We’ve Only Just Begun

After a long, cold winter, the Redbud and Dogwood trees are blooming and water temperatures are rising (Figure 1).  Spring seems to have finally sprung, and fish, and hopefully the endangered pallid sturgeon among them, will soon be spawning.  In an effort to better understand pallid sturgeon spawning, fertilization, hatch, and dispersal, Comprehensive Sturgeon Research Project (CSRP) biologists initiated weekly sampling efforts for Acipenseriformes (sturgeon and paddlefish) free embryos on April 15.  The work is occurring at two sites in Nebraska; one upstream of the confluence of the Missouri and Platte rivers (near river mile 600) and the other is located less than one mile up the Platte River.

Figure 1. Temperature and discharge of the Missouri River at U.S. Geological Survey streamgage 06601200 Decatur, Nebraska.

 In order to sample the swift waters for Acipenseriformes free embryos, CSRP researchers deploy a pair of very fine, cone shaped ichthyoplankton sampling nets attached to 100 pound lead weights into the water column using winches mounted to each side of an anchored boat.  The nets filter water through a 0.5 meter opening and the drifting embryos are captured by the nets.  The nets must be made with a very fine mesh (0.75 mm) to prevent the small tadpole-like larvae (7-8 mm) from slipping through.  

The sampling nets are simultaneously brought back up (Figure 2) to the surface after a set period of time (5 to 15 minutes, depending on the debris load suspended in the water column).  The contents of the sapling nets are emptied into pans, where Acipenseriformes free embyros are hand-picked from the debris.  Recently hatched sturgeon and paddlefish free embryos are too small and similar to differentiate, so they are preserved in alcohol and returned to the laboratory where they will be identified to genus using a microscope.  Sturgeon specimens will be sent to a genetics laboratory to determine if they are shovelnose sturgeon, or if we are very lucky, the endangered pallid sturgeon.  We haven’t caught any Acipenseriformes free embryos to date (April 30), but spawning season is just beginning.

Figure 2. Biologists sample the water column of the Missouri and Platte Rivers to collect sturgeon or paddlefish free embryos).

With contributions by Aaron DeLonay

Posted in Early life history | Tagged |

A Kettle of Fish

In the late fall or at the end of winter of previous seasons, Comprehensive Sturgeon Research Project (CSRP) biologists would send boats out into the field to seek out a few, rare pallid sturgeon females to implant with transmitters in hopes of tracking them to their spawning locations.  This has been our dominant approach to characterizing where and when spawning is occurring.  Beginning in 2014 the project focus has shifted slightly towards longer-term science objectives.  In addition to tracking reproductive females, biologists are also emphasizing recapturing and retagging as many telemetered pallid sturgeon as possible to reimplant them with tags and fresh batteries in hopes of maintaining a population of tagged pallid sturgeon that can be monitored through several reproductive cycles.  Biologists also hope to increase the number of tagged males in the study population to help identify possible aggregation areas and to answer the long-standing question of which sex ultimately chooses where spawning occurs. 

Since recapture efforts began in the fall of 2013, CSRP crews have recaptured more than 15 telemetered pallid sturgeon and identified three females (PLS11-019, PLS10-029, and PLS12-002) and one male (PLS10-032) pallid sturgeon nearing spawning condition.  Each of these fish has a long history with the CSRP and researchers will be particularly interested in their movements and behavior.  At the end of April, more than two dozen additional pallid sturgeon collected during the annual pallid sturgeon broodstock collection efforts will be implanted with transmitters and added to the study population.   During 2014, telemetry studies of habitat use and spawning will be augmented by laboratory studies of spawning, egg hatch, and free embryo dispersal to examine further the factors that may be limiting survival and recruitment of young sturgeon in the river.   

With contribution from Aaron DeLonay

CSRP Biologist Sabrina Davenport prepares to release a reproductive feamle pallid sturgeon.

