Science-Based Questions from the Basin
Stakeholders:
Since the April 10 forum, MRBA has interviewed many people and organizations to develop the following answers (in italics) to the questions below that were posed by the forum attendees. The answers below are MRBA's responses. They are not meant to reflect the official position of any state or federal agency, but rather to broaden the general population's knowledge of the needs of the basin's listed species. MRBA cannot guarantee the accuracy of all the answers. Those who disagree with any of the responses are encouraged to email MRBA at rhoper@midrivers.com with suggested corrections, and we will consider posting them on this page of our website.
Pallid Sturgeon:
Questions for the Presenters:
Pallid Sturgeon:
General:
· What are the feeding requirements of pallid sturgeon juveniles?
· What are other causes of mixed gonads besides environmental stress?
Based upon our current
knowledge of sturgeon biology, hermaphroditism is an abnormal condition in sturgeon and is
rare in healthy populations. Sturgeon are
gonochoristic; meaning that they are either male or female and that they do not change or
reverse sex during their lifetime. Several
factors may be responsible for abnormal hermaphroditism.
These include senescence (old age), genetic abnormalities, hybridization,
radiation, chemicals, diet, temperature, and environmental disturbances.
The pallid sturgeon is extremely rare. While sampling and monitoring for this fish is occurring, insufficient data currently exist at all locations to determine population trends for these narrow time periods.
· How does hybridization impact recovery of pallid sturgeon?
Any species can be thought of as a unique set of genes. These genes carry the biological code that results in the distinct appearance, behavior and biology of the species. Through environmental selection and adaptation this set of genes has uniquely evolved to allow a species to thrive in its habitat. Hybridization between two species results in offspring that do not have the full complement of either species’ genes. If hybridization occurs at a high rate the genetic integrity of the rare species will be compromised, leading to the effective extinction of the species.
·
Why can’t sturgeons
live in lakes?
Some sturgeon species can survive and reproduce in lakes and
reservoirs provided that all of their ecological requirements are met and there is
unrestricted access to essential habitat (i.e., spawning habitat). However, pallid and shovelnose sturgeon require
flowing water to thrive. The morphology (body
shape) and behavior of these fishes is highly adapted to life in the current. Dam construction and impoundment of reservoirs in
the United States has had a major impact on these species, often resulting in localized
extinctions in impacted rivers. The exact
cause of the demise of populations in impounded reaches is not well understood, but is
typified by declining numbers of large individuals and poor or no reproduction. Evidence suggests that the lack of riverine habitat
in dammed systems may make it difficult for sturgeon to feed or to find food. Also sturgeon may be unable to compete with lake
fishes and may be more susceptible to predation. In
addition these sturgeon likely require a specific set of physical conditions (current,
substrate, turbidity, temperature, etc.) to complete their life cycle (migrate, spawn,
hatch, develop and grow). This combination of
environmental conditions may only exist in a riverine environment.
·
What parts of the pallid
lifespan seem to have the highest percentage of mortality?
The greatest percentage of sturgeon mortality occurs within
the first year of life. Female sturgeon may
release greater than 20 percent of their body weight in eggs during a spawning season. This equates to tens or hundreds of thousands of
eggs. Many of these eggs will not hatch. Predators will eat many eggs. Those larvae that do hatch rise into the water
column to begin drifting downstream in the current. Many
of these drifting larvae will be eaten or will settle into habitat unsuitable for
survival. Only a small fraction will
eventually survive to develop into juveniles.
·
How does sediment relate
to the needs of the pallid?
The pallid sturgeon evolved in a turbid, sediment-laden
system. As an adult it prefers a sand bottom
and has highly developed sensory capabilities that allow it to feed in fast moving, muddy
water. Its light coloration and reduced eyes
are suggestive of adaptations to muddy or dark environments.
In clear water without sediment pallid sturgeon may find it difficult to
find or capture food, to compete with other species for food and space, or to reproduce
and escape predation at early life stages.
During reproduction pallid sturgeon are thought to require coarser
substrate. Spawning pallid sturgeon and
shovelnose sturgeon are suspected to broadcast their eggs over clean gravel, cobble or
rock. Shortly after the eggs are deposited
they become adhesive or sticky and attach on the surface of, or in the spaces between, the
spawning substrate. The eggs remain attached
until hatching several days later (5-8 days). During
development it is essential that eggs receive a continuous flow of water and suspended
sediment is not allowed to settle out and suffocate the eggs.
·
How does sediment load
impact pallid survival?
The amount and type of sediment carried by the river has a large impact on the habitat types that are created and how dynamic they are. What we have learned from studying habitat use of adult sturgeon is that they seem to relate positively to habitat structure and complexity. Sand bar complexes, changes in bottom depth, multiple channels and complex current patterns appear to be attractive to sturgeon. Prior to intensive river engineering, these habitats were created and maintained by the river through the interaction of the river with its floodplain. This process was characterized by dynamic channel migration, erosion and deposition of large amounts of sediment, and the retention of large woody debris. Sediment load has decreased dramatically with the regulation of the Missouri River. Hard engineered structures (dikes, revetment and levees) are now the dominant habitat components and serve to constrain the dynamic river’s predisposition to create and move habitat. Numerous mitigation projects are underway to rehabilitate habitat and to improve the suitability of existing habitat for pallid sturgeon and other species. Habitat use and selection studies are underway to try to determine what habitat elements are used and how suitable they may be for sturgeon.
