Prepared in cooperation with the Missouri River Recovery Program

Development of Working Hypotheses Linking 

Management of the Missouri River to 

Population Dynamics of Scaphirhynchus albus

(Pallid Sturgeon) 

Open-File Report 2015–1236

U.S. Department of the Interior

U.S. Geological Survey
Cover photograph index: 

Develop

Free e

Juvenile

Pallid sturgeon eggs

ing embryos

mbryos

Adult

Background image: shaded relief map of the Missouri River drainage basin, US Geological 

Survey, EROS Data Center.

Photographs by U.S. Geological Survey personnel
Prepared in cooperation with the U.S. Army Corps of Engineers, Missouri River Recovery 

Program

Development of Working Hypotheses Linking Management 

of the Missouri River to Population Dynamics of 

Scaphirhynchus albus (Pallid Sturgeon)

By Robert B. Jacobson, Michael J. Parsley, Mandy L. Annis, Michael E. Colvin, Timothy L. Welker, and Daniel A. 

James

Open-File Report 2015–1236

U.S. Department of the Interior

U.S. Geological Survey
ii

U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Director

U.S. Geological Survey, Reston, Virginia: 2016

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Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials 

as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Jacobson, R.B., Parsley, M.J., Annis, M.L., Colvin, M.E., Welker, T.L., and James, D.A., 2016, Development of 

working hypotheses linking management of the Missouri River to population dynamics of Scaphirhynchus albus (pallid 

sturgeon): U.S. Geological Survey Open-File Report 2015–1236, 33 p., http://dx.doi.org/10.3133/ofr20151236.

ISSN 2331-1258 (online)
iii

Contents

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

Introduction................................................................................................................................................................. 2

Purpose and Scope ................................................................................................................................................ 3

Background............................................................................................................................................................. 4

The Effects Analysis Process.............................................................................................................................. 5

Hypotheses and the Missouri River Recovery Management Plan....................................................................... 6

Approach to Process Hypotheses Formation and Filtering......................................................................................... 7

Hypothesis Categories............................................................................................................................................ 7

Filtering and Refinement Process ........................................................................................................................... 8

Working Hypotheses Linking Management of the Missouri River to Population Dynamics ...................................... 11

Implications of the Hypothesis Filtering Process....................................................................................................... 22

Summary and Conclusions....................................................................................................................................... 29

References Cited...................................................................................................................................................... 31

Figures

Figure 1. Components of the Missouri River Pallid Sturgeon Effects Analysis for Phases 1, 2, and 3........................ 3

Figure 2. Missouri River Basin and locations of river segments that are part of the Missouri River Pallid Sturgeon 

Effects Analysis. ............................................................................................................................................................ 5

Figure 3. Diagram showing an example of a conceptual ecological model for life-stage components for the source of 

dominant working hypotheses (right side) and working management hypotheses (left side)....................................... 10

Figure 4. Graphs showing the results of the first survey of dominant working hypotheses. A, Response scores. B, 

No relevant knowledge. ............................................................................................................................................... 14

Figure 5. Graphs showing the results of the second survey of dominant working hypotheses. A, Response scores. 

B, No relevant knowledge............................................................................................................................................ 14

Figure 6. Graphs showing the results of the survey of working management hypotheses, Upper Missouri River. A, 

Response scores. B, No relevant knowledge. GAPT refers to the Gavins Point Dam; DO, dissolved oxygen.. .......... 26

Figure 7. Graphs showing the results of the survey of working management hypotheses, Lower Missouri River. A, 

Response scores. B, No relevant knowledge.YSTN refers to the Yellowstone River and UPMOR refers to the Upper 

Missouri River; Lake Sak refers to Lake Sakakawea................................................................................................... 27

Figure 8. Cumulative growth in pallid sturgeon science peer-reviewed publications, 1992-2014. ............................ 28

Tables

Table 1. Categories of the hypotheses filtering process for the Missouri River Pallid Sturgeon Effects Analysis 

(EA)........... .................................................................................................................................................................... 9

Table 2. Candidate dominant working hypotheses before first round of expert survey............................................ 12

Table 3. Candidate dominant working hypotheses before second round of expert survey...................................... 15

Table 4. Candidate working management hypotheses before third survey ............................................................. 19

Table 5. Working set of management hypotheses after expert elicitation................................................................ 23
iv

Conversion Factors

Inch/Pound to International System of Units

Multiply By To obtain

Length

mile (mi) 1.609 kilometer (km)

Area

acre 4,047 square meter (m2)

acre 0.4047 hectare (ha)

acre 0.4047 square hectometer (hm2) 

acre 0.004047 square kilometer (km2)

Density

acres per mile 0.2515 hectares per kilometer (km)

International System of Units to Inch/Pound

Multiply By To obtain

Length

kilometer (km) 0.6214 mile (mi)

Area

hectare (ha) 2.471 acre

square kilometer (km2) 247.1 acre

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as °F = (1.8 × °C) + 32.

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as °C = (°F – 32) / 1.8.

To communicate effectively with stakeholders, managers, and other scientists working on the Lower Missouri River, this report uses a mix of 

U.S. customary units and International System of Units (SI) units of measure. 

Datum 

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 (NAVD 88).

Horizontal coordinate information is referenced to the World Geodetic System of 1984 (WGS 84).
v
1

Development of Working Hypotheses Linking 

Management of the Missouri River to Population 

Dynamics of Scaphirhynchus albus (Pallid Sturgeon) 

By Robert B. Jacobson,1 Michael J. Parsley,2 Mandy L. Annis,

1 Michael E. Colvin,3 Timothy L. Welker,4 and Daniel 

A. James5

Abstract

This report documents a process of filtering of hypotheses that relate Missouri River 

Scaphirhynchus albus (pallid sturgeon) population dynamics to management actions including flow 

alterations, channel reconfigurations, and pallid sturgeon population augmentation. The filtering process 

was a partnership among U.S. Geological Survey, U.S. Army Corps of Engineers, and U.S. Fish and 

Wildlife Service to contribute to the Missouri River Recovery Management Plan process. The objective 

of the filtering process was to produce a set of hypotheses with high relevance to pallid sturgeon

population dynamics and decision making on the Missouri River. The Missouri River Pallid Sturgeon 

Effects Analysis team filtered hundreds of potential hypotheses implicit in conceptual ecological models 

to develop a set of 40 candidate dominant hypotheses that were identified by experts as being important 

in pallid sturgeon population dynamics. Using a modified Delphi process and additional expert opinion, 

the team reduced this set of hypotheses to 23 working dominant hypotheses. We then matched the 23 

hypotheses with management actions that could influence the biotic outcomes, resulting in as many as 

176 potential effects between management actions and pallid sturgeon in the Missouri River. This 

number was consolidated to a candidate set of 53 working management hypotheses because some 

management actions applied to multiple life stages of the pallid sturgeon. We used an additional round 

of expert surveys to identify a set of 30 working management hypotheses. Finally, the set of working 

management hypotheses was filtered by the U.S. Army Corps of Engineers, Missouri River Recovery 

Program for actions that were within the agency’s authority and jurisdiction. This round resulted in a set 

of 21 hypotheses for initial modeling of linkages from management to pallid sturgeon population 

responses.

The initial set of candidate hypotheses provides a useful starting point for quantitative modeling

and adaptive management of the river and species. We anticipate that hypotheses will change from the 

set of working management hypotheses as adaptive management progresses. More importantly, 

 1

Columbia, Missouri. 2

Cook, Washington, retired. 3

Mississippi State University. 4

U.S. Army Corps of Engineers. 5

U.S. Fish and Wildlife Service.
2

hypotheses that have been filtered out of our multistep process are still being considered. These filtered 

hypotheses are archived and if existing hypotheses are determined to be inadequate to explain observed 

population dynamics, new hypotheses can be created or filtered hypotheses can be reinstated.

Introduction

This report documents a systematic process by which hypotheses about the effects between 

management actions and Scaphirhynchus albus (pallid sturgeon) populations in the Missouri River were 

developed and prioritized. The objective of this process was to develop hypotheses that would define the 

scope and type of effort needed to develop quantitative models linking management actions to pallid 

sturgeon population dynamics. The process is a step in the Missouri River Pallid Sturgeon Effects 

Analysis (EA), carried out as a partnership among U.S. Geological Survey USGS), U.S. Army Corps of 

Engineers (USACE), and U.S. Fish and Wildlife Service (USFWS) as part of the Missouri River 

Recovery Management Plan.

The EA team is charged with a multistep process, resulting in four supporting reports (fig. 1):

• Develop Conceptual Ecological Models (CEMs) to document and illustrate driver-stressorresponse ecological relations for Missouri River pallid sturgeon (Jacobson and others, 2015b) .

• Compile, assess, and document available information and modeling resources that can be used to 

understand historical and future changes of pallid sturgeon populations (Jacobson and others, 

2015a).

• Develop a filtered set of hypotheses to depict relations in the CEMs. The process of hypothesis 

formulation and filtering is documented in this report.

• Compile multiple lines of evidence by using the best available science to assess working 

management hypotheses. This will be the next report in the series and will include the best 

available combinations of qualitative and quantitative models, theoretical and empirical data, 

and expert opinion.

In a broader context, the EA process has three phases. The four reports are considered phase 1, 

and provide the scientific background needed to serve as a foundation for planning and adaptive 

management. Phase 2 will include incorporation of that foundation into design of an adaptive 

management process for pallid sturgeon in Missouri River management. Phase 3 is implementation of 

management actions under adaptive management.

