U.S. Department of the Interior

U.S. Geological Survey

Circular 1315

A Conceptual Life-History Model for Pallid 

and Shovelnose Sturgeon
Cover Photographs

1 Shovelnose and pallid sturgeon (photograph by A.J. DeLonay, U.S. Geological Survey).

2 Pallid sturgeon (photograph by A.J. DeLonay, U.S. Geological Survey).

3 Missouri River taken from the overlook at Ponca State Park, Ponca, Nebraska (photograph by E.C. Troutt, 

U.S. Geological Survey).

2

3

1
A Conceptual Life-History Model for Pallid 

and Shovelnose Sturgeon

By Mark L. Wildhaber, Aaron J. DeLonay, Diana M. Papoulias, David L. Galat, 

Robert B. Jacobson, Darin G. Simpkins, Patrick J. Braaten, Carl E. Korschgen, 

and Michael J. Mac

Circular 1315

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2007

Reprinted: 2008

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Although this report is in the public domain, permission must be secured from the individual copyright owners to 

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Suggested citation:

Wildhaber, M.L., DeLonay, A.J., Papoulias, D.M., Galat, D.L., Jacobson, R.B., Simpkins, D.G., Braaten, P.J., Korschgen, 

C.E., and Mac, M.J., 2007, A conceptual life-history model for pallid and shovelnose sturgeon: U.S. Geological Survey 

Circular 1315, 18 p.

ISBN 978-1-4113-1905-9
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Purpose and Scope .......................................................................................................................................2

Basis for the Conceptual Life-History Model............................................................................................3

Structure of the Conceptual Life-History Model ......................................................................................3

Processes and Conditions Controlling Life-Stage Transitions ......................................................3

Mature to Pre-Spawning to Spawning Adult...................................................................................5

Spawning Adults with Viable Gametes to Developing Embryos...................................................6

Developing Embryo to Free Embryo...................................................................................................6

Free Embryo to Larval Stage of Exogenous Feeding ......................................................................8

Larval Stage of Exogenous Feeding to Juveniles..........................................................................10

Juvenile to Immature Adult...............................................................................................................11

Population-Forecasting Model.........................................................................................................13

Summary........................................................................................................................................................14

References Cited..........................................................................................................................................14

Figures

1. Factors that may affect reproduction and survival of sturgeons .........................................3

2–9. Charts showing—

2. Conceptual model of Scaphirhynchus sturgeon life history ........................................4

3. Symbols and labels used in submodels of Scaphirhynchus sturgeon 

conceptual model ................................................................................................................5

4. Submodel for the transition from mature to pre-spawning adult in the

Scaphirhynchus sturgeon life-history conceptual model.............................................7

5. Submodel for the transition from spawning adults with viable gametes to

developing embryos in the Scaphirhynchus sturgeon life-history conceptual 

model .....................................................................................................................................8

6. Submodel for the transition from developing embryo to free embryo in the

Scaphirhynchus sturgeon life-history conceptual model.............................................9

7. Submodel for the transition from free embryo to larval stage of exogenous 

feeding in the Scaphirhynchus sturgeon life-history conceptual model .................10

8. Submodel for the transition from larval stage of exogenous feeding to juveniles 

in the Scaphirhynchus sturgeon life-history conceptual model................................11

9. Submodel for the transition from juvenile to immature adult in the 

Scaphirhynchus sturgeon life-history conceptual model...........................................12
iv

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F=(1.8×°C)+32

Multiply By To obtain

Length

millimeter (mm) 0.03937 inch (in.)

Conversion Factors
Abstract

Intensive management of the Missouri and Mississippi 

Rivers has resulted in dramatic physical changes to these rivers. These changes have been implicated as causative agents 

in the decline of pallid sturgeon. The pallid sturgeon, federally 

listed as endangered, is endemic to the turbid waters of the 

Missouri River and the Lower Mississippi River. The sympatric shovelnose sturgeon historically was more common and 

widespread than the pallid sturgeon. Habitat alteration, river 

regulation, pollution, and over-harvest have resulted in the 

now predictable patterns of decline and localized extirpation 

of sturgeon across species and geographic areas. Symptomatic of this generalized pattern of decline is poor reproductive 

success, and low or no recruitment of wild juveniles to the 

adult population. The purpose of this report is to introduce 

a conceptual life-history model of the factors that affect 

reproduction, growth, and survival of shovelnose and pallid 

sturgeons. The conceptual model provided here was developed 

to organize the understanding about the complex life history 

of Scaphirhynchus sturgeons. It was designed to be used for 

communication, planning, and to provide the structure for a 

population-forecasting model. These models are intended to 

be dynamic and responsive to new information and changes 

in river management, thereby providing scientists, stakeholders, and managers with ways to improve understanding of the 

effects of management actions on the ecological requirements 

of Scaphirhynchus sturgeons. As new scientific knowledge 

becomes available, it could be included in the model in many 

ways at various integration levels.

Introduction

Intensive management of the Missouri and Mississippi 

Rivers for purposes of navigation, flood control, and power 

generation has resulted in dramatic physical changes to these 

rivers (Ferrell, 1993; Ferrell, 1996; Galat and Lipkin, 2000). 

Historically, these rivers were characterized by a shifting, 

braided channel with abundant sandbars and accumulations 

of large woody debris. The shifting channel contained a wide 

variety of hydraulic environments that provided diverse habitat 

for many benthic fish species. In the 1800’s, training into a 

fast, deep, and single-thread channel to support navigation 

was begun. Wing dikes concentrated flow, and revetments and 

levees kept the channels in place and disconnected it from the 

flood plains. Reservoir regulation substantially changed the 

annual hydrograph, sediment load, and temperature regime 

of the Missouri and Mississippi Rivers. As in other large 

flood-plain rivers, agricultural pesticides, nutrient runoff, 

and increasing discharge of domestic and industrial effluents 

affect the aquatic biota and the ecological health of the Missouri River Basin (Tockner and Stanford, 2000). Proliferation of introduced and non-indigenous species has further 

threatened to diminish the ecological integrity of the river 

ecosystem (Pflieger, 1997; Galat and others, 2005). Together 

these changes in flow, channel morphology, water quality, and 

biota have been implicated as causative agents in the dramatic 

declines in native river fishes and their resource base in general, and with the decline of pallid sturgeon (Scaphirhynchus 

albus) in particular (Funk and Robinson, 1974; Hesse and others, 1989; Hesse and Sheets, 1993; Galat and others, 2005).

Since 1989, Missouri River Basin management agencies have been involved in revising the U.S. Army Corps of 

Engineers’ operating plan for the Missouri River mainstem 

reservoirs, and consulting on the implementation of the navigation and bank stabilization projects (U.S. Fish and Wildlife 

Service, 2000, 2003). As a result, several significant management activities have been initiated to benefit the endangered 

pallid sturgeon in the Lower Missouri River, including propagation efforts to supplement wild populations, physical habitat 

rehabilitation projects to improve riverine habitat conditions, 

and planned experimental reservoir releases to promote reproduction and increased survival of juvenile pallid sturgeon.

The pallid sturgeon is endemic to the turbid waters of 

the Missouri River and the Lower Mississippi River, from 

the mouth of the Missouri River downstream to New Orleans 

(Mayden and Kuhajda, 1997). The pallid sturgeon is rare 

throughout the Missouri River Basin and was federally listed 

as an endangered species in 1990 (Dryer and Sandvol, 1993). 

In the Lower Missouri River, no reliable pallid sturgeon 

population estimates exist; however, based on recent capture 

rates and the incidence of occurrence, managers estimate that 

A Conceptual Life-History Model for Pallid and 

Shovelnose Sturgeon

By Mark L. Wildhaber, Aaron J. DeLonay, Diana M. Papoulias, David L. Galat, Robert B. Jacobson, 

Darin G. Simpkins, Patrick J. Braaten, Carl E. Korschgen, and Michael J. Mac
only several thousand individuals remain in the Lower Missouri River (Duffy and others, 1996; U.S. Fish and Wildlife 

Service, 2000). Less than 200 wild pallid sturgeon are estimated to exist in the Upper Missouri River (Kapuscinski, 

2002). Hybridization of pallid sturgeon with the sympatric and 

closely related shovelnose sturgeon (S. platorynchus) has been 

documented and identified as a potentially serious threat to the 

persistence of the species (Carlson and others, 1985; Keenlyne 

and others, 1994; Wills and others, 2002).

The shovelnose sturgeon historically was more common and widespread than the pallid sturgeon (Becker, 1983). 

Before anthropogenic disturbances, distribution of the species 

included the Mississippi, Missouri, Ohio, and Rio Grande 

Rivers and their tributaries. Similar to the pallid sturgeon, the 

shovelnose sturgeon is declining and has been extirpated or 

is at risk of extirpation from considerable parts of its native 

range (June, 1977; Moos, 1978; Keenlyne, 1997; Quist and 

others, 2002). Of the 24 states that comprise the historical 

range of the shovelnose sturgeon, five list the species as extirpated, and eight list the species as either imperiled or vulnerable (Hesse and Carreirov, 1997; NatureServe, 2005). The 

World Conservation Union listed the species as “vulnerable” 

(Surprenaut, 2004). The “vulnerable” assessment reflects a 

past reduction in species range of 30 percent, and anticipates 

a further 30 percent reduction in population within the next 

10 years, or three generations. Despite these trends in population decline, the shovelnose sturgeon is still harvested commercially or as a sport fish in nine states. In fact, commercial 

demand for the shovelnose sturgeon has increased because of 

the increasing demand for caviar exacerbated by the collapse 

of sturgeon fisheries in Europe and Asia (Williamson, 2003). 

