Potential consequences of the proposed plot design and collection methods are identified and presented in 

 Table 4-9. Adverse effects on fish populations are generally low, and the fish assemblage has sufficient time 

 to recover between sampling visits. Methods for the Indicator can be a component of an integrated sampling 

 regime for several different indicators. 



A critical aspect of obtaining a representative sample of the fish assemblage under the proposed plot design 

 is determining the length of stream that must be sampled at each site. For this indicator, a sample of the 

 assemblage must be collected from a single pass through a prescribed length of stream (Karr et al. 1986, 

 McCormick and Hughes 1998). Repeated sampling of a stream reach is neither practical nor representative. 

 Thus, it is imperative that the length of stream to be sampled maximizes the number of species collected. A 

 small pilot study on a few selected streams was conducted to make this determination. Based on this study 

 (Fig. 4-4), a stream length equal to 40 times the mean channel width was selected as the area to be sampled 

 at each stream. This length of stream is sufficient to obtain approximately 90 percent of the fish species 

 inhabiting the reach. Sampling additional lengths of a stream does not substantially increase the number of 

 species obtained. Lyons (1992) reported similar results. 



Table 4-9. Effects of sampling 



Effects on stream fish assemblages and protected organisms, populations, habitats: 



Minimal impacts under normal conditions 



• Most individuals collected released alive (some retained as voucher specimens) 



• Some mortality due to electrofishing or seining, especially if large numbers 

 are collected and processed 



• Some impact due to physical disturbance of stream channel during seining, 

 but scale of sampling is small relative to entire watershed 



• May be minimal in some areas due to collection permit restrictions (no sampling) 



Effects of a single visit on subsequent visits: 



• Collecting replicate samples during a single visit not practical nor accurate 



• Entire reach is disturbed during sampling 



Most individuals collected are released alive, but need time to recover and 

 redistribute after collection 



• Studies indicate that fish assemblages recover after natural disturbances 

 such as floods or extended drought 



Effects on concurrent measurement of other indicators: 



• Methods are used in an integrated sampling regime for a variety of different 

 indicators. 



• No impact if proper sampling sequence is followed (e.g., collect chemical 

 samples prior to obtaining fish assemblage samples) 



4-16 



