Spreading the word on pallid sturgeon research

By Robert Jacobson, Kim Chojnacki, and Casey Hickcox

Columbia Environmental Research Center (CERC) scientists took to the road in March to share some of the center’s work over the last year with the Missouri River Natural Resource Conference (MRNRC) in Nebraska City, Nebraska. In total, CERC scientists authored or contributed to five posters and 12 presentations over the three-day conference. The conference was attended by individuals from over 50 organizations involved with various aspects of Missouri River science and management.  The annual MRNRC offers an opportunity for scientists to share their work with scientists, managers, and the public throughout the entire Missouri River basin.  Here is a list of this year’s presentations and posters by CERC scientists and collaborators:


  1. Survival and Drift Behavior of Pallid Sturgeon Free Embryos in an Artificial Channel By: Kevin Buhl and Travis Schaffer
  2. Identifying Floodplain Conservation Land Management Priorities and Science Needs for the Lower Missouri River By: Kristen Bouska, Garth Lindner, Robert Jacobson, and Craig Paukert
  3. Identifying Sturgeon Spawning Locations through Back-Calculations of Free-Embryo Drift: Complexities in Characterizing Drift Dynamics By: Edward A. Bulliner, Susannah O. Erwin, Kimberly A. Chojnacki, Amy E. George, Jake D. Faulkner, and Aaron J. DeLonay
  4. Hydrodynamic Modeling to Evaluate the Influence of Channel Morphology and Hydrology on Larval Drift of Pallid Sturgeon in the Lower Missouri River By: Susannah Erwin, Robert Jacobson, Christopher Holly, Eric Allen, Caroline Elliott, and Edward Bulliner
  5. Substrate Effects on Hatch and Initiation of Drift of Scaphirhynchus Sturgeon Species in an Artificial Stream By: Jake D.A. Faulkner, Aaron J. DeLonay, James S. Candrl, Kimberly A. Chojnacki, and David K. Combs


  1. Gonadosomatic Index and Fecundity of Lower Missouri and Middle Mississippi River Endangered Pallid Sturgeon Estimated Using Minimally Invasive Techniques By: Janice L. Albers, Mark L. Wildhaber, and Aaron J. DeLonay
  2. Trends and Variation in the Reproductive Ecology of Pallid Sturgeon in the Upper Missouri River Basin By: Patrick J. Braaten and David B. Fuller
  3. Empirically Modeling Interior Least Tern Habitat Response to River Hydrographs Using Landsat TM Imagery By: Edward A. Bulliner, Caroline M. Elliott, Robert B. Jacobson, Casey Lott, and Colin Sheppard
  4. Developing Models to Identify Successful Sturgeon Spawning Locations Using Free Embryo Collections, Lower Missouri River By: Kimberly A. Chojnacki, Edward A. Bulliner, Susanna O. Erwin, Amy E. George, David K. Combs, Jake D. A. Faulkner, and Aaron J. DeLonay
  5. Characterization of Patterns of Sturgeon and Paddlefish Spawning and Dispersal in the Lower Missouri River to Guide Restoration Actions By: Aaron J. DeLonay, Kimberly A. Chojnacki, Caroline M. Elliott, Susannah O. Erwin, David K. Combs, Amy E. George, and Edward Heist
  6. Assessment of Pallid Sturgeon Spawning Habitat on the Lower Yellowstone River By: Caroline M. Elliott, Patrick Braaten, Aaron J. DeLonay, Robert B. Jacobson, Eric Allen, David Combs, Casey Hickox, and Chad Vishy
  7. Bedform Dynamics and Sand Transport in the Lower Missouri River in Pallid Sturgeon Spawning Reaches By: Caroline Elliott, Robert Jacobson, Susannah Erwin, Edward Bulliner, Aaron DeLonay, Eric B. Allen, and Christopher Holly
  8. Quantifying and Defining Functional Habitat to Inform Recovery of Pallid Sturgeon in the Missouri River By: Susannah Erwin, Robert Jacobson, Caroline Elliott, Todd Gemeinhardt, Tim Welker, Aaron DeLonay, and Kimberly Chojnacki
  9.  Missouri River Pallid Sturgeon Effects Analysis: Progress and Prospects By: Robert B. Jacobson, Mandy L. Annis, Michael E. Colvin, Daniel A. James, Michael J. Parsley, Michael Randall, Tim L. Welker
  10.  Pallid Sturgeon Reproduction in the Yellowstone River, 2014 By: Mathew Rugg, Patrick Braaten, Kenneth Backes, Caleb Bollman, Christopher Wesolek, Caroline Elliott, David Combs Chad Vishy, Beau Griffith, Aaron DeLonay, and Robert Jacobson
  11.  Relationships Between Land Capability Potential Index (LCPI) Classes and the Distribution of Plant Species and Communities By: Matthew A. Struckhoff
  12.  Population Trends, Bend Use Relative to Available Habitat, and Within-River Bend Habitat Use of Eight Indicator Species of Missouri and Lower Kansas River Benthic Fishes: 15 Years After Baseline Assessment By: Mark L. Wildhaber, Wen-His Yang, Ali Arab, Nicholas S. Green, and Janice L. Albers
Posted in Education, Habitat mapping, Technology |

