Head Start

Posted on November 3, 2011 by Kimberly Chojnacki

The days are getting shorter and cooler, and researchers are already beginning to think about the next spring’s spawning migrations.  But, they may not be the only ones.  Female pallid sturgeon PLS11-007 was initially captured and implanted with telemetry devices on April 5, 2011.  She was not in reproductive condition at that time, but small white eggs were visible in the ultrasound and through a small incision during surgery.   Tracking crews relocated her 12 different times between April 5 and September 13, 2011.  Over the five-month observation period this female spent her time within just 0.6 miles of river.

With fall approaching, USGS Comprehensive Sturgeon Research Project field crews targeted this female for recapture. They wanted to see if her eggs had developed to the point where they can confidently predict that she will spawn in the spring of 2012.  This female pallid sturgeon was successfully located and recaptured in a drifted trammel net on September 16.  A minimally invasive ultrasound scan conducted on the boat showed the presence of large, maturing eggs.   The verdict was in – PLS11-007 will be ready to spawn next spring.

Female pallid sturgeon, PLS11-007, is released back into the Missouri River after an ultrasound evaluation determined that she will be in reproductive condition in the spring of 2012.

Perhaps PLS11-007 was listening when the results of the ultrasound scan were announced because she began moving upstream almost immediately.  Since the time of her recapture and ultrasound evaluation until October 7, the female pallid sturgeon has moved upstream more than 16 miles and into the Lisbon chute, near Arrowrock, Missouri.  By October 14, only a week later, she had navigated an additional 5 miles upstream of the Lisbon chute.  Ten days later tracking crews found she had swum 30 miles farther upstream and had passed the Grand River.  After another week, crews found her upstream an additional 24 miles.  From mid-September to Halloween, PLS11-007 had moved steadily upstream 75 miles.  Biologists tracking her are left wondering if she has decided to get a head start on her spring spawning migration and how far might she go before the cold and ice of winter settles in.  What makes some adult sturgeon start their spawning migrations in fall, while others wait until spring?  Do they have a specific destination in mind?  Do they know how far they need to go?  Only time will tell.

Map of telemetry locations for female pallid sturgeon PLS11-007 from April 5 to October 31, 2011.

Completed with contributions by Aaron DeLonay

Posted in Uncategorized |

Mapping baby sturgeon habitat at Hartsburg

Posted on October 19, 2011 by Kimberly Chojnacki

USGS scientists have been working this summer and fall with the U.S. Fish and Wildlife Service’s Columbia Fisheries Resource Office to map river habitat at sites where they are sampling for young sturgeon.  The crew is targeting age-0 sturgeon. These include fish that hatched this year and generally range in size from 10-110 millimeters, or fish that are a little less than half an inch long to about 4.5 inches long.  One of these river habitat sites is just upstream from Hartsburg, Missouri near river mile 161 on the right descending bank. At this site, a wing dike has been removed and there is large sandbar.  The USFWS has trawled 500-meter-long transects at this site for multiple years.  Several times this summer and early fall our habitat crew has coordinated to map depth, velocity, and substrate in conjunction with those sampling efforts.  

We have mapped the site about once a month since June. Our maps at the USGS gage upstream at Boonville, Missouri range in discharge from 131,000 to 246,000 cubic feet per second.  We mapped the entire bend in August using our multibeam echosounder to get an idea of how the bar fit into the larger hydraulic context of the bend in Missouri River.

Bathymetry of the Missouri River just upstream of Hartsburg, Missouri. Mapped using a multibeam echosounder on August, 18, 2011 when the discharge was 195,000 cubic feet per second at the USGS gage at Boonville, Missouri.

Our detailed maps focus on the region where the USFWS crews sample for young sturgeon.  We mapped the trawl locations in detail using GPS for navigation and positioning, a single-beam echosounder to measure depth and an acoustic Doppler current profiler (ADCP) to measure velocity on transects with 5-meter spacing.  We will combine this high-resolution depth and velocity data with the locations where young sturgeon were sampled in trawls. This will help us learn more about the places in the river where young sturgeon are found and how these habitats change with changes in discharge.

Detailed map showing depth-averaged velocity magnitude point data on transects with a 5-meter spacing and trawl beginning and ending locations upstream from Hartsburg, Missouri. Discharge was 246,000 cubic feet per second at the USGS gage at Boonville, Missouri.

