Searching High and Low

By Casey Hickcox and Aaron DeLonay

Each spring CSRP biologists evaluate their list of tagged fish and search the river for pallid sturgeon that are expected to spawn.  Because sturgeon do not reproduce every year there can be considerable variation in the numbers of tagged fish that are expected to spawn each year.  This year there are very few fish with telemetry tags downstream of Kansas City.  Currently, biologists believe there may be only one tagged reproductive female pallid sturgeon in the lower study section from the Kansas River confluence downstream to the mouth of the Missouri River.  This fish, pallid sturgeon PLS11-005, was last located on March 26 near river mile 244 and has since gone undetected.  With spawning season quickly approaching, the question of where PLS11-005 is and whether or not she is going to spawn this season was becoming critical.

In an effort to locate PLS11-005, two USGS tracking boats searched approximately 75 miles on April 21st between Kansas City and Waverly, Missouri (Figure 1). The area being searched had been identified based on the fish’s last known location.  Previous searches above and below the target area came up empty.  When an important tagged fish, like PLS11-005 goes missing it can be difficult to relocate.  Pallid sturgeon are mobile and can migrate more than twelve miles a day in the Lower Missouri River.  Tracking crews must search quickly, but carefully.   On any given day a missing sturgeon, like PLS11-005 could be located behind a river-training structure or sandbar capable of masking her telemetry signal, or she could have moved into a previously searched area and could go undetected that day. These are just some of the many challenges facing scientists trying to track and understand these rare and elusive fish using acoustic telemetry (see previous post, “Can You Hear Me Now.”)

Figure 1. Map of telemetry locations for female pallid sturgeon PLS11-005 and search efforts during April 2014.

On this day, she would indeed go undetected.  After 6 hours of searching with two different boats, only one tagged fish (a male located near river mile 344) was located.  An attempt by another boat on the following day also failed to locate PLS11-005 downstream of Waverly.   While biologists work to locate her, boats continue to track other tagged pallid sturgeon, including three reproductive females in the upper study section downstream of Gavins Point Dam.

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