercially in Wisconsin and Minnesota. A pond 

 of 28 acres was consigned to the rearing of pike perch at Mason City, Iowa. This 

 cooperative work produced 25,000 6-inch fish, and is unique in the fact that it is 

 the first large pond devoted to the rearing of pike perch to a fingerling size. Co- 

 operative work with the Chamber of Commerce of Green Lake, Wis., resulted in 

 a very successful collection and hatch of pickerel eggs. The cooperative establish- 

 ments supervised from the La Crosse station are visited at least twice each season 

 and advice and information regarding operations are made available to the 

 cooperating parties at all times. 



Collections of eggs of buffalofish and carp were made at field stations along the 

 upper Mississippi River. The buffalofish work was undertaken in cooperation 

 with the State of Arkansas. Eggs of both species were planted in favorable 

 waters in the vicinity where taken. This work was hindered by low water and 

 only mediocre results were obtained. Large numbers of gar were captured and 

 destroyed by the seine crews. Before the end of the year 2 lakes and 1 slough on 

 Goose Island, and about 12 miles below La Crosse, were prepared for bass rearing. 

 Other locations for further work of this character are under consideration. 



Bellevue (Iowa) substation. — This substation is operated as a plant for holding 

 rescued fish prior to distribution. There were 34,000,000 carp and 29,928,000 

 buffalofish eggs collected in this point. These were fertilized and planted in the 

 Mississippi River. The total collection of rescued fish in this field was 34,917,804. 



Marquette (Iowa) substation. — Buffalofish eggs numbering 62,190,000 and 79,- 

 250,000 carp eggs were collected at this station. Rescue operations included the 

 collection and planting of 68,167,173 fishes. 



Lynxville (Wis.) substation. — Rescue operations at Lynxville covered the han- 

 dling of 27,043,809 fishes. In addition this station was used for holding surplus 

 trout from La Crosse during the spring months. Aquarium specimens and fishes 

 for scientific investigations are collected and shipped from this point. 



Homer (Minn.) substation. — Vessels for the entire Mississippi rescue field are 

 overhauled and repaired at Homer. Other activities included the handling of 

 16,379,935 fishes in rescue operations and the use of a number of the station's 

 ponds by the division of scientific inquiry in experimental fish-cultural work. 



UPPER MISSISSIPPI WILD LIFE AND FISH REFUGE 



The following report is submitted covering the biological investi- 

 gations in the Upper Mississippi Wild Life and Fish Refuge: 



The river stages attained by the Mississippi River following heavy rains in late 

 May and early June, 1930, were of value in many respects, though loss of fry and 

 adult bass to the river was experienced in several of the ponds. The rises showed, 

 for example, the heights to which the screens across openings to the river should 

 be built and low points in the banks of the sloughs from which invasion by the 

 river might be expected. They showed which ponds could be most safely used 

 for brood ponds, and which possessed the best shore contours for the latter pur- 



