![[logo] US EPA](http://www.epa.gov/epafiles/images/logo_epaseal.gif){kind=logo}
Collecting Macroinvertebrates and Fish
The differences in their size and where they live require different sampling methods for collecting fish and macroinvertebrates (i.e., benthos).
Macroinvertebrates
D-Frame or Dip-Net
The D-Frame Net is used to dislodge the organisms from the substrate (bottom) so they float into the net. This method can be semi-quantitative if the level of effort is recorded (number of minutes and distance covered). This net can also be used to sample under the river banks and vegetation, collecting types of organisms not found elsewhere.
Artificial Substrate (Hester-Dendy)
The artificial substrate is used to allow the organisms to colonize
the plates mostly though drift. This provides a number of organisms
per square foot and is excellent for quantitative studies. The substrates
are placed in the stream for 4-6 weeks. Learn how Wisconsin DNR
uses
artificial substrates 
and more.
Ekman Dredge - for use in soft-bottomed (mud/sand) waters. Also provides quantitative sample.
Kick-Net
The kick-net is very popular for citizen monitoring with volunteers
and educational efforts in schools. There are methods used to make
it semi-quantitative, but its widest use is for education
and collecting lots of bugs. See how it is used in North
Carolina.
Review EPA's "Macroinvertebrate Field and Laboratory Methods for Evaluating the Biological Integrity of Surface Waters" (EPA 600-4-90-030) for more detailed information on these methods.
Fish
Electrofishing
Electrofishing is a harmless way to collect fish, take the needed
measurements, and return them to the waters. Electrofishing
uses a battery or alternator to send a mild electric pulse through
the water to stun the fish. Fish are collected in a net as they
float to the surface. Learn more about electrofishing
from the American Fisheries Society.
Hoop Nets
Hoop netting is the capture of fish by entrapment in an enclosed mesh trap. It has many of the advantages and disadvantages of gill netting; however, unlike gill netting, fish caught by hoop netting can be released with little or no harm to the fish. (from the US Geological Survey)
Seining
Seines are collection devices that trap fish by enclosing or encircling them. The fish are then sieved from the water by means of mesh panels. The bottom or lead line has lead weights strung or crimped onto it to weight the net. The top or float line includes cork, polystyrene foam, or plastic floats to keep the top of the seine near the water surface. The net is attached to wood or metal poles to handle the seine. (from The US Geological Survey)
More Field Methods
Some of the information needed while the fish are collected include length and weight measurements, as well as examining the fish for sores, tumors, and lesions.
Review EPA's "Fish Field and Laboratory Methods for Evaluating the Biological Integrity of Surface Waters" (EPA 600-R92-111) for more detailed information on these methods.
The following links Exit EPA webspace:
Learn more about electrofishing from the American Fisheries Society and the Ohio River Valley Sanitation Commission (ORSANCO).
Learn about US Geological Survey methods by viewing their document Methods for Sampling Fish Communities as Part of the National Water Quality Assessment Program (Open File Report 93-104) By Michael R. Meador, Thomas F. Cuffney, and Martin E. Gurtz.
Sampling protocols:
Facts about freshwater macroinvertebrates (Maryland DNR)
Lab Methods and Processing Identifications (Maryland DNR)