Research Update: Confirmed Pallid Sturgeon Spawning in the in 2007

The U.S. Geological Survey (USGS) stakeholders, scientists, and managers how sturgeon reproduction is affected in partnership with the Game with some of the preliminary results from by river flow and habitat availability. and Parks Commission (NGPC) and the 2007 field assessment of sturgeon The research is set up as a series of the U.S. Army Corps of Engineers have reproduction in the lower Missouri River. field experiments in which sturgeon confirmed spawning of two female pal- are tagged with combined acoustic lid sturgeon in the upstream reaches of Background on Sturgeon Research and radio transmitters (CART) that allow scientists to follow their move- the lower Missouri River in May 2007. The USGS and NGPC are involved Combined with supporting research in ments along the river. Physiological in a multi-year, collaborative research measurements were used to determine reproductive physiology, identification study to determine factors leading to the spawning potential of each . of spawning habitat, and early life history spawning and survival of the endangered Habitats used by the fish are to be this result provides new understanding pallid sturgeon and the closely related related to available habitats to predict of environmental factors (for example, . During spring 2007 areas selected for spawning. photoperiod, temperature, water quality, researchers tracked the movements of 195 and flow regime) that might affect repro- sturgeon between Omaha, Nebraska, and duction of this . The , (fig. 1). 2007 Field Experiment purpose of this fact sheet is to provide The purpose of the study is to determine The 2007 sturgeon field assess-

98° 97° 96° ment was intended to document

Study area sturgeon reproductive behavior and S o u t h habitat availability under conditions S o u t h V e of no flow modification from Gavins rm D a k o tt a i ll i Point Dam. Results from this assess- o Jam n ment will be compared to those of es r R e i v ve i the limited pulse-flow modification r R River I o w a 43° x I o w a Yankton u (“spring rise”) of 2006. Results from )" o # 800 i .!850 Û .! S subsequent years with and without ig Floyd River B flow modification will be needed for Gavins ^_ er iv ^_750 Sioux City R validation. Point State np.! x # )" u Park # io Discharges from Gavins Point Dam Dam S e l t were maintained at low levels during t i L March to mid-May 2007 because of .! 700 River continuing drought in the upper basin, N e b rr a s k a !( 42° # spring flooding downstream in !( Soldier and Missouri, and lack of navigation EXPLANATION traffic to Sioux City, Iowa. Cycling Pallid Sturgeon 541 ^_ Boyer River flows were initiated by the U.S. ^_ Initial capture !(. 650 Apex Platte Army Corps of Engineers on May 18, ^_ River ^_ Recapture 2007, to control elevations at which interior least terns and piping plovers Pallid Sturgeon 561 )"# Omaha nest on sandbars in the unchannel- !( Initial capture .! 600 !( Apex ized segment of the river. Flows were 41° !( Recapture stabilized at 18,000 cubic feet per # U.S. Geological Survey streamflow-gaging station second on June 3, 2007. Although !. River mile releases from Gavins Point Dam were River Segments 550.! relatively low from March through Gavins Point to Ponca 0 10 20 40 KILOMETERS Ponca to Sioux City mid-May, runoff from the James, Ver- Channelized downstream from Sioux City 0 10 20 MILES ² million, and Big Sioux River Basins provided a series of unplanned flow Figure 1. Study area for 2007 field assessment of sturgeon reproduction, Lower Missouri River.

