MISSISSIPPI VALLEY DIVISION / 

ENGINEER RESEARCH AND DEVELOPMENT CENTER – ENVIRONMENTAL LABORATORY

MVD/ERDC

 Conservation Plan for the Interior Least Tern, Pallid Sturgeon, 

 and Fat Pocketbook Mussel in the Lower Mississippi River 

 (Endangered Species Act, Section 7(a)(1))

 

 

 

 

July 22, 2013
2

TABLE OF CONTENTS

 Page

Executive Summary 4

PART I: INTRODUCTION 5

Background 5

Purpose and Scope 6

PART II: ENVIRONMENTAL SETTING 7

Geomorphology 7

Hydrology and Hydraulics 8

Habitat Classification and Distribution 9

Effects of Climate Change on the Mississippi River System 12

Part III: AUTHORIZED PROJECT DESCRIPTION 14

Channel Improvement Program 14

River Engineering Structures 14

Revetments 14

Dikes 15

Bendway Weirs 18

Hardpoints 19

Roundpoints 19

Chevrons 19

Dredging 20

PART IV: ENDANGERED SPECIES ACCOUNTS 22

Interior Least Tern (ILT) 22

Life History 22

Distribution 24

Breeding and Nesting 25

Wintering 26

Abundance 26

LMR Recovery Status 28

Pallid Sturgeon (PS) 28

Life History 29

Habitat 29

Movement 29

Feeding 30

Spawning 30

Rearing 31

Distribution and Abundance 32

LMR Recovery Status 35
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Table of Contents (concluded)

Fat Pocketbook Mussel (FPM) 36

Habitat 36

Movement 36

Feeding 37

Reproduction 37

Distribution and Abundance 37

LMR Recovery Status 37

PART V: LMR ENVIRONMENTAL BASELINE 38

Historical and Current Species Baselines in the LMR 38

Interior Least Tern 38

Pallid Sturgeon 39

Fat Pocketbook 42

Factors Affecting the Species 45

Habitat Loss and Modification 45

Maintenance Dredging 46

Water Diversion Entrainment 46

Sand and Gravel Mining 47

Commercial Harvest of Pallid Sturgeon 47

Pollution and Contaminants 47

Hydrokinetics 48

Hybridization of Pallid and Shovelnose Sturgeon 48

PART VI: EFFECTS ANALYSIS 49

Effects of the Program 49

Interior Least Tern 49

Pallid Sturgeon 50

Fat Pocketbook 51

Avoid and Minimize Components of the CIP 51

PART VII: MANAGEMENT AND CONSERVATION MEASURES IN THE LMR 52

Partnerships 52

Conceptual Model 54

Conservation Plan Outline 55

Implementation 58

Elements of Adaptive Management 59

PART VIII: CONTRIBUTORS/REVIEWERS 61

PART IX: LITERATURE CITED 62
4

EXECUTIVE SUMMARY

Conservation Plan for the Interior Least Tern, Pallid Sturgeon, and Fat Pocketbook 

Mussel, in the Lower Mississippi River 

(Endangered Species Act, section 7(a)(1))

Section 7(a)(1) of the Endangered Species Act (ESA) requires all Federal agencies to use 

their authorities as appropriate to carry out programs for the conservation (i.e., recovery) of 

endangered and threatened species. For more than a decade the U.S. Army Corps of Engineers 

(USACE) has worked with the U.S. Fish & Wildlife Service (USFWS) and state conservation 

agencies to identify and resolve endangered species and ecosystem management issues 

associated with USACE civil works projects to provide flood risk management infrastructure and 

to facilitate navigation in the Lower Mississippi River (LMR). It has become apparent that the 

very programs that have most significantly affected the river are potentially the most important 

and cost-effective tools to maintain and enhance its ecological functions. This is accomplished 

by considering and incorporating ecological engineering opportunities during the design phase of 

channel improvement and channel maintenance projects. Early consideration of conservation 

designs results in localized improvements in habitat function and value, with little to no effect on 

flood risk management, navigation, or project cost. The USACE has also opportunistically 

implemented cost-effective secondary channel restoration actions in the LMR by sharing 

responsibilities and resources with partner agencies. Cumulatively, both the site-specific 

engineering action and the restoration opportunities have significantly benefitted the habitat 

baselines of endangered species associated with the LMR channel. Herein, the USACE outlines 

the programmatic mechanisms by which the Channel Improvement Program of the Mississippi 

River and Tributaries project is being utilized to implement conservation measures that maintain 

and improve habitat values within the LMR for recovery of endangered and other trust species 

inhabiting the river channel. This program has been developed under informal consultation with 

the USFWS, and complies with section 7(a)(1) of the ESA, USACE Environmental Operating 

