EPA-OW: NRSA Fish (Boat), 2009:  Fish sample collection in large non-wadeable rivers

  • Summary
  • Analytes
  • Revision
  • Data and Sites
Official Method Name
Section 5.5: Non-Wadeable Rivers-Fish (of National Rivers and Streams Assessment: Field Operations Manual (2009))
Current Revision
April 2009
WATER  (Waterbody type - Non-wadeable stream)
Electrofishing Unit
Method Subcategory
Method Source
  National Rivers and Streams Assessment: Field Operations Manual (2009)
EPA-841-B-07-009 - National Rivers and Streams Assessment: Field Operations Manual (2009)
Brief Method Summary
The fish sampling method is designed to provide a representative sample of the fish community, collecting all but the rarest fish inhabiting the site. It is assumed to accurately represent species richness, species guilds, relative abundance, size, and anomalies. The goal is to collect fish community data that will allow the calculation of an Index of Biotic Integrity (IBI) and Observed/Expected (O/E) models. Boat electrofishing is the preferred method of sampling. If electrofishing is not possible due to safety concerns, high turbidity, or extremes in conductivity, complete the “Not Fished” section of the field form and comment why. The time and effort necessary to sample the reach in its entirety is prohibitive in the context of the survey, thus sub-sampling is required. Electrofishing will occur in a downstream direction at all habitats along alternating banks (see section 5.5.3), over a length of 20 times the mean channel width (Transects A through F). Collection of a minimum of 500 fish is required. If this target is not attained, sampling will continue until 500 individuals are captured or the downstream extent of the site (transect K) is reached. Identification and processing of fish should occur at the completion of each transect. If sampling cannot happen at any individual transect, record it on the field collection form.
Scope and Application
This method describes the procedure for collecting fish in non-wadeable rivers that are sampled as part of the U.S. EPA's National Rivers and Streams Assessment.
Applicable Concentration Range
Very low or very high conductivity can decrease the effectiveness of electrofishing equipment. Depths of over about 10 feet are also not sampled very effectively.
Quality Control Requirements
Sample Handling
Fish retained for laboratory identification or as vouchers should be preserved in the field following the precautions outlined in the MSDS. All personnel handling 10% buffered formalin must read the MSDS (Appendix D). Formalin is a potential carcinogen and should be used with extreme caution.
Maximum Holding Time
Relative Cost
3 - 6 hrs. per site/sample
Sample Preparation Methods
Processing of fish must be completed at the end of each transect; however, if fish show signs of stress (e.g., loss of righting response, gaping, gulping air, excessive mucus), change water or stop fishing and initiate processing.