The documents produced by the EA team are intended to inform Missouri River Recovery 

Program (MRRP) decisions about how to best manage the Missouri River and its resources to meet 

species-management objectives. For pallid sturgeon in the Missouri River, the species-management 

objective is to “Avoid jeopardizing the continued existence of the pallid sturgeon from U.S. Army 

Corps of Engineers actions on the Missouri River” (U.S. Fish and Wildlife Service, written commun., 

2013). The USFWS notes that this objective is consistent with species recovery goals (U.S. Fish and 

Wildlife Service, 2014) but is specific to Missouri River management actions. 

The CEM and quantitative model framework developed through the EA are intended to form 

part of the framework for future adaptive management of the Missouri River. We anticipate that the plan 

will include an ongoing assessment process similar to the EA, whereby new information from 

monitoring, assessment, and research efforts will be used to improve management actions in the future. 

An important part of this effort will be the option to refer previously developed CEMs if the need arises 

to provide and filter new hypotheses to explain observed changes in pallid sturgeon populations. 
3

Figure 1. Components of the Missouri River Pallid Sturgeon Effects Analysis for Phases 1, 2, and 3.

Purpose and Scope

The purpose of this report is to document a process by which working hypotheses were 

developed to link management of the Missouri River to population dynamics of pallid sturgeon. This 

report is the third in a series intended to document the EA process. The process generally follows the 

concepts of effects analysis as outlined in an article by Murphy and Weiland (2011), although with 

some deviation from the ideal Murphy and Weiland process as a result of practical considerations. 

This report documents the process of categorizing, prioritizing, and documenting a working set 

of hypotheses to link management actions to pallid sturgeon population dynamics. The process has 

involved multiple sequential steps to organize the hypotheses and evaluate them using expert opinion 

and available scientific information. 

The objective of the hypothesis development process has been to provide initial scope and 

structure to subsequent steps in the EA process. In particular, prioritized hypotheses are needed to 

constrain the scope of quantitative modeling because it would be impossible to model the large number 

of potential hypothetical influences that emanated from the CEMs. The priority hypotheses sought in 

this process are meant to be broadly articulated because they will be used as the foundation for 

sequential testing and refinement of hypotheses, and development of new hypotheses, as quantitative 

understanding evolves. 
4

Background

The pallid sturgeon is an endangered, benthic fish endemic to the turbid Missouri and 

Mississippi Rivers and the lower parts of larger tributaries. The pallid sturgeon was listed as endangered 

under the U.S. Endangered Species Act of 1973 (16 U.S.C. ch. 35 § 1531) in 1990 (U.S. Fish and 

Wildlife Service, 1993). Numerous factors have likely contributed to the species decline. The “Pallid 

Sturgeon Recovery Plan” (U.S. Fish and Wildlife Service, 1993) and the “Revised Pallid Sturgeon 

Recovery Plan” (U.S. Fish and Wildlife Service, 2014) reported that engineered modifications to the 

Missouri River have been the major factors in species decline, with potential contributions from 

commercial harvesting, and industrial and agricultural contaminants. In 2000, the USFWS published 

the “2000 Biological Opinion,” (U.S. Fish and Wildlife Service, 2000a) finding that USACE operations 

of the Missouri River were likely to jeopardize the existence of the pallid sturgeon through 

fragmentation of habitats, limiting migration to spawning and feeding areas, altering conditions and 

flows in spawning areas, reducing food sources through limited productivity of those food sources, and 

diminishing rearing habitat for age-0 sturgeon. The “Biological Opinion” and a 2003 amendment 

defined elements of a reasonable and prudent alternative (RPA) to avoid jeopardy to these Missouri 

River populations (U.S. Fish and Wildlife Service, 2000a, 2003). The pallid sturgeon RPA elements 

include (among others) implementation of adaptive management, monitoring, and research, in addition 

to restoration of 20–30 acres per mile (5–7 ha/km) of shallow-water habitat (SWH) downstream of 

Gavins Point Dam (fig. 2), increased pallid sturgeon propagation and augmentation, and implementation 

of spring rises and summer low flows in the flow regimes from Fort Peck and Gavins Point Dams.

Large-scale restoration of Missouri River channel and flood-plain habitats date from the 

Missouri River Bank Stabilization and Navigation Project Fish and Wildlife Mitigation Program 

(Mitigation Program), which was authorized in the Water Resources Development Act of 1986 (33 USC 

2309a; WRDA 1986), 5 years after completion of the Bank Stabilization and Navigation Program 

(BSNP) (National Research Council Committee on Missouri River Ecosystem Science, 2002). The 

Mitigation Program was intended originally to mitigate for habitat losses due to the BSNP, with a goal 

of restoring 166,750 acres of channel, sandbar, and meander-belt habitat, approximately 32 percent of 

the estimated lost habitat (U.S. Army Corps of Engineers, 1981). The goals for compliance with the 

amended biological opinion and for the Mitigation Program were formally collected into the MRRP in 

the Water Resources Development Act of 2007 (Public Law 110–114; WRDA 2007). WRDA 2007 also 

authorized mitigation projects along the main-stem Missouri River in the upper part of the river that 

includes Montana, North Dakota, Nebraska, and South Dakota, as well as restoration projects in the 

Yellowstone River and its tributaries in Montana and North Dakota. WRDA 2007 further authorized use 

of USACE funding to assist the Bureau of Reclamation with planning and construction of fish passage 

around the Lower Yellowstone Intake Diversion Dam (Intake Dam, fig. 2).

Implementation of fish, wildlife, and habitat restoration activities on the Missouri River has been 

guided by principles of adaptive management since adoption of the “2000 Biological Opinion” (U.S. 

Fish and Wildlife Service, 2000b) and the 2001 Master Manual revision (U.S. Army Corps of 

Engineers, 2001). Adaptive management was adopted more formally with creation of the Missouri 

River Recovery Implementation Committee (MRRIC), an advisory group to the USACE authorized in 

WRDA 2007. MRRIC includes committees that are closely aligned with the practice of adaptive 

management: the Science and Adaptive Management (SAM) work group and the Independent Science 

Advisory Panel (ISAP).
5

Figure 2. Missouri River Basin and locations of river segments that are part of the Missouri River Pallid Sturgeon 

Effects Analysis.

Emphasis on construction of conceptual ecological models and implementation of effects analyses were 

prominent recommendations of the ISAP to promote robust adaptive management of the river and its 

imperiled species (Doyle and others, 2011).

The Effects Analysis Process

The EA process is following the recommendation of Murphy and Weiland (2011), with minor 

deviation due to practical considerations. The EA process is essentially an attempt to formalize 

understanding of how the river system works in relation to pallid sturgeon population dynamics, how 

the river and population have been altered, and how future management actions may affect the 

population. The EA process is covered in a series of four reports.
6

The first report in the series documents development of conceptual ecological models (CEMs) 

for the pallid sturgeon in the Missouri River (Jacobson and others, 2015b). Two levels of CEMs were 

presented. A population-level CEM illustrated a life-stage based population structure, indicating how 

population augmentation factors could affect population dynamics and how life-stage specific factors 

could affect survival at each life-stage transition. Life-stage component-level CEMs were developed 

with a hierarchical structure to illustrate how independent geological and climatic factors, and 

management actions, could propagate through to affect habitat, ecological conditions, and pallid 

sturgeon survival (or life-stage transition) probabilities. The CEM development process produced many 

potential relations among factors and biotic responses, which were classified with relative uncertainty 

and relative influence. These “global” hypotheses were the starting place for the process documented in 

this report.

The second report in the series (Jacobson and others, 2015a) is a compilation of relevant data 

sources for informing pallid sturgeon science on the Missouri River. This document describes the 

current state of the science, documents the quantity of data available in various sources, and evaluates 

the applicability of available scientific information to the EA process.

The present report documents the process of filtering hypotheses to arrive at a working set to 

serve as the start of an adaptive management process. The fourth report in the series is an integration of 

information and quantitative models relating to the working set of hypotheses documented in this report.

Hypotheses and the Missouri River Recovery Management Plan

The working set of hypotheses documented in this report is not intended to be the exclusive set 

of all hypotheses about factors affecting pallid sturgeon population dynamics. Instead, the working set 

of hypotheses is intended to be a selection that is relevant to population dynamics and to decision 

making based on the present state of science. Relevance to decision making, in the short term, includes 

being within USACE jurisdictions and authorities.

The working set of management hypotheses identifies types of actions, but most management 

action types for the Missouri River would involve a range of alterations. For example, a working 

management hypothesis may identify naturalization of the flow regime, and this may then become the 

basis for quantitative modeling of how flow regime affects pallid sturgeon population dynamics. The 

term naturalization is used here to denote using the natural flow regime as a template for flow 

management, but manipulating elements (for example, magnitude, duration, or timing of events) to a 

socially acceptable level (Rhoads and others, 1999). Identification of the biologically effective and 

socially acceptable range of alteration within the flow naturalization action is a subsequent step that will 

be addressed in trade-offs with human considerations during structured decision making. More 

importantly, identification of management hypotheses should not limit planning for alternatives under 

the National Environmental Protection Act of 1969 (42 USC § 4321; NEPA) because those alternatives 

would, in most cases, address specific ranges of alterations within the management hypotheses actions.

Most importantly, under the umbrella of adaptive management, there should be no impediment to 

revisiting previously filtered hypotheses or developing new hypotheses if ongoing assessments indicate 

that the present working set is insufficient to explain observed population dynamics.

