Pallid Sturgeon Spawning in the Yellowstone River

Posted on August 17, 2012 by Hallie Ladd

Pallid sturgeon in the upper Missouri and Yellowstone rivers can live a long time.  Many are older than most of the biologists who study them.  Over the years, scientists have become very familiar with the few remaining wild sturgeon. One female pallid sturgeon in particular, currently known as code 30, has a long and storied relationship with sturgeon biologists.  Biologists met her for the first time in 1995 when she appeared in their nets during the early days of pallid sturgeon work.  Since that initial meeting, she was re-captured and released in 1996, 2002, and 2003.  After a few years of avoiding their nets, she was re-captured again in 2008.  Close examination in 2008 revealed that she was ready to spawn and biologists surgically implanted her with a radio transmitter.  Although she was tracked by biologists and finally determined to have spawned in the river in 2008, they were unable to determine precisely where spawning took place.

In 2010, code 30 was caught again in reproductive condition and ready to spawn.  This time, she was loaded into a large tank on a truck and taken to the hatchery where she contributed to the pallid sturgeon propagation effort.  Biologists spawned her in the hatchery and fertilized her eggs with milt from males captured in the river.  The eggs hatched and her offspring survived to be released back into the Missouri and Yellowstone rivers.  As biologists moved her from the hatchery back into the river they suspected that she was on a two-year reproductive cycle, spawning every other year in even years.  The stage was set for her to spawn again in 2012.

In April 2012, the reproductive status of female pallid sturgeon, code 30, was confirmed.  She had mature eggs and was ready to spawn.  Researchers from USGS and Montana Fish, Wildlife, and Parks (MFWP) kept close tabs on code 30 during May and June.  Radio-tracking efforts indicated that she was capable of rapid upstream and downstream movements.  After a 50-mile downstream migration, code 30 was recaptured for reproductive assessment on June 12.  Biologists used ultrasound to examine her ovaries and a hypodermic syringe to conduct an egg biopsy to determine how close she was to spawning, or if she had already spawned (see previous post “Did She or Didn’t  She” for a description of ultrasound).  The results clearly showed that she was still carrying all her eggs.

Biologists prepare to perform ultrasound and an egg biopsy on female pallid sturgeon, radio code 30, to determine how close to spawning she is or whether spawning may already have occurred. Biologists from Montana Fish, Wildlife and Parks determined that code 30 eventually spawned in the Yellowstone River on July 19-20, 2012.

During the next several days, the tracking boats followed her as she moved upstream and downstream past numerous ready-to-spawn male pallid sturgeon in the lower Yellowstone River (see previous post “Just One of the Guys”).  The female, code 30, and the males seemed to show little interest in each other.  All that changed dramatically one afternoon in the middle of June.  On June 19, pallid sturgeon female, code 30, joined a group of 11 telemetry-tagged, pallid sturgeon males in the Yellowstone River, 6.7-6.9 miles upstream of the confluence with the Missouri River. This tight aggregation of adults in a deep swift trough-like channel with a sand, gravel, and bedrock substrate indicated to biologists that spawning was likely underway.  Spawning was confirmed by drifting a net through the spawning aggregation.  The female, code 30, and several of her male suitors were quickly captured and pulled aboard the tracking boat.  The female had ovulated and was releasing eggs as she was taken from the net.  The males captured in the same net were releasing milt.  The spawning aggregation remained present at the site through noon on June 20.  Seventeen years after first meeting code 30, biologists were finally able to document precisely where and when pallid sturgeon spawn in the Yellowstone River.

Biologists were able to document the spawning of a female pallid sturgeon, radio code 30, as she released her eggs (shown above) during a recapture event targeting a spawning aggregation in the Yellowstone River.

Biologists returned to the site after several days to sample for embryos, free embryos, and larvae to document successful fertilization, hatch, and drift using methods similar to those used in the Lower Missouri River (see previous post “Searching for a needle in a haystack”).  Samples will be sent for genetic testing to determine whether the embryos and larvae captured at the site are pallid sturgeon or the more common shovelnose sturgeon that also spawn in the lower Yellowstone River.  Genetic testing may also determine which and how many males in the spawning aggregation contributed to fertilization.

