Survival and Drift Behavior of Pallid Sturgeon Free Embryos and Larvae in an Artificial Channel

Laboratory studies were conducted to quantify survival and dispersal behaviors of pallid sturgeon free embryos and larvae and to assess their tolerance to different water velocities.  The dispersal behavior experiments were conducted in two large oval flumes in 2014 and 2015.  Both flumes produced nominal water velocities of 0.15 m/s and were nearly identical, except for different water delivery systems in 2014 and the addition different substrates (sand and gravel) in 2015.  Experiments were initiated with 10 newly-hatched free embryos and survival and dispersal behavior were monitored every three hours for 21-28 days.  There was no difference in the overall survival of fish between flumes in a given year.  Estimated drift velocities decreased as the fish aged.  Fish were observed holding position along the bottom at 12 days posthatch (dph) in 2014 and at 9 dph in 2015.  In separate velocity challenge studies conducted in oval tanks, we exposed free embryos of pallid sturgeon and paddlefish and16-dph pallid sturgeon larvae to a graded series of velocities ranging from 0.00-0.45 m/s to estimate median lethal velocities (LV50).  Free embryos of both species (6-day LV50, 0.10-0.11 m/s) more sensitive to the test velocities than pallid sturgeon larvae (6-day LV50, 0.21 m/s).