Pallid Sturgeon Free Embryo Drift Experiment Starts

Missouri River scientists started a large-scale collaborative study on June 24 to improve understanding of the fate of pallid sturgeon free embryos (from hatch through first feeding) in the Upper Missouri River (figure 1).  The study is being led by scientists from the U.S. Geological Survey with strong collaboration with Montana Fish Wildlife and Parks, U.S. Fish and Wildlife, U.S. Army Corps of Engineers, Bureau of Reclamation, and Western Area Power Administration. The ambitious study will use pallid sturgeon free embryos produced at Garrison National Fish Hatchery as tracers to test dispersal models and better understand transport dynamics.

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Results of previous studies indicate that pallid sturgeon free embryos need to drift long distances before they can safely settle out of the water column and begin feeding.  Better understanding of the dynamics in which the free embryos move downstream, and how long they need to safely settle out and begin to feed, may lead to important recovery options for this endangered fish. Crews will follow the free embryos downstream twenty-four hours a day for over a week, using ichthyoplankton nets to sample the drifting population.

The free embryo drift experiment is being complemented by assessment of river hydraulics.  Scientists from the USGS Columbia Environmental Research Center are collecting an extensive collection of velocity data using acoustic Doppler current profilers, in concert with a rhodamine dye trace.  The dye trace is intended to quantify the dispersion processes that spread free embryos out along the river through retention. In addition, collaborators with Montana Fish Wildlife and Parks are using tiny plastic beads as a tracer; the beads are designed to mimic free embryo settling behavior.  If the beads adequately mimic drifting free embryos, further studies could eliminate the need to use live sturgeon; saving time, money and resources. Other boat crews will be measuring the hydraulics of the Missouri River at a very high resolution to gain a better understanding of how these tiny fish move through the differing habitat conditions.