By Pat Braaten and Aaron DeLonay

 

Posted in Reproductive Female, Yellowstone River |

Just One of the Guys

Posted on July 27, 2012 by Hallie Ladd

For more than a week in early June, USGS telemetry tracking boats from Missouri joined the Montana Wildlife Fish and Parks and the USGS Fort Peck Field Office as they raced up and down the Yellowstone River trying to keep up with dozens of large, migrating pallid sturgeon.  The biologists worked long hours collecting data on sturgeon movements and the pathways they travelled, all the while scratching their heads and speculating on why these sturgeon do what they do.  Despite traveling hundreds of miles back and forth to document the spring spawning migration, tracking crews continually returned to a few bends of the Yellowstone River downstream of Fairview, Montana.  Over the first few weeks of June, loose aggregations of up to a dozen telemetry-tagged, male pallid sturgeon were located near the site, a few miles upstream from the Missouri River confluence.  The typical sing-song chirp of a single telemetry tag usually heard from the receiver’s speaker was replaced by what sounded like a swarm of angry crickets as the tracking boats approached the site.  The biologists needed to know, why they were there, what are they doing, and what are they waiting for?

USGS boats surveyed the area with sidescan and DIDSON sonar to try and determine what the sturgeon might be doing and how closely they were interacting.  Sonar data showed that the males did not sit idly, but moved actively around the site.  Were they just feeding in the area, or were they waiting for a female to show up and spawn?  The only way to know for sure was to attempt to recapture some of the males.  If examination of the males revealed that they were ready to spawn, then the chances were good that the males had selected the spawning site and were just waiting on the females to arrive.

Biologists targeted the aggregation of male pallid sturgeon with drifted trammel nets on Thursday, July 14.  Three large male pallid sturgeon were caught in the weighted net as it dragged along the river bottom.  It took only minutes for USGS biologists to scan each sturgeon with a portable ultrasound device and determine that all three were “ripe” and ready to spawn.  Now that the biologists knew that the males were ready, it was their turn to wait.

By Aaron DeLonay

USGS biologists drift trammel nets on the Yellowstone River near Fairview, Montana to capture male pallid sturgeon.

 

A large male pallid sturgeon captured by the USGS on the Yellowstone River is scanned with a portable ultrasound device to determine if it is “ripe” and ready to reproduce.

 

Posted in Tracking, Yellowstone River |

On the Right Path

Posted on July 20, 2012 by Kimberly Chojnacki

“We have a boy, code 52, on his way to Intake Dam.  We’ve tracked him all day through bends and side channels.  He is a couple of miles away from the Dam.  Can you spare a crew to track him till dark?”

This was the phone message given from USGS Biologist, Pat Braaten to USGS crews as they were finishing a long day chasing large, fast moving pallid sturgeon up and down the Yellowstone River in Montana on Saturday, June 9The crews were working to assist the USGS Fort Peck Field Office and the Montana Fish Wildlife and Parks (MFWP) to document spawning locations and behavior in the lower Yellowstone River (see Headed North).

The crew responed, “On our way.”

In addition to documenting spawning migration behavior and finding spawning locations, the work on the Yellowstone River by USGS and MFWP is focused on trying to determine how pallid sturgeon use the river as they migrate (see Path of Least Resistance).  Most importantly, biologists were keenly interested in how easily pallid sturgeon migrate through the last few miles of river downstream from Intake Diversion Dam (about 73 miles upstream).  Managers and Engineers from the U.S. Army Corps of Engineers, Bureau of Reclamation, U.S. Fish and Wildlife Service, and MFWP are working to design a way for pallid sturgeon to pass over or around the dam, and continue their migration upstream (see Intake Diversion Dam Modification Project).  The pathway that the sturgeon choose, and the ease with which they can negotiate through the turbulent waters and jumble of rocks downstream of the dam could prove critical to the success of that project, and the long-term viability of this population.