Repeating Sturgeon Behaviors

By Hallie Ladd and Aaron DeLonay

Scientists in the Comprehensive Sturgeon Research Project have learned from long-term telemetry tracking studies that female pallid sturgeon in the Lower Missouri River can spawn as often as every 2 to 3 years and in some instances, return to the same areas to spawn (see previous post, “Pallids in the Platte”).  They have also learned that some female sturgeon in the Lower Missouri River begin migrating to their spring spawning locations in the fall of the preceding year.

Female pallid sturgeon PLS11-007 was first captured and tagged in non-reproductive condition during the spring of 2011 in the Lower Missouri near Boonville, Missouri at river mile 200.  She was recaptured on September 16, 2011 and an ultrasound evaluation indicated that she would be ready to spawn during the spring of 2012.   PLS11-007 began her upstream migration in late September, swimming upstream approximately 100 miles before pausing in mid-November.  In March of 2012 she moved upstream an additional 20 miles from her winter location to spawn on an outside bend near river mile 322.  Spawning is believed to have occurred on March 30-31st  at water temperatures ranging from 19.3 to 20 °C (see previous post, “An early Spawning Recorded”).  After spawning, PLS11-007 moved rapidly downstream and by early June had returned to the same bend in the river she started from the previous September.

Project scientists have patiently watched PLS11-007 for more than two years waiting for her to become reproductive again.  During that time she has used little more than a mile of river to feed and to prepare to spawn again.  On September 25, 2014, PLS11-007 was targeted and recaptured at river mile 200.8.  Reproductive assessments revealed that she was once again in reproductive condition and will likely spawn in the spring of 2015.  Project scientists are eager to learn if she will begin upstream migration again in the fall and select the same spawning location as in 2012.  Critical behaviors in sturgeon, like reproduction, are not random events, but are structured by their biology and cued by environmental conditions.  Observing repeated behavioral patterns is critical to understanding how sturgeon respond to their environment and determining what conditions are likely to result in successful reproduction.

USGS student contractor Dusty Swedberg with female pallid sturgeon PLS11-007.  In 2012, CSRP scientists documented PLS11-007’s spawning migration and location.  Reproductive assessments recently revealed that PLS11-007 was once again in reproductive condition and will likely spawn in the spring of 2015. Project scientists are eager to learn if she will select the same spawning location as in 2012.

Posted in Recapture, Reproductive Female, Spawning |

Recapture Efforts Have Begun

By Hallie Ladd, Kim Chojnacki, and Aaron DeLonay

Since 2004, the Comprehensive Sturgeon Research Project (CSRP) has used telemetry tagging and tracking methods to locate individual sturgeon over long time periods and to record data on movements, behavior, and  habitat use.  In the Lower Missouri River the CSRP has over 80 telemetered pallid sturgeon with active acoustic tags.  Several of these fish, including three recently captured males, have a long-standing history with CSRP’s telemetry program.

