CHARACTERISTICS OF FISH POPULATIONS IN 

 UPPER MISSISSIPPI RIVER BACKWATER AREAS 



By 



Lyle M. Christenson 



and 



Lloyd L . Smith 



ABSTRACT 



Standing crops of fish and their fluctuations from year to year, age 

 and size class structure of the populations, and growth rates of the com- 

 mon species present in three backwater areas of the upper Mississippi 

 River were determined during the period 1947-52 under the auspices of the 

 Upper Mississippi River Conservation Committee. 



Standing crops as estimated from six collections following rotenone 

 treatment of blocked-off areas ranged from 39 to 605 and averaged 248 

 pounds per acre. 



Weight composition by species groups varied greatly among four col- 

 lections mad» in one study area but was characterized by the following 

 percentages: (1) Rough fish - 38 (2) Non-game predaceous species - 27 

 (3) Panfish - 13 (4) Game fish - 12 (5) Catfish - 11, and (6) Forage 

 fish - 1. Among the same four collections, the average composition in 

 pounds per acre was: (1) Rou^ fish - 112 (2) Non-game predaceous species 

 77 (3) Panfish - io C4) Game fish - 29 (5) Catfish - 30, and (6) Forage 

 fish - 2. 



Very few fish over 5 years of age were found and most of the game 

 fish and panfish were less than 3 years old. 



Growth rates of most species were greater than most of those 

 described in other waters of the north central States and in downstream 

 areas of the Mississippi River. 



Limited data on environmental factors are presented. Differences in 

 standing crop and species composition could not be related to changes in 

 the water level. 



INTRODUCTION 



Numerous attempts to remove fish popu- 

 lations in order 'o determine the productivity 

 ind population structure of various landlocked 

 waters have been made, but most were con- 

 ducted v/here populations were abnormal and 

 consequently the findings were not typical of 

 normal conditions (Solman, 50i.'). Many of 

 them were only partially successfjl because 

 recoveries of fish were incomplete . Until the 



research program of the Tennessee Valley 

 Authority was initiated, little attention had 

 been given to detailed studies of warm -water 

 fish populations of backwater areas in rivers 

 and impoundments . Surber (52, 5^ studied 

 the fish populations in some upper Mississippi 

 River sloughs before installation of navigation 

 dams; many of the conditions lie described stil) 

 exist. Meehean (32) attempted to show the 



L'' Undeiscored figures in parentheses refer to list of references beginning on page 50. 