Posted in Telemetry tracking | Tagged |

Should I Stay or Should I Go Now

During the past few months, Comprehensive Sturgeon Research Project (CSRP) biologists in Columbia have been planning and preparing for a controlled experiment to develop a better understanding of the behavior of pallid sturgeon embryos at the critical moment they emerge from the egg.  Pallid sturgeon eggs are adhesive and spend the first few days as developing embryos in the substrate near where they are spawned.  Once the embryos hatch they can either burrow into the substrate to continue their development in place, or swim up into the water column and be immediately swept away with the current.  The ability of pallid sturgeon free embryos to remain in or utilize available substrate to continue their development after hatching, even for a short period, would reduce the downstream dispersal distance that pallid sturgeon free embryos need before they transform into feeding larvae and settle to the bottom to begin feeding.  Researchers will use experimental streams with sand, gravel or cobble bottoms to help to determine the influence of these substrates on hatch and initiation of dispersal of pallid sturgeon free-embryos (see previous post “A Rocky Start”). 

In order to obtain pallid sturgeon embryos, which will be seeded into the controlled stream experiments, CSRP biologists conducted an inventory of the captive population held at the research center in search of reproductive individuals.  Each pallid sturgeon was weighed, measured, and a reproductive evaluation was performed using non-invasive ultrasound techniques to determine if the fish would be ready to spawn this spring (see previous posts, “Catch Me If You Can,” and “Did She or Didn’t She” for descriptions of ultrasound).  If a female was found to have late-stage, maturing oocytes (eggs), a biopsy was performed to remove a few of the eggs to determine how close she was to spawning.  Males also were examined with ultrasound for changes in density of testes and the development lobes that signify that they too will be ready to spawn in spring.   Individuals expected to be reproductive this spring were moved to a separate research pond where they will be monitored as temperatures rise and spawning season approaches. 


CSRP biologists conducted an inventory of the captive pallid sturgeon population held at the Columbia Environmental Research Center. Each pallid sturgeon was weighed, measured, and a reproductive evaluation was performed using non-invasive ultrasound techniques to determine if the fish would be ready to spawn this spring.

CSRP biologists have been planning and preparing for a controlled experiment to develop a better understanding of the behavior of pallid sturgeon embryos at the critical moment they emerge from the egg. Researchers will use experimental streams with sand, gravel or cobble bottoms to help to determine the influence of these substrates on hatch and initiation of dispersal of pallid sturgeon free-embryos (cobble substrate pictured above). The embryos will be obtained from the captive pallid sturgeon population at the Columbia Environmental Research Center.

As spring progresses, the fish will be moved to holding tanks inside the lab where their eggs and milt will be collected and combined under controlled conditions.  The fertilized eggs will be placed into the experimental streams where they will develop and hatch. Hatched embryos will be monitored to determine if different sized substrates influence the tendency of free embryos to stay in the substrate or initiate downstream dispersal in the current.  Although full expression of environmental conditions in the Missouri River cannot be replicated in our experiments, we can add useful understanding about early innate behaviors of pallid sturgeon that may influence management strategies for recovery. 


Completed with contributions from Sabrina Davenport and Aaron DeLonay

Posted in Sturgeon culture and propagation |

The Deer Island Restoration Project, Iowa

Story by Robert Jacobson

I finally had a chance to visit the Deer Island restoration site the week of April 1 (fig. 1).  Deer Island is a 2.5-mile long reach of the Missouri River near Little Sioux, Iowa where the US Army Corps of Engineers has nearly doubled the channel width while increasing habitat diversity.  Unlike all other shallow-water habitat (SWH) projects on the Lower Missouri River, the Deer Island project was designed to build habitat completely to the final condition.  Other projects have relied on a pilot channel or an initial widening effort that is expected to grow over time as the river takes advantage of the opportunity to erode and deposit sediment, adding habitat diversity by creating shallow, slow water.  The pilot approach minimizes construction costs – because the river does the work – but adds uncertainty about what the final state of the channel will look like and, critically, when it will be achieved.  The uncertainty about whether SWH restoration sites are still evolving means that evaluations of the SWH program have been aiming at a moving target. 