During the week of September 15th, three male pallid sturgeon (PLS07-019, PLS08-002, and PLS10-009) were recaptured upstream of Omaha, Nebraska between river miles 644 and 676.  The unique identifier for each fish informs scientists of the fish species, the year the fish entered the telemetry study, and the numerical order in which the fish was implanted.  For example, PLS07-019 is a pallid sturgeon (PLS) that was the 19th (019) fish implanted in 2007 (07).  A total of 295 telemetry locations has been recorded for PLS07-019, PLS08-002, and PLS10-009 between river miles 642-755.3.  In addition, each sturgeon has been captured, evaluated, and reimplanted several times during the project.  PLS07-019, for example, has been captured and evaluated by project scientists five times over the past seven years, and has been implanted with five different transmitters and data storage tags.  Over seven years, data storage tags implanted in pallid sturgeon can record tens of thousands of records of depth and temperature data for the habitats that sturgeon use.  Long-term telemetry data help scientists define migration patterns, identify spawning locations, and detect patterns of site fidelity (see previous post “Old Faithful”) and are fundamental to understanding how the river can be can be managed to support and augment pallid sturgeon populations.

At the time of recapture, all three fish received a reproductive evaluation and were determined to be in non-reproductive condition.  However, PLS08-002’s ultrasound revealed that he may be ready to spawn in 2015.  Scientists will continue to monitor these fish’s movement and reproductive patterns throughout the Missouri River to gain information for pallid sturgeon recovery efforts.

During the week of September 15th, three male pallid sturgeon (PLS07-019, PLS08-002, and PLS10-009) were recaptured between river miles 644 and 676. A total of 295 telemetry locations has been recorded for PLS07-019, PLS08-002, and PLS10-009 during their time in the Comprehensive Sturgeon Research Project telemetry program.


Posted in Recapture, Telemetry tracking |

Still Catching Free Embryo Sturgeon

By Alexandra Laboile, Kimberly Chojnacki, and Aaron DeLonay

Previous studies by CSRP scientists and others have indicated that the timing and duration of spawning for paddlefish and sturgeon in the Missouri River are dependent upon water temperature.  Each spring for the past three years, CSRP scientists began sampling the river in April for drifting free-embryo sturgeon and paddlefish to determine where and when spawning is occurring.  Scientists sampled this year near the confluence of the Platte and Missouri rivers not far downstream from Omaha, Nebraska (see previous post, “We’ve Only Just Begun”).  As expected, paddlefish free embryos were collected from mid-May to mid-June.  Data from previous years show that paddlefish generally spawn earlier and at cooler temperatures than most shovelnose sturgeon.  A few shovelnose sturgeon will spawn early, around the same time that paddlefish spawn, but most shovelnose sturgeon spawn slightly later during the month of June.  Scientists typically sample through the summer until the water temperature warms beyond the range where spawning occurs, and until free embryos are no longer collected.  In most years this happened by the end of July when water temperature approached 28 °C; however the summer of 2014 proved to be cooler than recent years.  Temperatures rarely exceeded 25 °C from July through August, and the drifting free embryos never stopped showing up in the nets.  For reasons as yet unknown, sturgeon in the Missouri River and its tributaries above Omaha, Nebraska continued to spawn well into summer.  During the week of August 11, scientists captured 152 free embryos, the most that had been collected in a single week all year. Compared to previous years when sturgeon free embryo numbers peaked in mid-June, this is very late to collect free embryos in such abundance.  While CSRP scientists have documented spawning by small numbers of shovelnose sturgeon in the early fall (see previous post, “A Most Unexpected Event“), they had never before observed shovelnose sturgeon spawning through the summer almost without interruption.  Are these sturgeon typical spring spawners that delayed reproduction or are they fall-spawning fish that reproduced early?  Why do sturgeon do this and not paddlefish?  Does the ability of shovelnose sturgeon to spawn over such a broad range of conditions explain why it is more common than the endangered pallid sturgeon?  Scientists are working to explain these observations.