·
What percent of the pallid
sturgeon’s problems are attributable to the reservoirs?
It is difficult to rank the factors negatively impacting the
status of the pallid sturgeon. While not an
exclusive list, snag removal, bank stabilization, dam construction, impoundment, levee
construction, wetland draining, floodplain development, extreme climatic cycles,
pollution, and commercial harvest have likely all had an historical impact. Several of these impacts and alterations began even
before naturalists first described the species in 1905.
At the present the mainstem reservoirs on the upper Missouri River
are a major impediment to the recovery of the species.
Impounded reaches are unsuitable for pallid sturgeon and the species cannot
survive there. The suitability of riverine
reaches of the Missouri River between the reservoirs for pallid sturgeon has been
significantly reduced. These areas exhibit
poor productivity, un-natural hydrological regimes (including power-peaking), disrupted
temperature regimes, and reduced turbidity and sediment load. The mainstem dams, and perhaps to some extent the
reservoirs themselves, also act as barriers that prevent sturgeon from migrating to
feeding or spawning areas, and prevent downstream dispersal of larval and juvenile
sturgeon. Impoundment of the reservoirs may
have also eliminated feeding areas and inundated potential sturgeon spawning locations.
The Pallid Sturgeon Recovery Plan estimates that 60 % of pallid
sturgeon habitat in the Missouri River has been directly impacted by impoundment and
reservoir operation. The remaining 40 % of the
Missouri River (the lower Missouri River), and the middle and lower Mississippi River have
been impacted primarily by channelization and levee construction.
·
If we don’t know
where pallid sturgeon spawn, how can we determine spawning cues?
A great deal of research has been conducted with many other
species of sturgeon. From these species we
have a general idea of when and under what environmental conditions pallid sturgeon can be
expected to spawn. Most sturgeon are thought
to spawn over coarse substrate (gravel, cobble, or rock) in the current. From field and hatchery observations of shovelnose
and pallid sturgeon we believe that they spawn between March and July at water
temperatures near 60-70° F. The increasing body of evidence from sturgeon
research worldwide indicates that photoperiod (day-length), temperature, and flow, among
other factors, are important for sturgeon spawning. Sturgeon
will spawn under a variety of conditions, but the data suggests that there is an optimal
combination of these factors that will result in successful spawning events. It also follows that some environmental conditions
do not promote good spawning. These may
include rapid temperature or flow changes, temperature and flow extremes, and incorrect
timing of temperature changes or flow events. The
optimal combination of environmental conditions is not yet known for pallid sturgeon. It is hoped that further monitoring and research
will refine our understanding of what is required. Over
time this information will help to bring management actions closer to creating optimal
spawning conditions over a greater portion of the species range.
·
What is the exploitation
rate of sturgeon?
The pallid sturgeon is protected throughout its range and
harvest of this species is not allowed. Still,
a few individuals are taken incidentally each year. Shovelnose
sturgeon are currently harvested by sport anglers in many states where it occurs and by
commercial fishermen in a handful of states on the lower Missouri River and the
Mississippi River. Harvest and exploitation
rates of this species are currently unknown. Although
many states have recently noticed an alarming increase in the commercial trade and harvest
of shovelnose sturgeon, few locations have adequate information to determine population
levels and rates of exploitation. Because
sturgeon are long-lived and slow to mature, they are easily and quickly over-exploited. There is also concern that indiscriminate harvest
of shovelnose sturgeon will also result in additional illegal harvest of pallid sturgeon. The U.S. Fish and Wildlife Service has been
monitoring trade in our native sturgeon species and is working with the States through
MICRA (Mississippi Interstate Cooperative Resource Association) to develop a coordinated
approach to monitoring and regulating commercial harvest.
More information on MICRA is available at this location: http://wwwaux.cerc.cr.usgs.gov/MICRA/
Monitoring and Research:
·
Given the rarity of the
pallid sturgeon and the lack of understanding of what it needs to increase its population,
how will scientists know what works or doesn’t work with respect to management
changes?
Many things are known
about the historical conditions that once existed on the Missouri and Mississippi River. Many things are known about sturgeon in
general. Sturgeon are one of the most heavily
studied groups of fishes in the world. We have
made good progress and are learning more about the pallid sturgeon each year. While we are not certain about all the specifics
regarding the needs of the pallid sturgeon, we know enough to begin the process of
augmenting populations with hatchery fish, restoring physical habitat, and proposing and
testing management practices that may enhance pallid sturgeon populations or improve the
condition of the ecosystem upon which it depends. The
species is critically endangered and we do not have the luxury of waiting until everything
is known about its ecological requirements before acting.