Figure 1. One of multiple rock and log structures at Deer Island restoration site. Photo is looking from east to west, across restoration area toward navigation channel.

The Deer Island site is fundamental to quantifying restoration on the Missouri River because it does not use a pilot approach and because it is located perfectly for a before/after comparison (fig. 2). An earlier USGS study on effects of the “spring rise” on pallid sturgeon habitat selected the exact same reach in 2006 because it was representative of the channelized Lower Missouri River between Sioux City, Iowa and Rulo, Nebraska. This study (Jacobson and others, 2009) developed detailed information about channel conditions, habitat availability, and background rates of channel change – a perfect pre-project comparison to quantify added habitat value. Ongoing biological and physical monitoring of the Deer Island site by the Missouri River Recovery Program – Habitat Assessment and Monitoring Project (HAMP) promises to help quantify the linkages between new habitat and biotic responses. 

Figure 2. Map of the Deer Island restoration site showing approximate limits of channel widening project and the area previously mapped and modeled by USGS.


Posted in Uncategorized |

Do You Want Ice With That?

Icy blasts of arctic air brought bitterly cold temperatures to the Missouri River Basin late in December 2013 and early January 2014.  The frigid temperatures created significant ice flows in portions of the Lower Missouri River, hampering pallid sturgeon tracking efforts.  In addition, low water levels have restricted access to the river at several locations between Kansas City and St. Louis.   This is not the first time that winter-related weather has delayed tracking activities (see previous posts “How Low Can It Go?” and “Ice Ice Baby”).  The river does not freeze solid in Missouri, instead “pads” of ice usually form and slowly fill the river, crushing and grinding together as they make their way downstream.  When the ice fills the river you can stand on the river bank and listen as it moves slowly past—if you are willing to brave the cold.  CSRP biologists prepare for winter tracking efforts by routinely checking ramp and river conditions and conducting maintenance on tracking vessels and equipment.  Taking these extra steps ensure that our crews are ready to get back on the water safely, conditions permitting.

Blasts of arctic air brought freezing temperatures throughout the Missouri River Basin near the end of December 2013 (source of graphic: National Oceanic and Atmospheric Administration).


Frigid temperatures created significant ice flows throughout the Lower Missouri River, hampering pallid sturgeon tracking efforts. Pictured is the Lower Missouri River at Hartsburg, MO near river mile 160.

Posted in Telemetry tracking |

Are You Ready For Spring?

It may seem a bit early to ask this question, but the spring spawning season is never far from CSRP biologist’s minds (see previous post Thinking Ahead).  Preparations for the 2014 spring season started early in the fall when crews began locating tagged female pallid sturgeon that they believed would become reproductive in the spring.  Once a targeted female had been located, biologists drifted trammel nets over her location until the fish became entangled in the net and could be pulled into the fishing boat.  The fish was then placed into an aerated holding tank where biologists used non-invasive ultrasound techniques to check for the presence of developing immature eggs (oocytes).  Any females determined to have oocytes will be intensively monitored in the spring of 2014 in the hopes of determining her spawning location.

During the week of September 16th, CSRP biologists recaptured and evaluated three female pallid sturgeon (PLS11-019, PLS10-029, and PLS12-002) expected to be in reproductive condition this coming spring.  PLS11-019 was first implanted with a telemetry transmitter in 2011 and released near river mile 717.1 near Sloan, IA.  PLS11-019 is expected to spawn for the second time in 2014 and will be tracked by biologists in the CSRP project.  She was first documented to have spawned in the Missouri River during the spring of 2012 between river miles 700 and 714.  Determining how often pallid sturgeon females spawn, and if they return to the same places to spawn time after time, is critical information for biologists.