Ten minute samples from ichthyoplankton nets deployed near the bottom of the Missouri River. Samples are sorted and searched for paddlefish and sturgeon free embryos.

Posted in Early life history, Spawning | Tagged , |

The Sounds of Sturgeon Research

By Aaron DeLonay, Kimberly Chojnacki, and Casey Hickcox

Recently, Comprehensive Sturgeon Research Project scientists documented a spawning event in the Yellowstone River when researchers followed a reproductive female sturgeon to a location where an aggregation of male sturgeon had been identified (See previous blog post “A Spawning Recorded in the Yellowstone River“). Capitalizing on the rare opportunity, researchers documented the natural spawning behaviors through sonar imaging and radio telemetry. While this was occurring, a CSRP tracking crew captured some of the sounds associated with the radio telemetry of a sturgeon spawning event.

Each radio transmitter carried inside a tagged pallid sturgeon emits a digitally–encoded radio signal every 5 seconds.  A radio receiver on the boat detects the transmitter using a large antenna and provides an audio signal through a speaker that the scientists use to track and locate each fish.  The audio signal the scientists hear sounds like the chirp of a cricket.  As the boat approaches a tagged sturgeon or when the antenna points in the direction of the fish, the chirp gets louder.   A spawning aggregation of tagged sturgeon sounds like a chorus of crickets to the scientists monitoring the event.

Click the links below to hear what sturgeon researchers heard when tracking this event.

Single Chirp – This is the signal a transmitter produces every five seconds which allows researchers to document their movements

Three Chirps – One of the struggles with radio telemetry is attempting to track a single fish when multiple tagged fish are present

Aggregation Audio– This is a recording of the telemetry sounds of a reproductive aggregation of tracked Yellowstone River sturgeon on June 27th, 2014.  The receiver decoded six different sturgeon telemetry tags in the above recording. Some of the tagged sturgeon came within range of the receiver after the recording started, some went out of range before it finished, and some were closer to the boat than others, and were louder.

Posted in Spawning, Technology, Telemetry tracking, Upper Missouri and Yellowstone Rivers | Tagged , , |

A Spawning Recorded in the Yellowstone River

By Patrick Braaten

Pallid sturgeon code 39 is shown being prepared for release following a post-spawn analysis

Figure 1. Researchers prepare to release pallid sturgeon code 39 following a post-spawn analysis to confirm a successful release of eggs during the spawning event.

She was initially captured in September 1993, but at the time, the sex and reproductive status of the 1325 mm, 15.9 kg pallid sturgeon were not determined. She was implanted with a passive integrated transponder (PIT) tag for future identification and released.  Six years later in April 1999, she was captured again and identified by her unique PIT number.  She measured 1356 mm and weighed 17.7 kg though her sex and reproductive state remained undetermined.  Her history over the course of the next 15 years is unknown as she eluded collection efforts implemented as part of pallid sturgeon propagation and research efforts in the Upper Missouri and Yellowstone rivers.  Her 15-year period of at-large anonymity ended on June 11, 2014, when she was unexpectedly encountered in a trammel net drifted in the lower Yellowstone River.  Reproductive assessment indicated that the unknown pallid sturgeon was indeed a female, in reproductive condition, and likely to spawn soon.  Measuring 1405 mm (approximately 4 feet and 7 inches) and weighing 17.5 kg (38.6 pounds), the spawn-ready female was implanted with radio transmitter code 39 and released.  Female code 39 joined the research population of three other female pallid sturgeon (codes 30, 35, 36) that were already identified as reproductively ready to spawn.

With a cast of four spawn-ready females and numerous telemetered male pallid sturgeon, crews from Montana Fish, Wildlife and Parks (MFWP) and the U.S. Geological Survey Columbia Environmental Research Center (CERC) focused efforts to maintain contact with the spawners and identify spawning locations.  Tracking teams were accompanied by habitat crews and crews equipped with a DIDSON acoustic “camera” – in an attempt to visualize spawning behavior (see previous post “Northbound”).