Selection of the working set has also been affected by practical consideration of its utility to the 

MRRP Management Plan (MRRMP). The MRRMP is a three-year planning process to develop an 

environmental impact statement (EIS) for the continuation of the MRRP. The USACE determined that 

CEMs, hypotheses, and quantitative models developed under the EA would be useful to the MRRMP, 

and so the decision was made to compress EA activities into the first year of the MRRMP process. This 
7

is a considerable challenge to the EA because the ideal effects analysis outlined in Murphy and Weiland

(2011) is clearly a multi-year process for a system as broad and complex as the Missouri River. The 

working solution to this challenge has been to pursue a compressed EA process in the short term (Phase 

1, fig. 1) to provide the MRRMP with needed information in the first year. Phase 1 is intended to be 

followed by development of an adaptive management plan which will include ongoing evaluation of 

information and hypotheses (Phase 2). Phase 2 may serve to broaden the set of hypotheses considered 

as well as contributing to design and implementation of research, monitoring, and assessment under 

adaptive management (fig. 1).

The MRRMP is being designed with adaptive management as a core concept. Because the 

MRRMP Adaptive Management Plan is being developed in parallel with the EA, it is not possible to 

cite the document here. However, early drafts emphasize the role of continued learning and 

collaborative decision making in the future of Missouri River management (A. Quinn, USACE, written 

commun., 2015). EA documents like the present report and the CEM report (Jacobson and others, 

2015b) make it abundantly clear that management decisions relating to pallid sturgeon jeopardy are 

made within a framework of substantial uncertainty. Rigorous application of methods of adaptive 

management (Phase 3) seems to be a promising strategy to continue with decision making in the face of 

this uncertainty. 

The geographic scope of the EA is the Upper Missouri River main stem from Fort Peck Dam to 

the headwaters of Lake Sakakawea, the Yellowstone River upstream from the confluence with the 

Upper Missouri River for an unspecified distance, the Lower Missouri River main stem from Gavins 

Point Dam to confluence with the Mississippi River at St. Louis, tributaries used by pallid sturgeon, and 

an unspecified distance downstream in the Mississippi River (fig. 2). The geographic scope is 

constrained, in part, by decision making authority of the USACE and in part by present understanding 

of the geographic distribution of pallid sturgeon. At present, the reservoir and inter-reservoir reaches 

from the headwaters of Lake Sakakawea to Gavins Point Dam would not be considered explicitly in the 

EA. The potential for inter-reservoir reaches with clear, cold water and hydropeaking releases to 

contribute to pallid sturgeon recovery was considered low but may be usefully considered in Phase 2.

The geographic scope also includes processes and conditions acting in Missouri River tributaries and the 

Mississippi River if those processes and conditions would likely affect population processes in the 

Missouri River.

Approach to Process Hypotheses Formation and Filtering 

The approach for this study was mostly based on a similar process aimed at recovery of 

Acipenser transmontanus (white sturgeon) in the Upper Columbia River (Gregory and Long, 2008). The 

study of the white sturgeon had many of the same issues as the pallid sturgeon found in the Missouri

River, with the primary similarity being landscape-level anthropogenic alterations that affected several 

aspects of the species life-history requirements. In both cases, linkages between requisite management 

actions and species’ responses to those actions had substantial uncertainties. An important difference 

was the time frame—the hypothesis filtering process on the Columbia River took 18 months, whereas 

only 8 months were available for our process along the Missouri River.

Hypothesis Categories

The starting point for development of the working set of management hypotheses was the lifestage component CEMs described in Jacobson and others (2015b). From those diagrams we 
8

progressively filtered and refined hypotheses according to a four-part categorization (table 1). All of the 

possible pathways depicted in the CEMs comprise our global hypotheses, a broad list of hypotheses that 

have a possible role in explaining decline of the pallid sturgeon. The global hypotheses were filtered to 

provide a candidate list of dominant working hypotheses based on experts’ survey responses. This 

resulted in the biologically based dominant working hypotheses. The dominant working hypotheses 

represent a scientific perspective of factors that contribute to population dynamics of the pallid sturgeon

in the Missouri River. The list of dominant working hypotheses is meant to include plausible, 

biologically relevant hypotheses without regard to specific management or mitigation actions.

The dominant working hypotheses have been developed from the right side of the component 

CEMs (fig. 3), and present the hypotheses as combinations of factors that contribute to high mortality at 

each life stage. These hypotheses indicate factors and processes that are responsible for decline, but do 

not address management actions that would reverse or mitigate decline by increasing survival of the 

pallid sturgeon. Mitigation is addressed through another category of hypotheses, working management 

hypotheses (table 1), which integrate management actions on the left side of the CEMs (fig. 3) with the 

biologically based, dominant working hypotheses on the right side. Working management hypotheses 

consider actions that could aid in species recovery without testing if the species fall within USACE 

jurisdiction. Because multiple management hypotheses may affect similar biological responses, more 

working management hypotheses than dominant working hypotheses were produced. Working 

management hypotheses will also likely be more spatially explicit as some management options would 

be more effective in some areas compared to other areas.

The final step in the hypothesis prioritization process involved filtering the working 

management hypotheses for those that fall within USACE authorities and jurisdictions. This step 

defined a set of initially modeled hypotheses that will guide modeling by the EA team. The initially 

modeled hypotheses (table 1) provide a scope for the quantitative modeling for the MRRMP in Phase 1 

(fig. 1). However, filtering the working management hypotheses to focus on USACE authorities and 

jurisdictions will not necessarily address all factors that potentially limit population growth in pallid 

sturgeon. Ongoing effects analyses under adaptive management in Phases 2 and 3, after the initial effort 

under the MRRMP, may address hypotheses outside of USACE authorities; for example, hypotheses 

that address the effects of municipal wastewater exposure to pallid sturgeon.

Filtering and Refinement Process

The initial approach to address the many combinations of ecological characteristics (fig. 3) 

(boxes) and influences (arrows) was to consider the primary biotic responses on the right-hand side of 

the CEM diagrams (fig. 3), which were categorized into growth and condition, direct mortality, and 

reproductive performance. These biotic characteristics are related to survival of the particular life stage 

(or production of viable gametes from adults), and thus, were considered biologically influential to 

population dynamics. As a first step, the EA team selected those pathways that experts had depicted as 

important and certain to develop a candidate list of working dominant hypotheses. The candidate set of 

working dominant hypotheses were written interpretations of the important pathways on the right side 

of the CEMs (fig. 3, table 2); these hypotheses were articulated as conditions that would promote (alone 

or with other effects) substantial mortality. 
9

Table 1. Categories of the hypotheses filtering process for the Missouri River Pallid Sturgeon Effects Analysis 

(EA)

[USACE refers to the U.S. Army Corps of Engineers]

Category Description

Global.......................... Set of possible, biologically important hypotheses, relevant to population dynamics. 

Derived from conceptual ecological models.

Dominant Working...... Set of plausible, biologically important hypotheses, relevant to population dynamics. 

Derived from importance values in conceptual ecological model, scored by expert 

elicitation survey.

Working Management.. Set of management hypotheses linking management actions to working dominant 

hypotheses. Derived from pathways identified in conceptual ecological models and 

matched to working dominant hypotheses. Scored by expert elicitation survey.

Initially Modelled......... Subset of working management hypotheses determined by USACE to be within 

jurisdiction and applicable authorities, and therefore selected for modeling in EA 

Phase 1.

We engaged 21 experts in a modified Delphi process, a structured communication technique, 

originally developed as a systematic, interactive forecasting method that relies on a panel of experts 

(Normand and others, 1998), to prompt expert opinion on prioritization of dominant working 

hypotheses. The experts were selected based on knowledge of pallid sturgeon science, or a strong 

understanding of Missouri River abiotic processes, or both. The experts represented Federal and State 

agencies, universities, and the private sector from throughout the Missouri River Basin. The experts 

offered professional opinions and were not asked to develop consensus or recommendations. The 

modified Delphi process consisted of a Web-based survey in which experts were asked to score the 

importance of the hypotheses from low to high, including a neutral response and the option to indicate 

that they did not have sufficient relevant knowledge to score the dominant working hypotheses (fig. 4). 

We evaluated the results of the survey and presented the information during a workshop, March 11, 

2014, where hypotheses with wide variance in score were discussed (fig. 4). Subsequent to the 

workshop, the experts participated in an additional survey with the same hypotheses, somewhat 

differently stated, and a few additional hypotheses were then introduced. The results were also evaluated 

and hypotheses with medians scoring higher than neutral (fig. 5) were retained as working dominant 

hypotheses for the next step of the filtering and refinement process.

The working management hypotheses are statements about the linkage between management 

actions and population dynamics, with a focus on actions that would mitigate population decline. Hence, 

working management hypotheses are based on dominant working hypotheses as targets, but may include 

multiple pathways for each dominant hypothesis. The EA team matched the working dominant 

hypotheses with potential management actions (left side of CEMs, fig. 3) based on relations in the 

CEMs. Because of the multiple pathways, this process yielded more hypotheses, but the number was 

subsequently narrowed by combining management actions that affected multiple-life stages of the pallid 

sturgeon. The team used these hypothesis statements in a second round of a modified Delphi process 

that elicited input from 25 experts from throughout the Missouri River Basin, representing a wide range 

of expertise from various government, academic and private sectors. Twenty-two individuals responded
10

Figure 3. Diagram showing an example of a conceptual ecological model for life-stage components for the 

source of dominant working hypotheses (right side) and working management hypotheses (left side).

to the survey, and the results were quantified and analyzed. The hypotheses with median scores higher 

than neutral were retained, resulting in the set of working management hypotheses.