The USGS tracking boat made it up to Intake Diversion Dam and located male pallid sturgeon, code 52, less than two miles downstream from the Dam.  He was still moving.  The tracking team listened to the telemetry receiver and followed as he swam steadily upstream along the right descending bank, reaching the Dam just as the sun began to set.  The tracking crew pulled their boat from the water in the dark, guided back to the boat ramp by the small fires set by campers and paddlefish fishermen.  Within hours the precise locations collected by the tracking boat were transferred to the habitat mapping crew, and the plan to map the depths and velocities of code 52’s pathway the next day, were completed before the hotel lights dimmed for the night.  Surprisingly, USGS tracking crews located code 52 again a few days later, almost 70 miles downstream near the confluence with the Missouri River.

 

Precise telemetry locations documenting the migration pathway of male pallid sturgeon, code 52, as it approached Intake Diversion Dam, Montana on June 9, 2012.

The sun sets below the horizon as USGS telemetry-tracking crews follow the upstream migration of male pallid sturgeon, code 52, below Intake Diversion Dam, Montana on June 9, 2012.

By Aaron DeLonay

Posted in Tracking, Yellowstone River |

Headed North

Posted on July 10, 2012 by Kimberly Chojnacki

With telemetered female pallid sturgeon done spawning in the Lower Missouri River, the USGS tracking crews from Missouri packed up their equipment at the beginning of June and headed north to Montana and the Yellowstone River.  It was a two day drive from Columbia, Missouri to Sidney, Montana where they joined biologists from Montana Fish, Wildlife and Parks (MFWP) and biologist, Pat Braaten, from the USGS Field Office in Fort Peck, Montana.  Pat and his colleagues from MFWP had 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.  The Missouri tracking crews were there to help document the migration behavior of large, fast moving, adult pallid sturgeon up the Yellowstone River, and to determine when and where they are spawning.   Every reach of river within the species’ range has been modified and altered by human activities.  Scientists hope that by comparing what pallid sturgeon do in different reaches of the Missouri River, they can gain insight into how sturgeon behavior may be altered in response to different threats, and why sturgeon do what sturgeon do.

Biologist, Dave Combs prepares a tracking boat (foreground) and a DIDSON survey boat (background) to search the Yellowstone River for tagged pallid sturgeon, Near Fairview, Montana. Pallid sturgeon in Montana are tagged with radio telemetry transmitters that are detected with large antennas mounted the boats.

By Aaron DeLonay

Posted in Tracking, Yellowstone River |

How to Drink From a Fire Hose

Posted on July 6, 2012 by Kimberly Chojnacki

Since 2009, larval sampling efforts have focused on capturing newly hatched and drifting larvae immediately downstream of a suspected pallid sturgeon spawning site (see previous posts “Searching for a needle in a haystack” and “Panning for biological gold”).  In 2012 Comprehensive Sturgeon Research Project (CSRP) biologists initiated systematic sampling for larval, free-embryo pallid sturgeon to assess fluxes of larvae from the Missouri to the Mississippi Rivers.  Biologists have been stationed in St. Charles, Missouri conducting weekly larval sampling since mid-April.  This task of the CRSP will focus on a single channel cross-section through September to provide some relative indication of the importance of the Mississippi River as nursery habitat for shovelnose and pallid sturgeon young of year.

Larval samples collected near the confluence of the Missouri and Mississippi Rivers. Sturgeon collected in the samples ranged from recently hatched larvae to larvae more than two weeks old.

Given the size of the Missouri River, trying to catch the small larvae as they drift past is a little like trying to drink from a fire hose.  Drifting larvae are collected using a pair of ichthyoplankton sampling nets that are deployed in the water column on either side of the boat for 5 to 15 minutes.  One-hundred pound lead weights hold the fine mesh nets in the swift current while samples are taken in the middle of the water column and within inches of the bottom.  Small meters with propellers are mounted at the openings of the nets to measure the amount of water strained by the nets. The samples collected in the nets are emptied into pans and sorted.  All sturgeon and paddlefish larvae collected are preserved in alcohol and transported back the office.  The individual fish are then measured, identified, and aged based upon their developmental stage.  The date the fish was collected, along with its age can help to determine when and where adult sturgeon are reproducing.  To date, 322 larval sturgeon and 343 larval paddlefish have been captured at the study site.

