PATTERNS OF SECONDARY PRODUCTION OF HEPTAGENIID MAYFLIES IN MAIN AND SIDE 
CHANNEL HABITATS

Karie S. Hiam, Leila Desotelle and Micheal D. Delong
Larger Rivers Studies Center, Biology Department, Winona State University, 
Winona, MN 55987

Rivers possess heterogeneous habitats even when a river seems to have a similar 
outward appearance. Since there are structural differences in a river system, 
there also may be differences in functional aspects of these habitats. Two 
structurally similar habitats, side channel and main channel, actually differ in 
some physical and chemical properties. Side channels have a lower current 
velocity, higher temperature, low turbidity, and are shallower than main 
channels.  Side channels may also be more productive than the main channel. 
Secondary production is a measure of energy flow in an ecosystem. This study 
examined the patterns of secondary production of heptageniid mayflies in main 
and side channel habitats. Samples of woody debris (snags) were collected along 
the shoreline of the main and side channel. Snags were collected from Reaches 5, 
6, and 8 of the Upper Mississippi River. Snags had to be submerged at least 10 
cm deep and could not be in contact with the bottom sediments for the portion of 
the snag that was sampled. A DTH snag sampler was placed around the snag to 
ensure capture of all invertebrates and the snag was cut to appropriate size. 
Snags were placed in a bag and preserved in 70% ethanol for later analysis. 
Physical and chemical properties including, dissolved oxygen, temperature, 
turbidity, current velocity and conductivity, were measured for each sample.  
Samples were cleaned and sorted in the laboratory to remove invertebrates. 
Densities of heptageniid mayflies were low in both habitats and did not differ 
significantly.  Low densities prevented the calculation of reliable secondary 
production estimates with the increment-summation method. However, it appears 
that production rates between main and side channel habitats were similar.  Our 
findings suggest that resources available on nearshore snags are similar between 
main and side channel habitats.

Keywords: invertebrate, Heptageniidae, mayfly, secondary production, main 
channel, side channel, snags