Spawning of Pallid Sturgeon for Crucial Experiments

By Kimberly Chojnacki, Aaron DeLonay, and Robert Jacobson

Researchers at the USGS Columbia Environmental Research Center (CERC) have been making preparations to spawn pallid sturgeon to provide eggs and larvae for experiments.  During March and April, the captive population of adult, hatchery-origin pallid sturgeon maintained at CERC were weighed and examined for reproductive readiness (figure 1).  Non-invasive ultrasound technology was used to determine if the pallid sturgeon would be ready to produce viable eggs and sperm in the coming weeks (see previous entry, Did she or didn’t she?).  Fish determined to be approaching reproductive condition were moved to indoor holding tanks so that water temperature could be tightly controlled and their condition could be closely monitored.  The reproductive readiness of female sturgeon was tracked using biopsies and microscopic examination of extracted eggs as the potential spawning day drew near.

Biologists at Columbia Environmental Research Center drawdown and seine a pond to collect reproductive pallid sturgeon. The pond has been specially designed to provide turbid, flowing water that pallid sturgeon need to thrive.  Photo by Aaron DeLonay.

As the female readiness to spawn became imminent, four male sturgeon were given a hormone injection to induce the production of sperm.  Within 48 hours biologists were able to collect milt containing viable sperm from the males.  The milt was refrigerated and stored with an extender until the females were ready.  Finally, at 3:00 am on Tuesday, May 5th, researchers administered the first of two hormone injections to four female pallid sturgeon.  The second, resolving dose was administered 12 hours later.  Ovulation occurred 14-18 hours after the resolving dose on the morning of Wednesday, May 6th.  Biologists began the process of extracting the ovulated eggs from the females at 7:00 am.

Eggs were fertilized in the laboratory with milt (sperm) from 4 males.  Extracted eggs were used in experiments to measure egg density and adhesiveness (figure 2).  Fertilized eggs were incubated in flowing water for approximately 4 days.  Hatched free embryos were used in outdoor stream experiments to evaluate initial dispersal behaviors (see previous entry, Studies of Lake Sturgeon Free Embryo Dispersal Begin).


Pallid sturgeon eggs become adhesive minutes after fertilization. Scientists are working to understand the factors that influence the adhesiveness of sturgeon eggs. (Photo by Aaron DeLonay, U.S. Geological Survey)

Improved understanding of the reproductive ecology of pallid sturgeon requires integration of controlled experiments with knowledge gained from studies of fish in the river.  The ability to carry out experiments on pallid sturgeon depends on having a captive population of adult fish available, the knowledge on how to spawn them and raise their young, and the facilities to study these fish in conditions that approximate the river conditions.

Posted in Uncategorized |

New shallow water surveying technology deployment at CERC

By Carrie Elliott, Robb Jacobson, Eric Allen, and Casey Hickcox

A USGS scientist uses a remotely controlled "z-boat" to survey the experimental ponds at the Columbia Environmental Research Center.

A USGS scientist uses a remotely controlled “z-boat” to survey the experimental ponds at the Columbia Environmental Research Center.

This spring, experiments to observe shovelnose sturgeon spawning behavior have been ongoing in ponds at the Columbia Environmental Research Center. To characterize the depths and velocities in the experimental ponds, we have deployed a new instrument for the first time. The “z-boat” is 1.80 m long, 0.90 m wide, remotely controlled vessel that houses a survey-grade single-beam echosounder, a precise real-time kinematic global positioning system antenna, and an acoustic Doppler current profiler.  It is controlled by an operator on shore and all the data are transmitted to laptop computers on shore that allow the data and boat navigation information to be viewed in real-time. We are using the z-boat to quantify the conditions in the ponds during the spawning behavior experiments and characterize water flow patterns created by circulators in the ponds over sand and gravel substrates (see figure 1). The z-boat will also be used to survey shallow water habitats on the Missouri River, Yellowstone River, and tributary environments that we cannot access with our larger hydroacoustic survey vessels.

Mapped water depth (left) and velocity (right) data of Pond 15 collected using the z-boat.

Figure 1. Mapped water depth (left) and velocity (right) data of Pond 15 collected using the z-boat.

Posted in Habitat mapping, Technology | Tagged , , |

Studies of Lake Sturgeon Free Embryo Dispersal Begin

By Aaron DeLonay and Kimberly Chojnacki

How much river does a fish need?  For pallid sturgeon on the Missouri River there is a concern that there is not enough river for downstream-dispersing larvae.  Field-based and laboratory work at the Columbia Environmental Research Center are focusing on critical unknowns in the dispersal process, using comparative studies with other sturgeon species to provide key insights.  Our first experiment this year is with lake sturgeon.

Figure 1. One of six experimental stream segments used to study the dispersal of free embryo sturgeon at the Columbia Environmental Research Center. The stream segment is 5 meters long and 0.5 meters wide, and is filled with cobble-sized rock to a depth of 12 centimeters. Streams are covered during studies.