Hatchery efforts need to be fully supported to augment populations while
allowing management actions time to work. Scientists
need to continue to conduct research on the basic biology of the species to further refine
our understanding of the species needs. A
robust monitoring program is also essential to relate management changes to observed
responses in sturgeon populations or indicators of ecosystem integrity. Finally, it will take time. Recovery of pallid sturgeon populations will likely
take decades. If the pallid sturgeon is to
avoid extinction it will take vision and commitment from the entire basin to sustain the
recovery process for the 40 or more years it will require to recover the species.
·
What actions are underway
to determine the spawning habits of pallid sturgeon (habitat, temperature, turbidity,
etc.)?
A monitoring program has been initiated and several research
studies are underway in the Missouri and Mississippi Rivers to learn more about pallid and
shovelnose sturgeon. Basic biological
questions about the reproductive cycle of sturgeon are being researched. The behavior of individual sturgeon is being
monitored using telemetry and remote sensing techniques.
Multi-State, multi-agency monitoring programs are developing better sturgeon
sampling methods to assess the response of sturgeon populations as more habitat is
rehabilitated and as management changes are implemented.
·
How are pallid sturgeons
tracked and how successful are the methods?
All pallid sturgeon captured in the wild or released from
hatcheries are tagged for future identification. Most
are implanted with PIT (Passive Integrated Transponders) tags that are about the size of a
grain of rice. These tags each have a unique
alphanumeric code and are implanted into the muscle of the fish with a special syringe. Biologists can detect PIT tags with a special
electromagnetic scanner. The scanner activates
the tag and causes it to send out its identification code for display on the scanner’s
screen. All of this is accomplished without
removing the tag or harming the fish. Other
external tags may also be used in conjunction with PIT tags.
The efficacy of these tags for pallid sturgeon is still being studied. No tagging system is 100% reliable. Researchers continue to work towards the
development of better more reliable tagging methods for sturgeon.
Some pallid sturgeon research programs also surgically implant a
number of sturgeon with radio or ultrasonic telemetry devices that send out a signal every
few seconds. These tags can be detected from
great distances (>100 meters) and are used to relocate tagged fish in the river to
determine movement and habitat use. There is
some mortality associated with telemetry studies, but the information gained is invaluable
in determining range and patterns of movement, and habitat use.
·
How many pallid sturgeon
have been tagged?
All hatchery fished released in
the river are tagged. Thousands of hatchery
fish have been released into the Missouri River. Perhaps
fewer than a few hundred have been implanted with telemetry devices over the years.
·
What studies have been
done on the pallid sturgeon in the Mississippi?
There have been many studies on
the pallid sturgeon in the Mississippi River. Information
and annual summaries of all activities involving pallid sturgeon can be reviewed at the
following U.S. Fish and Wildlife Service web site: http://www.r6.fws.gov/moriver/
Propagation:
· Can native populations of pallid sturgeon be revived without artificial propagation (hatcheries)?
In some Recovery Priority Areas (RPA)
hatchery propagation will be essential to augment very low population levels. While hatcheries will play a large role in the
initial efforts it is a short-term solution. The
ultimate recovery of the species depends upon the suitability of available habitat and the
ability of the river ecosystem to support a healthy sturgeon population. The goal of the recovery program is a naturally
reproducing, self-sustaining population.
·
How much propagation of
pallid sturgeons has taken place and at what cost?
Efforts to propagate pallid sturgeon in hatcheries have been
ongoing for over 10 years. Both State and
Federal fish hatcheries have been involved. The
entire program has included dozens of professionals and technicians. However, sturgeon propagation is difficult and
expensive. It requires expertise and large
amounts of space. The hatcheries currently
involved in the program require substantial modifications to spawn and rear sturgeon. Efforts to collect and maintain captive
population of adults to guard against extinction in the wild require a large new facility
or substantial additions to currently existing hatcheries.
An estimate of the resources expended to date is not readily available. Fish culturists at the Gavin’s Point National
Fish Hatchery (http://www.r6.fws.gov/gavinspoint/)
or the Garrison Dam National Fish Hatchery (http://www.r6.fws.gov/garrisondam/)
can provide descriptions of their current facilities and costs required to raise young
sturgeon large enough to tag and release.
·
What is the survival rate
for hatchery-reared pallid sturgeon?
This is the subject of ongoing monitoring efforts. The survival rate is difficult to ascertain from
current sampling efforts, but individual sturgeon that are recaptured are growing well and
appear to be in excellent condition. We will
learn more as the numbers of hatchery progeny released into the wild increases.
·
Does the stocking program
contribute to hybridization of pallid sturgeon?
Unknown. The first
hatchery-reared sturgeon released into the river will soon reach reproductive maturity (or
they may already have). It is possible that
initially they may contribute to the hybridization problem.
However they will also contribute to pure pallid sturgeon reproduction. Hybridization occurs for a number of reasons. One reason is that there simply aren’t enough
individuals, and finding a mate during spawning season can be very difficult. Through hatchery stocking we hope to increase not
just the numbers of sturgeon, but their densities as well.