As a final step in Phase 1 prioritization, the working management hypotheses were submitted to 

the USACE and USFWS for comment and agreement. Based on criteria related to legal authorities and 

jurisdiction, the agencies indicated which hypotheses were not relevant to the present decision-making

process. These decisions were conservative in the sense that there was emphasis on retaining a broad 

set of hypotheses to be reviewed in the structured decision-making process.
11

Working Hypotheses Linking Management of the Missouri River to Population 

Dynamics 

Extraction of hypotheses relating primary biotic responses (growth, condition, mortality, and 

reproduction) to survival resulted in a list of 40 candidate dominant hypotheses (table 2). The first round 

of survey resulted in a substantial range of variability among and within hypotheses (fig. 4). The first 

round of survey also allowed for suggestions for new hypotheses, which were discussed at the March 

11, 2014 workshop. One of the points discussed during the workshop was the need for separate 

hypotheses for the Yellowstone River from those for the Upper Missouri River. Based on the workshop 

discussion, the EA team added nine hypotheses, which were submitted for the second round of survey 

(table 3). The second round resulted in remarkably similar results (fig. 5). Based on the criterion of 

median scores above neutral, we selected 23 hypotheses as the set of dominant working hypotheses 

(table 3). 

Matching potential management actions (left side of CEMs, fig. 3), with each hypothesis in the 

working set, resulted in 176 potential hypothesis combinations because more than one management 

action could be associated with most of the dominant working hypotheses. However, in many cases, a 

single management action could also affect multiple-life stages, which could therefore be combined. 

This possibility allowed the total number of candidate management hypotheses to be reduced to 53 

(table 4). Although only one expert survey was possible in the time available, the strong consistency in 

the two rounds of survey for the dominant working hypotheses indicate that the results would be 

unlikely to change much with a subsequent rounds (figs. 6 and 7). Based on the criterion of selecting 

hypotheses that have medians ranking above neutral, 30 working management hypotheses were selected 

to move forward (table 5).

Of the 30 working management hypotheses, 21 remained for initial modeling after the USACE 

and the USFWS agreed about authorities and jurisdictions. Hypotheses that will not be modeled during 

Phase 1 include the following actions:

• Removal of Fort Peck Dam. USACE does not have authority to remove the dam.

• Removal of Intake Dam, removal or construction of passage at Cartersville Dam (Yellowstone 

River). Removal of Intake Dam was not considered relevant to model at this time because 

construction of a passage system had already been approved and design and construction were in 

progress. The USACE determined that it was outside of their authority to remove or create 

passage at Cartersville.

• Regulation of agricultural and urban runoff to decrease endocrine-disrupting chemical exposure. 

The actions are outside of the USACE authority.

• Flow management on the Platte River to encourage spawning. The action is outside of the 

USACE authority.

The decision to remove hypotheses from consideration during Phase 1 is intended to focus efforts on 

modeling that will be relevant to decisions that need to be made under the MRRMP. Any hypothesis 

that is removed at this step—or any other step in the process—is available in later phases as needed to 

explain observed pallid sturgeon population changes. Processes to reexamine the reserved hypotheses 

will be an integral part of ongoing adaptive management of
12

Table 2. Candidate dominant working hypotheses before first round of expert survey 

[Key for labels: A, Adult; E, Embryo; F, Free embryo; L (first position), Larvae (exogenously feeding); J, Juvenile; 

U, Upper River; L (second position), Lower River. For this survey the Yellowstone and Upper Missouri Rivers 

were combined as Upper River]

Number Label Hypothesis Statement

1 AU1a Barriers to upstream migration prevent access to functional spawning sites with supportive 

hydraulics and substrate, thereby decreasing probability of producing viable gametes.

2 AU1b Hydrology-related events are inadequate to cue aggregation of reproductive adults, thereby 

decreasing probability of mates to find one another.

3 AU2a Take of prespawn adults through poaching or other mechanisms has increased direct mortality.

4 AU3a Population augmentation has increased numbers of conspecifics, increasing competition for 

food resources in a fragmented system with decreased productivity, thereby decreasing 

growth, condition, and fecundity.

5 AL1a Habitat alterations have decreased separation of reproductive shovelnose and pallid sturgeon in 

space and time, thereby increasing hybridization.

6 AL1b Habitat alterations have decreased availability of functional spawning habitat while also 

increasing availability of attractive, sub-optimal spawning habitat, thereby decreasing 

probability of mates finding one another.

7 AL1c Hydrology-related events are inadequate to cue aggregation of reproductive adults, thereby 

decreasing probability of mates to find one another.

8 AL2a Channelization and changes in flow regime have decreased food availability which results in 

decreased growth, condition, and fecundity.

9 AL2b Channelization and changes in flow regime have increased velocities, decreased habitat 

suitability and complexity, resulting in decreased growth, condition, and fecundity.

10 EU1a Hypolimnetic releases of cold water have increased embryo incubation time which results in 

increased predation prior to hatch.

11 EU1b Decreased turbidity has increased efficacy of predators and predation prior to hatch.

12 EU1c Increased numbers of predators have increased predation prior to hatch.

13 EL1a Decreased turbidity has increased efficacy of predators and predation prior to hatch.

14 EL1b Increased numbers of introduced or invasive predators have increased predation prior to hatch.

15 EL1c Channelization and changed flow regimes have increased scour and sediment deposition in 

embryo incubation areas resulting in increases in direct mortality of developing embryos by 

detachment, entrainment, or sedimentation (by crushing or smothering).

16 FU1a Hypolimnetic releases of cold water have increased embryo development time which results in 

increased predation prior to settling.

17 FU1b Decreased turbidity has increased efficacy of predators and predation prior to settling.

18 FU1c Increased numbers of predators has increased predation prior to settling.

19 FU1d Barriers to upstream migration limit available downstream dispersal distance such that 

dispersing free embryos settle in habitats that are not suitable for first feeding, thereby 

increasing direct mortality.

20 FU1e Barriers to upstream migration limit available downstream dispersal distance such that 

dispersing free embryos settle in anoxic headwaters of downstream reservoirs increasing 

direct mortality.

21 FU2a Changes in flow regime, water quality, and(or) local habitat in settling areas have decreased the 

prey base for first-feeding, decreasing growth, condition, and survival.

22 FL1a Channelization has decreased post-hatch refugia in substrate interstices resulting in increased 

direct mortality from predation.

23 FL1b Reservoirs have decreased turbidity, resulting in increased efficacy of predators and increased 

direct mortality from predation.

24 FL1c Channelization has decreased suitable hydraulics to intercept and retain drifting free embryos, 

resulting in increased direct mortality by starvation, inability to transition to first feeding.
13

Table 2. Candidate working dominant hypotheses before first round of expert survey - Continued

Number Label Hypothesis Statement

25 FL2a Channelization has decreased supportive habitat conditions for first feeding (increased 

velocities, lack of habitat complexity) decreasing growth, condition, and survival.

26 FL2b Changes in flow regime, water quality, and(or) channel complexity in settling areas result in 

lack of suitable food for first feeding and decreases to growth, condition, and survival.

27 LU1a Reservoirs have decreased turbidity, resulting in increased efficacy of predators and increased 

direct mortality from predation.

28 LU1c Reservoirs have created anoxic conditions in headwaters where many free embryos settle, 

resulting in increased direct mortality.

29 LU2a In areas upstream of reservoir headwaters, increased summer reservoir releases result in 

increased velocities, decreases in supportive habitat, and decreases in growth, condition, and 

survival.

30 LU2b Changes in flow regime have decreased productivity of suitable foods, decreasing growth, 

condition, and survival.

31 LL1a Reservoirs have decreased turbidity, resulting in increased efficacy of predators and increased 

direct mortality from predation.

32 LL1b Increased numbers of introduced or invasive predators increase predation

33 LL1c Changes in flow regime and channelization have resulted in increased quality of physical 

habitat for predators, resulting in increased predation.

34 LL2a Changes in flow regime and channelization have resulted in increased velocities, decrease in 

supportive channel complexity, and decreases in growth, condition, and survival.

35 LL2b Changes in flow regime and channelization have resulted in decreased productivity of suitable 

food, decreasing growth, condition, and survival.

36 JU1a Reservoir releases have altered flow and temperature regimes, increasing bioenergetic demands 

and decreasing growth, condition, and survival.

37 JU1b Reservoir releases have altered flow and temperature regimes, decreasing productivity and food 

availability, and resulting in decreases in growth, condition, and survival.

38 JU1c Population augmentation has increased numbers of conspecifics, increasing competition for 

food resources in a fragmented system with decreased productivity, thereby decreasing 

growth, condition, and survival.

39 JL1a Reservoir releases have decreased flow variation, resulting in decreased productivity and food 

availability, and decreases in growth, condition, and survival.

40 JL1b Channelization has decreased channel complexity, resulting in decreased productivity and food 

availability, and decreases in growth, condition, and survival.
14

Figure 4. Graphs showing the results of the first survey of dominant working hypotheses. A, Response scores. B, No relevant knowledge. 

Figure 5. Graphs showing the results of the second survey of dominant working hypotheses. A, Response scores. B, No 

relevant knowledge. 
15

Table 3. Candidate dominant working hypotheses before second round of expert survey 

[Hypotheses shaded in gray were those selected as working dominant hypotheses. Key for labels: A, Adult; E, Embryo; F, 

Free embryo; L, Larvae (exogenously feeding); J, Juvenile; YR, Yellowstone River; MR, Upper Missouri River]

Number Label Hypothesis

Prespawn and spawning adults

1

Upper River

AU1a 

- MR

ADULTS, UPPER RIVER, MISSOURI - Barriers to upstream migration prevent 

access to functional spawning sites with supportive hydraulics and substrate.

2 AU1a 

- YR

ADULTS, UPPER RIVER, YELLOWSTONE - Barriers to upstream migration 

prevent access to functional spawning sites with supportive hydraulics and 

substrate.