By Carrie Ellliott

Posted in Uncategorized |

Scientific Meetings

Posted on October 12, 2011 by Kimberly Chojnacki

With the end of summer, project scientists have turned some of their attention to analyzing data and presenting results at scientific meetings.  Scientific meetings add to the depth and rigor of our science.  One of the most important functions of a scientific meeting is their contribution to peer-review.  Presentations allow us to talk about preliminary results and solicit feedback on approaches and interpretation; this feedback strengthens our final reports or articles.   Scientific meetings also allow us learn about the innovations and ideas of other research groups, so we can adopt and adapt their approaches to understanding the ecology of the Missouri River.  In return, innovations and ideas that we’ve developed are disseminated to the scientific community.   Finally, presentations at scientific meetings help build the stature of the science program on the Missouri River by informing the world about the quality and quantity of Missouri River science.

Janice Albers presents study results at the 6th International Symposium on Sturgeon in Wuhan, China in 2009. USGS scientists and their collaborators in the Comprehensive Sturgeon Research Project provided six presentations at the symposium on topics ranging from reproductive readiness, migration, spawning, and population assessment of Missouri River sturgeons.

Scientific meetings are highly variable in subject matter, scope, and attendance.  With the interdisciplinary orientation of our sturgeon project it can be a challenge to select the meetings that are most effective for communication.  Our attendance has varied recently from management-oriented meetings (National Conference of Ecosystem Restoration), to discipline-specific meetings (American Fisheries Society Annual Meeting), and to specialized multi-disciplinary conferences (Coherent Flow Structures in Geophysical Flows at the Earth’s Surface).  Unquestionably, the scientific meeting that is most relevant for our project is the annual Missouri River Natural Resources Conference, to be held this year March 13-16 in Pierre, South Dakota (http://www.mrnrc2011.com/CallForPapers.htm).  More than any other venue, the MRNRC meeting promotes discussion of science among scientists, managers, and stakeholders.  Some recent and upcoming presentations from our project are:

  • Sturgeon Use of the Lower Missouri River Floodplain: Presentation at 72nd Midwest Fish & Wildlife Conference, Des Moines, Iowa, December 4-7, 2011; Michael W. Archer, Ryan L. Ruskamp, J. David Adams, Justin D. Haas, Gerald E. Mestl, and Aaron J. DeLonay
  • Leveraging Large Volumes of Data to Support Research of Pallid Sturgeon in the Lower Missouri River: Presentation at World Sturgeon Conservation Society Meeting, Nanaimo, British Columbia, July 11-14, 2011; Kimberly A. Chojnacki, Chad J. Vishy, Emily K. Pherigo, and Aaron J. DeLonay
  • Mobile Mapping of the Endangered Pallid Sturgeon: Presentation at American Fisheries Society 141st Annual Meeting, Seattle, Washington, September 4-8, 2011; Kimberly A. Chojnacki  and Aaron J. DeLonay
  • Use of the Osage River by telemetry-tagged pallid sturgeon: Presentation at American Fisheries Society 141st Annual Meeting, Seattle, Washington, September 4-8, 2011; Sabrina A. Davenport,  Emily K. Pherigo, Chad J. Vishy, Kimberly A. Chojnacki, Diana M. Papoulias and Aaron J. DeLonay
  • Shovelnose Sturgeon: Presentation at 4th Annual Sturgeon and Paddlefishes Conference, Nanaimo, British Columbia, Canada, 11-14 July 2011; Aaron J. DeLonay
  • Use of Telemetry to Intensively Monitor Reproductive Status, Habitat Use and Behavior of Pallid Sturgeon in the Lower Missouri River: Presentation at World Sturgeon Conservation Society Meeting, Nanaimo, British Columbia, July 11-14, 2011; Aaron J. DeLonay, Diana M. Papoulias, Mark L. Wildhaber, Kimberly A. Chojnacki, Brandon McElroy, Robert B. Jacobson, Gerald E. Mestl
  • Deployment of DIDSON in the Lower Missouri River to Examine Sturgeon Behavior: Presentation at American Fisheries Society 141st Annual Meeting, Seattle, Washington, September 4-8, 2011; Aaron J. DeLonay, Chad J. Vishy, Brandon McElroy, and Kimberly A. Chojnacki
  • Modeling Effects of Climate Change on Pallid Sturgeon in the Missouri River: Presentation at Joint Statistical Meeting, Miami Beach, Florida, July 30 – August 4, 2011; Rima Dey, Christopher K. Wilke, Mark L. Wildhaber,  Edward H. Moran,  Christopher J. Anderson, and Kristie J. Franz
  • Larval Paddlefish and Shovelnose Sturgeon in the Upper Missouri River Basin including the Flow–Regulated Missouri River below Fort Peck Dam, Milk River, and Yellowstone River: Presentation at Montana AFS Meeting, Great Falls, Montana, February 7-10, 2011; David B. Fuller, Ryan D. Lott, and Patrick J. Braaten
  • Riverscape Genetics of the Endangered Pallid Sturgeon: Presentation at American Fisheries Society 141st Annual Meeting, Seattle, Washington, September 4-8, 2011; Edward J. Heist, Kimberly A. Chojnacki, and George R. Jordan
  • Simplification of habitat complexity metrics to guide restoration of large rivers: Presentation at American Geophysical Union Annual Meeting, San Francisco, CA, December 5-9, 2011; Robert B. Jacobson, Brandon McElroy, Caroline Elliott, and Aaron J. DeLonay
  • Conceptualizing and Communicating Ecological River Restoration: Presentation at National Conference on Ecosystem Restoration, Baltimore, Maryland, August 1-5, 2011; Robert B. Jacobson and Jim Berkley
  • Influence of bifurcation geometry on fluvial fish migration patterns: Presentation at American Geophysical Union Annual Meeting, San Francisco, CA, December 5-9, 2011; Brandon McElroy, Pat Braaten, Robb Jacobson
  • Understanding Habitat Needs for Rare Fish with Long Term Telemetric Studies: Pallid Sturgeon in the Lower Missouri River: Presentation at American Fisheries Society 141st Annual Meeting, Seattle, Washington, September 4-8, 2011; Brandon McElroy, Robert Jacobson, and Aaron DeLonay
  • Distinguishing Bed-load and Bed-material-load Fluxes with Repeat Bathymetric Data: Presentation at Coherent Flow Structures in Geophysical Flows at Earth’s Surface Conference, Simon Fraser University, British Columbia, August 3 – 5, 2011; Brandon McElroy and David Abraham
  • Effects Of Early Life-Stage Exposure To Selenium By Egg Injection On Pallid Sturgeon (Scaphirhynchus albus) And Shovelnose Sturgeon (Scaphirhynchus platorynchus): Presentation at SETAC North America 32nd Annual Meeting, Boston, Massachusetts November 13-17 2011; Diana M. Papoulias, Donald E. Tillitt, Mandy L. Annis, Diane K. Nicks, and Matthew Schwarz
  • Multi-Scale Modeling of Riverine Ecosystems and Responses of Fish Populations in the Context of Global Climate Change and Predictive Uncertainty:  Presentation at Model Fusion Conference, London, England 28-29 November 2011; Mark L. Wildhaber, Christopher K. Wikle, Christopher J. Anderson, Kristie J. Franz, Edward H. Moran, and Rima Dey
  • Modeling Large River Fish Population Responses to Global Climate Change: Missouri River Sturgeon Example: Presentation at 2nd Biennial Symposium of the International Society for River Science, Berlin, Germany, August 8-12, 2011; Mark L. Wildhaber, Christopher K. Wikle, Christopher J. Anderson, Kristie J. Franz, Edward H. Moran, and Rima Dey
Posted in Uncategorized |

Which came first, the sturgeon or the egg?

Posted on October 4, 2011 by Emily Pherigo

Freshly fertilized pallid sturgeon eggs in a laboratory environment.

While the Comprehensive Sturgeon Research Project (CSRP) at the USGS Columbia Environmental Research Center (CERC) is focused on pallid sturgeon (Scaphirhynchus albus) and the closely-related shovelnose sturgeon (S. platorynchus), the CERC also conducts behavioral, physiological and toxicological research on other sturgeon species.  Those species include the shortnose sturgeon (Acipenser brevirostrum), lake sturgeon (Acipenser fulvescens), and white sturgeon (Acipenser transmontanus).

Although there are similarities in rearing the various sturgeon species, there are also some differences. Larvae of some species, like pallid and shovelnose sturgeon, move into the water column soon after hatch and may drift with the current for long distances before settling to the bottom and feeding. Larvae of other species, like the lake sturgeon pictured above, do not drift great distances and the young are mottled in appearance to hide from predators as they search for food.

