Laboratory examination of juvenile pallid sturgeon habitat preferences with focus on predation

Information on habitat requirements of pallid sturgeon (Scaphirhynchus albus) is crucial to support recovery efforts for this endangered species. We conducted a laboratory study to identify preferred water velocity, water depth, and substrate type and the effects of predation on habitat choice. Three velocity ranges (0 cm/s, 5-15 cm/s and 16-25 cm/s), two water depth, and three substrate types (sand, gravel and control) were tested. Investigation of velocity preferences indicated that juvenile pallid sturgeon prefer moderate velocities. Juvenile pallid sturgeon used shallow segments less than deep segments and positively selected sand and negatively selected gravel. Introduction of predators to the preferred substrate type (sand) resulted in a shift to less preferred substrates (primarily control) at no and low velocity treatments, but juvenile pallid sturgeon maintained positive selection for sand in high velocity trials. Preferred habitats identified in our study comprise moderate velocities, deep water, and sand substrate, but habitat selection changed under the threat of predation.