Principles, Civil Works Ecosystem Restoration Policy (ER 1165-2-501), and supports the 

conservation intent of EO 13186 Responsibilities of Federal Agencies to Protect Migratory 

Birds.
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PART I: INTRODUCTION

Background

The Lower Mississippi River (LMR) extends 953.5 miles from the confluence of the 

Ohio River to the Head of Passes where the river subdivides into several distributaries to the

Gulf of Mexico. In response to the 1927 flood, the Mississippi River and Tributaries (MR&T) 

project was initiated by the USACE. The project consists of levees, revetments, flood storage 

reservoirs, and floodways to reduce flood risk, as well as dikes, and other river training structures 

in the channel to facilitate low-water navigation by towboats. Construction of the MR&T project, 

which still continues today, has resulted in one of the most highly engineered large river 

channels on the planet.

The construction of the Mississippi River levee system altered natural patterns of surface 

water drainage within the region and reduced the floodplain by over 80% (Baker et al. 1991). 

Channel engineering for navigation over the past 30 years has resulted in a gradual but 

significant loss of secondary channels and in the area of associated seasonally flooded in-channel 

habitats in the LMR. About 23 secondary channels and roughly 14,000 acres of associated 

higher elevation habitats have been lost in the LMR since the 1960’s due to natural realignments 

and/or channel modifications, including closure dikes, conducted under the MR&T Project 

(Williams & Clouse 2003). Dikes constructed along the main channel have resulted in sediment 

accretion and loss of aquatic surface area during low water periods. 

While the development of the Mississippi River for year-round navigation and flood 

protection has provided enormous economic benefit to the United States, it has also resulted in a 

general decrease of channel habitat complexity in the LMR (e.g., Williams & Clouse 2003). 

Cumulative impacts have affected three endangered species inhabiting the LMR: Interior least 

tern (ILT), pallid sturgeon (PS), and fat pocketbook mussel (FPM), all of which are dependent 

upon in-channel and seasonally flooded habitats. 

Despite river engineering activities over the past century, the LMR has not experienced 

any known extirpations or extinctions of channel species, such as have occurred in other large 

rivers of the United States. There are several reasons for this: 1) the LMR remains 

unimpounded, experiencing a natural flood cycle hydrograph; 2) although size and quantity of 

sediment input to the system has been significantly reduced through bank protection and 

construction of multiple impoundments of all major LMR tributaries, large quantities of stored 

sediment are available in its large channel that are continuously reworked during flood cycles; 3) 

implementation of the Clean Water Act throughout the drainage basin has significantly improved 

water quality in the LMR; and 4) the proactive nature of USACE, specifically Mississippi Valley 

Division, in carrying out its continuing responsibilities under the Endangered Species Act. 

These factors all contribute to maintain the LMR channel as a highly functional and valuable 

fluvial ecosystem.

The current local status of the three endangered species in the LMR also reflects the 

ecological functionality and value of the river channel. Although considered endangered 

throughout their ranges, LMR populations of ILT and PS are wide-spread and locally common in 

the river channel. While there are no historical records of FPM from the LMR channel proper, it 
6

was either present in low numbers and unreported, or it has invaded the channel in recent years

due to developing favorable conditions. Although the ecological requirements of the three 

species are not completely understood, the aquatic habitats available in the LMR, including point 

bars, gravel bars, eroded shorelines, functional side channels, and forested backwaters in the 

batture, have provided, and continue to provide both direct and indirect benefits to the 

endangered species, and all other channel dependent species. 

The USACE, Mississippi Valley Division (USACE-MVD) is responsible for construction 

and maintenance of the Mississippi River and Tributaries Project in the LMR, as well as for 

maintaining its ecological function. For more than a decade, the USACE-MVD LMR districts 

have been working with state and Federal partners to maintain habitat complexity and reduce 

impacts to trust species by developing and applying cost-effective engineering and best 

management practices to routine channel maintenance and construction activities in the LMR 

(e.g., USFWS 2012a; DuBowy 2011). 

Purpose and Scope

This Conservation Plan (Plan) is being prepared pursuant to Section 7(a)(1) of the 

Endangered Species Act, as amended, which requires all Federal agencies to use their authorities 

to carry out programs for the conservation (i.e., recovery) of endangered and threatened species. 

