Experimental displacement trials of the red sea urchin Strongylocentrotus franciscanus (Aggassiz, 1863) (Echinodermata: Echinoidea) at different current velocities

Abstract

Displacement of marine animals is affected by diverse environmental factors, including hydrodynamics performance. We evaluated the effect of current velocity on the displacement of the sea urchin Strongylocentrotus franciscanus in an experimental flume, in both light and dark conditions. We observed that movement of S. franciscanus was directly proportional to the current speed. Our results differ from previous studies in the amount and the direction of displacement of other strongylocentrotids, because sea urchins displacements were similar in the current direction and countercurrent irrespective of current velocity and our results showed displacements of circa 7 m per day, smaller to that reported for experiments in the same urchin species in British Columbia. The differences may be due to the absence of predators or food, or the trials in day and night conditions. Day and night differences in the displacement of S. franciscanus were not observed.