Eggs collected from the lake sturgeon female spawned in the laboratory on April 15th (see previous entry, “Stream studies back in action”) hatched in the early morning hours on Monday, April 20th.  A team of researchers counted out a total of 4800 newly hatched (day-0) lake sturgeon free embryos; 800 free embryos for each of the six experimental stream segments (three with gravel, and three with cobble substrate, see figure 1).  The stream segments were then “seeded” by releasing the free embryos into the substrates of the experimental streams and slowly increasing the water flow over the substrate to 15 centimeters per second.  The streams were monitored around-the-clock to see if free embryos stayed in the stream substrate or dispersed downstream.  Nets at the end of each segment were checked at six-hour intervals for free embryos that dispersed.  Free embryos collected in the nets were counted and preserved for later laboratory measurements of size and development.  On Friday, April 24th, after a 96-hour (4-day) monitoring period the substrate of each segment was removed and any free embryos remaining were collected in the nets downstream.  On Tuesday, April 28th, the experiment was repeated with 8-day old lake sturgeon free embryos (figure 2). Researchers will monitor the streams and record free embryo dispersal over the next 4 days.  The same studies will be repeated with pallid sturgeon and shovelnose sturgeon through May and into June. 

Figure 2. Researchers count out 800 eight-day old, free embryo lake sturgeon for studies of downstream dispersal in experimental streams.  (Photo by Aaron DeLonay)

The development and dispersal strategy of each sturgeon species is adapted to the conditions where it lives.  Comparing the dispersal strategies of newly hatched and 8-day old free embryos of the three sturgeon species (lake sturgeon, pallid sturgeon, and shovelnose sturgeon) in experimental stream systems provides researchers with an estimate of the time each species spends dispersing downstream.  Importantly, the experiments are designed to indicate the extent to which the species delay dispersal by residing for some period of time in the substrate just after hatch.  When and how long free embryos disperse, in part, determines the length of free-flowing river required for the completion of the free embryo life stage and where habitats that support the transition to the exogenously feeding larval stages should be located.


Posted in Early life history, Stream studies | Tagged , , , , |

What a Difference a Day Makes

By: Kimberly Chojnacki and Aaron DeLonay

Scientists at the USGS, Columbia Environmental Research Center have initiated research that closely examines the differences in early life stages of three sturgeon species; lake sturgeon, pallid sturgeon, and shovelnose sturgeon.  On Wednesday, April 15th the first of the three species was induced to spawn in the laboratory.  Milt from three male lake sturgeon was used to fertilize eggs from one female lake sturgeon (see previous entry, “Stream studies back in action”).  The embryos from that spawning event began to hatch during the early morning on Monday, April 20th.  Sturgeon embryos hatch without well-developed eyes, mouth, or fins and rely on a large yolk sac to fuel rapid early development (figure 1).  Researchers began collecting newly hatched free embryos soon after hatch to examine the rapid growth and developmental changes that occur during this early life stage.  Each day, 20 free embryos are photographed, measured, and examined for changes in developmental characteristics.

Figure1. Newly hatched lake sturgeon free embryos. Sturgeon embryos hatch without well-developed eyes, mouth, or fins and rely on a large yolk sac to fuel rapid early development. (Photo by: Kimberly Chojnacki)

Some of the similarities and differences between lake sturgeon and pallid sturgeon (spawned in the laboratory during 2014, see previous entry, “A Change Will Do You Good”) are apparent, even at this early stage.  By the time the sturgeon free embryos are three days-old, the eyes are pigmented and they are developing fins and mouth parts, including barbels (figure 2).  Lake sturgeon free embryos are already much darker in color than pallid sturgeon, with a dark stripe beginning at the rostrum (or snout).  Pallid sturgeon are pale in comparison, with a dark tail.

Figure 2. Lake sturgeon free embryos at 3 days post hatch. Free embryos at this stage have only a rudimentary mouth, their pectoral fins are only beginning to develop, and they rely on a large yolk sac for food. (Photo by: Kimberly Chojnacki)

All sturgeon are not the same.  Each species is uniquely adapted to survive in the environment in which it lives.  Characterizing and comparing the growth, development, and behavior during the earliest life stages of these fascinating species helps researchers to understand what each needs to thrive.  Comparisons among species may help to explain why one species may be doing well, while another is declining or rare.  The work to understand sturgeon early life stages will continue with pallid sturgeon and shovelnose sturgeon through the spring and summer of 2015.

Posted in Early life history, Uncategorized | Tagged , , , , , |

Stream studies back in action

By Aaron DeLonay, Robert Jacobson, Kim Chojnacki, and Casey Hickcox

USGS Biologist prepares to artificially spawn a female lake sturgeon in the laboratory at the Columbia Environmental Research Center.

Final preparations are underway to initiate lake sturgeon laboratory and artificial stream studies at the Columbia Environmental Research Center (CERC).  One 46.5 lb. female and three males have been selected for the study.  The female and males were induced for artificial spawning by the injection of hormone. Milt from the males was collected throughout the second week of April and has been cryo-preserved for future studies. Eggs were collected from the female early on the morning of Wednesday, April 15.  Following egg collection, CERC scientists conducted a specific gravity study using a small number of eggs to improve understanding of the fate of eggs on spawning grounds. The fertilized eggs are being incubated in a recently completed laboratory incubation system located at CERC.  Embryos will be used to seed an artificial stream, and released into two substrates within the stream: one substrate composed of gravel and one composed of cobble.  The objective of the stream studies is to compare behavior of lake sturgeon free embryos, which are known to hide in interstices, with pallid and shovelnose sturgeon.  The artificial streams will be monitored for 96 hours (4-days).  The stream will then be cleared and re-seeded with day-8 embryos, followed by a 96-hour monitoring period. These studies will be repeated later in the spring with pallid sturgeon and shovelnose sturgeon.

Posted in Early life history, Spawning, Sturgeon culture and propagation | Tagged , |

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 , , |