The closely related, but allopatric shovelnose species from 

the Mobile River Basin, the Alabama sturgeon (S. suttkusi) is 

extremely rare and close to extinction (Mayden and Kuhajda, 

1996). 

The decline of sturgeon populations is a global phenomenon (Birstein, 1993). Habitat alteration, river regulation, pollution, and over-harvest have resulted in the now predictable 

patterns of decline and localized extirpation of sturgeon across 

species and geographic areas. Symptomatic of this generalized pattern of decline is poor reproductive success and low, 

or no, recruitment of wild juveniles to the adult population. 

Evidence from various monitoring efforts suggests that recruitment of wild pallid sturgeon to the adult population is limited 

or non-existent throughout most of the Missouri River (U.S. 

Fish and Wildlife Service, 2000; Jordan, 2006). Some reproduction (larvae were collected and verified) of the endangered 

pallid sturgeon has been documented in the Lower Missouri 

River (Louise Mauldin, U.S. Fish and Wildlife Service, oral 

commun., 2004; Kerry Reeves, University of Missouri, oral 

commun., 2007) and in the Middle Mississippi River (Hrabik, 

2007). Collections of young-of-year pallid sturgeon in the 

upper Missouri River Basin (Braaten and Fuller, 2005) provide 

evidence that pallid sturgeon may be spawning in the Yellowstone River or Missouri River below Fort Peck Dam, although 

juveniles have not been captured there for decades (Jordan, 

2006). In contrast, the closely-related shovelnose sturgeon 

is reproducing, and recruitment is occurring in the Missouri 

River (Moos, 1978; Keenlyne, 1997).

Despite evidence of substantial decline, the shovelnose 

sturgeon remains relatively common in the Lower Missouri 

and Mississippi Rivers (Becker, 1983). The persistence and 

resiliency of the shovelnose sturgeon in comparison to the 

pallid sturgeon may be partly because of its earlier maturity, 

lower trophic status, and adaptability to a broader range of 

environmental conditions. The shovelnose sturgeon matures 

earlier and attains a smaller maximum size than the pallid 

sturgeon (Keenlyne and Jenkins, 1993). The smaller shovelnose sturgeon primarily subsists on invertebrates, whereas the 

larger pallid sturgeon becomes piscivorous relatively early in 

life (Modde and Schmulbach, 1977; Keenlyne, 1997; Carlson 

and others, 1985). Pallid sturgeon also are highly adapted to 

large, turbid, riverine environments, and are believed to not 

use tributaries or clear-water riverine habitats that are frequented by shovelnose sturgeon (Mayden and Kuhajda, 1997). 

Despite these differences, the morphological, physiological, 

and genetic similarity between the taxa clearly indicates that 

these two sympatric species are closely related (Bailey and 

Cross, 1954; Campton and others, 2000; Simons and others, 

2001; Snyder, 2002).

This report and the model developed within focus on the 

pallid and shovelnose sturgeon, hereafter referred to as Scaphirhynchus in this report.

Purpose and Scope

The purpose of this report is to introduce a conceptual 

life-history model (hereafter referred to as model in this 

report) of the factors that affect reproduction, growth, and survival of Scaphirhynchus sturgeons. The model is intended as 

a tool to organize, visualize, and prioritize hypotheses relating 

to how the complex life history of Scaphirhynchus sturgeons 

relates to the spatial and temporal complexity of large interjurisdictional rivers. The model and its primary components 

are described, with some emphasis on specific components to 

illustrate its hierarchical nature.

The model was developed to provide a framework to help 

guide scientific approaches needed for a better understanding 

of the ecological requirements of the pallid sturgeon. Although 

there is some emphasis on delineating how Scaphirhynchus

sturgeon ecology relates to river management variables, it also 

attempts to include all conceivable conditions and processes 

that might affect Scaphirhynchus sturgeon ecology to make it 

applicable to a wide range of research hypotheses. Within this 

context, pallid sturgeon ecological needs can be explored as 

they relate to species recovery efforts, as well as the broader 

aspects of river-system management. It was designed to be 

adaptable for communication and as a science planning tool. 

The model is intended to be dynamic and responsive to new 

information and changes in river management, thereby provid2 A Conceptual Life-History Model for Pallid and Shovelnose Sturgeon
ing stakeholders, managers, and researchers with an improved 

understanding of tradeoffs among management alternatives.

Basis for the Conceptual Life-History 

Model

Multiple abiotic and biotic factors have been proposed as 

critical for maintaining healthy populations of Scaphirhynchus

sturgeons (fig. 1). Among the abiotic factors, physical factors 

(for example, hydrologic cues, temperature, turbidity, depth, 

and velocity) and features of in-channel habitat are believed 

to be important (U.S. Fish and Wildlife Service, 2000, 2003). 

Biotic (nutrition, competition, predation, productivity) and 

abiotic chemical (for example, water quality) factors also are 

important contributors to reproductive success and survival. 

An understanding of how all these factors alone and combined affect recruitment of Scaphirhynchus to each life stage 

is needed to provide rigorous and defensible information for 

use by all stakeholders to resolve issues surrounding pallid 

sturgeon recovery actions. This need was the motivation for 

development of the conceptual life-history model.

This model also was designed to provide the framework 

for a quantitative population forecasting model to predict 

future population size and distribution of pallid and shovelnose sturgeon on the Missouri River. The population forecasting modeling effort will synthesize extant and anticipated data 

from research studies and the Missouri River Recovery fish 

monitoring programs (Pallid Sturgeon Population Assessment 

Program, Habitat Assessment and Monitoring Program, and 

Bank Stabilization and Navigation Project Mitigation Program) to describe population status, probable bottlenecks, and 

additional information needs.

Structure of the Conceptual LifeHistory Model

The conceptual life-history model for Scaphirhynchus

sturgeon is consistent with—and could be incorporated as 

a submodel within—a system-wide, adaptive ecosystem 

management model for the Missouri and/or Mississippi River 

Basins. Such a comprehensive ecosystem model could include 

similar life-history submodels for other key species, such as 

the piping plover (Charadrius melodus) and least tern (Sternula antillarum), and/or it could incorporate socio-economic 

benefits.

The life history of sturgeon (fig. 2) is divided into distinct 

life stages (boxes) with transitions from one life stage to the 

next (diamonds). The direction of sturgeon development is 

identified by arrows. Numerous conditions and processes 

determine whether or not individual sturgeon complete the 

transition from one life-stage to the next (ovals). In refining the model, lines of varying thickness could be drawn to 

indicate the importance of each connection among conditions 

and processes.

The spatial extent of the model is intended to capture 

scales relevant to individuals and the population. Because 

sturgeon in large rivers may move long distances during the 

course of their lives, the model illustrates the potential for sturgeon to use different parts of the river mainstem, or its tributaries, in specific ways during different life stages. The model 

also can accommodate fine-scale, three-dimensional models of 

habitat use and availability, and fish behavior during specific 

life stages, nested within the broader geographic extent. The 

model is designed to be dynamic, so it can be refined as new 

information is attained. Consequently, other important conditions, processes, and connections may be present that have not 

yet been identified in the current model, but will need to be 

incorporated in the future as more information is collected on 

the ecology of Scaphirhynchus sturgeon.

Our current (2007) state of knowledge is insufficient to 

prioritize the relative importance of the various connections to 

reproduction and survival. The model is intended as a starting 

framework to build the necessary scientific foundation. We 

anticipate that the conceptual model will be refined iteratively as scientists work collaboratively to share knowledge. 

It also may be useful to the broader community of Missouri 

River managers, stakeholders, and scientists to ensure that 

the Scaphirhynchus sturgeon framework is consistent with 

conceptual models of other priority management species, and 

with a comprehensive, ecosystem-level adaptive management 

model.

Processes and Conditions Controlling Life-Stage 

Transitions

The following section discusses the conceptual model 

(fig. 2) by life-stage transition. For each life-stage transition, a 

Reproduction and Survival of

Pallid and Shovelnose Sturgeon

Channel Morphology

Connectivity

Sediment

Water Quality

Temperature

Exploitation

Non-natives Genetics

Contaminants

Disease

Flow

Figure 1. Factors that may affect reproduction and survival of 

sturgeons.

Structure of the Conceptual Life-History Model 3
submodel is presented based on a general understanding of the 

biological transition. For each transition, a list of hypothesized 

processes and conditions (fig. 3) that may affect the probability of a successful transition is presented.

The two primary categories of processes identified as 

affecting the transition between life stages for Scaphirhynchus sturgeons were direct mortality through human activities and/or non-human predators and rate-affecting processes 

that affect survival, growth, and development (especially of 

functionally reproductive individuals) (white rectangles in fig. 

3). Human activities identified as contributing to direct mortality include human predation in the form of fishing, dredging, 

boating, and entrainment by water intakes (represented by 

red rectangles in fig. 3). The groups of predators identified as 

contributing to direct mortality include native and non-native 

fishes, and non-fish predators (for example, macroinvertebrates, birds, also represented by red rectangles in fig. 3). 

