1993 1994 1995 



YEAR 



DTranscrlptlon BSpecles ID IDNocomIs sp. 

 DCottus sp. BGenutIO 



Figure 4-5. Comparison of different errors in the identification offish species 

 (McCormick, unpublished data). 



Summary 



Measurennent error is difficult to assess because repeatability is not possible using single-sample data collection 

 methods. However, relevant Information can be obtained indirectly through the estimation of other variance 

 components. Performance criteria established to control important sources of measurement error in the 

 indicator can be achieved with the implementation of appropriate control measures. Control measures applied 

 to field identifications of fishes resulted in a substantial reduction of errors to within the performance criteria 

 initially established for the monitoring program. 



Guideline 9: Temporal Variability - Within the Field Season 



It is unlikely in a monitoring program that data can be collected simultaneously from a large number of 

 sites. Instead, sampling may require several days, weeks, or months to complete, even though the data 

 are ultimately to be consolidated into a single reporting period. Thus, within-field season variability 

 should be estimated and evaluated. For some monitoring programs, indicators are applied only within a 

 particular season, time of day, or other window of opportunity when their signals are determined to be 

 strong, stable, and reliable, or when stressor influences are expected to be greatest. This optimal time 

 frame, or index period, reduces temporal variability considered irrelevant to program objectives. The use 

 of an index period should be defended and the variability within the index period should be estimated and 

 evaluated. 



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