3 AU1b 

- MR

ADULTS, UPPER RIVER, MISSOURI - Hydrology-related events (for example, 

pulsed flows, water temperature variation, during the adult reproductive period) 

are inadequate to cue aggregation of reproductive adults, decreasing probability 

of mates to find one another. 

4 AU1b 

- YR

ADULTS, UPPER RIVER, YELLOWSTONE - Hydrology-related events (for 

example, pulsed flows, water temperature variation, during the adult 

reproductive period) are inadequate to cue aggregation of reproductive adults, 

decreasing probability of mates to find one another. 

5 AU2a ADULTS, UPPER RIVER - Take of prespawn adults through poaching or other 

mechanisms is a significant source of direct mortality. 

6 AU3a ADULTS, UPPER RIVER - Number of conspecifics creates density-dependent 

competition for available prey, leading to reduced pallid growth, condition, and 

fecundity.

7

Lower River

AL1a ADULTS, LOWER RIVER - Decreased separation of reproductive shovelnose and 

pallid sturgeon in space and time has resulted in increased hybridization, 

decreased genetic distinctness.

8 AL1b ADULTS, LOWER RIVER - Too much attractive spawning substrate decreases 

probability of pallid mates finding one another.

9 AL1c ADULTS, LOWER RIVER - Hydrology-related events (for example, pulsed flows, 

water temperature variation, during the adult reproductive period) are inadequate 

to cue aggregation of reproductive adults, decreasing probability of mates to find 

one another. 

10 AL2a ADULTS, LOWER RIVER - Decreased food availability has led to decreased 

growth, condition, and fecundity.

11 AL2b ADULTS, LOWER RIVER - High water velocity and insufficient habitat 

complexity (for example, lack of refugia to conserve energy) have led to 

decreased growth, condition, and fecundity.

Gametes and Developing Embryos

12

Upper River

EU1a GAMETES, EMBRYOS, UPPER RIVER - Vertical transmission of contaminants 

causes significant loss of viability in gametes or direct mortality in developing 

embryos.

13 EU1c GAMETES, EMBRYOS, UPPER RIVER, MISSOURI - Probability of predation 

prior to hatch is high due to hypolimnetic releases of cold water that prolong 

embryo incubation time.

14 EU1d GAMETES, EMBRYOS, UPPER RIVER, MISSOURI - Predation rate on 

embryos prior to hatch is high due to low turbidity (increased efficacy of sightfeeding predators).

15 EU1e GAMETES, EMBRYOS, UPPER RIVER - Predation rate on embryos prior to 

hatch has increased due to increased numbers of predators.
16

Table 3. Candidate working dominant hypotheses before second round of expert survey - Continued

Number Label Hypothesis

Gametes and Developing Embryos (Continued)

16

Lower River

EL1a GAMETES, EMBRYOS, LOWER RIVER - Vertical transmission of contaminants 

causes significant loss of viability in gametes or direct mortality in developing 

embryos.

17 EL1b GAMETES, EMBRYOS, LOWER RIVER - Predation rate on embryos prior to 

hatch has increased due to low turbidity (increased efficacy of sight-feeding 

predators).

18 EL1c GAMETES, EMBRYOS, LOWER RIVER - Predation rate on embryos prior to 

hatch has increased due to increased numbers of predators.

19 EL1d GAMETES, EMBRYOS, LOWER RIVER - Direct mortality of embryos by 

detachment, entrainment, or sedimentation (by crushing or smothering) has 

increased due to increased scour and sediment deposition at embryo incubation 

locations.

Free Embryos

20

Upper River

FU1a FREE EMBRYOS, UPPPER RIVER, MISSOURI - Probability of predation prior to 

settling is high due to hypolimnetic releases of cold water that prolong free 

embryo development.

21 FU1b FREE EMBRYOS, UPPPER RIVER, MISSOURI - Predation rate on free embryos 

prior to settling is high due to low turbidity (increased efficacy of sight-feeding 

predators).

22 FU1c FREE EMBRYOS, UPPPER RIVER - Predation rate on free embryos prior to 

settling has increased due to increased numbers of predators.

23 FU1d FREE EMBRYOS, UPPPER RIVER - Free embryos transported into headwaters of 

reservoirs suffer direct mortality through lethal water-quality conditions, such as 

anoxia. 

24 FU1e FREE EMBRYOS, UPPPER RIVER -Free embryos transported into headwaters of 

reservoirs starve because habitat conditions are unsuitable for first feeding (areas 

without sufficient prey base). 

25 FU1f FREE EMBRYOS, UPPER RIVER - Free embryos are transported into nonsupporting habitats because barriers limit upstream adult migration or reservoirs 

limit downstream dispersal.

26 FU1g FREE EMBRYOS, UPPER RIVER, MISSOURI - Free embryos are transported 

into non-supporting habitats because of increased velocities associated with flow 

management.

27 FU2a FREE EMBRYOS, UPPER RIVER. MISSOURI - Changes in flow regime, water 

quality, and/or local habitat in settling areas have decreased the prey base for 

first-feeding, significantly decreasing growth, condition, and survival.

28

Lower River

FL1a FREE EMBRYOS, LOWER RIVER - Direct mortality has increased due to 

predation because substrate does not provide sufficient refugia. 

29 FL1b FREE EMBRYOS, LOWER RIVER - Predation rate on free embryos prior to 

settlement has increased due to low turbidity (increased efficacy of sight-feeding 

predators). 

30 FL1c FREE EMBRYOS, LOWER RIVER - Direct mortality has increased due to 

starvation, inability to transition to first feeding because hydraulic conditions do 

not allow a free embryo to settle into areas with prey.

31 FL2a FREE EMBRYOS, LOWER RIVER - Growth, condition, and survival have 

decreased because increased water velocity and lack of habitat complexity have 

led to unsuitable habitat conditions for first feeding.
17

Table 3. Candidate working dominant hypotheses before second round of expert survey - Continued

Number Label Hypothesis

Free Embryos (Continued)

32

Lower 

River

FL2b FREE EMBRYOS, LOWER RIVER - Growth, condition, and survival have 

decreased because flow regime, water quality, and lack of habitat complexity at 

settling locations have resulted in lack of suitable prey resources for first feeding.

Exogenously Feeding Larvae

33

Upper River

LU1a EXO LARVAE, UPPER RIVER, MISSOURI - Predation rate on larvae has 

increased due to low turbidity (increased efficacy of sight-feeding predators).

34 LU1b EXO LARVAE, UPPER RIVER - Predation rate on larvae has increased due to 

increased numbers of introduced or invasive predators.

35 LU1c EXO LARVAE, UPPER RIVER - Exo larvae dispersing into headwaters of 

reservoirs suffer direct mortality through lethal water-quality conditions, such as 

anoxia. 

36 LU1d EXO LARVAE, UPPER RIVER - Exo larvae disperse into non-supporting habitats 

because barriers limit upstream adult migration or reservoirs limit downstream 

dispersal.

37 LU2a EXO LARVAE, UPPER RIVER, MISSOURI - Exo larvae disperse into nonsupporting habitats because of increased velocities associated with flow 

management.

38 LU2b EXO LARVAE, UPPER RIVER, MISSOURI - Growth, condition, and survival in 

the Missouri River have decreased due to seasonal reservoir water releases that 

alter water velocity and habitat.

39 LU2c EXO LARVAE, UPPER RIVER. MISSOURI - Growth, condition, and survival 

have decreased due to changes in flow regime, water quality, and/or local habitat 

that have decreased the prey base.

40

Lower River

LL1a EXO LARVAE, LOWER RIVER - Predation rate on larvae is high due to low 

turbidity (increased efficacy of sight-feeding predators).

41 LL1b EXO LARVAE, LOWER RIVER - Predation rate on larvae has increased due to 

increased numbers of introduced or invasive predators.

42 LL1c EXO LARVAE, LOWER RIVER - Predation rate on larvae has increased due to 

increased quality of physical habitat for predators.

43 LL2a EXO LARVAE, LOWER RIVER - Growth, condition, and survival have decreased 

due to altered flow regime and channelization that increase water velocity and 

decrease supportive channel complexity. 

44 LL2b EXO LARVAE, LOWER RIVER - Growth, condition, and survival have decreased 

due to altered flow regime and channelization that decreases river productivity 

(prey resources).

Juveniles

45

Upper River

JU1a JUVENILES, UPPER RIVER, MISSOURI - Growth, condition, and survival have 

decreased due to altered flow and temperature regimes that change bioenergetic 

dynamics.

46 JU1b JUVENILES, UPPER RIVER, MISSOURI - Growth, condition, and survival have 

decreased due to altered flow and temperature regimes that decreases river 

productivity (prey resources).

47 JU1c JUVENILES, UPPER RIVER, MISSOURI - Growth, condition, and survival have 

decreased due to increased conspecific competition. 
18

Table 3. Candidate working dominant hypotheses before second round of expert survey - Continued

Number Label Hypothesis

Juveniles (Continued)

48

Lower River

JL1a JUVENILES, LOWER RIVER - Growth, condition, and survival have 

decreased due to moderated discharge variation that reduces river 

productivity (prey resources).

49 JL1b JUVENILES, LOWER RIVER. Growth, condition, and survival have 

decreased due to insufficient habitat (channel complexity) that reduces 

river productivity (prey resources).

the Missouri River and will be addressed in the Adaptive Management Plan (A. Quinn, U.S. Army 

Corps of Engineers, written commun., 2015).

