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Validation of Standard Methods

Validation of a method is the evaluation of its efficiency (i.e., the ability of the method to catch the fish that are actually there). Standard sampling and validation are complementary. Standardization of sampling methods can reduce variation in efficiency. However, even with method standardization, efficiency can still differ from site to site or from season to season. For example, a method may capture a higher proportion of fish when current velocity is low than with the same method fished when current velocity is high.

A sampling method can be validated by comparison of CPUE to estimates of actual abundance of fish at a site. This may be done through mark-recapture or some other abundance estimation technique to tell how well the samplling method catches fish that are actually present at the site. However, validation without standarization is very inefficient. If methods are not consistent among sites, you would have to validate the different methods each time you used them. If you had to validate 100 different methods, you would have few samples and little information about each method--in direct contrast to using a few standard methods, which could be validated at a much wider variety of sites. Use of a few standard methods, validated under a wide variety of conditions, provides the most accurate and precise data outside of labor-intensive population estimates.

In addition, conversion of data, say of fish captured using a previous nonstandard method, so they can be compared to data sets collected using North American standard techniques is often desired.

Please take the opportunity with your comments below to notify others of current research on validation and calibration of North American standard sampling methods, and conversion among techniques.