So that hopefully when spawning occurs, the likelihood of finding the right
mate at the right time will be much greater.
·
Are sturgeon numbers too
small to realistically expect reproduction numbers sufficient to achieve recovery goals? If yes, should hatchery-raised fish be a reasonable
alternative?
In
some areas sturgeon numbers may have dropped below critical levels or they may have been
extirpated. Hatchery raised fish are being
used, but they are a short-term measure designed to reintroduce or augment populations
that are not self-sustaining. However, while
pallid sturgeon densities are very low everywhere, pallid sturgeon are still responding to
the environmental conditions in the river and are still reproducing. This may be evidenced by the relatively high
incidence of reported hybrid sturgeon. The
recovery effort is seeking management practices that will both increase pallid sturgeon
populations and reduce the threat of hybridization. Current
levels of hybridization may be the result of habitat alteration and river regulation. Shovelnose sturgeon and pallid sturgeon may have
once spawned at different places or times, but now habitat alterations, barriers to
migration, and disrupted flow regimes have forced these two species to spawn at the same
place and time. Implementation of selected
management practices with hatchery stocking may prove an effective tool to prevent
hybridization even at low densities.
Flows and Habitat:
·
Can we physically provide
enough habitat without changing the flows?
The short answer is
that habitat manipulation can provide more shallow water habitat than can be provided just
by changing flows. However when discussing
habitat it must be understood that habitat is more than just rocks, sand and water. Habitat is an ecological concept that is more
complex than just the physical form of the landscape or the bottom of the river. Habitat is best thought of as a mosaic that changes
through time. Each piece can be characterized by physical measures such as depth,
substrate type, water velocity, and bottom form. The
value of the habitat mosaic to an individual species is determined by what the pieces are
used for and when, how the pieces are arranged, and how the mosaic changes through time. When restoring and rehabilitating habitat it is
important to create not only the physical pieces, but to restore some of the processes
that maintain the values, diversity, and dynamic character of the habitat mosaic. In a riverine environment, flow is one of these
essential processes.
·
What is the relationship
between flow volume and velocity in regards to the needs of the sturgeon?
Pallid sturgeon are a
fish of the current. They require moving water
with moderate velocity to thrive and reproduce. Some
information is available on the velocities that sturgeon use for various stage of their
life history. More are studies are underway. This information can be used to create or enhance
habitat projects that are suitable for selected life stages of sturgeon.
Flow volume considerations for
pallid sturgeon are related more to ecosystem-level processes and physical dynamics of the
system. The considerations here are more
indirect: What discharges will create the particular habitat types that may be used by
sturgeon or their food resources? What
discharges are necessary to connect floodplain wetlands to the river to increase
productivity, stimulate invertebrate production, or to promote spawning of other fish
species? How do flow volumes influence the
availability and arrangement of habitat types in the river mosaic? We know what the historic flow volumes for
individual reaches of the river were before regulation.
We have a general understanding of the importance of flow and its
relationship to a healthy river system. We
need to define and better quantify these relationships to best manage the system.
Finally, changes in flow
volumes and velocities are not the only considerations. Other factors that are important
include water temperature, water quality, the size and timing of a spring rise, etc.
·
What beneficial effects
are being seen from current fish and wildlife mitigation project sites?
The mitigation program emphasizes restoring habitat types as
opposed to focusing on single species, such as the pallid sturgeon. Few sites have ongoing monitoring efforts to
determine whether the physical manipulations have had desirable biological effects. More biological monitoring of these sites is
necessary to determine all the benefits. Information
on the mitigation program can be found at the following Internet location: http://www.nwk.usace.army.mil/projects/mitigation/index.htm.
·
Why is it believed that a
spring rise will increase pallid sturgeon recruitment despite the fact that recruitment
appears to be no better in the Boonville reach, where a natural spring rise occurs, than
in any other reach?
While far from ideal,
we know that conditions somewhere in the lower Missouri River (below Gavin’s Point
Dam) are suitable for pallid sturgeon spawning. The
only place where pallid sturgeon larvae have been found in the lower river Missouri River
is in the Boonville reach. Immature pallid
sturgeon and hybridized shovelnose / pallid sturgeon are almost exclusively reported from
the lower Missouri River and the Mississippi River. This
is in stark contrast to the inter-reservoir reaches (above Gavin’s Point) where the
pallid sturgeon population consists entirely of older adults with no evidence of juveniles
or immature fish. One obvious difference
between these segments is the presence of a somewhat “natural” hydrograph,
including a spring rise.
A spring rise below Gavin’s
Point would have several benefits for the pallid sturgeon and the Missouri River
ecosystem. These benefits and their rationales
have been outlined extensively in the 2000 Biological Opinion. They can be reviewed at the following website: http://www.nwd-mr.usace.army.mil/mmanual/opinion.html
·
What river reaches have
the highest likelihood for recovery?
