Effects of Water Currents on Fresh‐Water Snails Stagnicola Palustris and Physa Propinqua

Three size groups of Stagnicola palustris nuttalliana and Physa propinqua were exposed to six water velocities, between 0.5 and 3.0 ft/sec., in a plexiglass flume on six different substrates. The snails were tested for ability to remain attached to the substrate and the data analyzed by a factorial analysis of variance. The middle—size group of snails was dislodged easier than the older two size groups. Stagnicola was less easily dislodged than Physa. The greatest dislodgment occurred from sand, followed by clay, caliche rock, plexiglass, pea gravel and basalt rock. Increased water velocity caused greater dislodgment.