PLS10-029 was first telemetry tagged in the spring of 2010 near river mile 563.7.   She was last in reproductive condition in the spring of 2012 and is also ready to spawn again after only 2 years.  Tracking efforts and retrieved data storage tag (DST) data have shown her to make spring migrations up the Platte River in both 2011 and 2012 (See previous post “Where Are You When I’m Not Looking?”).   It is likely that PLS10-029 spawned in the Platte River in 2012.  Since then she has spent most of the last two years between Plattsmouth and Bellevue, NE.  Biologists expect that she will again migrate up the Platte River in the spring of 2014.

PLS12-002 was first telemetry tagged in the fall of 2012 near river mile 576.2.  Based on the presence of a coded wire tag, biologists were able to determine that PLS12-002 was originally produced in a hatchery.  PLS12-002 was last located at river mile 513 during October 2013’s river sweep.  PLS12-002 is evidence that hatchery-produced pallid sturgeon can grow and reach reproductive condition in the contemporary Missouri River.  Whether hatchery progeny will spawn with other pallid sturgeon at the same spawning locations, and successfully contribute to the recovery of the species has not yet been established.  Biologists are hopeful that fish such as PLS12-002 will provide that needed insight.  All three females will again be targeted for recapture in the spring of 2014 for evaluations of reproductive readiness.

Initial recapture and current telemetry locations for three reproductive female pallid sturgeon (PLS11-019, PLS10-029, and PLS12-002) expected to spawn in the spring of 2014.


Posted in Recapture, Reproductive Female |

Long Distance Runner

The phone rang late on a Saturday morning near the end of the 2013 CSRP sampling season.  Crews that were out hoping to catch another female pallid sturgeon to implant and track were calling in with news.  The weekend crew leader said, “It’s a reproductive male, should we tag it?”  The 3.7 kg (8.2 lb) male pallid sturgeon was captured by CSRP biologists on trotlines set at river mile 177.2 near Boonville, Missouri.  He was more than 70 river miles downstream from the closest reproductive female.  Could he possibly swim upstream to reach one of the tagged females in time?  The decision was made to tag him and take the chance.  The epic story of PLS13-002 had begun.

Biologists were able to determine that PLS13-002 was originally produced in a hatchery by the presence of a coded wire tag, and that he was in reproductive condition by the use of noninvasive ultrasound techniques.  After a quick ultrasound scan, PLS13-002 was surgically implanted with a telemetry transmitter and data storage tag, and was then released back into the Missouri River.  Typically, fish are expected to rest after a surgery and do not display much movement in the days following a procedure.  Therefore, CSRP biologists were quite surprised when they located PLS13-002 21 miles upstream just five days after his implantation.

Approximately one month later, CSRP biologists tracking one of this year’s females (see previous post Gang of Eight) were surprised when they detected PLS13-002 more than 200 miles upstream near Leavenworth, KS.  There he was, at what biologists believed to be a spawning location.  And he didn’t stop there.  PLS13-002 traveled another 190 miles upstream where he reached his migration apex just above Plattsmouth, NE at river mile 593, near another tagged female.  It is impossible to know how many spawning locations he may have visited and how many females he may have met along the way.  With spawning season over and his journey at an end, PLS13-002 turned and began his downstream descent.  Biologists located him again almost 490 miles downstream near Hermann, Missouri at river mile 105.6 by July 17, 2013.

During his springtime migration, PLS13-002 had traveled upstream over 415 miles at an average rate of 6.5 miles/day.  Upstream and downstream migrations combined totaled almost 900 miles in a little over 3 months.  Such long migrations are not an uncommon occurrence among pallid sturgeon tracked by CSRP biologists, but the precise strategy behind such migrations still remains something of a mystery.  Did PLS13-002 have a predetermined destination in mind or did he simply keep swimming trying to find as many females as possible before the end of spawning season?  Why do some male pallid sturgeon display such long migrations while others may only migrate 30 miles to reach their spawning locations?  Are they seeking out the best spawning conditions or are they seeking females? These questions are fundamental to understanding how fish use the river and how the river can be managed to increase their populations.