All three rounds of surveys for dominant and management hypotheses included the opportunity 

for experts to select “Don’t know, no relevant knowledge.” The number of responses in this category 

provides useful context for the hypothesis scores, indicating a level of uncertainty that may inform how 

hypotheses are addressed in the future. Hypotheses with high numbers of unknown responses, for 

example, may be candidates for resurrection from the reserve, for increased effort to decrease 

uncertainties during development of quantitative models, or for increased effort in design of research 

and monitoring. Management hypotheses with more than one-third of the experts selecting “Don’t 

know, no relevant knowledge” include:

• Reduction of main-stem Missouri River flows from Fort Peck Dam during the spawning season 

will increase downstream turbidity by increasing proportional contribution from the turbid Milk 

River, thereby decreasing predation of embryos, free embryos, and exogenously feeding larvae.

• Removal of anoxic, flocculant sediment in the headwaters of Lake Sakakawea will decrease 

mortality of free embryos and exogenously feeding larvae due to lethal water quality.

• Increasing dissolved oxygen in headwaters using air diffusers or similar methods will increase 

survival of free embryos and exogenously feeding larvae.

• Naturalization of flow regime on the Platte River (Nebraska), will allow migration, spawning, 

and recruitment to the Missouri River population.

• Removal of migration barriers on the Kansas River will allow migration, spawning, and 

recruitment to the Missouri River population.

• Removal of migration barriers in the Osage River will allow migration, spawning, and 

recruitment to the Missouri River population.

• Channel reconfiguration in the Middle Mississippi River will increase retention, growth, 

survival, and recruitment of pallid sturgeon to the Missouri River population.

Five of these seven hypotheses address abiotic conditions outside of the main-stem Missouri 

River and the high rate of uncertainty may reflect the fact that the attention of pallid-sturgeon scientists 

has been focused on main-stem processes and has only lately moved toward the role of tributaries (U.S. 

Fish and Wildlife Service, 2014). Most of these highly uncertain hypotheses have both abiotic and biotic 

components, and focused effort on one or the other may provide enough information to reject or 

continue pursuit of a hypothesis.
19

Table 4. Candidate working management hypotheses before third survey

Number What Management Hypothesis

Upper Missouri River

1

Remove Fort 

Peck Dam

Removing Fort Peck Dam will allow reproductive pallid sturgeon to access upstream 

functional spawning sites, increasing spawning success.

2 Removing Fort Peck Dam will result in increased effective drift distance for 

dispersing free embryos, decreasing downstream mortality.

3

Removing Fort Peck Dam will naturalize the flow regime, resulting in increased 

productivity, increased flow cues, and increased use of complex overbank 

habitats.

4 Removing Fort Peck Dam will increase and naturalize turbidity levels, resulting in 

decreased predation on embryos, free embryos, and exo larvae.

5

Alter Flow 

Regime at 

Fort Peck

Naturalized flow releases at Fort Peck will result in increased productivity through 

increased hydrologic connections with low-lying land and flood plains in the 

spring, and decreased velocities and bioenergetic demands on exo larvae and 

juveniles during low flows in summer and fall.

6 Naturalized flow releases at Fort Peck will result in increased reproductive success 

through increased aggregation and spawning success of adults.

7

Naturalized flow releases at Fort Peck will result in increased hydrologic connection 

with low-lying land, increased growth rates, shorter drift distance, and increased 

survival of free embryos.

8

Reduction of main-stem Missouri River flows at Fort Peck Dam during the 

spawning season will increase downstream turbidity by increasing proportional 

contribution from the turbid Milk River, thereby decreasing predation of embryos, 

free embryos, and exo larvae.

9

Reduction of main-stem Missouri River flows from Fort Peck Dam during free 

embryo dispersal will decrease main-stem velocities and drift distance thereby 

decreasing downstream mortality of free embryos and exo larvae.

10

Provide spring pulsed flow releases from Fort Peck to draw reproductive adults up 

Missouri River where potential dispersal distance (greater than Yellowstone) will 

decrease downstream mortality of free embryos and exo larvae.

11 In case where fish passage has been enhanced on Yellowstone, operate Fort Peck 

releases to NOT draw reproductive adults up the Missouri.

12 Install 

temperature 

control, 

multilevelrelease device 

at Fort Peck

Warmer flow releases at Fort Peck will increase system productivity and food 

resources, increased growth and condition of exo larvae and juveniles.

13 Warmer flow releases at Fort Peck will increase growth rates, shorten drift distance, 

and increase survival of free embryos.

14 Warmer flow releases at Fort Peck will result in increased growth rates of 

exogenously feeding larvae, increase probability of surviving the first winter.

15

Sediment bypass 

at Fort Peck 

or other 

sediment 

augmentation.

Installing sediment bypass at Fort Peck will increase and naturalize turbidity levels, 

resulting in decreased predation on embryos, free embryos, and exo larvae.
20

Table 4. Candidate working management hypotheses before third survey - Continued

Number What Management Hypothesis

Yellowstone River

16 Construct fish 

passage at 

Intake on 

Yellowstone 

River

Fish passage on the Yellowstone River will allow access to additional functional 

spawning sites, increasing spawning success.

17

Fish passage on the Yellowstone River will result in increased effective drift 

distance, decreasing downstream mortality of free embryos and exo larvae.

18 Removal of 

Intake on 

Yellowstone 

River

Fish passage on the Yellowstone River will allow access to additional functional 

spawning sites, increasing spawning success.

19 Fish passage on the Yellowstone will result in increased effective drift distance, 

decreasing downstream mortality of free embryos and exo larvae.

20

Construct fish 

passage at 

Intake and 

Cartersville 

Dams on 

Yellowstone 

River

Fish passage on the Yellowstone River will allow access to additional functional 

spawning sites, increasing spawning success.

21

Fish passage on the Yellowstone River will result in increased effective drift 

distance, decreasing downstream mortality of free embryos and exo larvae.

22

Removal of 

Intake and 

Cartersville 

Dams on 

Yellowstone 

River

Fish passage on the Yellowstone River will allow access to additional functional 

spawning sites, increasing spawning success.

23

Fish passage on the Yellowstone River will result in increased effective drift 

distance, decreasing downstream mortality of free embryos and exo larvae.

Yellowstone and Missouri Rivers

24

Channel 

reconfiguration

Reconfiguration of channel substrate in spawning patches will increase interstitial 

space, retention, and survival of free embryos.

25

Reconfiguration of channels in both rivers will increase complexity and retention of 

free embryos, decreasing effective drift distance, and thereby decreasing 

downstream mortality. Reconfiguration will also increase productivity and food 

resources, decreasing bioenergetic demand.

26 Propagation Population augmentation will increase density of reproductive adult fish, resulting in 

sufficient numbers of gametes and embryos to support natural recruitment.

Lake Sakakawea

27

Operate Garrison 

Dam to draw 

down Lake 

Sakakawea

Drawdown of Lake Sakakawea will increase effective drift distance, decreasing 

downstream mortality of free embryos and exo larvae.

28 Improve 

headwaters 

water quality

Removal of anoxic, flocculant sediment at headwaters of Lake Sakakawea will 

decrease mortality of free embryos and exo larvae due to lethal water quality.

29 Increasing dissolved oxygen in headwaters using air diffusers or similar methods 

will increase survival of free embryos and exo larvae.
21

Table 4. Candidate working management hypotheses before third survey - Continued

Number What Management Hypothesis

Lower Missouri River

30

Alter flow regime 

at Gavins Point

Naturalization of the flow regime at Fort Peck will improve flow cues in spring 

for aggregation and spawning of reproductive adults.

31

Naturalization of the flow regime at Fort Peck will improve connectivity with 

marginal habitats and low-lying lands, increase primary and secondary 

production, and increase growth and condition of exogenously feeding larvae 

and juveniles.

32

Naturalization of the flow regime at Fort Peck will decrease velocities and 

bioenergetic demands, resulting in increased growth and condition for exo 

larvae and juveniles.

33 Alteration of the flow regime at Fort Peck will prepare substrate in spawning 

patches, resulting in increased success in spawning and incubation.

34 Alteration of the flow regime at Fort Peck will decrease scour during incubation, 

resulting in increased embryo survival.

35 Alteration of the flow regime at Fort Peck can be optimized to decrease main-stem 

velocities, decrease effective drift distance, and avoid downstream mortality. 

36 Temperature 

management at 

Fort Randall and 

Gavins Point

Operation of a temperature management system at Fort Randall and(or) Gavins 

Point will increase water temperature downstream of Gavins Point, providing 

spawning cues for reproductive adults.

37

Operation of a temperature management system at Fort Randall and(or) Gavins 

Point will increase water temperature downstream of Gavins Point, increasing 

growth rates for free embryos, exo larvae, and juveniles.

38

Channel 

reconfiguration

Re-engineering of channel morphology in selected reaches will create optimal 

spawning conditions—substrate, hydraulics, and geometry—to increase 

probability of successful spawning, fertilization, embryo incubation, and freeembryo retention, and to separate reproductive pallid sturgeon and shovelnose 

sturgeon, thereby decreasing probability of hybridization.

39

Re-engineering of channel morphology in selected reaches will increase channel 

complexity and bioenergetic conditions to increase prey density (invertebrates 

and native prey fish) for exo larvae and juveniles. 

40 Re-engineering of channel morphology will increase channel complexity and 

maximize bioenergetic conditions for resting, migration, and foraging of adults. 

41

Re-engineering of channel morphology in selected reaches will increase channel 

complexity and serve specifically to intercept and retain drifting free embryos in 

areas with sufficient prey for first feeding and for growth through juvenile 

stages.

42

Re-engineering of channel morphology in selected reaches will increase channel 

complexity to increase primary and secondary productivity, and prey-fish 

production thereby increasing growth and condition of exo larvae through 

juvenile stages.