A USGS research vessel observes pallid sturgeon spawning activities

Figure 2. A USGS research vessel uses DIDSON sonar imaging on the Yellowstone River to document pallid sturgeon spawning activities on June 27, 2014.

For the next several days after being implanted with the telemetry transmitter, pallid sturgeon female code 39 exhibited the pre-spawn “roaming” behavior frequently observed in female pallid sturgeon in the Yellowstone River – alternating sequences of upstream and downstream migrations of 15-30 miles.  Code 39 skirted around and occasionally through a large aggregation of male pallid sturgeon located between rivermile 5.1 – 5.5 of the Yellowstone River while exhibiting her up- and downstream roaming behavior.  A quick recapture of code 39 on June 22 upstream from the male aggregation indicated that she was still carrying her eggs following her most recent passage through the male aggregation. The roaming behavior of code 39 changed on the evening of June 26 as her upstream migration slowed when the male aggregation was encountered at rivermile 5.3 – 5.5.  By morning on June 27, code 39 and numerous males were engaged in spawning activity that persisted through late evening.  DIDSON imaging was deployed during the prolonged spawning event to document spawning activities and fish interactions at the spawning patch (see aggregation and spawning location videos below).  Spawning activities were completed by the morning of June 28 as code 39 was solitary downstream from the spawning patch; her recapture indicated a 20% loss of body weight due to egg deposition.  Habitat crews quantified depth, velocity and substrate conditions in the spawning patch (see previous post “Yellowstone River Habitat Update”).

Videos (click to view in new window):

Image Linking to DIDSON Footage

Video 1: ARIS (Adaptive Resolution Imaging Sonar) imagery showing aggregations of pallid sturgeon and other fishes over coarse substrate deposits in the Yellowstone River, North Dakota.

Image Linking to DIDSON Footage

Video 2: ARIS (Adaptive Resolution Imaging Sonar) imagery showing telemetry-tagged pallid sturgeon over spawning substrate in the Yellowstone River, North Dakota. Spawning locations in the Yellowstone River appear to be characterized by sand dunes interspersed with deposits of sorted, coarse gravels.

Code 39 was the last of the four telemetered females to spawn in 2014.  Spawning by female codes 30 and 35 in the lower Yellowstone River was verified earlier, in mid-June.  Crews from MFWP verified spawning by female code 36 also in mid-June; however, in contrast to the other three telemetered females, spawning by code 36 occurred in the upper Yellowstone River system – most likely in the Powder River.  Codes 30, 35 and 36 were the focus of spawning investigations in 2012, and if the 2-year reproductive periodicity is maintained, these three females will again be the focus of spawning events in 2016.  Fitted with a long-term transmitter, reproductive progression in code 39 will also be assessed through the next several years to determine her reproductive periodicity.  However, unlike female codes 30, 35, and 36, female code 39 will likely be used in the pallid sturgeon propagation program upon reaching spawn-readiness in the next 2-3 years as her genetics have not yet been incorporated into the conservation propagation program.

Posted in Recapture, Reproductive Female, Spawning, Telemetry tracking, Upper Missouri and Yellowstone Rivers | Tagged , , |

July River Sweep

By Kimberly Chojnacki and Aaron DeLonay

The researchers of the Comprehensive Sturgeon Research Project (CSRP) have defined a “river sweep” as an attempt to search for telemetered pallid sturgeon in as much of the Lower Missouri River (from the Gavins Point Dam near Yankton, South Dakota to the confluence near St. Louis, Missouri) as possible. CSRP researchers teamed up with collaborators at the Nebraska Game and Parks Commission (NGPC) during late-July to search approximately 560 river miles of the Lower Missouri River (figure 1). Forty telemetered pallid sturgeon were located during this river sweep effort, including two females (PLS10-029 and PLS12-002), and one male (PLS10-032) that were in reproductive condition during the spring of 2014 (see previous post “A Kettle of Fish”). Researchers will now focus on recapturing telemetered fish that need new telemetry transmitters or a reproductive evaluation (especially those fish there were in reproductive condition during the spring spawning season).