In order to study the early life stages of sturgeon species in the laboratory, it is important to learn how to propagate (breed) and culture (grow) them.  James Candrl, a fish biologist at CERC, has been supporting the CSRP by breeding and caring for sturgeon since 2001.  In the 2011 spring and summer, James raised four different species of sturgeon for studies on diet and starvation, early behavior, and the effects of environmental contaminants on survival and development.  Each of these experiments has one thing in common – the need for live, healthy sturgeon eggs, larvae, and juveniles.  James knows that ”the better you are at propagating and culturing sturgeon, the better your experiment will be.” So, through research and observation, he strives to raise healthy fish, comparable to what might be in the wild.

Click here to view a short video of a pallid sturgeon embryo.  As hatch time nears, sturgeon embryos become more active inside the chorion (egg shell).

Unlike many other fish species, pallid sturgeon eggs and newly hatched larvae are fairly big.  However, because the large and muddy Missouri River is home to the pallid sturgeon, it is difficult to observe these early life stages in the wild.  Therefore, many studies seeking to understand this time in the pallid sturgeon life cycle must be conducted in the laboratory.  Studies that examine early development and behavior provide insight into how far newly hatched sturgeon drift, what habitats are needed when sturgeon begin feeding, what juvenile sturgeon eat, and how long a young sturgeon can go without feeding.  These experiments help predict if they survive in the wild and what may happen if food sources are limiting in the river.

Newly hatched pallid sturgeon larva have a large yolk sac which sustains them until their mouths are fully formed and they are able to feed.

Laboratory studies are very helpful in conducting field work, too.  Research at the CERC helps guide scientists when and where to sample for larval pallid sturgeon, so they may have the greatest success in catching a drifting fish.  In the event that a larval sturgeon is captured in the river, knowledge gained from laboratory studies will help determine how old the fish is as well as when and where its parents spawned.

Scientists track the development and growth of sturgeon embryos and larvae. By knowing the temperature of the water and the developmental stage of the embryo, scientists can predict when it will hatch. This pallid sturgeon is very near hatching indicated by the tail extending to the head and the presence of eyes.

Completed with contributions by Aaron DeLonay and James Candrl.

Posted in Larval Sampling, Sturgeon culture and propagation, Uncategorized | Tagged , |

Down the Wide Missouri

Posted on August 9, 2011 by Emily Pherigo

With access to the river limited by high water downstream of Gavins Point Dam, our collaborators with Nebraska Game and Parks Commission (NGPC) traveled downstream to help search the Missouri River for telemetered pallid sturgeon from St. Joseph to St. Charles, MO. With four boats tracking in tandem, crews searched 420 river miles on six days between June 15 and June 23, 2011.

With the spawning season behind us and the intensive Comprehensive Sturgeon Research Project (CSRP) telemetry tracking effort completed, the tracking crews change their focus from following reproductive adults and locating spawning sites to characterizing post-spawn and non-reproductive habitat of pallid sturgeon.  It is a big river and sturgeon can move long distances between seasons.  The entire length of the Lower Missouri River must be searched repeatedly to locate individual fish.  This extensive systematic tracking strategy is used throughout the year to describe seasonal patterns of movement and locate important habitats.  At least once a month a consolidated effort is made to track the Missouri River from Gavins Point Dam to the Missouri and Mississippi river confluence.  The goal is to find as many tagged sturgeon as quickly and efficiently as possible to create a snapshot of where the sturgeon are during that short period of time.  We’ve come to call this effort a river sweep.  Under conditions of average to low flows and all 6 boats with crews available, the 811 river miles can be covered in a week.  however, when the river is high or stormy weather and ice are present, a river sweep can take two weeks if not longer.

Due to high water the June 2011 river sweep was shortened. The abbreviated river sweep resulted in locating 23 different telemetered pallid sturgeon in 420 river miles. The busiest day was June 22 when 8 individual pallid sturgeon were located in a 35 mile stretch downstream of Jefferson City, Missouri.

