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PROPOSED STANDARDIZED ASSESSMENT METHODS (SAMS) FOR ELECTROFISHING LARGE RIVERS
Citation:
Flotemersch, J E. AND K A. Blocksom. PROPOSED STANDARDIZED ASSESSMENT METHODS (SAMS) FOR ELECTROFISHING LARGE RIVERS. Presented at National Biological Assessment and Criteria Workshop, Couer d'Alene, ID, March 31 - April 04, 2003.
Impact/Purpose:
The goal of this research is to develop methods and indicators that are useful for evaluating the condition of aquatic communities, for assessing the restoration of aquatic communities in response to mitigation and best management practices, and for determining the exposure of aquatic communities to different classes of stressors (i.e., pesticides, sedimentation, habitat alteration).
Description:
The effects of electrofishing design and sampling distance were studied at 49 sites across four boatable rivers ranging in drainage area from 13,947 to 23,041 km2 in the Ohio River basin. Two general types of sites were sampled: Run-of-the-River (Free-flowing sites or with small low-head dams that store rather than regulate waters) and Restricted Flow Sites (heavily influenced by navigational Lock and Dam structures built to support commercial traffic). Principal Components Analysis using habitat variables validated this classification of sites. The electrofishing design used for the study permitted the concomitant evaluation of multiple fine-scale bioassessment electrofishing design scenarios and the determination of the effect of distance on metric scores. We conclude from this study that the degree of impoundment of a river plays a critical role in characterizing sites and that different sampling methods or assessment techniques will be required to adequately describe different categories of systems. At Run-of-the-River sites, a daytime main-channel-border electrofishing design that electrofished 1000 m on one bank or 500 meters on paired-banks was effective and efficient at characterizing the study sites based on the metrics tested. At Restricted Flow sites, we suggest a switch from day to night electrofishing be considered. If night electrofishing is not feasible, we suggest increasing the electrofishing distance at these sites to a 1000-m paired-banks design or a 2000 m single-bank design. In addition to an increased distance, metrics based on fish species prone to diel movement should be interpreted with caution in Restricted Flow rivers. These results apply for rivers of this size in this region, but could likely be applied elsewhere in the absence of similar research.