The rate-affecting processes identified as affecting survival, 

growth, and development include habitat, contaminants, disease, prey availability, and competition (represented by white 

wavy rectangles in fig. 3). Competitors are represented by the 

same groups identified as predators, but not necessarily the 

same species. The condition factors considered as determinants of the importance of rate-affecting processes on survival, 

growth, and development include biotic (represented by green 

rectangles in fig. 3) and abiotic (represented by blue rectangles 

in fig. 3) factors. The biotic conditions identified include the 

food web and the nutrients cycled within it, competition, and 

Upstream

Downstream

Stocking

Spawn

Incubate

Drift

Over-winter

Drift Drift

Migrate

Migrate

Grow Grow

Grow

Grow

Grow

Grow Grow

Transition

probability

Transition

probability

Transition

probability

Transition

probability

Transition

probability

Transition

probability

Transition

probability

Transition

probability

Transition

probability

Transition

probability

Transition

probability

Larval stage of

exogenous

feeding

Immature

adults

Conditions 

and 

processes

Conditions 

and 

processes

Conditions 

and 

processes

Conditions 

and 

processes

Conditions 

and 

processes

Conditions 

and 

processes

Conditions 

and 

processes

Conditions and processes

Conditions 

and 

processes

Conditions 

and 

processes

Conditions 

and 

processes

Developing

embryos

Free embryo

Juveniles

Mature adults

Pre-spawning

adults

Non-spawning

adults Gametes

Gametes

Spawning

adults

Indicates distinct life stages

Indicates transition from one 

 life stage to the next

Determines whether individual sturgeon 

 complete the transition from one life stage 

 to the next

Indicates direction of sturgeon development

EXPLANATION

Figure 2. Conceptual model of Scaphirhynchus sturgeon life history.

4 A Conceptual Life-History Model for Pallid and Shovelnose Sturgeon
Human

activities

Human

predation:

Fishing

Human

predation:

Fishing

Dredging

Boats

Entrainment/

intakes

Non-native

fishes

Native fishes

Other than

fishes

Non-human

predation

Condition factors

Disease

Disease

Habitat

Prey availability

Competition

Contaminants

Development

and behavior

Flow

Channel

engineering

Reservoir

operation

Fish origin

Non-native

fishes

Native fishes

Other than

fishes

Con-specifics

Nutrients

food web

Hydraulic

habitat

Water

quality

Channel

morphology

Sediment

Sediment

Temperature

Light

Hydraulic

habitat

Connection between model components

EXPLANATION

Contributor to direct mortality 

Rate-affecting process affecting survival, 

growth, and development

Nutrients

food web

Biotic condition factor affecting survival, 

 growth, and development 

Abiotic condition factor affecting survival, 

 growth, and development 

genetic origin of the sturgeon. The abiotic conditions identified include light, temperature, sediment, water quality, and 

hydraulic habitat. Hydraulic habitat is defined as the result of 

the flow and channel morphology, both of which are affected 

directly by management.

For the various life-stage submodels, the processes and 

conditions identified are similar. The consistency among 

submodels is because of the general nature of the categories 

identified, and the fact that each submodel represents the 

same genus. As the conceptual model is refined, it is likely 

that submodels will be altered to reflect dominance of different processes for different life stages. Variations of the model 

could be developed for different geographic areas or pallid 

sturgeon management units.

Mature to Pre-Spawning to Spawning Adult

Existing evidence suggests that there is minimal to no 

recruitment of young pallid sturgeon to the adult population 

throughout the Missouri River Basin (U.S. Fish and Wildlife 

Service, 2000; Jordan, 2006). A suggested cause for recruitment 

failure is the lack of successful reproduction because of absent 

or improper environmental cues (Quist and others, 2004).

The timing of spawning for fish that spawn seasonally 

generally is believed to have evolved in synchrony with the 

seasonal hydrologic and environmental conditions that provide 

the best possible chance of survival for offspring (Balon, 1975; 

Munro and others, 1990). Most North American sturgeon 

spawn between the spring equinox and summer solstice, 

with a spawning run peak often coinciding with the annual 

peak flow (Cech and Doroshov, 2004). Historically, North 

American sturgeon have been reported to spawn from spring 

to mid-summer, depending on latitude and water temperature [lake sturgeon (Acipenser fulvescens), Eddy and Surber, 

1947; pallid sturgeon, Forbes and Richardson, 1920; shovelnose sturgeon, Christenson, 1975; green sturgeon (Acipenser 

medirostris), Van Eenennam and others, 2005; shortnose 

sturgeon (Acipenser brevirostrum), Taubert, 1980; Atlantic 

sturgeon (Acipenser oxyrhynchus), Van Enennaam and others, 

1996; gulf sturgeon (Acipenser oxyrhynchus desotoi), Fox and 

others, 2000]. During the spawning season, specific environmental cues can trigger or be associated with the physiological 

changes in the fish that results in spawning activity: migration, 

aggregation, courtship, ovulation, oviposition, and fertilization 

(Rankin and others, 1983). Although the biochemical, physiological, and behavioral events generally are synchronized, they 

Figure 3. Symbols and labels used in submodels of Scaphirhynchus sturgeon conceptual model. 

Structure of the Conceptual Life-History Model 5
can become decoupled and the result is unsuccessful spawning 

(Dettlaff and others, 1993).

The effect of hydrology on spawning has not been 

described for shovelnose or pallid sturgeon, but fishery biologists speculate that spawning runs are similarly dependent 

on river flow (Becker, 1983; Keenlyne and Jenkins, 1993; 

U.S. Fish and Wildlife Service, 2000). Migrations of shovelnose sturgeon into smaller streams, presumably for spawning, have been reported when sufficient water is available 

(Becker, 1983); however, similar use of small tributaries 

by pallid sturgeon has not been documented. The spawning 

behavior sequence from migration and aggregation at the 

spawning site through egg deposition has not been documented for the shovelnose or pallid sturgeon. The timing, 

periodicity, and location of spawning events in relation to the 

substrate and overlying water conditions (temperature, turbidity, flow, and velocity) also are unknown. This information is critical when determining how to improve availability 

of optimal spawning habitat and by designing experimental 

flows intended to promote reproduction and survival of 

young sturgeon.

Spawning areas of other North American sturgeon species most often are characterized by coarse or hard substrates. 

White sturgeon (Acipenser transmontanus, Scott and Crossman, 1973; Parsley and others, 2002); green sturgeon (A. 

medirostris, Houston, 1988); shortnose sturgeon (A. brevirostrum, Taubert, 1980; Buckley and Kynard, 1985); Atlantic 

sturgeon (A. oxyrinchus oxyrinchus, Scott and Crossman, 

1973); gulf sturgeon (A. oxyrinchus desotoi, Fox and others, 

2000); and lake sturgeon (A. fulvescens, Scott and Crossman, 

1973; LaHaye and others, 1992; Bruch and Binkowski, 2002) 

all spawn primarily over gravel, cobble, boulder or bedrock. 

Limited data exist about the substrate preferences of spawning 

pallid and shovelnose sturgeon. Pallid and shovelnose sturgeon 

are assumed to spawn in river current over coarse substrate in, 

or adjacent to, the main river channel (Becker, 1983; Mayden 

and Kuhajda, 1997). Eggs of most sturgeon species are broadcast over spawning areas, become adhesive soon after release, 

and attach to the substrate until hatch (Breder and Rosen, 

1966).

Sturgeons differ from most teleosts by their late puberty 

and biennial or longer ovarian cycles (Dettlaff and others, 

1993). In fishes, gametogenesis and reproduction are controlled primarily by a number of different hormones (Sullivan and others, 1997). Likewise, these hormones are in turn 

modulated by environmental and biological stimuli (Rosenblum and others, 1987). Thus, the maturation of gametes and 

their release is the end result of a cascade of physiological 

events partially under endogenous biological controls, but also 

controlled by environmental conditions (Dettlaff and others, 

1993; fig. 4).

As with many temperate species, sturgeon reproduction follows seasonal cycles (Cech and Doroshov, 2004). It 

is widely believed that the pineal organ, through synthesis 

of melatonin by its photoreceptors, triggers and perhaps 

synchronizes the biochemical, physiological, and behavioral aspects of reproduction in fishes (Rankin and others, 

1983). In addition to photoperiod, reproduction in sturgeon 

is controlled by water temperature (Dettlaff and others, 

1993). Most of the enzymatic biochemical processes during 

gametogenesis and gamete release are temperature sensitive. 

In addition to these variables, other environmental conditions that may be important in gamete maturation and release 

include substrate, flow, turbidity, numbers of fish present, behavior of conspecifics, and presence of pheromones 

(Rankin and others, 1983).

A similar set of conditions and processes that determine 

the probability of a sturgeon transitioning from a mature adult 

to pre-spawning adult (fig. 4) also determine the probability of 

whether or not a pre-spawning adult spawns, and whether or 

not the non-spawners and spawners successfully survive and 

transition back into the pool of adult sturgeon to spawn again 

(figs. 2 and 4). Although the conditions and processes that 

regulate these transitions may be similar, the importance of 

each probably is different for each transition.

Factors that may play a role in limiting spawning activity 

for sturgeon could include non-synchronized hydrology, temperature, migration impediments, lack of spawning substrate, 

inadequate numbers of reproductive adults, hybridization with 

closely related sympatric species, predation, and contaminants. 

Unfortunately, the exact spawning location and the relative 

suitability of spawning conditions for these sturgeon species 

are not known. In addition, spawning behavior of both species 

is not well documented, and scientists have only begun to 

describe the reproductive physiology (Wildhaber and others, 

2005, 2006).

