HR: 09:15h
AN: B51A-04    [Abstracts]
TI: A Multiscale Analysis of the Relationship Between Current Velocity and Invertebrate Drift: Do Faster Currents Transport More Food?
AU: * Rader, R B
EM: russell_rader@byu.edu
AF: Brigham Young University, Department of Integrative Biology, 401 WIDB, Provo, UT 84602 United States
AB: Salmonids may select feeding stations to maximize their net energy intake (NEI). Variation in NEI is based on the assumption that there is a positive linear relationship between food availability and current velocity. Three to four drift samples were collected from each of three riffles nested in three reach types nested in three Rocky Mountain streams for 4 to 6 weeks. We calculated regressions between current velocity at the net, Reynolds number for a riffle, and slope for a reach against the biomass of invertebrates collected for 10 hours during the day and again at night at each scale. We expected positive correlations between drift and current velocity within the same riffle because the effects of other factors on drift should be similar within the same riffle (e.g. benthic densities). Ninety percent of the regression slopes for nets within riffles were not different from zero. However, the number of positive slopes increased as scale increased when we compared hydraulically rough to smooth riffles and steep to low-gradient reaches. Rougher riffles and steeper reaches tended to produce more drift than smooth riffles and low-gradient reaches. Drift density was not correlated with current velocity within riffles, but became more predictable at intermediate scales.
DE: 9810 New fields (not classifiable under other headings)
SC: Biogeosciences [B]
MN: 2005 Joint Assembly