Upstream spawning migration of male pallid sturgeon PLS13-002 in 2013. During his springtime spawning migration, PLS13-002 traveled approximately 6.5 miles per day upstream, a feat not uncommon for pallid sturgeon.

Completed with contributions by Sabrina Davenport and Aaron DeLonay


Posted in Telemetry tracking |

Where The Boys Are

For the past several seasons CSRP biologists have intensively and meticulously tracked female pallid sturgeon to their spawning locations.  All this attention on females is because biologists can easily tell when a female spawns by the presence or absence of eggs.  When the female is tagged with eggs, migrates, then stops, and is recaptured without any eggs it is easy to conclude that she must have spawned.  Knowing where these spawning sites are is critical to understanding why there are so few young pallid sturgeon being added to the population each year.  But finding the “spot” on the map where spawning happens is only part of the story.  What are the males doing while females are migrating upstream and what part do males play in when and where females stop to spawn?  Spawning locations are defined by where a female deposits her eggs, but which sex really chooses the spot on the map, and why?

For the first time in the Lower Missouri River, CSRP biologists documented a small aggregation of reproductive male pallid sturgeon this spring.  On May 22, 2013 CSRP biologists set out to recapture telemetered male pallid sturgeon PLS08-048, near the Platte River, Nebraska at rivermile 594.7.  Biologists were curious to know if the male was reproductive and ready to spawn with nearby females.  A trammel net was drifted over the tagged fish several times, but the targeted fish was not captured on that day.  Instead, four different male pallid sturgeon without telemetry tags were caught.  Three out of these four males were in reproductive condition at the time of capture.  The following day,  May 23rd, a fourth reproductive male pallid was captured just upstream of the male aggregation recorded the previous day.

CSRP researchers have previously documented loose aggregations of males in the Yellowstone River, North Dakota a few miles upstream of the confluence with the Missouri River (see previous post  Just One of the Guys).  These aggregations of males in the Yellowstone have occurred near suspected spawning locations.  Biologists are hoping to learn if male pallid sturgeon are selecting spawning locations early in the season before females with eggs arrive.  They want to know the factors that male sturgeon use to select spawning sites and whether or not females are selecting spawning sites using the same factors or if they are relying on the judgment of the males who have already arrived.  If biologists can determine which sex is selecting spawning sites, and what factors are preferred as “good” spawning habitat, then it is possible to determine how much spawning habitat is available and maybe predict spawning success.

CSRP Biologist Sabrina Davenport with a reproductive male pallid sturgeon. Two additional reproductive male pallid sturgeon were caught during the recapture effort near the confluence of the Platte and Missouri Rivers early in the spring of 2013.

Posted in Recapture |

A Rocky Start

If asked to describe the first few weeks of a baby pallid sturgeon’s life in the Missouri River, most biologists will tell you the embryos attach to a hard surface, develop, hatch, and enter the fast-flowing water to drift downstream.  Despite catching a very few free embryos over the last 10 years, no one has actually observed this phase of the sturgeon’s life cycle in the river.  Instead we’ve used scientific deduction and reasoning to come up with a plausible scenario of how a pallid sturgeon begins its life in the river.

Recently, however, laboratory observations of pallid behavior at these earliest stages, together with new data on post-hatch behaviors of other riverine sturgeons, have led to an alternative hypothesis to the hatch-and-drift paradigm.  Our flume studies of 2012 and 2013 have indicated that newly-hatched pallid sturgeon survive for only a few hours at water velocities > 0.10 m/s.  It isn’t until the sturgeon are 12 days old that they can survive at velocities of 0.23 m/s. 

How then can newly hatched pallid sturgeon survive velocities in the range of 1.5-3 m/s, typical of the Missouri River? Recently, scientists working on reproductive ecology of the white sturgeon have shown that free embryos hunker down in the interstices among rocks for a few days and develop fins and swimming muscles, before venturing into the drift.  Might this also be true for the pallid sturgeon?

