Timed Search Technique Used to Evlauate Freshwater Mussel (Bivalvia: Unionidae) Species Richness in Headwater Streams: Is a Single One-Hour Visit Enough?

ABSTRACT

Freshwater mussels were sampled in the upper Mackinaw River basin, Illinois, for five years to determine if a single, one-hour visit was enough to adequately characterize the species richness at a headwater stream site when using the timed search technique. Eight sites were each handpicked for one person-hour every year, and species richness was calculated to determine if it varied by year for five years. During 39 person-hours, 2,692 live individuals of 14 species were collected. Species accumulation curves and Spearman's correlation analysis suggested that a single, one-hour visit was not adequate when using the timed search technique to determine species richness in headwater streams of the Mackinaw River basin and might not be sufficient in other basins.