The pallid sturgeon recovery program remains committed to
restoring self-sustaining populations of sturgeon in all six Recovery Priority Areas. Each Recovery Priority Area has had significant
impacts and impediments to recovery remain in each river reach. On the Missouri River, the river reach between
Kansas City and the mouth at St. Louis has many of the essential elements to recovery
(variable flows, warm water, high turbidity, shallow water, etc.). It is part of the longest continuous river reach
(Gavin’s Point Dam to the Gulf of Mexico) with no barriers to impede movement or
dispersal. There are also numerous
opportunities for physical habitat enhancement.
The Recovery Priority Area designations can be found in the Pallid Sturgeon Recovery Plan available at the following website: http://ecos.fws.gov/docs/recovery_plans/1993/931107.pdf
Geographic Distribution:
·
Do we know about the
historical demographics of the pallid sturgeon?
Our knowledge of historical sturgeon demographics is limited. The
species was not described until 1905, well after habitat alteration began on these rivers
and after the caviar trade decimated all the large sturgeon populations in North America. The species received little attention by
biologists until after the closure of the last large mainstem dams on the Missouri river. We have historical records of the distribution of
the species in the Missouri and Mississippi Rivers from Montana to St. Louis, and from St.
Louis to the Gulf of Mexico. Records also indicate some evidence of use of the lower
portions of a few major tributaries. The
distribution is consistent with a obligate large river fish that has a strong affinity for
sand and swift, turbid water. Unfortunately we
know little about the historic abundance of the species, age or sex composition of the
populations, or the location of important habitats or localized concentrations of the
species.
·
Do pallid sturgeon only
exist in North America?
Yes. There are 8 species of sturgeon native to North
America. Three of the species, the shovelnose
sturgeon, pallid sturgeon, and the lake sturgeon are native to the Missouri River.
· Are there pallid sturgeon in the Mississippi from St. Louis to the Gulf?
Yes. They are very rare and hybridization is commonly
reported.
·
How far north did the
sturgeon originally live?
Montana.
Tributaries:
·
What role do tributaries
play in pallid spawning?
Pallid sturgeons are
essentially mainstem fish. The role
tributaries play for pallid sturgeon spawning is unknown at this time.
·
What are the tributary
influences or impacts to pallid sturgeon reproduction?
Are they being studied?
Unknown. There are studies being conducted in the
Yellowstone and Platte rivers.
·
Why aren’t pallid
sturgeons surviving on the Yellowstone reach?
Unknown. While the Yellowstone and the reach of the Missouri
River below the confluence have good riverine habitat, there are potential problems that
have been recognized. One possible problem is
the check dams on the lower Yellowstone. These
dams limit the extent of movement of fish upriver. This
may prohibit the sturgeon from reaching potential spawning areas in the spring. Another potential problem is that sturgeon larvae
drift downstream with the current after hatching. This
drift behavior continues for up to 13 days. It
is possible that drifting larvae may reach Lake Sakakawea, settling out and dying in the
soft sediments of the headwaters of the lake.
·
Given the depth
limitations, is the Platte a viable habitat for pallid sturgeon? If so, why?
It may be. Small numbers of pallid sturgeon have been captured
in the lower Platte River in the spring and early summer.
Despite its many impacts (water depletions, barriers, power peaking, rapid
temperature fluctuations) it may provide feeding or spawning opportunities. In addition some opportunities for habitat
enhancement and restoration to benefit the pallid sturgeon may be possible in the lower
Platte River that are not feasible on the Missouri River given current constraints on the
system.
·
How important are the
Missouri’s tributaries to the life history of sturgeon?
Not known at this time, but
future monitoring and research will help to determine this.
Temperature:
·
What is the proper water
temperature for pallid sturgeon and other native species?
The exact seasonal temperature profile required by pallid
sturgeon is unknown, but the temperature regime that existed in the pre-regulation river
can be used as a starting point. The pallid
sturgeon is a warm water species with a geographic range than spans from Montana to
Louisiana. The species is adapted to a
riverine environment that begins warming in the spring to a temperature suitable for
spawning between March and July. Spawning is
thought to occur near 60-70° F. Water temperature peaks in mid to late summer and
declines to a winter low. Of course this
seasonal temperature profile is coupled closely to regional precipitation and the river’s
hydrograph. Evidence from other sturgeon
species suggests that both a favorable temperature profile and an appropriate hydrograph
are necessary for good reproduction and survival of young sturgeon.
·
What is the optimal
temperature range for larval and adult pallid sturgeon?
The optimal temperature ranges for this species and other life stages have not been determined. Pallid sturgeon tolerate very low winter water temperatures approaching 32° F and summer water temperatures often exceed 86° F. The upper lethal temperature limit for this species has not been determined. Spawning is thought to occur somewhere near the range of 60-70° F.
·
Do thermal power plant
discharges pose a threat, particularly in low-water conditions?
Possibly. This is
a facility and site-specific issue. It depends
on the location of the facility with respect to the habitat and biology of the species,
the intake structure and volume, the outlet location and relative volume, and the nature
and extent of the thermal gradient.