U.S. Department of the Interior USGS Fact Sheet 2007–3053 U.S. Geological Survey Printed on recycled paper July 2007 pulses that are reflected in the USGS Preliminary Results from 2007 temperature (fig. 3). The reproductive Sioux City streamflow-gaging station condition of each fish was determined In March and April 2007, 8 pallid and record (fig. 2). through ultrasonic and endoscopic 176 shovelnose sturgeon were surgically The variable hydrology was dis- examination and by visual examina- implanted with CART series transmitters tion of the gonads during implantation. tributed among three geomorphically that permitted researchers to track their Of the pallid sturgeon implanted, two distinct river segments (fig. 1). From movements in the river. The fish also females and three males were in repro- Gavins Point Dam (river mile 811) to were implanted with archival data stor- ductive condition and expected to Ponca State Park (river mile 753.5), age tags (DST’s) that record depth and the river is characterized by complex during 2007. Another 11 pallid sturgeon that had been implanted previously with transmitters in 2006 also were tracked 40,000 2007 2006 Gavins Point Dam Gavins Point Dam within and below this river reach. The Sioux City reproductive readiness to spawn was 30,000 assessed for each female pallid and shovelnose sturgeon at the time of 20,000 implantation using the polarization index measurement, which is an indica- DISCHARGE, tion of how soon a female will spawn; 10,000 the egg polarization index decreases IN CUBIC FEET PER SECOND 2006 Flow Modification as the time of spawning draws near. A 0 polarization index value of 0.07 or less 25 indicates that spawning is imminent. Additional shovelnose sturgeon were 20 Sioux City captured weekly throughout the spring to monitor when the sturgeon population 15 within these river segments would be physiologically capable of spawning. 10 Intensive tracking efforts were initi-

IN DEGREES CELSIUS 5 ated in April on the two female pallid WATER TEMPERATURE, WATER sturgeon in reproductive condition. In 0 early May, based on water temperature 2/24 3/16 4/5 4/25 5/15 6/4 and behavioral movements, 24 hour con- 2007 tinuous tracking efforts were initiated. Two boats operated by NGPC conducted Figure 2. Hydrograph and water temperature showing variation of Missouri River environmental conditions during March through May 2007. reaches with dynamic sandbars, multiple channels, and islands. From Ponca State Park to Sioux City, Iowa (river mile 734), the river channel is transitional to the engineered, navigation channel. This reach has been narrowed and stabilized with bank revetment and some wing dikes, but maintains some mid-chan- nel sandbars and channel complexity. Downstream from Sioux City, the river has been channelized for navigation and is mostly a single-thread channel with rare mid-channel sand bars. Variable hydrology and morphology of the mainstem Missouri River and tributaries resulted in a range of poten- tial interactions between environmental cues and habitat availability for sturgeon Figure 3. Pallid sturgeon PLS07-004 during spring 2007. Although it will be (acoustic tag 541) after recapture (above) challenging to isolate which factors had and data storage tag and combined the greatest affect on sturgeon spawning, acoustic radio transmitter (right). Photo- the large number of tagged fish in this graphs by Aaron DeLonay, U.S. Geologi- field assessment will provide an exten- cal Survey. sive dataset for analysis. spawning occurred under optimal condi-

760 tions, or whether or not enough hatched or young survived to add to the pallid sturgeon population. Although Relocation events spawning occurred in 2007 without flow 740 Recapture location modification from Gavins Point Dam, fish may have responded to natural spring pulses from tributaries. Data from 720 pallid sturgeon will be compared with observations on shovelnose sturgeon to assess spawning and characterize repro- RIVER MILE 700 ductive strategies of the two species.

