LIGHT TRAP STUDY OF LARVAL AND JUVENILE FISH FROM MUD LAKE (UPPER MISSISSIPPI 
RIVER, POOL 11)

Alan Butler and Daniel Call
Dept. of Natural & Applied Sciences, University of Dubuque, Dubuque, IA  
52001

Mud Lake is a lake in lower Pool 11 that was recently deepened in areas by 
dredging to provide improved habitat for overwintering fish.  In this study, 
a light trap technique was deployed at night on 16 occasions between June 25 
and September 10, 2007, to collect larval and juvenile fish for the purpose 
of obtaining a preliminary assessment of the lake as spawning/nursery 
habitat.  A trap was deployed for 0.5 hr. each at several locations at two 
depths, one approximately 0.3 m below the surface and the other approximately 
0.3 m above the bottom.  Several samples were also collected where the trap 
was left in place overnight.  A total of 102 fish were collected, 
representing nine families: Lepisosteidae, Clupeidae, Cyprinidae, 
Catastomidae, Ictaluridae, Atherinidae, Moronidae, Centrarchidae, and 
Percidae.  Larval or juvenile fish that were identified included the 
following: longnose or shortnose gar (Lepisosteus sp.), gizzard shad 
(Dorosoma cepedianum), a species of shiner (Notropis sp.), bullhead minnow 
(Pimephales vigilax), quillback (Carpiodes cyprinus), channel catfish 
(Ictalurus punctatus), brook silverside (Labidesthes sicculus), white bass 
(Morone chrysops), bluegill (Lepomis macrochirus), and logperch (Percina 
caprodes).  The brook silverside was the most commonly captured species (50% 
of total), followed by white bass (19%) and Notropis shiners (9.8%).  Traps 
set near the surface captured a higher proportion of the total than those set 
deeper.  Five of six brook silversides collected on July 3rd possessed single 
pouched outgrowths, primarily in the abdominal region below the stomach and 
presumably caused by a parasite.  The traps also collected numerous insects, 
dominated in number by the water boatman (Order Hemiptera, Family Corixidae).  
A crustacean fish parasite (fish louse, Argulus sp.), was collected as a 
free-swimming organism on two occasions.  This preliminary study has 
demonstrated the utility of the light trap technique for collecting immature 
fish in the Mississippi River, and for assessing areas as spawning and 
nursery habitat.  Expansion of the trapping effort by inclusion of additional 
trapping methods, an extended trapping season, daylight trapping, and 
increased trapping hours overall would likely add to the list of fish species 
that are spawning and developing in Mud Lake.

Keywords: larval fish, light trap, Mississippi River, Pool 11, habitat


Address of Alan Butler: Dept. of Natural & Applied Sciences, Univ. of 
Dubuque, Dubuque, IA 52001; tel. 563-589-3152; FAX 563-589-3688; e-mail 
abutler@dbq.edu.

Preferred Format: Poster; willing to convert to platform, if necessary 
(PowerPoint).

The presenter and first co-author is an undergraduate student.