One fish located, PLS06-015, has been tracked continuously by CSRP since October 2, 2006.  Over the nearly five years, PLS06-015 has been located as far upriver as river mile 650 and as far downriver as river mile 100.  Another fish initially telemetered in 2006 and located during the June 2011 river sweep was PLS06-003.  Although absent from the telemetry study for 3 years due to an expired transmitter battery, PLS06-003 re-entered the study in March 2010 when she was captured a mere 1.2 miles from her last telemetry location in February 2007.  In addition to the two fish from 2006, fish captured and implanted in other years were represented as well, including: 1 initially telemetered in 2007, 4 initially telemetered in 2008, 4 initially telemetered in 2009, 4 initially telemetered in 2010, and 8 of which were tagged in 2011.

Two pallid sturgeon initially telemetered in 2006 exhibit very different movement patterns over the last five years. PLS06-015, a male, has covered hundreds of miles and even explored the Osage River, a tributary downstream of Jefferson City, Missouri. PLS06-003, a female, appears to have stayed relatively stationary. However, she, too, could have wandered after her original transmitter battery expired and her movements would have gone undetected. Where was she when we weren't looking?

 Completed with contributions by Aaron DeLonay.

Posted in River Sweep, Tracking, Uncategorized |

Island living

Posted on August 2, 2011 by Emily Pherigo

A panoramic view taken from the main channel side of an island on the Yellowstone River. Upstream is to the right side of the picture while downstream is to the left. The middle of the picture looks straight across to the descending right bank.

Columbia Environmental Research Center (CERC) crews assisted USGS biologist Pat Braaten and Montana Fish, Wildlife and Parks biologist Jason Rhoten in examining pallid sturgeon on the Yellowstone River from June 29 through July 8.  Various pallid sturgeon were located and attempts were made to track their pathways, map their habitat, and conduct underwater sonar surveys using dual frequency identification sonar (DIDSON) to learn about their behavior. Read more about DIDSON on an earlier blog post.

Depth measurements using the acoustic Doppler current profiler (ADCP) were collected around the island where female code 79 was located multiple times during the month of June, 2011.

One telemetered pallid sturgeon, also known as female code 79, was located on the downstream tip of an island.  She had been re-located at this spot several times during the course of the summer.  The depth of the habitat surrounding the island was mapped while another boat attempted to DIDSON the fish.  The following DIDSON video visualizes swimming behavior of pallid sturgeon female code 79 (larger fish) along with two smaller fish in the fast-moving environment of the Yellowstone River.  The two smaller fish are likely sturgeon, but it is nearly impossible to distinguish between pallid sturgeon and shovelnose sturgeon at that size.  While viewing the following video, notice the high amount of sand passing through the habitat location.

DIDSON footage of sturgeon in the Yellowstone River.

 

Posted in Uncategorized, Yellowstone River |

Did she or didn’t she?

Posted on July 20, 2011 by Emily Pherigo

When the spring spawning migration finally ends and the tagged female is recaptured, all is not over.  The question on everyone’s mind is, “Did she spawn, or didn’t she?”

Using a portable ultrasound unit similar to those used in modern emergency rooms, biologist Sabrina Davenport scans the belly of the fish for any sign of the large mass of dark grey and black eggs that were there two months ago (see Catch Me If You Can blog post for a picture of Davenport performing an ultrasound on a pallid sturgeon). It only takes a few moments to confirm that all her eggs are gone and that only the thin filmy tissue of her ovaries remains.  She is taken out of the water and quickly weighed.  Female PLS11-008 lost 16% of her body weight when she released several thousand eggs on the bottom of the Missouri River in spring 2011.  See Female prerogative blog post for more information on PLS11-008.

Pre-spawn ultrasound image of PLS11-008: the green arrow points to ripe eggs visible as lighter specs in this side view of the abdominal cavity.

 

Post-spawn ultrasound image of PLS11-008: the green arrow points to the ovary in this side view of the abdominal cavity. The absence of eggs visible in the pre-spawn ultrasound image collected 2 months prior indicates PLS11-008 successfully spawned in 2011.

Davenport then places the female back into the shallow tank and proceeds to perform a minor surgical procedure to recover the data storage tag (DST).  The DST recorded the water temperature and depth of PLS11-008 at 30 minute increments during her entire upstream migration.  In conjunction with telemetry, the data from the DST helps biologists characterize her migration route, determine the spawning time frame, and document environmental conditions at the spawning location.   

Depth data from the DST (represented by the grey line on the graph) is highly variable when PLS11-008 is swimming upstream indicating the use of a variety of depths during migration. When stopped at her apex, or most upstream location, there is a period of little change in depth in relatively deep water. This pattern of a pronounced period of little change in depth over 24-36 hours usually in deep water after the rapid, frequent depth changes associated with upstream migration (weeks) is what biologists associate with spawning.