Sturgeon larva captured near the confluence of the Missouri and Mississippi Rivers. This young sturgeon has used all its yolk reserves and must settle to the bottom and search for food on its own.

With contributions from Aaron DeLonay

Posted in Larval Sampling, Uncategorized |

Old Faithful???

Posted on June 25, 2012 by Kimberly Chojnacki

Perhaps one of the most interesting fish in the CRSP’s portfolio is male pallid sturgeon PLS08-006.  This individual was originally implanted with a telemetry device in the spring of 2008 and has since been located on 93 occasions between river miles 582 and 641.  In the past, the movement pattern of PSL08-006 has consisted of an upstream migration in the fall, followed by a downstream migration in the spring.  USGS ecologist Aaron DeLonay believes that spawning may have previously occurred between river miles 638-641 (the area of the river where the fish has been located in the spring).  Interestingly, PLS08-006 has made this migration regardless of his reproductive condition.  For the first time in four years, PLS08-006 has not returned to his annual upstream location, leaving CRSP biologists to wonder what has changed.  Biologists are also wondering what is so special about river mile 582-583 during the summer and early fall?  The fish’s behavior indicates a keen sense of spatial awareness and a strong, long-term pattern of fidelity to multiple locations, but why? If this pattern is common among pallid sturgeon, what would such a strong level of fidelity mean for population recovery and habitat construction efforts?  Along with its telemetry transmitter, PLS08-006 was also implanted with a data storage tag (DST) that records temperature and depth at a 15 minute interval everywhere the fish travels (see previous post “Where Are You When I’m Not Looking”).  When downloaded, the data from the DST device may be able to give biologists valuable insight into PLS08-006’s migratory patterns.  Until then, we will continue to track this fascinating male and his travels in the Missouri river.

Telemetry locations of male pallid sturgeon PLS08-006 from March 2008 through May 2012.

Posted in Uncategorized |

River Sweep May 21 – 29, 2012

Posted on June 7, 2012 by Kimberly Chojnacki

With spawning season coming to an end, Comprehensive Sturgeon Research Project (CSRP) researchers are beginning to focus more on extensive tracking efforts and less on tracking individuals to their spawning sites.  We have defined a “river sweep” as an attempt to search for telemetered pallid sturgeon in as much of the Missouri River as possible, from the Gavins Point Dam near Yankton, South Dakota to the confluence near St. Louis, Missouri.  CSRP biologists teamed up with the Nebraska Game and Parks Commission to search for as many telemetry tagged pallid sturgeon as possible from May 21 – 29. Crews searched the Missouri from river mile (RM) 753.5 above Sioux City, Iowa to the Missouri and Mississippi River confluence near St. Louis.  Forty-five fish, including two previously reproductive females, were located during this month’s river sweep (see Previous Posts Down the Wide Missouri and  Meet the Ladies of 2012).  PLS09-011 was found near her spawning location at RM 580.7 while PLS11-007 was located approximately 75 miles downstream of her spawning site.  

Map showing pallid sturgeon telemetry locations during the river sweep from May 21 - 29, 2012.

Posted in Uncategorized |

Panning for biological gold

Posted on May 30, 2012 by Kimberly Chojnacki
 
Telemetry crews tracked female pallid sturgeon PLS11-007 to her spawning location (see previous post An Early Spawning Recorded) on March 30 and 31.  Additional crews were deployed April 3 in an effort to confirm a successful spawning at this site.  Researchers sampled for larvae using ichthyoplankton sampling nets, which are cone shaped nets made from very fine mesh with a sampling cup at the bottom. The nets are attached to 100 pound weights to keep them stable in the flow of the river. 

An ichthyoplankton sampling net being deployed in the Missouri River.