·
Would warm water outlets
help pallid sturgeon?
No, there are not
enough of them.
Shovelnose Sturgeon:
·
What are the differences
between pallid and shovelnose sturgeons?
There are numerous differences
between the two species. The pallid sturgeon
grows to a larger size and takes longer to become sexually mature than the shovelnose. It
is often lighter in coloration than shovelnose, though this is not always the case. The pallid sturgeon also can be differentiated from
the shovelnose based upon various characteristics, such as barbell placement and length,
head and rostrum (snout) length, mouth width, the number scutes (bony plates) on its belly
and the number of rays in some of its fins.
Habitat, behavior and life
history studies of the two species have also noted some distinct differences. Pallid sturgeon appear to use deeper habitats with
swifter currents. Adult pallid sturgeon also
prey on other fish, as they grow older, whereas shovelnose sturgeon eat almost exclusively
invertebrates.
Genetic studies of the species
are also underway and scientists are increasing able to differentiate between the two
species based upon genetic tests. The possible
occurrence of hybridization has complicated the development of these tests and no genetic
test is yet 100% reliable. However the genetic
evidence supports the recognition of the two species as distinct and indicates that the
two species have some degree of reproductive isolation.
More genetic and taxonomic work is needed throughout the entire geographic
range of the shovelnose and pallid sturgeon to adequately characterize the diversity that
currently exists within theses species and to quantify the impacts of hybridization.
·
Is the shovelnose
population also declining?
Yes. While the
shovelnose sturgeon is common in some areas, it has been extirpated (eliminated) from
significant portions of its range. The primary
causes of these localized extinctions have been dam construction, impoundment and
irrigation withdrawal. Currently there are
concerns that commercial harvest and domestic caviar production may be causing localized
declines on the lower Missouri and Mississippi Rivers.
·
Can we translate studies
of shovelnose sturgeons to the needs of pallid sturgeon?
Yes, in some cases. The
shovelnose is closely related and shares many biological and ecological attributes with
the pallid sturgeon. However it is clear that
there are significant differences. These
differences may in large measure explain why one species is very rare and listed as
endangered, and the other is not. Researchers
often conduct studies with both species to describe similarities and differences that may
increase our biological understanding and aid in the recovery and management of these
species.
Contaminants:
·
What are the effects of
pesticides and other contaminants on the pallid sturgeon’s lifecycle?
Pollution and degraded water quality have been persistent
problems in most of our nation’s large rivers for the past 150 years. Recent improvements accompanying the treatment of
wastewater, regulation of surface water discharges and pesticide registration have been
dramatic. Prior to these improvements many
aquatic species were impacted. The historical
impact of pollution on pallid sturgeon is largely unknown.
Because pallid sturgeon are large long-lived, late-maturing fishes that prey
on other fishes, they are more likely to be affected by contaminants that accumulate over
time or are magnified through the food chain. Currently
several states have fish consumption advisories on shovelnose sturgeon flesh and eggs due
to elevated levels of chlordane and PCBs.
Recent concerns have surfaced over a class of contaminants
known as endocrine disruptors that may cause abnormalities in gonad development,
disruption of reproductive maturation, and impaired reproductive function in many species
of wildlife. For the same reasons listed
above, sturgeon may be particularly susceptible to endocrine disrupting chemicals. Abnormal hermaphroditism (mixed sex individuals)
has been detected in Missouri River sturgeon at relatively high rates, but the causative
agent or and ultimate impacts have not been determined.
· Do excess contaminants in the tributaries cause problems with the spawning of pallid sturgeon?
Unknown at this time.
·
In low-flow situations,
what is the impact of point source discharges, specifically sewage discharges, on the
sturgeon? And what monitoring is being done?
Point source discharges are regulated and monitored through a
number of state and federal programs and permitting processes. Sewage discharges may introduce high levels of
nutrients and may contribute to reduced dissolved oxygen concentrations in the water. In addition, sewage effluent may also include
various contaminants and chemicals that may have toxic or long-term effects on aquatic
organisms. As development in the Missouri
River Basin increases the amount of wastewater and contaminants entering the rivers is
expected to increase. The impact of any single
point source or class of point source discharges on pallid sturgeon has not been examined.
Predation:
· What is the impact of non-native sport fish, especially rainbow trout, on pallid sturgeon?
The
direct effective of non-native species on pallid sturgeon is largely unknown. The net
effect of any species introduction on the pallid sturgeon may be either positive or
negative. Introduced species may compete for
limited food or habitat resources, or may prey directly on eggs, larvae or juveniles of
native species. Conversely, sturgeon may
themselves prey upon non-native species.
The
detrimental impacts of non-native species are often exacerbated by other factors, most
often habitat alteration or degradation. As
habitat conditions degrade or change, native species are less equipped to withstand
competition or predation by new species, and native populations often decline. In many biological communities, the resiliency of
native species and their ability to persist in the presence of introduced species is
directly related to habitat quality.
