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 , , , |

Yellowstone River Habitat Update

By Carrie Elliott

In the Northern Great Plains mid-late June is marked by spectacular thunderstorms, an occasional mosquito swarm, and pallid sturgeon spawning season on the Yellowstone River.  The week of June 16 the U.S. Geological Survey CSRP habitat crew mapped a 4 kilometer long reach of the Yellowstone River where pallid sturgeon spawning has been documented in multiple years (figures 1 and 2).  Mapping was done with an acoustic Doppler current profiler and RTK GPS to generate maps of velocity, depth, and bed elevation in transects with a 15 meter spacing.  These data along with side-scan sonar and sediment sampling information will allow us to monitor, model, and understand what pallid sturgeon spawning habitat is  under near-natural conditions.   This reach, a just a few miles downstream from the historic Fairview Bridge has had many male and female pallid sturgeon present over the past few weeks this year and contains the locations where spawning was documented in 2012 and 2013. 

Figure 1. USGS Hydrologic technican Eric Allen monitoring ADCP and RTK GPS survey data quality as it comes in on the Yellowstone River near Fariview, MT.

Posted in Habitat mapping, Upper Missouri and Yellowstone Rivers | Tagged |

Northbound

By Kimberly Chojnacki and Aaron DeLonay

In mid-June, 4 USGS research crews from the Lower Missouri River packed up their equipment and headed north to the Upper Missouri and Yellowstone Rivers in Montana (figure 1).  Two boats and crews were deployed to help track the migration behavior of large, fast moving, adult pallid sturgeon up the Yellowstone River, and to determine when and where they are spawning (figure 2).  Another boat and crew carried advanced sonar equipment to observe and record spawning behavior.  And a hydrology research crew was deployed to characterize habitat at spawning sites.  The crews drove two days from Columbia, Missouri to Sidney, Montana where they joined biologists from Montana Fish, Wildlife and Parks (MFWP) and researcher, Pat Braaten, from the USGS Project Office in Fort Peck, Montana. Pat and his colleagues from MFWP have been tracking adult pallid sturgeon on the upper Missouri River from Lake Sakakawea upstream to Fort Peck Dam, and up the Yellowstone River to Intake Dam (figure 1).

Figure 1. Map of the Upper Missouri River and Yellowstone River study area.

The large rivers used by pallid sturgeon have been modified and altered to meet human needs, including flood control, irrigation, navigation, hydropower, and recreation.  The Upper Missouri and Yellowstone rivers are unique within the range of the pallid sturgeon in that the morphology of their channels has not been significantly altered and the Yellowstone still retains a natural hydrograph and temperature regime unaltered by large dams.  Scientists hope that by observing and comparing the behavior of pallid sturgeon in different parts of its range, they can gain insight into how sturgeon migration, spawning, and recruitment may be altered in response to different threats. 

Figure 2. A USGS Comprehensive Sturgeon Research Project telemetry crew tracks radio telemetered pallid sturgeon in Montana.

Posted in Upper Missouri and Yellowstone Rivers | Tagged , |

A Change Will Do You Good

By Aaron DeLonay, Amy George, and Kimberly Chojnacki

Rows of hatching jars lined the shelves in the laboratory at USGS this spring and summer.  In each jar, pallid sturgeon and shovelnose sturgeon gently tumbled in the 18 °C water as USGS scientists closely monitored and documented fish development.  The eggs came from a captive population of pallid sturgeon adults held at the Center for research purposes and from shovelnose sturgeon adults captured from the Lower Missouri River.  Four pallid sturgeon and ten shovelnose sturgeon females were induced to spawn using hormone injections in the laboratory.  The eggs were fertilized by multiple males of the corresponding species and each family lot was placed in separate jars to develop and hatch.  Scientists monitored each group of eggs for fertilization, development, and survival to hatch.  After hatch, three to six sturgeon were removed and preserved in formalin at 2-4 hour intervals around the clock to document the rapid growth and developmental changes that occur during this early life stage.  Free embryos hatch without a well-developed mouth, eyes or fins, and must rely a large yolk sac to fuel their rapid development (figure 1).  At 18° C, the development from newly hatched free embryo to exogenously feeding larvae takes about 14 days for both species.  Although their abilities are limited, sturgeon are capable of changing their depth and orienting to water flow even before the initiation of feeding.  Once the larvae began feeding, behavioral and developmental changes are not as rapid and samples were taken every 12 hours.  At this stage, they have fins, eyes, a mouth bordered by four fleshy barbels, and resemble sturgeon in miniature.  Scientists at USGS closely examined the timing and trajectory of developmental changes to better estimate where  sturgeon free embryos collected by our crews in the Missouri River may have been spawned, how early life stages of sturgeon disperse along the river, and where habitats needed for early feeding may be located.  Differences in developmental timing, behavior, and requirements between species may provide insight into why one species, the shovelnose sturgeon, is reproducing and recruiting, while the pallid sturgeon is not.

Figure 1. Pallid sturgeon free embryos preserved 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.

Posted in Early life history |