A map showing the location of the CSRP River Sweep in mid-July.

Figure 1. Map showing search effort and pallid sturgeon telemetry locations during the river sweep from July 15-23, 2014.

Posted in Recapture, Reproductive Female, River Sweep | Tagged , , |

Mapping the Chutes

By Robert Jacobson and Casey Hickcox

The R/V Slim Funk in ADCP configuration is shown.

Figure 1. The R/V Slim Funk outfitted with an acoustic Doppler current Profiler (ADCP) and an Odom survey-grade single-beam echosounder maps river velocities and bathymetry for two dimensional modeling.

The presence of pallid sturgeon (Scaphirhynchus albus) on the Federal Endangered Species List generally boils down to their inability to reproduce in the wild. Scientists suspect shallow-water habitat lost when the Missouri River was re-engineered in the mid-19th to mid-20th century to be a contributing factor in this loss of natural recruitment. Understanding the dynamics of the hydrology, hydraulics, and habitats in those shallow environments is critical for informed restoration, but working in the shallow depths can be quite challenging.

Graphic of the model produced from mapping the Lisbon and Jameson Chutes

Figure 2. Digital elevation model used for hydrodynamic modeling of habitats at Lisbon-Jameson area of the Lower Missouri River. The topographic data were developed by combining extensive bathymetric mapping data with LiDAR elevations of the floodplain.

High water throughout June and early July offered research boats extended access to shallow water habitat restoration areas on the Lower Missouri River. Over several weeks, CSRP scientists documented water depths and velocities in the Lisbon and Jameson chutes near Arrow Rock, Missouri (approximately 1.9 and 2.8 miles long, respectively)along with approximately 8.5 miles of the adjacent mainstem channel. By establishing transects perpendicular to the mainstem river at 50 meter intervals and in the chutes at 20 meters, researchers used an acoustic Doppler current profiler (ADCP) to measure water velocities while an Odom survey-grade single-beam echosounder recorded river bathymetry at a resolution that will support two-dimensional hydrodynamic models of the river-chute complex (see Figure 2). These models are intended to be used to gain a better understanding of the environments available to sturgeon larvae and juveniles, including the potential for drifting free embryos to be intercepted and retained in the chutes.

Posted in chute, Habitat mapping, Technology | Tagged , , , |

It’s more than just gravel and sand!

By Aaron Delonay, Robert Jacobson, and Casey Hickcox

Scientists hypothesize that pallid sturgeon (Scaphirhynchus albus), like other sturgeon species, spawn over hard or coarse substrate such as bedrock, cobble or gravel. The type, size, or composition of coarse substrate that adult pallid sturgeon select when spawning  is currently a focus of research for the Comprehensive Sturgeon Research Project (CSRP). To investigate, researchers refine their knowledge of substrate use by following telemetry-tagged adults to identify spawning locations.  Once spawning locations are identified sediment samples and hydraulic data are collected to characterize the selected habitat. Studies of pallid sturgeon spawning in the Yellowstone River provide research teams the opportunity to characterize spawning substrate in what is believed to be the least altered pallid sturgeon habitat within the species’ range.

USGS hydrologists prepare to deploy a BM-54 bed-material sampler on the Yellowstone River.

Figure 1. Scientists lower a bed-material sampler to the bed of the Yellowstone River to sample sediment.

A sidescan sonar image sample shows highlighted areas of suspected gravel substrate.

Figure 2. Side-scan sonar imagery of the bottom of the Yellowstone River collected at a frequency of 400 kHz and a range of 50 meters. Researchers identify areas of exposed gravel (outlined in red) by looking at the shape, texture and brightness of the deposits on the sandy bottom.