Spawning Adults with Viable Gametes to 

Developing Embryos

The production of embryos that can develop normally 

and hatch requires conditions suitable for egg fertilization 

and minimization of direct loss of eggs (fig. 5). Because this 

life-stage transition includes spawning adults at the point of 

release of gametes and eggs at fertilization, the processes and 

conditions critical to it are a combination of those critical 

during the previous reproductive stage and the developing 

embryo to free embryo life-stage transitions. Successful 

transition through this stage is dependent on healthy viable 

gametes and environmental conditions, especially temperature 

and the presence or absence of egg predators (Dettlaff and 

others, 1993).

Developing Embryo to Free Embryo

Early life stages of riverine fishes tend to be the most 

sensitive to environmental stressors (Scheimer and others, 

2001). Fluctuations in water temperature, reduced oxygen, 

poor egg quality, and contaminant exposure are known to 

result in abnormal development and high mortality in this 

life stage of sturgeon (Dettlaff and others, 1993; fig. 6). 

6 A Conceptual Life-History Model for Pallid and Shovelnose Sturgeon
Temperature and dissolved oxygen are primary environmental factors on the rate of embryo development (Jobling, 

1995). Oxygen requirements of eggs generally increase with 

development, being greatest at hatch. Adhesive sturgeon 

eggs may be susceptible to smothering by fine particulates 

in an extremely turbid environment. Maternal contribution to 

the egg determines the quality of the nutritional reserves in 

the egg, and ambient temperature and oxygen determine the 

rate at which the yolk nutrition is used (Dettlaff and others, 

1993). Sturgeon embryos must have the necessary nutritional 

sources for complete development, but also have sufficient 

yolk reserves beyond hatch until exogenous feeding begins. 

Chemical contaminants could be of concern in the large rivers used by Scaphyrinchus sturgeon (Ruelle and Keenlyne, 

1993; Harsbarger and others, 2000). Early life stages generally are most sensitive to contaminants with exposure occurring during maternal yolk deposition and/or during incubation through contact with water or sediments. Although 

shovelnose and pallid sturgeon have been successfully reared 

in captivity, few data exist on their tolerance levels to speFlow

Human

predation:

Fishing

Dredging

Boats

Entrainment/

intakes

Mature adults Pre-spawning adults Transition

probability

Human

activities

Light

Fish origin

Con-specifics

Nutrients

food web

Water

quality

Channel

morphology

Sediment

Temperature

Reservoir

operation

Channel

engineering Contaminants

Disease

Habitat

Prey availability

Development

and behavior

Competition

Non-native

fishes

Native 

fishes

Other than

fishes

Hydraulic

habitat

Human

predation:

Fishing

Disease Sediment

Connection between model components

EXPLANATION

Contributor to direct mortality 

Rate-affecting process affecting survival, 

growth, and development

Nutrients

food web

Biotic condition factor affecting survival,

 growth, and development

Abiotic condition factor affecting survival, 

 growth, and development

Figure 4. Submodel for the transition from mature to pre-spawning adult in the Scaphirhynchus sturgeon life-history conceptual 

model.

Structure of the Conceptual Life-History Model 7
cific environmental stressors. Given the documented waterquality changes reported for many locations along the Lower 

Missouri River (Galat and others, 2001; Hesse and others, 

1989), it is possible that a bottleneck to recruitment will occur 

at this stage of sturgeon life history.

Free Embryo to Larval Stage of Exogenous 

Feeding

Limited spawning success and recruitment could be 

bottlenecks to self sustaining pallid sturgeon populations. 

The larval stage often functions as a recruitment bottleneck 

for fish because of decreased mobility and sensory ability, 

and increased vulnerability to anthropogenic environmental alteration (Scheidegger and Bain, 1995; Humphries 

and others, 2002). Although documentation of spawning 

by pallid sturgeon is a critical first step towards assessing population status and recovery, successful spawning 

does not ensure successful recruitment to the juvenile or 

adult life stages; rather, biotic and abiotic factors operating 

during the post-hatch life stages may establish recruitment 

bottlenecks that cause high mortality during the posthatch life stage (Dettlaff and others 1993; fig. 7). Limited 

numbers of larval sturgeon are collected from the Mississippi and Missouri Rivers (Louise Mauldin, U.S. Fish and 

Wildlife Service, oral commun., 2004; Kerry Reeves, University of Missouri, oral commun., 2007; Hrabik, 2007). 

This suggests one or more of the following factors may be 

responsible: lack of successful spawning, low recruitment, 

high mortality, ineffective sampling methods, inadequate 

sampling of drift and settling locations, or rapid dispersal 

Human

predation:

Fishing

Dredging

Boats

Entrainment/

intakes

Native 

fishes

Other than

fishes

Non-native

fishes

Flow

Human

activities

Water

quality

Channel

morphology

Sediment

Temperature

Reservoir

operation

Channel

engineering

Light

Habitat

Eggs released

Non-human

predation

Spawning adults with

viable gametes

Transition

probability Developing embryos

Hydraulic

habitat

Human

predation:

Fishing

Disease Sediment

Connection between model components

EXPLANATION

Contributor to direct mortality 

Rate-affecting process affecting survival, 

growth, and development

Nutrients

food web

Biotic condition factor affecting survival,

 growth, and development

Abiotic condition factor affecting survival, 

 growth, and development

Figure 5. Submodel for the transition from spawning adults with viable gametes to developing embryos in the Scaphirhynchus

sturgeon life-history conceptual model.

8 A Conceptual Life-History Model for Pallid and Shovelnose Sturgeon
and washout of sturgeon larvae in the Missouri and Mississippi Rivers. Given the sensitivity of the post-hatch life 

stage to mortality, it is important to identify determinants 

of post-hatch survival in pallid sturgeon.

Few data are available on the post-hatch life stage 

of pallid and shovelnose sturgeon. Post-hatch life stage 

spans from hatching to the initiation of feeding (hereafter 

referred to as post-hatch larvae in this report). Larval sturgeon raised at 17–18 o

C (degrees Celsius) initiate feeding 

at around 10 days (Dettlaff and others, 1993). Initiation 

of feeding probably would occur before day 10 at warmer 

water temperatures. Pallid sturgeon larvae in hatcheries 

initiate feeding between days 4 and 6 post-hatch (Herb 

Bollig, U.S. Fish and Wildlife Service, oral commun., 

2006). In natural settings, shovelnose sturgeon initiate 

exogenous feeding at about 16 mm (millimeters) long, and 

feed on dipterans and emphemeropterans (Braaten and 

others, 2007). After hatching, larval pallid and shovelnose sturgeon in laboratory studies drift for up to 13 days 

(Kynard and others, 2002). The prolonged drift period of 

larval sturgeon necessitates a similarly long stretch of freeflowing water to complete the ontogenetic drift cycle. Larvae are suspected to be intolerant of sediments that deposit 

in river-reservoir transition zones; therefore, a recruitment 

bottleneck for sturgeon in riverine reaches terminated by a 

reservoir may be related to insufficient length of free-flowing water. Initiation of feeding on or about day 10, coupled 

with the finding that sturgeon start using benthic habitats 

on or about day 8, indicates occupation of benthic habitats 

is food related (Dettlaff and others, 1993).

Dredging

Boats

Flow

Fish origin

Water

quality

Channel

morphology

Sediment

Temperature

Reservoir

operation

Channel

engineering

Disease

Habitat

Embryo

development

Non-human

predation

Light

Contaminants

Non-native

fishes

Native

fishes

Other than

fishes

Human

activities

Developing

embryos

Free

embryo

Transition

probability

Hydraulic

habitat

Human

predation:

Fishing

Disease Sediment

Connection between model components

EXPLANATION

Contributor to direct mortality 

Rate-affecting process affecting survival, 

growth, and development

Nutrients

food web

Biotic condition factor affecting survival,

 growth, and development

Abiotic condition factor affecting survival, 

 growth, and development

Figure 6. Submodel for the transition from developing embryo to free embryo in the Scaphirhynchus sturgeon life-history 

conceptual model.

Structure of the Conceptual Life-History Model 9
Larval Stage of Exogenous Feeding to Juveniles

Population viability of Scaphirhynchus sturgeons through 

the larval feeding stage hinges on elucidating the primary 

natural and anthropogenic factors that contribute to survival 

during this period (fig. 8). The stage when larval fish begin 

feeding often is called the “critical period” because they 

are extremely susceptible to mortality if food of the proper 

size and nutritional value is not available within a short time 

(Gisbert and Williot, 1997; Deng and others, 2003; Gisbert 

and Doroshov, 2003). Lack of food during the transition from 

endogenous to exogenous feeding has deleterious effects on 

the sturgeon digestive tract (Gisbert and Doroshov, 2003) that 

may diminish growth and survival (Gisbert and Williot, 1997; 

Gisbert and Doroshov, 2003). Similarly, restricted availability 

and limited intake of food during the first feeding life stage 

may suppress growth (Deng and others, 2003).

Planktonic larvae must be transported by river currents to 

appropriate habitats where nutritional food is abundant and environmental conditions are benign. Longitudinal fragmentation by 

reservoirs, temperature reductions below dams, channelization, 

and bank stabilization collectively may have altered developmental rates and natural drift patterns, increased transport distances, 

and reduced in-channel retention and food production.