After 5 to 15 minutes in the water column, the sampling nets are brought back to the surface.  The samples are then emptied into pans and scientists then search for “biological gold,” specifically any larval fish that could be sturgeon. To prevent anylarval pallid sturgeon being missed, all larval fish belonging to the Acipenseridae family (sturgeon and paddlefish) are preserved in alcohol.  These larvae are then taken back to the office for further identification under a microscope.  

Hallie Ladd, Beau Griffith and Jeff Beasley, Five Rivers Services, LLC biologists sorting through larvae samples collected from the Missouri River.

During the three days of sampling that followed the spawning of PLS11-007, only one sturgeon larvae was captured on April 5.  The larvae was determined to be newly hatched, approximately five to six days post fertilization. 

Crews tracked female pallid sturgeon PLS09-011 to her spawning site a few weeks later (see previous post Spawn with the Wind), then subsequently collected larval samples for four days.   It was determined, using microscopic evaluation, that there were as many as eight sturgeon larvae captured near this spawning site.  These larvae were also newly hatched, approximately six to eight days post fertilization. 

A newly hatched probable sturgeon larvae captured near the spawning site of PLS09-011 in Nebraska.

Ultimately, genetic testing will be required to determine if any of the larvae caught at either site are pallid sturgeon. 

See previous posts Searching for a needle in a haystack, and Day old sturgeon caught in the Lower Missouri River for more information on 2011 larval sampling and catch.

Posted in Uncategorized |

Spawn with the Wind

Posted on May 7, 2012 by Kimberly Chojnacki

The upstream migration of female pallid sturgeon PLS09-011 continued on April 18th and 19th (see previous posts Going, going…).  However, she disappeared for the next few days until being located more than 50 miles downriver from her previous location on April 25(fig. 1). 

Figure 1: Telemetry locations of female pallid sturgeon PLS09-011 from March 1 to April 27, 2012.

 

On April 26, she moved upstream approximately one mile.  To the surprise of researchers, she began moving up and down an outside bend revetment (large rock used to stabilize the river bank), which is behavior indicative of spawning.  Biologists Justin Haas, Brian Hoffman, Ryan Ruskamp and Erik Prenosil from the Nebraska Game and Parks Commission were able to maintain contact with PLS09-011 throughout the day, until about 3am the following morning. They recorded her movements as often as every fifteen minutes. 

Around midday on April 27, PLS09-011 moved out into the main channel of the Missouri River.  Crews from USGS then braved gale force winds (fig. 2) and high waves to successfully recapture this very valuable fish.  Research biologists were able to determine that this female had spawned.  

Figure 2: Windspeed map from Intellicast.com on April 27, 2012.
 

Below is an image illustrating the weather conditions endured by tracking and recapture crews on April 27.  We certainly appreciate the dedication and tenacity of our devoted field crews! 

Figure 3: High winds cause waves to break over the bow of a USGS tracking vessel on April 27, 2012.

Posted in Uncategorized |

Going, going…

Posted on April 24, 2012 by Kimberly Chojnacki

Female pallid sturgeon PLS09-011 was originally implanted with telemetry devices in the fall of 2009 as a non-reproductive female. She was targeted for recapture and determined to be in reproductive condition in March, 2012 (see the previous post Meet the Ladies of 2012). Since the time of her last reproductive assessment, the Comprehensive Sturgeon Research Project (CSRP) biologists have been closely monitoring the movements of PLS09-011 in the Missouri River. She weighs approximately ten pounds, giving her the ability to travel long distances in a short period of time. In the beginning of April, PLS09-11 was located at river mile (RM) 591.6 (roughly four miles downstream of the Platte River confluence with the Missouri River). On April 18, 2012, tracking crews located PLS09-011 at RM 633.9, 42.3 miles upstream from her location at the beginning of the month.  To date, her most rapid movement occurred between the dates of April 13-17, when she moved approximately 30 miles in just four days! Biologists will continue to watch PLS09-0011 throughout the spring in an attempt to document spawning.

Telemetry locations of female pallid sturgeon PLS09-011 from March 1 to April 16, 2012.

Posted in Uncategorized |