Female prerogative

To the casual observer, the movements of PLS11-008 may seem awfully indecisive.  We know she is reproductive; she has black eggs at a stage appropriate for spawning this spring.  But she waited for more than a month in a short reach near Rocheport, Missouri until moving suddenly 30 miles upstream to near Arrow Rock, Missouri.  It was fairly easy to interpret her behavior when she was moving 3-5 miles per day upstream.  She moved along the slower velocities on the insides of bends and maneuvered her way through the cross overs.

Movements of PLS11-008 on May 13, 2011 as she navigates a channel crossover upstream of Boonville, Missouri.

She got a little confused around some wing dikes, but moved steadily upstream, a behavior we’ve come to associate with successful spawning migrations.  However, when she got near the apex of her journey around May 15 her movements became erratic.  She stopped for about 24 hours at the outlet of the Lisbon Chute near a pile of old, submerged bank revetment where flow from the chute converged with the main channel.  This was a good fit for a spawning site and we prepared to mobilize habitat, egg, larvae, and re-capture crews.  But the next time we located her she was on the inside bend 1 mile upstream, and the next day, May 17, she was on the outside of a bend at rivermile 216, another place that matches our concept of a spawning site (but does it match hers?).  Again, we prepared to deploy the post-spawn crews, but on the morning of May 18 she was found yet another mile upstream, still on the outside bend over coarse substrate. A big challenge for us is when to make the decision to mobilize the considerable resources of people, boats, and instrumentation that are needed to characterize spawning habitat and to attempt to validate that eggs have been fertlized and hatched. The decision has to be made in real time based on our interpretations of patchy movement data of a relatively small fish at the bottom of a deep and opaque river.  

About Emily Pherigo

Emily is no longer with the Comprehensive Sturgeon Research Project. When she was here, she was a biologist contracted to the Comprehensive Sturgeon Research Project. Most of her time was spent at a computer performing QA/QC on data or updating figures and graphs most used by Aaron DeLonay. However, she occasionally made it to the river, where she enjoyed seeing pallid sturgeon and was reminded why she entered the natural resources field.
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