Additional Research 680 Accomplishments In addition to the results summarized 660 above, the 2007 research efforts have yielded additional accomplishments: 03/26 04/09 04/23 05/07 05/21 06/04 06/18 • Observations of movement and 2007 habitat use by pallid sturgeon Figure 4. Relocation events for female pallid sturgeon PLS07-004 (acoustic tag 541, fig. 3). and shovelnose sturgeon indicate that spawning occurs during an the intensive tracking efforts. The USGS The first female, captured on March 26, extended time at multiple loca- conducted extensive river tracking 2007, at river mile 659.7 with an egg tions within the study segments. efforts for all tagged sturgeon and served polarization index of 0.17, moved 109.1 Female reproductive movement as reserve vessels for the intensive pallid river miles upstream before spawning seems to be characterized in both sturgeon tracking efforts. Field crews upstream from Ponca State Park within species by a significant and rapid from the NGPC and USGS relocated the Missouri National Recreational upstream movement, followed by each reproductive female pallid stur- River segment, probably in mid-May. sporadic downstream movement. geon more than 100 times in a 2-month It was recaptured after moving down- Movement patterns of reproduc- interval before attempting to recapture stream to river mile 756.5 on May 23, tive male sturgeon appear to be them to determine if they had spawned 2007 (fig. 4). The second female was more complex. Data indicate that (fig. 4). captured on March 29, 2007, at river some reproductive male pallid and Both female pallid sturgeon showed mile 650.3 with an egg polarization shovelnose sturgeon show more intervals of rapid upstream movement, index of 0.12, and moved nearly 50 diverse movement patterns during followed by intervals of slower down- miles upstream from the implantation the spawning. stream movement with extended pauses. location before spawning in the chan- • Telemetry data document that This characteristic movement pattern nelized reach downstream from Sioux reproductive and non-reproduc- was noted by the USGS in an earlier City, Iowa (river mile 734), probably in tive shovelnose sturgeon used the phase of this study in 2005 and 2006. late April to early May. This fish was mainstem and some tributaries to The earlier study focused on spawning recaptured on May 25, 2007, at river the Missouri River before, during, individuals of the closely related shov- mile 676.7 after moving downstream. and after spawning. In contrast, elnose sturgeon. We infer that spawning Both fish were in good overall physical pallid sturgeon used only mainstem generally occurs at the upstream apex of condition upon recovery. Missouri River habitat or areas these movements. The USGS and NGPC This is the first direct evidence that near tributary confluences. None of recovered the two telemetry-tagged pal- pallid sturgeon spawn in the Missouri the 5 tagged pallid sturgeon have lid sturgeon females from the Missouri National Recreational River segment been observed in Missouri River River. USGS researchers re-examined and in the channelized river upstream tributaries. each female with ultrasound and an from the Platte River. The DST data, in endoscope in the field to determine if combination with telemetry relocations, • Hydrologists mapped 10 high- spawning occurred. After a positive are the first complete records of pallid probability spawning reaches as indication from the non-invasive meth- sturgeon that migrated and spawned. determined from fish tracking data. ods, a small surgical incision was made Analysis of depth data recorded by DST Maps include depth, velocity, and to visually examine the gonads and to tags also indicates a characteristic pat- substrate distributions that will retrieve the DST tags from the abdomi- tern of behavior that may be associated be analyzed to delineate physical nal cavity. with spawning. Whereas researchers factors that contribute to sturgeon Both female pallid sturgeon were successfully documented spawning, this reproduction. determined to have spawned completely. study does not reveal whether or not • Water-quality monitors at multiple For more information contact: USGS streamflow-gaging stations along the river recorded changes in Michael Mac, Director Gerald Mestl temperature, pH, turbidity, and dis- U.S. Geological Survey Nebraska Game and Parks Commission solved oxygen as they varied with Columbia Environmental Research Center 2200 North 33rd Street discharge. These water-quality 4200 New Haven Road Lincoln, Nebraska 68503 changes will be analyzed to assess Columbia, Missouri 65201 Phone: 402-471-1512 their roles as cues in spawning Phone: 573-876-1900 Email: [email protected] behavior. Email: [email protected] • Research biologists with the USGS and the South Dakota Game, Fish, and Parks have been sampling the Missouri River area below Gavins Point Dam for eggs and larval sturgeon using fine meshed nets. Once these samples are analyzed, additional verification may be obtained that sturgeon spawned and eggs hatched in that area.

Channelized segment of the Missouri River (river mile 707.5) downstream from Sioux City, Iowa, in late May to early June, 2007 (photograph by Joanna Reuter, U.S. Geological Survey).