TESTING THE FUNDAMENTAL ASSUMPTION UNDERLYING THE USE OF LTRMP FISH DATA: 
DOES VARIATION IN LTRMP CPUE DATA REFLECT VARIATION IN THE ABUNDANCE OF 
FISHES

John H. Chick1, Chad R. Dolan1, Eric N. Ratcliff1, Eric J. Gittinger1, 
Valerie A. Barko2 and Brian S. Ickes3

1Illinois Natural History Survey, Great Rivers Field Station, 8450 Montclair 
Ave, Brighton, IL  62012

2Missouri Department of conservation, Open River and Wetlands Field Station, 
3815 E. Jackson Blvd., Jackson, MO  63755

3U. S. Geological Survey, Upper Midwest Environmental Sciences Center, 2630 
Fanta Reed Raod, La Crosse, WI  54603

Most of the techniques available for sampling fishes, including all those 
used in the Long Term Resource Monitoring Program (LTRMP), provide catch-per-
unit-effort data as an indicator of abundance.  An underlying assumption of 
the use of CPUE data is that a relationship exists between CPUE and the 
actual abundance (numbers of biomass per unit area) of fishes.  In general, 
the relation between CPUE and abundance is depicted as a linear relationship 
of the form:

	C/E = qN

       Where:
       C/E = catch per unit effort for a particular species
	N = is the true abundance (i.e., number per area) for that species, and
	q = is the gear-specific catchability coefficient.

We test for relationships between CPUE data from LTRMP day electrofishing 
with density estimates from block-net rotenone sampling in backwater 
habitats.  The project was conducted at two reaches of the UMRS:  1) Pool 26, 
and 3) the La Grange Reach of the Illinois River.  At each reach, multiple 
backwater lakes were selected for sampling based on a minimum size of 5 
hectares and sufficient depth to allow sampling.  Within each backwater, 
three ¼ acre block nets were be deployed in random locations, and fish within 
the nets were sampled using rotenone.  Potassium permanganate was applied 
outside of the nets to deactivate rotenone leaking through the mesh.  On the 
same day the three block nets were deployed, three day electrofishing samples 
were made at random locations following standard LTRMP methodology.  This 
allowed us to use regression analysis to test for a linear relationship 
between CPUE from day electrofishing with density and biomass estimates from 
block net sampling, using each backwater lake as replicates.

Keywords:  fish sampling, day electrofishing, Long Term Resource Monitoring 
Program, backwater lakes, Mississippi and Illinois rivers

1.  John H. Chick, Illinois Natural History Survey, Great Rivers Field 
Station, 8450 Montclair Ave, Brighton, IL  62012; Phone (618)466-9690, Fax 
(618)466-9688, email chick@inhs.uiuc.edu
2. Platform presentation, will NOT change to poster
3.  No student authors