Across The River And Into The Trees

These weren’t just the last words of General Jackson in the Hemingway novel.  On Friday, April 12th, biologists located PLS11-004, a reproductive, female pallid sturgeon during her upstream migration, presumably to spawn.  In the morning PLS11-004 was observed crossing the river channel approximately one mile below the chute at Cranberry Bend (fig. 1).  This was exciting because she was heading upstream toward the chute, which is of particular interest to biologists.  The chute at Cranberry Bend, like many others along the Missouri River, is thought to enhance habitat diversity which may aid in the recovery of pallid sturgeon.  Pathways that fish take through chutes may also provide information to help in design fish-passage projects.  Documenting when and how pallid sturgeon use these habitats will help biologists to better understand the utility of such habitats to pallid sturgeon.

 At approximately 2:40 that afternoon PLS11-004 reached the downstream entrance of the chute at Cranberry Bend, and found herself at a bit of a fork in the road, or in this case the river.  Both channels present different tradeoffs, but we can only speculate how PLS11-004 weighed the pros and cons at this intersection.  The next chirp of the hydrophone let biologists know she had forgone the mainstem and was on a path up through the chute.  With biologist hot on her trail, she spent the next three hours making her way through and around the numerous clumps of trees scattered throughout the chute (fig 2.).  In the end the trees did not appear to be used as a resting place, as Jackson envisioned, but none the less afforded something more suitable for PLS11-004 as she continued her migration upstream.  A few days later, USGS hydrologists mapped the velocities in the chute and mainstem in an attempt to quantify why she selected this path.

Figure 1. Point locations, and 24 hour time, showing the movement path of PLS11-004 as she negotiated the Missouri River from river mile 279 to 282 nearly Waverly, MO.


Figure 2. Although female pallid sturgeon PLS11-004 seemed to navigate the cluttered chute with ease, biologist, on the other hand, had to give careful consideration to their every move in their large river vessel.


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