Predation and competition also must be low for larvae to 

survive to the juvenile life stage. Because the feeding larval 

Entrainment/

intakes

Fish origin

Human

activities

Water

quality

Temperature

Disease

Contaminants

Habitat

Prey availability

Development

and behavior

Non-human

predation

Flow

Free embryo Larval stage of

exogenous feeding

Transition

probability

Dredging

Boats Channel

morphology

Sediment

Reservoir

operation

Channel

engineering

Competition

Non-native

fishes

Native

fishes

Other than

fishes Non-native

fishes

Native

fishes

Other than

fishes

Light

Hydraulic

habitat

Human

predation:

Fishing

Disease Sediment

Connection between model components

EXPLANATION

Contributor to direct mortality 

Rate-affecting process affecting survival, 

growth, and development

Nutrients

food web

Biotic condition factor affecting survival,

 growth, and development

Abiotic condition factor affecting survival, 

 growth, and development

Figure 7. Submodel for the transition from free embryo to larval stage of exogenous feeding in the Scaphirhynchus sturgeon lifehistory conceptual model.

10 A Conceptual Life-History Model for Pallid and Shovelnose Sturgeon
sturgeon are small, they are particularly susceptible to mortality from predation. The Lower Missouri River water clarity 

has increased since impoundment; which may have increased 

predation risk to small sturgeons that historically relied on the 

river’s high turbidity as cover from sight-feeding piscivores 

fishes such as sauger (Sander canadense), goldeye (Hiodon 

alosoides), walleye (Sander vitreus vitreus), and smallmouth 

bass (Micropterus dolomieu) (Hesse and others, 1989). Most 

of the other more than 60 species of the Missouri’s riverine 

fishes feed on zooplankton at the larval stage, and several 

juveniles and adults of native fishes (for example, paddlefish) 

and non-native fishes [for example, bighead carp (Hypophthalmichthys nobilis)] also feed primarily on zooplankton (Berry 

and others, 2005; Pflieger, 1997), all of which may be directly 

competing with sturgeon larvae for food resources.

Juvenile to Immature Adult

At age 1, shovelnose sturgeon and pallid sturgeon closely 

resemble adults. Juvenile and adult sturgeon have few natural 

Juveniles

wild/hatchery

Entrainment/

intakes

Fish origin

Human

activities

Water

quality

Temperature

Disease

Contaminants

Habitat

Prey availability

Development

and behavior

Non-human

predation

Larval stage of

exogenous feeding

Transition

probability

Dredging

Boats Channel

morphology

Sediment

Reservoir

operation

Channel

engineering

Competition

Non-native

fishes

Native

fishes

Other than

fishes

Non-native

fishes

Native

fishes

Other than

fishes

Light

Nutrients

food web

Flow

Hydraulic

habitat

Human

predation:

Fishing

Disease Sediment

Connection between model components

EXPLANATION

Contributor to direct mortality 

Rate-affecting process affecting survival, 

growth, and development

Nutrients

food web

Biotic condition factor affecting survival,

 growth, and development

Abiotic condition factor affecting survival, 

 growth, and development

Figure 8. Submodel for the transition from larval stage of exogenous feeding to juveniles in the Scaphirhynchus sturgeon life-history 

conceptual model.

Structure of the Conceptual Life-History Model 11
predators and annual mortality is thought to be relatively low 

(Quist and others, 2002). The factors most likely to affect 

sturgeon of this age class are human exploitation, availability 

of food resources, habitat quality, and competition (fig. 9). 

Because of their life-history traits (late maturity and infrequent 

spawning) shovelnose and pallid sturgeon are extremely susceptible to impacts of overharvest (Bajer and Wildhaber, 2007; 

Quist and others, 2002). Many species of sturgeon have yet to 

recover from previous episodes of over-exploitation (Williams 

and others, 1989).

Pallid sturgeon, like shovelnose sturgeon, primarily 

consume invertebrates when less than 1-year old (Becker, 

1983; Modde and Schmulbach, 1977), but unlike shovelnose 

sturgeon, they primarily are piscivorous juveniles and adults 

(Gerrity and others, 2006). Previous field collections of 

shovelnose and pallid sturgeon adults indicate that part of their 

diets are made up of benthic macroinvertebrates (Modde and 

Schmulbach, 1977; Keenlyne, 1997; Carlson and others, 1985; 

Gerrity and others, 2006). The diet of the shovelnose sturgeon 

is comprised almost exclusively of macroinvertebrates (Gerrity 

and others, 2006). Recent evidence (George and others, 2007; 

Gerrity and others, 2006) indicates that several Macrhybopsis

chubs are important items in diets of pallid sturgeon; populations of several of these chub species have declined. (Pflieger 

and Grace, 1987; Hesse and others, 1989; Galat and others, 

2005). 

Human

predation:

Fishing

Dredging

Boats

Entrainment/

intakes

Human

predation:

Fishing

Disease Sediment

Connection between model components

EXPLANATION

Contributor to direct mortality 

Rate-affecting process affecting survival, 

growth, and development

Nutrients

food web

Biotic condition factor affecting survival,

 growth, and development

Abiotic condition factor affecting survival, 

 growth, and development

Disease

Contaminants

Habitat

Prey availability

Development

and behavior

Human

activities

Juveniles

wild/hatchery

Immature adults

wild/hatchery

Transition

probability

Channel

morphology Channel

engineering

Reservoir

operation

Competition

Non-native

fishes

Native

fishes

Other than

fishes

Fish origin

Water

quality

Temperature

Sediment

Light

Nutrients

food web

Flow

Hydraulic

habitat

Figure 9. Submodel for the transition from juvenile to immature adult in the Scaphirhynchus sturgeon life-history conceptual model.

12 A Conceptual Life-History Model for Pallid and Shovelnose Sturgeon
The species composition of prey fishes in the river has 

changed since the 1940s (Berry and others, 2005; Hesse and 

others, 1989). Although gizzard shad (Dorosoma cepedianum) are habitat generalists, (Leslie and Timmins 1998a, 

1998b; Galat and others, 2005), their spawning in rivers is 

believed to occur in shallow, slow-velocity habitats such as 

backwaters and main-channel borders (Scott and Nielsen, 

1989). Adult gizzard shad are detritivores and periphyton 

grazers that strongly affect sediments and nutrients within the 

water column of lakes (Vanni, 1996). This led Arrington and 

Winemiller (2003) to speculate that gizzard shad may markedly affect ecosystem dynamics in lowland rivers where they 

are abundant. It is unknown if such changes in preyfish species 

composition may have negatively affected the pallid sturgeon.

Information on growth rates of shovelnose and pallid 

sturgeon in the wild is limited because of the lack of effective 

age and growth methodologies; however, understanding the 

age and growth of shovelnose and pallid sturgeon is essential 

for assessing population status and forecasting population 

trends. Critical to any fish species recruitment is overwinter 

survival (Hurst and Conover, 1998). Availability of nonlethal temperatures and adequate quantity and quality of food 

resources is critical for overwintering survival and recruitment 

of any temperate fish species. No information is available on 

the conditions necessary for overwinter survival of shovelnose 

and pallid sturgeon.

Whereas there are some limited data collected by telemetry on temperature, water velocity, turbidity, and substrate 

use by pallid sturgeon in the Missouri River (Bramblett and 

White, 2001), it cannot be assumed that the preferred habitat 

is available to the fish. Most of the Lower Missouri River 

has been forced into a single channel by structures meant to 

improve navigation, and the waters of this channel are well 

mixed. Only in the case of tributaries and long chutes and side 

channels do temperature and water quality of moving water 

differ significantly from that present in the thalweg of the 

Missouri (Galat and others, 2001). If pallid sturgeon need to 

select temperature and water quality regimes that vary from 

that present in the thalweg, the options in the altered river are 

extremely limited.

Shovelnose and pallid sturgeon are well adapted to bottom habitats of large rivers with swift, turbid, free-flowing 

water; however, the pallid sturgeon do not use small tributaries or clear-water riverine habitats that are frequented by 

shovelnose sturgeon (Mayden and Kuhajda, 1997). Bramblett 

and White (2001) suggest that pallid sturgeon exhibit some 

selectivity for sand bottom that may be affected by temperature and turbidity. Since sand is the primary substrate present in the Missouri River, it is not clear whether or not the 

temperature, turbidity, and substrate associations detected in 

the field are the result of habitat choice, or the predominance 

of those habitats. Furthermore, since there is no information 

on habitat associations or habitat choice of shovelnose and pallid sturgeon before alterations of their habitat, it is not known 

whether or not the preferred habitat of either species exists in 

the Missouri River.

Population-Forecasting Model

Successful recovery of endangered fish species requires 

detailed understanding of their life history, the environments 

in which they live, and the aquatic community with which they 

interact. Fish have different ecological requirements throughout their ontogenetic development. The ability of fish to meet 

these requirements at various life stages determines the restrictive nature of potential ecological bottlenecks. Interactions 

with other individuals within the population and with other 

species within the community (for example, competition, predation) along with the use of the food resources (for example, 

macroinvertebrates) and the physical habitat in which they live 

determine the success of fishes for surviving each bottleneck. 

Individually-based models used in conjunction with explicit 

models of space incorporating spatial and temporal variation, 

could be used to predict the physiology, behavior, growth, 

survival, and reproduction of fishes under changing environmental conditions to estimate the restrictive nature of each 

bottleneck (Wildhaber and Lamberson, 2004). Such understanding requires integration of knowledge across multiple 

disciplines including biology, hydrology, geomorphology, and 

climatology.