There is no indication that
rainbow trout, specifically, are having an adverse impact on pallid sturgeon. While it is a non-native species in many locales,
the rainbow trout is a coldwater species that inhabits areas with clear water. Areas that support significant populations of trout
or salmon (such as the tail waters of large dams) likely do not provide habitat conditions
suitable for pallid sturgeon. In this
instance, the primary impact to pallid sturgeon is habitat alteration.
·
What are the impacts of
predation on the pallid from non-native species?
The impact of predation on sturgeon populations is unknown, but is
likely substantial. Early life stages of
sturgeon (eggs, larvae and juveniles) experience very high mortality in the wild. Much of this mortality may be due to predation. Whether or not non-native species contribute
significant additional mortality is unknown. Some
research has been completed with no evidence to indicate that non-native species are
consuming sturgeon. Certainly more research
will be conducted. However, this research
should also examine the influence of altered or degraded habitat conditions on the
susceptibility of sturgeon to predation. Reduced
turbidity, altered water velocities, or lack of suitable habitat may make sturgeon easier
for native and non-native predators to find and consume.
Recovery Plans/BiOp:
·
What are the specific goals for recovery of
the pallid sturgeon?
The long-term objective of the pallid sturgeon recovery
program is to downlist and delist the species through protection, habitat restoration, and
propagation activities by 2040. Downlisting
and delisting would be initiated when pallid sturgeon are reproducing naturally and
populations are self-sustaining within designated river reaches. Under the current preliminary criteria
downlisting may be considered when (1) a population structure with at least 10 percent
sexually mature females occurring within each recovery—priority management area has
been achieved, and when (2) sufficient population numbers are present to maintain
stability. However, these preliminary criteria
may be modified or expanded in the future.
The Pallid Sturgeon Recovery Plan can be obtained in its entirety
at the following URL: http://ecos.fws.gov/docs/recovery_plans/1993/931107.pdf
·
What is the recovery goal
in terms of shallow water habitat?
The Recovery Plan has no prescriptive goal or target for the
amount of habitat restoration required. The
recovery plan broadly seeks to provide benefits to the pallid sturgeon through the
restoration of “habitats and functions of the Missouri and Mississippi River
ecosystems while minimizing impacts on other uses of the rivers.” This includes enhancing habitat diversity,
emulating pre-regulation hydrographs, providing a natural temperature regime, restoring
the sediment transport equilibrium, reintroducing large woody debris, and removing
barriers, or making provisions for passage through barriers to allow free movement of
sturgeon within recovery priority areas.
However, through the Endangered Species Act consultation process
between the U.S. Army Corps of Engineers and the U.S. Fish and Wildlife Service (FWS) on
the operation and maintenance of the Missouri River Projects it was determined that
current operations jeopardize the continued existence of the three endangered species,
including the pallid sturgeon. It was
determined that in order to avoid jeopardizing the existence of these species while
continuing to operate these projects, the Corps must implement a five part Reasonable
and Prudent Alternative. One element of this
Reasonable and Prudent Alternative is the restoration of a portion of the historic habitat
base in riverine sections to benefit the listed birds and fish. A quantitative goal for
this element of 20-30 acres of shallow water habitat per mile in the lower river was set.
It is important to distinguish
between the measures listed in the 2000 Missouri River Biological Opinion and the Pallid
Sturgeon Recovery Plan. The Recovery Plan
seeks to outline the actions necessary to recover and delist the species. The Biological Opinion does not. It attempts only to preclude a federal action (in
this case the operation and maintenance of the Missouri River Projects) from jeopardizing
the continued existence of an endangered species. The Pallid Sturgeon Recovery Plan can be obtained in
its entirety at the following URL: http://ecos.fws.gov/docs/recovery_plans/1993/931107.pdf. The 2000 Biological Opinion document can be located
at the following Internet URL: http://www.nwd-mr.usace.army.mil/mmanual/opinion.html.
Management:
·
Why is commercial fishing
(of sturgeon) still allowed?
The shovelnose sturgeon is listed as neither federally threatened nor endangered. Therefore the States regulate sport and commercial harvest of this species. Many States are considering banning commercial harvest because of the possibility of incidental take of the endangered pallid sturgeon and recent concerns over possible over-exploitation of native sturgeon stocks for the caviar trade. The Pallid Sturgeon Recovery Plan proposes a temporary moratorium on commercial fishing of all sturgeon species. Compliance by all States is necessary to achieve this. The Recovery Plan also encourages States to work with the U.S. Fish and Wildlife Service to determine the impact of sturgeon commercial and sport fishing on pallid sturgeon.
Terns and Plovers:
· Do we need another year like 1997 to maintain the trends in numbers and habitat that we see today?
It would certainly help.
· Are there any mechanical methods being used to manage vegetation on islands and sandbars?
Yes there are. These methods include mowing,
plowing, application of herbicides, and the use of dredge material. These methods do not seem to work as well as using
the natural river processes to scour the vegetation from islands and sandbars.
· Is recovery possible without habitat creation below the unchannelized reaches?
No, whether it is “natural” or not,
additional habitat creation is necessary.