To test this hypothesis, scientists at CERC are using outdoor artificial streams with two types of bottom substrate onto which the sticky, newly fertilized pallid eggs are ‘seeded’ (Figure 1).  In one stream, the small cobble substrate does not allow the pallids anywhere to hide after hatching so that they immediately drift upon hatching (Figure 2).  In a second stream, the eggs are adhered on and down inside a pile of larger rocks. Upon hatch, the embryos have more opportunity to maintain their position in among the boulders and emerge to drift after a few days of development.  Nets placed downstream of the rocks in both streams will catch the drifting free embryos.  If the pallids do delay their drift, then we would expect there to be a few days difference between the streams in the peak collection of free embryos in the nets.


Figure 1. Fertilized pallid sturgeon embryos are gently dispersed over the rock substrate. The PVC pipes are used to support a canopy of shade cloth to more closely mimic the muddy depths of the Missouri River.

Figure 2. Fertilized pallid sturgeon embryos are gently dispersed over the gravelrock substrate. The PVC pipes are used to support a canopy of shade cloth to more closely mimic the muddy depths of the Missouri River.

The vulnerability of these tiny fragile larvae, and their urgent need to find a hospitable environment where they can feed and grow before their yolk is gone, strongly suggests this life stage could be a survival bottleneck for the population.    Although we will likely never be able to simulate in the laboratory the complex and extreme conditions in the Missouri River we must begin to think outside-the-box and creatively find ways to observe ecologically relevant pallid sturgeon early-life behavior.

By Diana Papoulias

Posted in Early life history |

Rain, Rain and More Rain

The 7-day precipitation forecast from the National Oceanic and Atmospheric Administration issued on May 27 showed local rainfall potential of approximately 5 inches for portions of north Missouri (figure 1).  Unfortunately, this forecast was relatively accurate and heavy rainfall swelled the Missouri River as the major storm moved through the mid-west.

Figure 1. The 7-day precipitation forecast from the National Oceanic and Atmospheric Administration issued on May 27.

Heavy rainfall during the last part of the week caused episodes of local flash-flooding and pushed the Missouri River over the National Weather Service floodstage of 23 feet at Jefferson City just before midnight on May 30, 2013.  Water levels finally crested at just over 30 feet on Sunday, June 2.  

 High flow presents several challenges and opportunities to researchers attempting to track pallid sturgeon in the Lower Missouri River.  First, we face the fundamental logistical challenge of finding boat ramps that are open, and if open, are not covered with mud and woody debris.  Flood waters can complicate the task of locating open boat ramps by causing road closures on low-lying roads, especially those in the floodplain approaching boat ramps (figure 2). 

Figure 2. Flood waters of the Missouri River and its tributaries cause road closures and prevent biologists from reaching boat ramps.

 Rising water can mobilize and carry large amounts of woody debris (figure 3), which severely complicates tracking, recapture and larval sampling efforts.  This woody debris isn’t just tree branches and limbs.  Entire large trees, roots and all, are frequently seen being swept downstream in the muddy current. 

 It can also be a challenge for crews to hear the telemetry transmitters of pallid sturgeon during flood flows because the debris and rushing water increases the noise in the telemetry signal, like static on a radio station.  Additionally, flood waters can increase habitat complexity by inundating sandbars and dikes, which can interrupt the transmitter signal (see previous blog entry “Sometimes It Takes Two”).  Although river conditions may occasionally prevent us from tracking these endangered sturgeon during high water, tags implanted inside fish will continue to record depth and temperature, and we will retrieve the data when the fish are recaptured later this year (see blog entry “Where Are You When I’m Not Looking”).

Figure 3. Large amount of woody debris are picked up and carried downstream by the rising waters of the Missouri River.

But the floodwaters also supply opportunities.  Some scientists have hypothesized that flood stages are instrumental in providing larval sturgeon access to near-shore and overbank areas.  High-water events present the opportunity to characterize habitats and drift in these areas.   In addition, high water helps habitat modeling studies that require sufficient depths that hydroacoustic boats can collect depth and velocity data over a broad range of habitats.

Posted in Flooding |