One approach is to use mathematical and empirical 

models to integrate knowledge across disciplines to develop 

individual-based, spatially and temporally explicit models to 

benefit research, management, and monitoring efforts by predicting demographic trends under current and potential future 

conditions (Wildhaber and Lamberson, 2004). The environmental experience of individual fish of a given species varies 

greatly. This variation is a function of the individual, the environment in which it finds itself, and the choices it makes; this 

variation can translate into population trends that may not have 

been predicted based on the average individual. These spatial 

and temporal patterns of individuals can then be used within 

an age-structured demographic model that is compartmentalized by the stage-structured conceptual model presented in this 

report to forecast population changes (Bajer and Wildhaber, 

2007). The latter model contains parameters for each age class 

that often includes the number of individuals, probability of 

survival to the next age class, and reproductive rate to name a 

few. Using this population matrix, estimates can be made as to 

whether or not a population is stable, increasing or declining, 

and which parameters of the population model (that is, age 

classes and associated parameters) have the most effect on the 

population.

An example of the value of such a modeling approach is 

demonstrated by Bajer and Wildhaber (2007) who developed 

age-structured demographic models for the pallid and shovelnose sturgeon in the Lower Missouri River to conduct sensitivity analyses for the populations. Potential effects of increased 

fishing mortality on the shovelnose sturgeon also were evaluated. Populations of pallid and shovelnose sturgeon were most 

sensitive to age zero mortality rates as well as mortality rates 

of juveniles and young adults. Overall, fecundity was a less 

sensitive parameter; however, increased fecundity effectively 

Structure of the Conceptual Life-History Model 13
balanced greater mortality among sensitive age classes in 

both populations. The model predicts that management that 

increases population-level fecundity and improves survival of 

age zero, juveniles and young adults should most effectively 

benefit both populations. Evaluation of reproductive values 

indicated that populations of pallid sturgeon dominated by 

ages more than 35 years rapidly could lose their potential for 

growth, particularly if recruitment remains low. Under the 

initial parameter values the population of shovelnose sturgeon 

in the Lower Missouri River was predicted to decline by 1.65 

percent annually, causing the commercial yield also to decline. 

Modeling indicated that the commercial yield could substantially increase if exploitation of females in ages less than 12 

years was restricted.

Summary

In the model presented, human activities at the process 

level that affect survival, growth, and development are considered critical determinants of successful transition between 

all life stages, whereas non-human predation is not considered 

critical once the fish has reached the juvenile stage. For the 

human activities identified, entrainment is considered a critical 

determinant of successful transition between life stages once 

the fish has reached the larval stage, whereas fishing is considered critical only after the fish has reached the juvenile stage.

For rate-affecting processes identified as critical for survival, growth, and development, habitat is considered a critical 

determinant of successful transition between all life stages, 

whereas contaminants and disease are considered critical to all 

life stage transitions except from spawning adults with viable 

gametes to developing embryos. Prey availability and competition for food are considered critical once the fish reach the free 

embryo stage.

The critical rate-affecting processes help to determine 

which of the condition factors are critical to the life-stage transition being considered. Hydraulic habitat, sediment, temperature, water quality, and light are considered critical determinants of successful transition for all life stages. The presence 

of con-specifics is only considered critical once the adult life 

stage has been reached, whereas fish origin is considered a 

critical determinant of successful transition between all life 

stages once a developing embryo has been formed. Finally, the 

nature of the food web and the available nutrients are considered critical determinants of successful transition between all 

life stages once the exogenously feeding larval stage has been 

reached.

The conceptual model provided here was developed 

to organize the understanding of the complex life history of 

Scaphirhynchus sturgeons. It was designed for communication, planning, and to provide the structure for a populationforecasting model. These models are intended to be dynamic 

and responsive to new information and changes in river 

management, thereby providing scientists, stakeholders, and 

managers with ways to improve understanding of the effects of 

management actions on the ecological requirements of Scaphirhynchus sturgeons.

As new scientific knowledge becomes available, it could 

be included in these models in many ways at various levels of 

integration. The set of processes, conditions, and the connections between them that are identified in the conceptual life-history model were identified based on the current knowledge as 

supported by scientific publications. The components identified 

in the model and the connections between them could change 

when future data are collected that may improve the model. 

The cumulative knowledge of the scientific and management 

community dealing with sturgeon provide the assurance that 

the information on which the model is based in current and critical or missing data are identified. At the quantitative level, the 

transition probabilities, the strength of the connections between 

conditions and rate-affecting processes, rate-affecting processes 

and processes, and processes and transition probabilities (for 

example arrows), and submodels that empirically describe 

the processes are all defined by the data from basic research. 

Updating the scientific knowledge on which the model is based 

and using that base to define the current structure and parameterization of the model provides the ability to capture and track 

such changes in a working model that everyone can use.

References Cited

Arrington, D.A., and Winemiller, K.O. 2003, Diel changeover 

in sandbank fish assemblages in a neotropical floodplain 

river: Journal of Fish Biology, v. 63, p. 442–459.

Bailey, R.M., and Cross, F.B., 1954, River sturgeon of the 

American genus Scaphirhynchus: characters, distribution 

and synonymy: Papers of the Michigan Academy of Science, Arts and Letters, v. 39, p. 169–208.

Bajer, P.G., and Wildhaber, M.L., 2007, Population viability 

analysis of Lower Missouri River shovelnose sturgeon with 

initial application to the pallid sturgeon: Journal of Applied 

Ichthyology, v. 23, p. 457–464.

Balon, E.K., 1975, Reproductive guilds of fishes—A proposal 

and a definition: Journal of the Fisheries Research Board of 

Canada, v. 32, p. 821–864.

Becker, G.C., 1983, Fishes of Wisconsin: Madison, Wis., University of Wisconsin Press, 1,053 p.

Berry, C.R, Jr., Wildhaber, M.L. , and Galat, D.L. , 2005, Population structure and habitat use of benthic fishes along the 

Missouri and lower Yellowstone Rivers—Volume 3—Fish 

distribution and abundance: Final report of Missouri River 

benthic fish study PD–95–5832 to U.S. Army Corps of 

Engineers and Bureau of Reclamation, 268 p.

14 A Conceptual Life-History Model for Pallid and Shovelnose Sturgeon
Birstein, V.J., 1993, Sturgeons and paddlefishes—threatened 

fish in need of conservation: Conservation Biology, v. 7, 

p. 773–787.

Bramblett, R.G., and White, R.G., 2001, Habitat use and 

movements of pallid and shovelnose sturgeon in the Yellowstone and Missouri Rivers in Montana and North Dakota: 

Transactions of the American Fisheries Society, v. 130, 

p. 1,006–1,025.

Braaten, P.J., Fuller, D.B., and McClenning, N.D, 2007, 

Diet composition of larval and young-of-year shovelnose 

sturgeon in the upper Missouri River: Journal of Applied 

Ichthyology, v. 23, p. 517–521.

Braaten, P.J., and Fuller, D.B., 2005, Fort Peck flow modification biological data collection plan—summary of 2004 

activities: Fort Peck, Mont., Montana Department of Fish, 

Wildlife and Parks, 63 p.

Breder, C.M., and Rosen, D.E., 1966, Modes of reproduction 

in fishes: Neptune City, N.J., T.F.H. Publications, 941 p.

Bruch, R.M., and Binkowski, F.P., 2002, Spawning behavior 

of lake sturgeon (Acipenser fulvescens): Journal of Applied 

Ichthyology, v. 18, p. 570–579.

Buckley, J., and Kynard, B., 1985, Habitat and behaviour of 

pre-spawning and spawning shortnose sturgeon, Acipenser 

brevirostrum, in the Connecticut River, in Binkowski, F.P., 

and Doroshov, S.I., eds., North American sturgeons—biology and aquaculture potential: Dordrecht, Netherlands, Junk 

Publishers, p. 111–117.

Campton, D.E., Bass, A.L., Chapman, F.A., and Bowen, B.W., 

2000, Genetic distinction of pallid, shovelnose, and Alabama sturgeon—emerging species and the U.S. Endangered 

Species Act: Conservation Genetics, v. 1, p. 17–32.

Carlson, D.M., Pflieger, W.L., Trial, L., and Haverland, P.S., 

1985, Distribution, biology, and hybridization of Scaphirhynchus albus and Scaphirhynchus platorynchus in the 

Missouri and Mississippi River: Environmental Biology of 

Fishes, v. 14, p. 51–59.

Cech and Doroshov, 2004, Environmental requirements, preferences, and tolerance limits of North American sturgeons, 

in LeBreton, G.T.O., Beamish, F.W.H., and McKinley, R.S., 

eds., Sturgeons and paddlefish of North America: Netherlands, Kluwer Academic Publishers, p. 73–86.

Christenson, L.M., 1975, The shovelnose sturgeon (Scaphirhynchus platorynchus Rafinesque) in the Red Cedar—

Chippewa Rivers system Wisconsin: Wisconsin Department 

of Natural Resources, Research Report Number 82, 23 p.

Deng, D.F., Koshio, S., Yokoyama, S., Bai, S.C., Shao, Q., 

Cui, Y., Hung, S.S.O, 2003, Effects of feeding rate on 

growth performance of white sturgeon (Acipenser transmontanus) larvae: Aquaculture, v. 217, p. 589–598.

