United States Environmental Protection Agency	Office of Research and Development

National Exposure Research Laboratory
Research Abstract

GPRA Goal 2 - (Clean and Safe Water)

FY 2004 Annual Performance Measure (APM) #255

Significant Research Findings:

Prototype indicators of condition for deep
river fish assemblages developed

Electrofishing in Boatable Rivers:

Does Sampling Design Affect Bioassessment Metrics?

Fish assemblages are among the indicators frequently used in the bioassessment of
surface waters. Correlations have been successfully demonstrated between fish
indices of biotic integrity (IBIs) and human activities that influence streams and
rivers. Although IBIs have been widely applied in wadeable streams and are
slowly gaining popularity for the assessment of large rivers, their application in
large rivers has been relatively limited. Electrofishing is commonly used to collect
fish for bioassessments because it is widely considered to be the single most
comprehensive and effective method for collecting fishes in streams and rivers.
Although a wide variety of field electrofishing designs are currently in use, studies
that compare these designs are limited. This study was undertaken to: 1) compare
commonly used boat-based electrofishing designs; 2) determine the sampling
distance at which the values of common bioassessment metrics begin to stabilize;
and 3) study the influence of physical site characteristics on the designs. The
primary goal of this study was to provide an analysis of electrofishing designs that
will enable agencies or individuals charged with bioassessment and monitoring of
boatable waters to select the best electrofishing designs relevant to the needs of
each study. A second goal of the study is to support the development of a Large
River Bioassessment Protocol (LR-BP) for bioassessment and monitoring
activities.

Data were collected from 60 boatable sites using an electrofishing design that
permitted comparisons of the effects of designs and distances on fish assemblage
metrics. Sites were classified a priori as Run-of-the-River (ROR) or Restricted
Flow (RF). Data representing four different design options (i.e., 1000 and 2000 m
for both single and paired banks) were extracted from the dataset and analyzed.

Results and	This research detected significant differences in many common measures of fish

Impact	assemblage condition as a result of field design. To further the development of a

standardized design with known performance, the percent change in assemblage
measures (metrics) was plotted against cumulative electrofishing distance. The
percent change in the metrics was found to decline sharply when electrofishing
covered a distance of approximately 1000 m, after which metrics usually varied by
less than 10 percent. These results demonstrate that electrofishing designs that

Scientific
Problem and
Policy Issues

Research
Approach

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cover distances of 1000 m of shoreline are sufficient for bioassessments on
boatable rivers (assuming the river is similar to those in this study), regardless of
whether the shoreline is along a single bank or distributed equally among paired
banks. However, at sites with depths > 4 m (where electrofishing can be less
representative), nighttime electrofishing (which is more effective in deeper waters)
or daytime electrofishing designs to cover 2000 m may be advisable to obtain
more representative samples.

With development of this standardized method, regulatory agencies have a new
tool for determining the condition of large rivers, an integral part of achieving
water quality for all surface waters. The method has been adopted, and is in-use, as
the standard method used by the Huntington District of the U.S. Army Corps of
Engineers for bioassessment of waters within their jurisdiction, and by the state of
Kentucky as their standard method for conducting state-wide assessments.
Additional applications of the method are pending for 2005.

Research	Research Team: Joseph E. Flotemersch and Karen Blocksom, National

Collaboration and Exposure Research Laboratory, U.S. Environmental Protection Agency, 26 W.

Research	Martin Luther King Dr., Cincinnati, OH 45268 USA.

Products

For a listing of recent publication, presentation, and workshops on this and related
research, please consult the contact information below.

Future Research Using the field design that resulted from this research, data is being collected to
compare the effects of different electrofishing configurations on measures of fish
condition in large rivers. Information gained from this study will be used to
standardize data sets collected using different electrofishing configurations in
efforts to examine fish condition at large scales (e.g., basin-wide, regional,
national).

Contacts for	Questions and inquiries can be directed to:

Additional	Joseph E. Flotemersch, Ph.D.

Information	US EPA

National Exposure Research Laboratory
Cincinnati, Ohio 45268
Phone:513/569-7086

E-mail: flotemersch.joseph@epamail.epa.gov

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