relation of scale structure to the life history of 

 the bluegill in some upper Mississippi River 

 sloughs. Tarzwell (57, 58) and Eschmeyer (19), 

 employing a technique similar to that used in 

 these studies, obtained information on fish popu- 

 lations in restricted areas of TVA reservoirs. 



The studies discussed here were initiated 

 primarily to evaluate the standing fish popu- 

 lations of representative backwater areas created 

 by the navigation dams on the upper Mississippi 

 River. At normal pool levels these areas are 

 connected with the main and side channels and 

 form an important part of the total fish-producing 

 waters. 



Collection of data on fish populations in 

 the backwaters has been an integral part of a 

 broad fishery investigation carried on by the 

 Upper Mississippi River Conservation Com- 

 mitteer' since its beginning. Under auspices 

 of this organization the populations of seven 

 backwater areas in the upper river were studied. 

 The present discussion is limited to three areas 

 in the Minnesota -Wisconsin section of the river: 

 Miller Lake, area A, and area B. Collections 

 were made by means of toxicants in Miller 

 Lake in August 1957, in area A in July 1948, 

 and in area B in July 1948 , August 1949 and 1951 , 

 and September 1952. The objectives of the 

 study were to determine (1) fish productivity, 

 (2) fluctuations in the populations from year to 

 year, (3) population structure, (4) rate of 

 growth of the common species present, and (5) 

 effects of navigation -pool drawdowns on the fish 

 populations of these backwater areas. 



Description of the backwater areas 



Miller Lake: --Miller Lake. 



3/ 



a backwater 



area in pool 8 of the upper Mississippi River 

 lock and dam system, is located approximately 

 2 miles below the interstate bridge at La Crosse, 

 Wisconsin, on the Wisconsin side of the river 

 (fig. 1). On August 15, 1947, the date offish 

 collection, it covered an area of il.9 acresl' . 

 The water level at the pool -control point ap- 

 proximately 1 mile below La Crosse was 630.97 

 feet (elevation above mean sea level). The 

 normal level at this gauge is 631 .00 feet. 



Two outlets connect the lake indirectly 

 with the main channel. One, appriximately 

 70 feet wide and 5 feet deep, empties into a 

 large running s'.jgh. The other, approximately 

 15 feet wide, drains into a shallow ditch that 

 has no appreciable current at normal pool le' el . 

 There is a single inlet less than 3 feet in maxi- 

 mui.i width which is very shallow and choked 

 with weeds . The amount of water entering the 

 backwater from this source is negligible. Silt 

 deposited periodically during high water stages 

 forms the bottom. 



A heavy growth of coontail, Ceratophyllum 

 demersum , was on the periphery of the lake and 

 in the bays at the time of poisoning. The water 

 temperature 1 foot below the surface was 80° F. 

 and the turbidity was 320 ppm as measured with 

 a U.S. Geological Survey standard platinum 

 needle scale. 



Areas A and B:- -Areas A and B lie west 

 of Fountain City, Wisconsin, in pool number 

 5 -A (fig. 2). The main channel of the river 



2/ The Upper Mississippi River Conservation Committee was organized in 19lt3. It is composed 

 ~ of representatives from Minnesota, Wisconsin, Iowa, Illinois, Missouri, the U.S. Fish and 

 Wildlife Service, and the U.S. Corps of Engineers. The primary purpose of the Committee 

 is to conduct biological and economic studies concerning fish and wildlife of the upper 

 Mississippi River. 



3/ Descriptive information and raw data pertaining to Miller Lake are from a preliminary 

 "" report (unpublished) prepared by D.W. Kelley and John Greenbank, parts of which appeared 



in the Fourth Progress Report of the Technical Committee for Fisheries of the Upper 



Mississippi River Conservation Committee, January 27, 19U8. 



h/ Original determinations of areas of Miller Lake, area A and area B, and of area B in 

 ~ 1951 were made from plane-table maps. Acreages of area B for the years 19h9 and 1952 

 are estimates based on the original maps. 