Deng, X., Van Eenennaam, J.P., Doroshov, S.I., 2002, Comparison of early life stages and growth of green and white 

sturgeon: in Van Winkle, W., Anders, P.J., Secor, D.H., and 

Dixon, D.A. eds., Biology, management, and protection of 

North American sturgeon: Bethesda, Md., American Fisheries Society, Symposium 28, p. 237–248.

Dettlaff, T.A., Ginsburg, A.S, and Schmalhausen, O.I., 1993, 

Sturgeon fishes: Developmental biology and aquaculture: 

Berlin, Springer-Verlag, 300 p.

Dryer, M.P., and Sandvol, A.J., 1993, Recovery plan for the 

pallid sturgeon (Scaphirhynchus albus): Bismarck, N. Dak., 

U.S. Fish and Wildlife Service, 55 p.

Duffy, W.G., Berry, C.R., and Keenlyne, K.D., 1996, Biology of the pallid sturgeon with an annotated bibliography 

through 1994: Brookings, S. Dak., South Dakota State 

University, Cooperative Fish and Wildlife Research Unit, 

Technical Bulletin 5, 32 p.

Eddy, S., and Surber, T., 1947, Northern fishes with special 

reference to the Upper Mississippi Valley, (Revised Edition), Minneapolis, Minn., University of Minnesota Press, 

276 p.

Ferrell, J., 1993, Big Dam Era—A legislative history of the 

Pick-Sloan Missouri River Basin Program: Omaha, Nebr., 

U.S. Army Corps of Engineers, 228 p.

Ferrell, J., 1996, Soundings—100 years of the Missouri River 

navigation project: U.S. Army Corps of Engineers, U.S. 

Government Printing Office: 1996–555–110, 171 p.

Forbes S.A., and Richardson, R.E., 1920, The fishes of Illinois; (2d ed.): Champagne, Ill., Natural History Survey of 

Illinois, v. 3, p. 1–357.

Fox, D.A., Hightower, J.E., and Parauka, F.M., 2000, Gulf 

sturgeon spawning migration and habitat in the Choctawhatchee River system, Alabama–Florida: Transactions of the 

American Fisheries Society, v. 129, p. 811–826.

Funk, J. L., and Robinson, J.W., 1974, Changes in the channel 

of the Lower Missouri River and effects on fish and wildlife: Jefferson City, Mo., Missouri Department of Conservation, 52 p.

Galat, D.L., and Lipkin, R., 2000, Restoring ecological integrity of great rivers: historical hydrographs aid in defining 

reference conditions for the Missouri River: Hydrobiologia, 

v. 422, p. 29–48.

 Galat, D. L., Wildhaber, M.L., Dieterman, D.J. 2001, Population structure and habitat use of benthic fishes along the 

Missouri and Lower Yellowstone Rivers—Volume 2—Spatial patterns of physical habitat variables along the Missouri 

and Lower Yellowstone Rivers: Final report of Missouri 

River benthic fish study PD–95–5832 to U.S. Army Corps 

of Engineers and Bureau of Reclamation, 91 p.

References Cited 15
Galat, D.L., Berry, C.R., Gardner, W.M., Hendrickson, J.C., 

Mestl, G.E., Power, G.J., Stone, C., and Winston, M.R., 

2005, Spatiotemporal patterns and changes in Missouri 

River Fishes, in Rinne, J.N., Hughes, R.M., and Calamusso, 

B., eds., Historical changes in large river fish assemblages 

of the Americas: Bethesda, Md., American Fisheries Society Symposium, v. 45, p. 249–291.

George, S.G., Hoover, J.J., Murphy, C.E., and Killgore, K.J. 

2007, The real poop on pallid sturgeon ecology—fecal 

analysis as a technique for reconstructing diet and inferring 

habitat and behavior: Journal of Applied Ichthyology, v. 23.

Gerrity, P.C., Guy, C.S., and Gardner, W.M., 2006, Juvenile 

pallid sturgeon are piscivorous—a call for conserving native 

cyprinids: Transactions of the American Fisheries Society, 

v. 135, p. 604–609.

Gisbert, E., Dorosov, S.I., 2003, Histology of the developing 

digestive system and the effect of food deprivation in larval 

green sturgeon (Acipenser medirostris): Aquatic Living 

Resources, v. 16, p. 77–89.

Gisbert, E., Williot, P., 1997, Larval behavior and effect of the 

timing on initial feeding on growth and survival of Siberian 

sturgeon (Acipenser baeri) larvae under small scale hatchery production: Aquaculture, v. 156, p. 63–76.

Harshbarger, J.C., Coffey, M.J., and Young, M.Y., 2000, 

Intersexes in Mississippi River shovelnose sturgeon 

sampled below St. Louis, Mo., USA: Marine Environmental 

Research, v. 50 p. 247–250.

Hesse, L.W., and Carreirov, J.R., 1997, The status of paddlefish, pallid sturgeon, lake sturgeon, and shovelnose sturgeon—a summary of information regarding status, distribution, and current management strategies within their present 

range: Bettendorf, Iowa, Mississippi Interstate Cooperative 

Resource Association, 52 p.

Hesse, L.W., and Sheets, W., 1993, The Missouri River hydrosystem: Fisheries, v. 18, p. 5–14.

Hesse, L.W., Schmulbach, J.C., Carr, J.M., Keenlyne, K.D., 

Unkenholz, D.G., Robinson, J.W., and Mestl, G.E., 1989, 

Missouri River fishery resources in relation to past, present, 

and future stresses, in Dodge, D.P., ed., Proceedings of the 

International Large River Symposium: Canadian Special 

Publication of Fisheries and Aquatic Sciences, v. 106, p. 

352–371.

Houston, J.J., 1988, Status of the green sturgeon, Acipenser 

medirostris, in Canada: The Canadian Field Naturalist, 

v. 102, p. 286–290.

Hrabik, R.A., Herzog, D.P., Ostendorf, D.E., and Petersen, 

M.D., 2007, Larvae provide first evidence of successful 

reproduction by pallid sturgeon, Scaphirhyncus albus, in the 

Mississippi River: Journal of Applied Ichthyology, v. 23, 

p. 436–443.

Humphries, P., Serafini, L.G., and King, A.J., 2002, River 

regulation and fish larvae: variation through space and time: 

Freshwater Biology, v. 47, p. 1,307–1,331.

Hurst, T.P., Conover, D.O., 1998, Winter mortality of youngof-the-year Hudson River striped bass (Morone saxatilis)—size-dependent patterns and effects on recruitmen: 

Canadian Journal of Fisheries and Aquatic Sciences, v. 55, 

p. 1,122–1,130.

Jobling, M., 1995, Environmental biology of fishes: London, 

Chapman and Hall, 455 p.

Jordan, G.R., 2006, Pallid sturgeon (Scaphirhynchus albus)

range-wide stocking and augmentation plan: Billings, 

Mont., U.S. Fish and Wildlife Service, 79 p.

June, F.C., 1977, Reproductive patterns in seventeen species of 

warmwater species in a Missouri River reservoir: Environmental Biology of Fishes, v. 2, p. 285–296.

Kapuscinski, K., 2002, Population abundance estimation 

of wild pallid sturgeon in recovery-priority management 

area #2 of the Missouri and Yellowstone Rivers during 

1991–2001 in 2002 upper basin pallid sturgeon work group 

annual report: Fort Peck, Mont., Montana Department of 

Fish, Wildlife and Parks, p. 294.

Keenlyne, K.D., 1997, Life history and status of the shovelnose sturgeon, Scaphirhynchus platorynchus: Environmental Biology of Fishes, v. 48, p. 291–298.

Keenlyne K.D., Jenkins L.G., 1993, Age at sexual maturity of 

the pallid sturgeon: Transactions of the American Fisheries 

Society, v. 122, p. 393–396.

Keenlyne, K.D., Graham, L.K., and Reed, B.C., 1994, 

Hybridization between the pallid and shovelnose sturgeons: 

Proceedings of the South Dakota Academy of Science, 

v. 73, p. 59–66.

Kynard, B., Henyey, E., Horgan, M., 2002, Ontogenetic 

behavior, migration, and social behavior of pallid sturgeon, 

Scaphirhynchus albus, and shovelnose sturgeon, S. platorynchus, with notes on the adaptive behavior of body color: 

Environmental Biology of Fishes, v. 63, p. 389–403.

LaHaye, M., Branchard, A., Gendron, M., Verndon, R., and 

Fortin, R., 1992, Reproduction, early life history, and 

characteristics of the spawning grounds of the lake sturgeon 

(Acipenser fulvescens) in Des Prairies and L’Assomption 

Rivers near Montreal, Quebec: Canadian Journal of Zoology, v. 70, p. 1,681–1,689.

Leslie, J.K., and Timmins, C.A., 1998a, Age 0+ fish occurrence in modified habitat in south-western Ontario: Cana16 A Conceptual Life-History Model for Pallid and Shovelnose Sturgeon
dian Technical Report of Fisheries and Aquatic Sciences, 

p. 2,219.

Leslie, J.K., and Timmins, C.A., 1998b, Seasonality of fish 

larvae in surf zone and tributary of Lake Erie—a comparison: Canadian Technical Report of Fisheries and Aquatic 

Sciences, p. 2,197.

Mayden R.L., Kuhajda B.R., 1996, Systematics, taxonomy, 

and conservation status of the endangered Alabama sturgeon, Scaphirhynchus suttkusi Williams and Clemmer (Actinopterygii, Acipenseridae): Copeia, v. 2, p. 241–273.