During the last week in June, researchers sampled the substrate of a 500 meter x 150 meter section of the Yellowstone River (between river mile 5.4-5.7) where pallid sturgeon had been documented to spawn days earlier.  Researchers used a heavy torpedo-shaped, bed-material sampler (see Figure 1) and then a 15-cm pipe dredge to systematically sample the river bottom.  Sampling of bed material was supplemented with bathymetric and velocity mapping, and sonar imagery using side-scan sonar (see Figure 2) and DIDSON.   Two other sites (near river mile 5.3 and river mile 6.3-6.5) were also sampled where spawning was documented in 2013. Scientists hope that quantification of spawning conditions in the least-altered reaches of the Yellowstone River will provide a model of functional spawning habitat that can be translated to other, more altered areas of the species’ range.  Researchers from the CSRP working in the Lower Missouri have also documented spawning habitat, but the river there is highly altered.  Scientists in the Lower Missouri River are concerned that the habitats selected by pallid sturgeon there represent only the best available in a highly engineered river, and may not be necessarily suitable for successful reproduction.  Over 130 sediment samples collected from the Yellowstone River will be analyzed using special graduated sieves to document grain-size distributions.  The samples collected will be compared with substrates known to be available in the mainstem Missouri River.

Posted in Habitat mapping, Spawning | Tagged , , , |

Unpredictable Water in the Missouri River

By Aaron Delonay, Robert Jacobson, and Casey Hickcox

As the temperatures in the Missouri River Basin begin to rise each spring, snowmelt and spring storms typically introduce large quantities of water into the system. This water becomes runoff that enters numerous tributaries that collectively join the main channel of the Missouri River to create a pulse of discharge often referred to as the annual “spring rise”. In most years the mainstem reservoir system stores much of the spring rise, but annual spring rises of 100,000 cubic feet per second (cfs) or more can exist on the Lower Missouri River during extreme runoff years and especially downstream of the Platte and Kansas rivers.

Pallid sturgeon, like many fish species, spawn over a range of temperatures in the spring when seasonal rises in rivers occur. Based upon observations of our telemetry tagged sturgeon, most spawning in the Lower Missouri River occurs between 16-22 °C (61-72 °F). For pallid sturgeon, water temperatures appear to be the primary influence on when and for how long spawning activity occurs during the spring. Seasonal flow changes and river discharge may also influence pre-spawning behaviors, particularly spring migration, and may play a role in determining the precise timing of adult aggregations and spawning events.

During much of this year’s reproductive window (the time when sturgeon are expected to spawn), the Lower Missouri River near Boonville, Missouri, maintained a relatively low flow with only one small pulse that added about 30,000 cfs (figure 1). In areas upriver near Sioux City, Iowa, flow was low and even less variable through the reproductive window (figure 1). Only after the expected peak of pallid sturgeon spawning activity had passed did the Missouri River near Booneville see substantial increases in flow as the river rose 13 feet and discharge increased by over 100,000 cfs in less than 4 days. At Sioux City, meanwhile, cooler water temperatures extended the expected spawning period for pallid sturgeon to early June. A spring rise peaking at over 80,000 cfs occurred in late June due to heavy rainfall in the Big Sioux River, however this pulse was probably too late to influence sturgeon migration and spawning.

Figure showing the discharges vs Temperatures for two Missouri River sites: Boonville, MO & Sioux City, IA

Figure 1. The Missouri River discharge (blue) for Boonville, Missouri (top) and Sioux City, Iowa (bottom) since January 1st shown against the interquartile range for the measured discharge over the past century. The temperature (red) is shown over the same time period with the range over which most pallid sturgeon spawn are expected to spawn (pale hatching shown from 16-22 degrees C) identified.

Pallid sturgeon have evolved in a river with naturally variable flow and temperature, but management of the Missouri River also creates conditions that are outside of the range of natural variability. CSRP research addresses the question of how well sturgeon can adjust to unnatural variability and still maintain a sustainable population. Long-term studies that include the kind of variability experienced with the extreme flows of 2011, the drought of 2012, and the lack of an early spring rise in 2014, help to answer this question.

Posted in Drought, Flooding, Spawning | Tagged , , , |