· What is the long-term prognosis for the sandbar habitat for terns and plovers?
Poor without manipulation, excellent
otherwise.
· Why is there habitat (sandbars) that is not used by terns and plovers?
Just because it is not used does not mean it
is not needed.
· Could delta areas of the river be transformed into bird habitat?
Yes.
· Is there a plan to have early successional sandbars?
Yes.
· Who manages artificial sandbars constructed for mitigation purposes?
The Corps manages artificial sandbars created
through the operation of the reservoirs. The
permitee is required to manage sandbar habitat if creation of sandbar habitat is a
condition of a 404 permit.
· Why did plovers seem to respond better than terns to the increase in habitat after 1997?
It is not clear that plovers did respond
better.
· Of the nests that are inundated, how many birds re-nested?
Nests that are destroyed early in the nesting
season often result in birds re-nesting.
· Are there physical characteristics of habitat that cannot be measured? Do we need to develop new tools or techniques?
Major new advances in this area probably are
not needed. There are advancements in biological characteristics.
· How does habitat in one region affect recovery in other regions?
We don’t know, but this will be studied
in the future.
· What beneficial effects are being seen from current fish and wildlife mitigation project sites?
None of the mitigation projects have included tern and
plover habitat to date.
Monitoring and Research:
· Of the fledged birds, is there information on their long-term survivability (are they banded?)
All the captive-reared birds were banded, so
there is data available.
· Has there been an increase in other birds or other predators since changes in the environment, and what impact has that had on terns and plovers?
Yes.
·
What is the extent of
habitat mapping studies on the
Very extensive.
Recovery Plans/BiOp:
· Once recovery goals have been achieved for the tern and plover, what is the long-term plan for maintaining populations?
Predator control, maintaining sandbar
habitat, and other things that will be included in long-term management plans.
· How close are we to de-listing plovers and terns?
Need to maintain populations for 10 years,
then the Service has to evaluate the 5 listing factors.
· Were target recovery levels established knowing the high inter-annual variation in the tern and plover populations?
Yes.
Wintering:
· What are the challenges associated with wintering grounds?
· Where do the birds winter, and what management actions are taken on the wintering grounds to protect the birds?
Plovers winter along the Gulf coast.
General:
·
What are the differences
between the
The differences are largely geographic and
they can inter-breed.
·
What is the correlation of
the graph for the least tern to the total population in the
We know of no such correlation for the least
tern.
ESA Questions:
· How do federal agencies comply with Section 7a (ESA) in consulting with the tribes and what efforts have been made?
Federal agencies are required by Executive
Order to conduct Government-to-Government consultations with the Tribes.
· How does the FWS limit “incidental take” from commercial sturgeon harvest?
· What species takes priority when the needs of several species are in conflict?
Those species that are provided protection
under the Endangered Species Act are given the highest protection.
· What are the interrelationships between different environmental statutory requirements with ESA?
The courts eventually rule on conflicts.
· With intensive attention directed at recovery of two birds and one fish, is attention being given to inadvertent and potentially harmful impacts to other species?
No.
· Is the ESA flawed by not mandating a phase-out of recreation (predator) fish?
No.
· What efforts need to be undertaken to educate the public on ESA & recovery efforts?
The MRBA April 10 forum was a step towards
providing public education in ESA and recovery efforts.
Recovery Plans/BiOp:
· What are the respective roles of the Recovery Plans and the Biological Opinions in meeting recovery goals?
· Who is on the Threatened and Endangered Species Recovery Teams?
State and federal biologists.
· How often do the recovery teams meet?
As needed. Usually about once a year.
· Why does the least tern recovery plan call for meeting population goals for 15 years and the piping plover plan call for 10?
This is probably based on the biological
needs of the species.
· What programs are available for individual landowners to create habitat improvements on their own land?
· When and how do you start the de-listing process?
The Service must be petitioned to begin the de-listing process.
Monitoring and Research:
· Does the Service monitor the progress towards recovery goals?
Yes.
· What specific field studies are being done for the three species?
Many. The
states and the federal agencies are both doing studies.
· Is the international research into species recovery being utilized?
Yes.
· What % of recovery programs in the mountain/plains region have been successful?
· What % of recovery programs in the mountain/plains region have been abandoned?
· Do the agencies have the resources to answer the critical questions?
No they do not.
But there are on-going efforts to obtain more resources.
Philosophical:
· How appropriate are the spring releases for all three of the listed species?
This is largely a political question. From a scientific perspective, the effect of flow
changes cannot be evaluated without trying them. More
research needs to be done on the existing river reaches that currently have various
magnitudes of flow frequencies and duration.
· Can species survive in the system given the current and future reality of it being such a highly altered and regulated system?
Yes, through cooperation of affected parties.
· Can we manage for one species without harming another? (i.e does a spring rise conflict with the nesting period of the birds?)
Yes.
· Does a successful recovery under ESA necessarily result in a “healthier” river overall?
Overall, yes.
·
Would water ownership of
the
No.