Panning for biological gold

Telemetry crews tracked female pallid sturgeon PLS11-007 to her spawning location (see previous post An Early Spawning Recorded) on March 30 and 31. Additional crews were deployed April 3 in an effort to confirm a successful spawning at this site. Researchers sampled for larvae using ichthyoplankton sampling nets, which are cone shaped nets made from very fine mesh with a sampling cup at the bottom. The nets are attached to 100 pound weights to keep them stable in the flow of the river.

An ichthyoplankton sampling net being deployed in the Missouri River.

After 5 to 15 minutes in the water column, the sampling nets are brought back to the surface. The samples are then emptied into pans and scientists then search for “biological gold,” specifically any larval fish that could be sturgeon. To prevent anylarval pallid sturgeon being missed, all larval fish belonging to the Acipenseridae family (sturgeon and paddlefish) are preserved in alcohol. These larvae are then taken back to the office for further identification under a microscope.

Hallie Ladd, Beau Griffith and Jeff Beasley, Five Rivers Services, LLC biologists sorting through larvae samples collected from the Missouri River.

During the three days of sampling that followed the spawning of PLS11-007, only one sturgeon larvae was captured on April 5. The larvae was determined to be newly hatched, approximately five to six days post fertilization.

Crews tracked female pallid sturgeon PLS09-011 to her spawning site a few weeks later (see previous post Spawn with the Wind), then subsequently collected larval samples for four days. It was determined, using microscopic evaluation, that there were as many as eight sturgeon larvae captured near this spawning site. These larvae were also newly hatched, approximately six to eight days post fertilization.

A newly hatched probable sturgeon larvae captured near the spawning site of PLS09-011 in Nebraska.

Ultimately, genetic testing will be required to determine if any of the larvae caught at either site are pallid sturgeon.

See previous posts Searching for a needle in a haystack, and Day old sturgeon caught in the Lower Missouri River for more information on 2011 larval sampling and catch.

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