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Sampling Techniques
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Although most professional monitoring is done with electroshocking gear, alternative tools and methods do exist, some of which may prove very effective under the right conditions. For example, basic dipnets are often used in riffles to capture those hard to find madtom, darter and sculpin species, and can be surprisingly valuable when sampling undercut banks (see fig.1a,b). Additonally, when sampling a narrow channel (small stream or ditch), dipnets often prove to be the best low-budget tool around.
Before entering a stream with a dipnet or seine, it is wise to check with state agencies regarding regulations that might apply to netting certain species of fish.
Figure 1
Figure 1: Casper dipnetting into an undercut bank
Seines (see fig. 2) are effective in streams of any size, provided proper techniques are employed. High gradient streams where water is 3-4' deep can make seining difficult and dangerous, and is only recommended for experienced seiners. It should be noted that with both seines and dipnets, larger species (large suckers, bass, etc.) are difficult to capture.
Please see the Chapter on Fish Protocols from EPA's Rapid Bioassessment Protocols and EPA's Fish Field and Laboratory Methods for Evaluating the Biological Integrity of Surface Waters for more information on fish sampling techniques. The US Geological Survey also has an excellent guide to sampling fish - Methods for Sampling Fish Communities as a Part of the National Water-Quality Assessment Program (USGS Open-File Report 93-104).
Figure 2. Seining. Jeff, Nick and Andy disturbing susbstrate in the Chagrin River, OH.