43

Water quality 

management

Regulation of agricultural runoff and municipal waste discharge will decrease 

exposure to endocrine-disrupting chemicals, thereby decreasing incidence of 

intersex and increasing reproductive success of adults.

44

Regulation of agricultural and urban runoff will decrease biological oxygen 

demand, increase dissolved oxygen, and thereby increase growth, condition and 

survival of free embryos and exo larvae.

45 Sediment bypass 

at Gavins Point

Operation of a sediment bypass system at Gavins Point Dam will increase 

turbidity and decrease mortality of free embryos and exo larvae from predation.

46 Control of native and non-native predators through harvest or other mechanisms 

will increase survival of embryos, free embryos, and exo larvae.
22

Table 4. Candidate working management hypotheses before third survey - Continued

Number What Management Hypothesis

Lower Missouri River (Continued)

47 Competition 

control

Increasing/allowing commercial harvest of shovelnose sturgeon will decrease 

probabilities of hybridization between shovelnose and pallid sturgeon.

48 Control of conspecific species through harvest or other mechanisms will decrease 

competition for food and space for exo larvae and juveniles.

49 Flow regime Platte 

River

Naturalization of flow regime on the Platte River (Nebraska), will allow 

migration, spawning, and recruitment to the Missouri River population.

50

Migration barriers

Removal of migration barriers on the Kansas River will allow migration, 

spawning, and recruitment to the Missouri River population.

51 Removal of migration barrier in the Osage River will allow migration, spawning, 

and recruitment to the Missouri River population.

52

Channel 

reconfiguration, 

Mississippi 

River

Channel reconfiguration in the Middle Mississippi River will increase retention, 

growth, survival, and recruitment of pallid sturgeon to the Missouri River 

population.

53 Propagation Increasing numbers of pallid sturgeon propagated will decrease probability of 

hybridization with shovelnose sturgeon.

For example, the hypothesis regarding Platte River flow regime can be considered in two parts: 

a) flow management on the Platte River may have an appreciable effect on flow regime in the Lower 

Platte River, given available water and geographic locations of Platte River reservoirs; and, b) given a 

more favorable flow regime, pallid sturgeon might use the Platte River for successful reproduction. The 

former question can be addressed with existing data and understanding (and has been investigated 

through the Platte River Recovery Implementation Program, (Parham, 2007; Smith, 2011)). The latter is 

a more difficult question. Ancillary information gathered during investigations of reproductive ecology 

of pallid sturgeon in the main-stem Missouri River has documented spawning of pallid sturgeon in the 

Platte River (DeLonay and others, 2012; DeLonay and others, 2016) but a more definitive answer about

whether pallid sturgeon use of the Platte River would result in increases in population may require 

specifically focused future research.

Implications of the Hypothesis Filtering Process

The need to filter through global, to dominant working, to working management, to initially 

modeled hypotheses is a simple practicality. Among the thousands of possible linkages from 

management to pallid sturgeon population dynamics, a reasonable number of hypotheses need to be 

selected to start the modeling process and to define the required scope and supporting hydrology and 

hydraulic models. The process we used to do this necessarily depended on expert opinion to a large 

extent. Experts from throughout the basin and of varying backgrounds were invited to participate to 

limit potential bias in perspective and expertise. This process was systematic and quantitative, and 

importantly, it was documented so those hypotheses that were not carried forward at each step were 

documented and can be resurrected at any time as needed. The Adaptive Management Plan, which is 

currently (2015) being created, will address the process needed to reanalyze these reserve hypotheses.
23

Table 5. Working set of management hypotheses after expert elicitation

[Shaded hypotheses were considered by USACE to be outside their jurisdictions or authorities. Unshaded hypotheses are identified as the 

initially modeled set under EA Phase 1]

What Original 

Number

Working 

Set 

Number Management Hypothesis

Upper Missouri River

Remove Fort 

Peck Dam

1 1 Removing Fort Peck Dam will allow reproductive pallid sturgeon to 

access upstream functional spawning sites, increasing spawning 

success.

2 2 Removing Fort Peck Dam will result in increased effective drift 

distance for dispersing free embryos, decreasing downstream 

mortality of free embryos and exogenously feeding larvae.

3 3 Removing Fort Peck Dam will naturalize the flow regime, resulting in 

increased productivity for all life stages, increased flow cues for 

spawning adults, and increased use of complex overbank habitats. 

4 4 Removing Fort Peck Dam will increase and naturalize turbidity levels, 

resulting in decreased predation on embryos, free embryos, and 

exogenously feeding larvae.

Alter flow 

regime at Fort 

Peck

5 5 Naturalized flow releases at Fort Peck will result in increased 

productivity through increased hydrologic connections with lowlying land and flood plains in the spring, and decreased velocities 

and bioenergetic demands on exogenously feeding larvae and 

juveniles during low flows in summer and fall. 

6 6 Naturalized flow releases at Fort Peck will result in increased 

reproductive success through increased aggregation and spawning 

success of adults.

9 7 Reduction of main-stem Missouri River flows from Fort Peck Dam 

during free embryo dispersal will decrease main-stem velocities and 

drift distance thereby decreasing downstream mortality of free 

embryos and exogenously feeding larvae.

Temperature 

control, 

multilevelrelease device 

at Fort Peck

12 8 Warmer flow releases at Fort Peck will increase system productivity 

and food resource availability, thereby increasing growth and 

condition of exogenously feeding larvae and juveniles.

13 9 Warmer flow releases from Fort Peck will increase growth rates, 

shorten drift distance, and increase survival of free embryos.

Sediment bypass 

at Fort Peck or 

other sediment 

augmentation.

15 10 Installing sediment bypass at Fort Peck will increase and naturalize 

turbidity levels, resulting in decreased predation on embryos, free 

embryos, and exogenously feeding larvae.

Our process built on hundreds of person-years of experience in the EA team and supporting 

experts, previous integrative efforts (2014 recovery plan, (U.S. Fish and Wildlife Service, 2014), and on 

a steadily increasing foundation of pallid sturgeon science. Research, monitoring, and assessment of 

pallid sturgeon have increased markedly since about 2000, as indicated by the number of peer-reviewed 

scientific publications that emerge from a standard reference search (fig. 8). The surge generally 

coincides with the 2000 and 2003 “Biological Opinions” and the 2004 “Missouri River Master Manual,” 

which together called for increasing emphasis on building the scientific foundation for managing the 

Missouri River to promote recovery of the pallid sturgeon (U.S. Fish and Wildlife Service, 2000b, 2003; 

Quist and others, 2004; U.S. Army Corps of Engineers, 2006). 
24

Table 5. Working set of management hypotheses after expert elicitation - Continued

What Original 

Number

Working 

Set 

Number Management Hypothesis

Yellowstone River

Construct fish 

passage at Intake 

on Yellowstone 

River

17 11 Fish passage at Intake Dam on the Yellowstone River will allow access 

to additional functional spawning sites, increasing spawning success 

and effective drift distance, and decreasing downstream mortality of 

free embryos and exogenously feeding larvae.

Removal of Intake 

on Yellowstone 

River

18 12 Fish passage at Intake Dam on the Yellowstone River will allow access 

to additional functional spawning sites, increasing spawning success 

and effective drift distance, and decreasing downstream mortality of 

free embryos and exogenously feeding larvae.

Construct fish 

passage at Intake 

and Cartersville 

Dams on 

Yellowstone 

River

19 13 Fish passage at Intake and Cartersville Dams on the Yellowstone River

will allow access to additional functional spawning sites, increasing 

spawning success and effective drift distance, and decreasing 

downstream mortality of free embryos and exogenously feeding 

larvae.

Removal of Intake 

and Cartersville 

Dams on 

Yellowstone 

River

20 14 Fish passage at Intake and Cartersville Dams on the Yellowstone River

will allow access to additional functional spawning sites, increasing 

spawning success and effective drift distance, and decreasing 

downstream mortality of free embryos and exogenously feeding 

larvae.

Upper Basin 

propagation

26 15 Stocking at optimal size classes will increase growth rates and survival 

of exogenously feeding larvae and juveniles.

27 16 Stocking with appropriate parentage and genetic diversity will result in 

increased survival of embryos, free embryos, exogenously feeding 

larvae, and juveniles.

Lake Sakakawea

Operate Garrison 

Dam to draw 

down Lake 

Sakakawea

28 17 Drawdown of Lake Sakakawea will increase effective drift distance, 

decreasing downstream mortality of free embryos and exogenously 

feeding larvae.

Lower Missouri River

Alter flow regime 

at Gavins Point

31 18 Naturalization of the flow regime at Gavins Point will improve flow 

cues in spring for aggregation and spawning of reproductive adults.

32 19 Naturalization of the flow regime at Gavins Point will improve 

connectivity with marginal habitats and low-lying lands, increase 

primary and secondary production, and increase growth and condition 

of exogenously feeding larvae and juveniles.

33 20 Naturalization of the flow regime at Gavins Point will decrease 

velocities and bioenergetic demands, resulting in increased growth 

and condition for exogenously feeding larvae and juveniles.

36 21 Alteration of the flow regime at Gavins Point can be optimized to 

decrease main-stem velocities, decrease effective drift distance, and 

minimize mortality.

Temperature 

management at 

Fort Randall and 

Gavins Point

37 22 Operation of a temperature management system at Fort Randall and(or)

Gavins Point will increase water temperature downstream of Gavins 

Point, providing spawning cues for reproductive adults.
25

Table 5. Working set of management hypotheses after expert elicitation - Continued

What Original 

Number

Working 

Set 

Number Management Hypothesis

Lower Missouri River (Continued)

Channel 

reconfiguration

39 23

Re-engineering of channel morphology in selected reaches will 

create optimal spawning conditions -- substrate, hydraulics, and 

geometry -- to increase probability of successful spawning, 

fertilization, embryo incubation, and free-embryo retention.