 Surgery also provides an opportunity to visually inspect the ovaries, or reproductive organs, for reproductive condition, abnormalities, or anomalies.  An incision roughly an inch long does not provide a very big window through which to observe the gonads, but it is usually enough to get a glimpse. 

 

An inch long incision in the abdomen of a sturgeon is big enough to implant and remove a DST tag and get a glimpse of the gonads.

 

Before PLS11-008 is slipped back into the river, biologists insert a fine gauge needle into her tail and take a blood sample.  Blood samples taken before and after spawning are analyzed for reproductive hormones.  Comparing profiles of reproductive hormones before and after spawning attempts help project scientists understand why some female sturgeon spawn successfully and others may not.  See Bloody business post for pictures and more information. 

PLS11-008 was released at her capture location and will continue to contribute to extensive telemetry studies looking at long term movements and reproductive cycles of known adult pallid sturgeon.

Completed with contributions by Aaron DeLonay.

Posted in Recapture, Reproductive Female, Uncategorized | Tagged , , |

It’s hard enough to catch a pallid sturgeon once, but twice?!

Posted on July 15, 2011 by Emily Pherigo

 

USGS employees Beau Griffith (left) and Becky Welly (right) hold a telemetered pallid sturgeon they recaptured in a trammel net. The wooden object with 2 white buoys to the right of Welly is called a "Buck" or a "Mule" and is used to pull the net along in the current.

Any fisherman will tell you that just knowing where a fish is located is not enough to catch it.  If it were, we would call it “catching” instead of “fishing.”   Recapturing telemetry tagged pallid sturgeon takes skill, experience, hard work, and a little bit of luck. 

Telemetered pallid sturgeon are targeted for recapture in the spring after spawning, in the fall of the year before the next spawning season, and at any time our database tells us that the transmitter battery is nearing the end of its life.  Examining the same pallid sturgeon before and after the spawning season allows scientists to determine whether or not a sturgeon was in reproductive condition and if it spawned successfully.  Knowing this important information helps us to understand each fish’s motivation and more accurately interpret the behavior of the fish we are tracking.  Comparing the behavior and physiology of fish that successfully spawn to those that do not provides important insight into how environmental conditions in different years may influence the location, timing, and success of spawning.

The chosen gear for recapturing telemetry tagged pallid sturgeon is a drifted trammel net.  The trammel net is 120 feet long and 6 feet deep with three layers of net hung between a “float” line and a “lead” line.  The buoyant float line lifts the top of the net towards the surface of the water while the heavy lead line sinks to the bottom of the river.  The middle net has 3 to 4 inches square mesh while the two outer nets have 16 inches square mesh.  The inner net is deeper than the outer layers of large mesh, allowing more of the finer, inner net to fish along the bottom where sturgeon can become entangled in it.  The larger, outer mesh is made of heavier twine which holds the trammel net together when it becomes caught, or snagged, on rocks and logs.  Trammel nets fished this way for sturgeon perform more like reinforced, or tied down, gill nets than typical trammel nets.

 

It's not uncommon to become snagged while drifting a trammel net in the Lower Missouri River. This stump was hauled in during efforts to recapture a telemetry tagged sturgeon.

Once a telemetered pallid sturgeon in need of recapture is identified and located, the habitat is evaluated for safety.  Sometimes the water is too deep or too swift to attempt fishing for the tagged pallid sturgeon.  Rock dikes, submerged trees, navigation buoys, and commercial boat traffic in the area may further complicate or terminate the effort.  However, if no hazards are near, crews begin recapture efforts.

 

Once the area is declared safe for fishing, the trammel net is deployed from the front of a reversing boat. The "buck" which is thrown out first, can be seen floating in the river.

 

Moving upstream of the targeted fish, the trammel net is let out into the water in a shallow u-shaped arc.  One end of the float line is tied to a special float called a “buck” or a “mule” that catches the current and pulls the net downstream.  The other end of the float line is held at the bow of the boat.  Heavy weights are added to the lead line to sink it quickly and to ensure it fishes as close to the bottom as possible.  The net and boat drift downstream with the current until the net drifts past the location of the targeted fish or snags the bottom.  If the fish is captured, there is celebration.  If not, it is lather, rinse, repeat – drifting over the fish’s location until it moves to another location, the net becomes too damaged to continue, or the day is over. 