Mayden R.L, Kuhajda B.R., 1997, Threatened fishes of the 

world: Scaphirhynchus albus (Forbes & Richardson, 1905) 

(Acipenseridae): Environmental Biology of Fishes, v. 48, 

p. 420–421.

Modde, T., and Schmulbach, J.C., 1977, Food and feeding behavior of the shovelnose sturgeon, Scaphirhynchus 

platorynchus, in the unchannelized Missouri River, South 

Dakota: Transactions of the American Fisheries Society, 

v. 106, p. 602–608.

Moos, R.E., 1978, Movement and reproduction of shovelnose 

sturgeon Scaphirhynchus platorynchus (Rafinesque) in the 

Missouri River, South Dakota: Vermillion, South Dakota, 

University of South Dakota, Ph.D. Dissertation, 213 p.

Munro, A.D., Li-Lianb, C., and Nqankee, K., 1990, Preliminary observation on environmental control of ovulation and 

spawning in a small tropical Cyprinid (Barbus tetrazona), 

Proceedings: Tokyo, Japan, Second Asian Fisheries Forum, 

p. 17–22.

NatureServe, 2005, NatureServe Explorer: An online encyclopedia of life [web application] (Version 4.5): Arlington, 

Virginia, NatureServe, [accessed October 19, 2005, at http://

www.natureserve.org/explorer].

Parsley, M.J., Anders, P.J., Miller, A.I., Beckman, L.G., 

and McCabe, G.T., Jr., 2002, Recovery of white sturgeon 

populations through natural production—understanding 

the influence of abiotic and biotic factors on spawning and 

subsequent recruitment, in Van Winkle, W., Anders, P.J., 

Secor, D.H., and Dixon, D.A., eds., Biology, management, 

and protection of North American sturgeon: Bethesda, Md., 

American Fisheries Society, Symposium 28, p. 55–66.

Pflieger, W.L., 1997, The fishes of Missouri: Jefferson City, 

Mo., Missouri Department of Conservation, 372 p.

Pflieger, W.L., and Grace, T.B., 1987, Changes in the fish 

fauna of the Lower Missouri River, in Matthews, W.J., and 

Heins, D.C., eds, Community and evolutionary ecology of 

North American stream fishes: Norman, Okla., University 

of Oklahoma Press, p. 1,940–1,983.

Quist, M.C., Guy, C.S., Pegg, M.A., Braaten, P.J., Pierce, 

C.L., Travnichek, V.H., 2002, Potential influence of harvest 

on shovelnose sturgeon populations in the Missouri River 

system: North American Journal of Fisheries Management, 

v. 22, p. 537–549.

Quist, M.C., Boelter, A.M., Lovato, J.M., Korfanta, N.M., 

Bergman, H.L., Latka, D.C., Korschgen, C., Galat, D.L., 

Krentz, S., Oetker, M., Olson, M., Scott, C.M., and Berkley, 

J., 2004, Research and assessment needs for pallid sturgeon 

recovery in the Missouri River—Final report to the U.S. 

Geological Survey, U.S. Army Corps of Engineers, U.S. 

Fish and Wildlife Service, and U.S. Environmental Protection Agency: Laramie, Wyo., William D. Ruckelshaus 

Institute of Environment and Natural Resources, University 

of Wyoming, 82 p.

Rankin, J.C., Pitcher, T.J., and Duggan, R.T., 1983, Control 

processes in fish physiology: New York, John Wiley and 

Sons, p. 298.

Rosenblum, P.M., Pudney, J., Callard, I.P., 1987, Gonadal 

morphology, enzyme histochemistry and plasma steroid 

levels during the annual reproductive cycle of male and 

female brown bullhead catfish, Ictalurus nebulosus Lesueur: 

Journal of Fish Biology, v. 31 p. 325–261.

Ruelle, R., and Keenlyne, K.D., 1993, Contaminants in Missouri River pallid sturgeon: Bulletin of Environmental 

Contamination and Toxicology, v. 50, p. 898–906.

Scheidegger, K.J., and Bain, M.B., 1995, Larval fish in natural 

and regulated rivers: assemblage composition and microhabitat use: Copeia, v. 1, p. 125–135.

Schiemer, F., Keckeis, H., Winkler, G., and Flore, L., 2001, 

Large rivers—the relevance of ecotonal structure and hydrological properties for the fish fauna: Archives für Hydrobiologie Supplement 135—Large Rivers, v. 12, p. 487–508.

Scott, W.B., and Crossman, E.J., 1973, Freshwater fishes of 

Canada: Fisheries Research Board of Canada Bulletin, 

v. 184, 966 p.

Scott, M.T., and Nielsen, L.A., 1989, Young fish distribution 

in backwaters and main-channel borders of the Kanawha 

River, West Virginia: Journal of Fish Biology, v. 35, 

p. 21–27.

Simons, A.M., Wood, R.M., Heath, L.S., Kuhajda, B.R., and 

Mayden, R.L., 2001, Phylogenetics of Scaphirhynchus 

based on mitochondrial DNA sequences: Transactions of 

the American Fisheries Society, v. 130, p. 359–366.

Snyder, D.E., 2002, Pallid and shovelnose sturgeon larvae—

morphological description and identification: Journal of 

Applied Ichthyology, v. 18, p. 240–265.

Sullivan, C.V., Berlinksky, D.L., Hodson, R.G., 1997, Reproduction, in Harrell, R.M., ed., Striped bass and other 

morone culture: Amsterdam, Netherlands, Elsevier Sciences, p. 11–73.

References Cited 17
Surprenaut, C., 2004, Scaphirhynchus platorynchus, in IUCN 

2004, 2004 IUCN Red list of threatened species: [downloaded on October 17, 2005, at http://www.iucnredlist.org].

Taubert, B.D., 1980, Reproduction of shortnose sturgeon (Acipenser brevirostrum) in Holyoke Pool, Connecticut River, 

Mass.: Copeia, v. 1,980, p. 114–117.

Tockner, K., and Stanford, J.A., 2000, Riverine floodplains: 

present state and future trends: Environmental Conservation, v. 29, p. 308–330.

U.S. Fish and Wildlife Service, 2000, Biological opinion on 

the operation of the Missouri River main stem reservoir 

system, operation and maintenance of the Missouri River 

bank stabilization and navigation project, and operation of 

the Kansas River reservoir system: Bismarck, N. Dak., U.S. 

Fish and Wildlife Service, 286 p.

U.S. Fish and Wildlife Service, 2003, Amendment to the 2000 

biological opinion on the operation of the Missouri River 

main stem reservoir system, operation and maintenance of 

the Missouri River bank stabilization and navigation project, 

and operation of the Kansas River reservoir system: Minneapolis, Minn., U.S. Fish and Wildlife Service, 308 p.

Van Eenennaam, J.P., Linares-Casenave, J., Deng, X., and 

Doroshov, S.I., 2005, Effect of incubation temperature on 

green sturgeon embryos, Acipenser medirostris: Environmental Biology of Fishes, v. 72, p. 145–154.

Van Eenennaam, J.P., Doroshov, S.T., Moberg, G.P., Watson, 

J.G., Moore, D.S., and Linares, J., 1996, Reproductive 

conditions of the Atlantic sturgeon (Acipenser oxyrinchus) 

in the Hudson River: Estuaries, v. 19, p. 769–777.

Vanni, M. J., 1996. Nutrient transport and recycling by 

consumers in lake food webs: implications for algal communities, in Polis, G.A. and Winemiller, K.0., eds., Food 

webs—Integration of patterns and dynamics: Chapman and 

Hall, p. 81–95.

Wildhaber, M.L., and Lamberson, P.J., 2004, Importance of 

the habitat choice behavior assumed when modeling the 

effects of food and temperature on fish populations: Ecological Modelling, v. 175, p. 395–409.

Wildhaber, M.L., Papoulias, D.M., DeLonay, A.J., Tillit, D.E., 

Bryan, J.L., Annis, M.L., and Allert, J.A., 2005, Gender 

identification of shovelnose sturgeon using ultrasonic and 

endoscopic imagery and the application of the method to the 

pallid sturgeon: Journal of Fish Biology, v. 67, p. 114–132.

Wildhaber, M.L., Papoulias, D.M., DeLonay, A.J., Tillitt, D.E., 

Bryan, J.L., and Annis, M.L., 2006, Development of methods to determine the reproductive status of pallid sturgeon 

in the Missouri River: U.S. Geological Survey, 81 p.

Williams, J.E., Johnson, J.E., Hendrickson, D.A., Contreras-Balderas, S., Williams, J.D., Navarro-Mendoza, M., 

McAllister, D.E., and Deacon, J.E., 1989, Fishes of North 

America endangered, threatened, or of special concern—

1989: Fisheries, v. 14, no. 6, p. 2–20.

Williamson, D.F., 2003, Caviar and conservation—Status, 

management, and trade of North American sturgeon and 

paddlefish: Washington, D.C., TRAFFIC North America, 

World Wildlife Fund, p. 252.

Wills, P.S., Sheehan, R.J., Heidinger, R., Sloss, B.L., and 

Clevenstine, R., 2002, Differentiation of pallid sturgeon 

and shovelnose sturgeon using and index based on meristics and morphometrics, in Van Winkle, W., Anders, P.J., 

Secor, D.H., and Dixon, D.A., eds., Bethesda, Md., Biology, 

management, and protection of North American sturgeon: 

American Fisheries Society, Symposium 28, p. 

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