Carpsucker 



One hundred and forty-six carpsucker weighing 39^4 pounds were caught 

 in trap nets during the season. The mean catch for the entire season 

 was 0,5 fish per net lift and 1.3 pounds of fish per net lift. Mean 

 catches for individual netting periods fluctuated between 0.2 and 1,6 

 fish and between 0.6 and 3.2 pounds per net lift. Catch was highest 

 during the June spawning period. Catch in the large mesh buffalo nets 

 set in the main channel was also highest at this time. 



Sheepshead 



One hundred and ninety-eight sheepshead weighing 2U7 pounds were 

 caught in trap nets during the season. The mean catch for the entire 

 season was 0,6 fish per net lift and 0.8 pounds per net lift. Mean 

 catches of individual netting periods fluctuated from 0.3 to 1.3 fish 

 and from 0.2 to 1.8 pounds of fish per net lift. The catch rate increased 

 during June| declined during July and August; and increased slightly dur- 

 ing September. 



k 



SUMMARY AND DISCUSSION 



1. In order to study seasonal trends in trap net catches, five 

 permanent netting stations were selected in backwaters of the Upper 

 Mississippi River a few miles below La Crosse, Wisconsin. One trap net 

 was fished at each of these stations, for nine 10-day netting periods 

 that were evenly spaced between May l5 and September 25, 19^8. 



2. Eleven species were caught in quantities large enough to note 

 catch trends during the season. Fluctuations in mean catch during this 

 four and a half month period were considerable. They were greatest for 

 the black crappie and the bluegill, and least for the carp and the white 

 crappie, 



3. Three species, the black crappie, the white crappie, and the 

 bluegill were cauj^,ht in quantities large enough to allow study of causes 

 of catch fluctuations. These causes may be divided into twc groups, (1) 

 those that resulted in changes in abundance of fish, and (2) those that 

 resulted in changes in the rate of activity of the fish. Evidence was 

 gathered that both abundance and activity rate of bluegills and black 

 crappies changed considerably during the season. 



U, About iiO percent of the black crappies, 60 percent of the white 

 crappies^ and 90 percent of the bluegills, caught during August and 

 September were fish of the I9U6 and 19ii7 year classes that had not been 

 available during May and June. The 19ii7 year class was not available 

 during the early part of the season because these fish were too small to 

 be retained in the nets. The 19[i6 year class was not available because 

 these fish were apparently not in the netting area during the spawning 

 seasono 



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