41 24

Re-engineering of channel morphology in selected reaches will 

increase channel complexity and bioenergetic conditions to 

increase prey density (invertebrates and native prey fish) for 

exogenously feeding larvae and juveniles. 

42 25

Re-engineering of channel morphology will increase channel 

complexity and minimize bioenergetic requirements for resting 

and foraging of exogenously feeding larvae and juveniles.

43 26

Re-engineering of channel morphology in selected reaches will 

increase channel complexity and serve specifically to intercept 

and retain drifting free embryos in areas with sufficient prey for 

first feeding and for growth through juvenile stages.

Water quality 

management 44 27

Regulation of agricultural runoff and municipal waste discharge 

will decrease exposure to endocrine-disrupting chemicals, thereby 

decreasing incidence of reproductive impairments and increasing 

reproductive success of adults.

Flow regime 

Platte River 50 28

Naturalization of flow regime on the Platte River (Nebraska), will 

allow migration, spawning, and recruitment to the Missouri River 

population.

Propagation 

Lower Basin

56 29 Stocking at optimal size classes will increase growth rates and 

survival of exogenously feeding larvae and juveniles.

58 30

Stocking of fish with appropriate genetic heritage and at river 

locations with appropriate habitats will increase growth and 

survival of exogenously feeding larvae and juveniles.

Concerted science efforts include the Pallid Sturgeon Population Assessment Project, the Habitat 

Assessment and Monitoring Project (HAMP), the Comprehensive Sturgeon Research Project, and early 

life-stage research carried out at the South Dakota State University. The current (2015) state of the 

considerable scientific information on pallid sturgeon has been compiled in two recent documents: (U.S. 

Fish and Wildlife Service, 2014; DeLonay and others, 2016). However, it should be noted that despite 

the large and increasing knowledge base on pallid sturgeon reproductive ecology, research has yet to 

prove one or more critical processes that are responsible for lack of population growth.

Our process of hypothesis formulation and filtering has been built on the foundation of previous 

work. Previous direction and prioritization of pallid sturgeon science have come from multiple sources 

including the Recovery Plan for the pallid sturgeon (U.S. Fish and Wildlife Service, 1993) and the 

revised plan (U.S. Fish and Wildlife Service, 2014), comprehensive workshops in 2004 and 2008 (Quist 

and others, 2004; Bergman and others, 2008), specific project reviews (Sustainable Ecosystems 

Institute, 2004, 2005, 2007, 2008), results of the “spring rise” plenary group process (Jacobson and 

Galat, 2008), and deliberations of the MRRIC ISAP (Doyle and others, 2011). 
26

Figure 6. Graphs showing the results of the survey of working management hypotheses, Upper Missouri River. 

A, Response scores. B, No relevant knowledge. GAPT refers to the Gavins Point Dam; DO, dissolved oxygen.

These reports provided recommendations on broad areas of information that were lacking for 

pallid sturgeon recovery and those recommendations have been responsible for much of the direction of 

pallid sturgeon research from 2004 to the present (2015). However, these previous reports were not 

conceived in a framework that emphasized decision making under adaptive management, and therefore 

they did not develop specific hypotheses related to management actions and biotic responses as 

presented herein.
27

Figure 7. Graphs showing the results of the survey of working management hypotheses, Lower Missouri River. 

A, Response scores. B, No relevant knowledge. YSTN refers to the Yellowstone River and UPMOR refers to the 

Upper Missouri River; Lake Sak refers to Lake Sakakawea. 

The focus needed to address management-relevant models necessarily requires filtering 

hypotheses down to an initial core set. In this filtering process, we have engaged a broad range of expert 

opinion and added their judgments to our own experience, judgment, and knowledge of the scientific 

literature. The result is a set of working management hypotheses to inform the quantitative modeling 

framework.
28

Figure 8. Cumulative growth in pallid sturgeon science peer-reviewed publications, 1992-2014.

The working management hypotheses developed and documented in this process are intended to 

be used in an adaptive management context. We anticipate, based on parallel development of the 

Adaptive Management Plan (A. Quinn, USACE, written commun., 2015), hypotheses, and the adaptive 

management process, will evolve to maintain the maximum relevance to Missouri River decision

making. The following points are germane to how this initial set of management hypotheses will operate 

in the adaptive management context:

• Although we have filtered hypotheses to begin the modeling process, no hypothesis is ever 

“lost.” Documentation of the hypotheses in this report and the CEM report (Jacobson and others, 

2015b) serves to put them into a “hypothesis reserve” from which they can be resurrected at any 

time (fig. 1). This idea is fundamental to adaptive management—as new information comes 

available through systematic hypothesis testing in the course of management, hypotheses can be 

sequentially tested against the increasing information base, and if existing hypotheses are 

inadequate to explain observed behaviors, hypotheses can be resurrected from the reserve or 

created anew.

• The selection of hypotheses by this process is intended to define an initial, practical scope for 

development of quantitative models, but as quantitative models progress, we expect that the 

modeling results will begin to provide a quantitative basis for evolving, iterative hypothesis 

development. The expert-opinion based process we relied on in filtering for this report will be 

replaced progressively with quantitative model results that will indicate priority hypotheses.

Because the component life-stage models are tied to a population-level model (Jacobson and 

others, 2015b), ongoing development of management hypotheses will be strongly governed by 

their mathematical leverage on population dynamics. 
29

• The quantitative models that will be developed to address the working management hypotheses 

will form a framework that will be useful for redesign and implementation of monitoring, 

assessment, and adaptive management on the Missouri River for pallid sturgeon recovery. The 

quantitative models will be available to identify critical information needs, such as model 

assumptions and uncertain model parameters, the metrics that will be most effective in 

evaluating system performance, and the information that will be most useful in decision making.

The initial set of working management hypotheses is important because it serves to start the 

redesign of the modeling framework for the Missouri River adaptive management process.

However, the initial seeding of hypotheses should progressively give way to more robust 

hypotheses. Approaches for utilizing new hypotheses and the reevaluation of reserved 

hypotheses will be determined in the Adaptive Management Plan that is currently (2015) being 

created.

Summary and Conclusions

This report documents a process of filtering of hypotheses that relate pallid sturgeon population 

dynamics of the Missouri River to management actions, including flow alterations, channel 

reconfigurations, and population augmentation. The process was part of the Missouri River Recovery 

Management Plan and undertaken as a partnership among U.S. Geological Survey, U.S. Army Corps of 

Engineers, and U.S. Fish and Wildlife Service. The objective of the filtering process was to produce an 

initial set of hypotheses linking management actions to pallid sturgeon population dynamics for 

application in Missouri River decision making. The filtered hypotheses will be used to determine the 

scope and nature of quantitative models required to guide adaptive management.

The process of filtering hypotheses started with conceptual ecological models (CEMs) that 

illustrated concepts of population dynamics at the population level and a series of component life-stage 

models that illustrated concepts relating survival of selected life stages to management actions, resulting 

ecological factors, and biotic responses. The CEMs were developed from workshops involving experts 

knowledgeable about pallid sturgeon biology and Missouri River processes throughout the upper and 

lower Missouri River Basin. Participants indicated hypothetical relations among management actions, 

ecological factors and biotic responses, based on perceived importance and uncertainty of the relations.

The pathways drawn through the CEMs comprise the global set of hypotheses of every factor that was 

thought to plausibly affect pallid sturgeon population dynamics.

The Missouri River pallid sturgeon Effects Analysis (EA) team selected those relations in the 

global set that were of high importance to life-stage survival. These 40 hypotheses comprised a 

candidate set of dominant working hypotheses. The EA team compiled the candidate set from the CEMs

and constructed a modified Delphi process to get expert opinion on their importance in explaining 

population dynamics. The Delphi process consisted of a Web-based survey, a workshop, and a followup Web-based survey. Twenty-three hypotheses that scored with medians above neutral were selected to 

move forward in the process. The EA team then matched the 23 hypotheses with management actions 

that could influence the biotic outcomes. Because there are multiple pathways through the CEMs, 176 

potential linkages were identified. From those, the EA team consolidated linkages that applied to 

multiple life stages to define a candidate set of 53 working management hypotheses. We constructed 

another Web-based survey with a larger number of sturgeon and Missouri River experts to score the 

candidate set. Thirty of the 53 working management hypotheses had median scores above neutral and 
30

were selected to be filtered by the USACE for actions that were within the agency’s authority and 

jurisdiction. This filtering by the USACE resulted in a set of 21 initially modeled hypotheses. 

The filtered set of hypotheses provides a useful starting point for quantitative modeling of 

linkages between management actions and pallid sturgeon population dynamics on the Missouri River.

The modeling structure developed to address these hypotheses in the EA is intended to be the 

framework for adaptive management of pallid sturgeon in the Missouri River, and following the 

concepts of adaptive management, it is meant to be flexible and accommodating of future information.

More importantly, hypotheses that have been filtered out of the multi-step process illustrated here may 

be further considered. These hypotheses have been archived in this report and the CEM report (Jacobson 

and others, 2015b) and can be considered to be part of a hypothesis reserve. If existing hypotheses are 

determined to be inadequate to explain observed population dynamics, hypotheses are available to be 

resurrected from the reserve or created anew. The guidelines and approach for possible reevaluation of 

filtered hypothesis and (or) hypotheses refinement will be addressed in the Adaptive Management 

Report, which is under development.
31

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