 

Pallid sturgeon can be very good at avoiding nets. It is necessary to locate telemetered pallid sturgeon between capture attempts because they move if harassed by repeated drifts of the net. The trammel net and buck sit on the deck of the boat waiting for the next attempt.

 

 Completed with contributions by Aaron DeLonay.

 

Posted in Methods, Recapture, Uncategorized |

Drift and retention of sturgeon larvae

Posted on July 8, 2011 by Kimberly Chojnacki

After sturgeon eggs hatch, the free-embryo larvae can drift as many as 17 days before “settling” into river habitats.  Previous analysis has indicated that if they drift at average water velocity in the river (4.5 – 7 miles per hour) they can be transported 100’s of miles downstream.  This means that many sturgeon larvae hatched in central Missouri would settle in the Mississippi River.  But it has also been hypothesized that under some hydraulic conditions larvae could be transported into marginal habitats along the river — eddies, backwaters, tributary mouths, low floodplain areas – where they will be retained, or at least slowed in their transit.

Hydroacoustic mapping boat R/V Lucien Brush mapping habitat during high water in the North Overton Bottoms Side-channel chute, Big Muddy National Fish and Wildlife Refuge.

This summer the USGS habitat team is working with the US Fish and Wildlife Service, Columbia Fisheries Office, to characterize some of these areas and the velocity patterns just upstream that could influence transport into them.  We are assessing potential retention habitats by mapping velocity patterns with an acoustic Doppler current profiler and bottom contours with a multi-beam depth sounder.   There is particular interest among river managers in the potential for larvae to be transported and retained in side channels that have been constructed for habitat restoration.  The depths and velocity patterns at inlets and outlets from side channels and at tributary confluences can be particularly complex because of complex flow around river-training structures (wing dikes).

Multibeam bathymetry (top) and current velocities (bottom) at the mouth of the Osage River mapped during high water June, 2011. Sturgeon telemetry positions (black squares) show concentrations in slow, deep water.

Young fish may also be retained in shallow-water habitat areas within the main channel, particularly if those areas are vegetated.   Flooded, vegetated areas have lower velocities and it has been hypothesized that they provide refuge from high velocities in the main channel and increased opportunities to young sturgeon to feed.

Flooded vegetation along the Missouri River, June 30, 2011. Flooded, low-lying, vegetated floodplains may provide refuge or food for young sturgeon.

Posted in Uncategorized |

Path of least resistance?

Posted on June 29, 2011 by Emily Pherigo

 

The black circles and red dashed line indicate the upstream migration pathway of reproductive female, Code 56, in the Yellowstone River on June 4, 2011. The inset image is a cross-section of the river’s depth and velocity in the side channel across the specified telemetry location (black line). The fastest water is indicated by red, and the slowest water is indicated by the purple end of the spectrum.

USGS hydrologists and biologists joined with biologists from Montana Fish, Wildlife, and Parks to radio track pallid sturgeon as they navigated the Yellowstone River during late May and Early June.  Following one fish over the course of a day with telemetry allowed them to map the fish’s pathway as it migrated upstream (see previous post about tracking in the Yellowstone River).   Using an acoustic Doppler current profiler (ADCP) to measure the depth and velocity of the river at recorded telemetry locations, they obtained detailed information about the habitats and energetic requirements of the pallid sturgeon’s migration.

The black circles and red dashed line indicate the upstream migration pathway of reproductive male, Code 19, in the Yellowstone River on June 8, 2011. The inset image is a cross-section of the river’s depth and velocity across the specified telemetry location (black line). The fastest water is indicated by red, and the slowest water is indicated by the purple end of the spectrum.

 

This year pallid sturgeon in the Yellowstone River have had more options during migration -the high water this spring is providing access to side channels and overtopped sandbars unavailable in most years.  The female, Code 56, swam from one side channel, directly across the main channel and straight into another side channel.  The male, Code 19, crossed the channel four times and went through one very small side channel.  Why did they select side channels in their pathway?  And does the pathway have a relation to the morphology of the river?  These are questions we hope to be able to address because of the hydrologic conditions this year.

Completed with contributions by Brandon McElroy

Posted in Habitat mapping, Uncategorized, Yellowstone River | Tagged |