The purpose of the Plan is to describe how the MR&T Channel Improvement Program can be 

utilized to conserve ILT, PS, and FPM in the LMR. This Plan also describes results of the 

MVD’s efforts to implement monitoring and other conservation efforts with the goal of 

recovering the species in the LMR. Continued implementation of these activities to maintain and 

enhance LMR aquatic habitat diversity is the primary goal of the Plan. Specific conservation 

measures are recommended to meet the purpose and goal of the Plan, but are contingent upon 

opportunity and annual appropriations, and other authority and budgetary constraints. 

The Channel Improvement Program civil works project encompasses the LMR channel 

within the jurisdiction of the MVD and the Memphis, Vicksburg, and New Orleans Engineer 

Districts. This Plan does not address issues related to other USACE regulatory responsibilities, 

water diversions, or the 45-ft channel below New Orleans. The PS range encompasses all of the 

LMR within the scope of the Plan; ILT range includes over 600 miles of the River above Baton 

Rouge, LA; known range of FPM includes over 400 miles of the channel above the Old River 

Control Complex. Customary yearly evaluations of effects of project construction at scattered 

sites along the river, without consideration of cumulative or system-wide effects, do not 

adequately address potential impacts to any of the three species. Therefore, a system-wide or 

landscape approach was taken in the analyses of Channel Improvement Program project effects 

on the PS, ILT, and FPM. 
7

PART II: ENVIRONMENTAL SETTING

The Mississippi River is one of the world's largest alluvial river systems, having a 

drainage basin of 1,245,000 square miles, encompassing 41 percent of the contiguous United 

States and parts of two Canadian provinces. Worldwide, the Mississippi River ranks third in 

drainage area, seventh in length, and sixth in average discharge. The main stem of the river 

courses 2,348 miles from Lake Itasca in northern Minnesota to the Head of Passes. Above St. 

Louis, the river is impounded by 27 Locks and Dams. Between the mouths of the Missouri River 

at St. Louis, MO, and the Ohio River at Cairo, IL, is a 200-mile reach referred to as the Middle 

Mississippi River (MMR). 

The Lower Mississippi River (LMR) begins at the confluence of the Mississippi and 

Ohio Rivers in southern Illinois and flows southward 955 miles in a meandering pattern to Headof-Passes, LA, where the channel subdivides into several distributaries to the Gulf of Mexico. 

The LMR has two distinct reaches, although Schumm et al. (1994) further subdivides the LMR 

into 24 reaches based on geomorphology and channel maintenance activities. From Cairo at the 

mouth of the Ohio River (RM 953) south to Baton Rouge, the river has well-defined point bars 

and forested floodplains adjacent to the river (Baker et al. 1991). Minimum navigation channel is 

maintained at 9 feet, but is authorized for 12 feet. Below Baton Rouge, the river flows through

the Deltaic Plain 235 miles to the Gulf. The channel is deeper to accommodate ocean-going 

traffic (45 feet deep navigation), and meander loops, sandbars, and floodplain are much reduced 

(Baker et al. 1991).

Geomorphology

The Lower Mississippi River Valley (LMRV) lies within the Central Gulf Coastal Plain

physiographic province. A northward extending lobe, the Mississippi Embayment of this

province follows the axis of the Mississippi Basin and comprises the northern part of the LMRV

(Schumm et al. 1982). Virtually all LMRV landforms and deposits are the result of fluvial, 

Aeolian, or marine processes.

The LMRV variesin width between 40 and 110 miles and includes parts of Missouri, Illinois,

Tennessee, Kentucky, Arkansas, Mississippi, and Louisiana. According MR&T (2012), the

topography of the 53,000 square mile LMRV is characterized by a flat to slightly undulating surface

underlain by alluvial and terrace deposits. Average floodplain elevationsin the LMRV decline from

about 325 feet mean sea level (msl) in extreme southern Illinoisto about 40 feet msl at the northern

edge of the deltaic plain. The average down valley slope is only 0.6 feet/mile. Average relief in the

upper part of the LMRV is about 25 feet and declines progressively southward. Uplands bordering the

LMRV typically attain elevations of about 200 feet above those of the adjacent floodplain. Upland

elevations also steadily decline southward.

Soilsin the LMRV range up to 300 feet in depth and consist mainly of sands and silt, grading

progressively to very fine sands and silts in the lower portion of the area with extensive deposits of

clay scattered through these formations. Typical of streamsflowing through alluvial valleys, the

LMR developed a highly sinuous course, creating numerous meander loops, bends, and oxbow lakes. 

The meandering characteristics of the present-day river may not have fully developed until about 

5000 to 6000 years ago (Baker et al. 1991). Historically, the river shifted its channel frequently and
8

reworked parts of its alluvial meander belt, thus contributing to the complexity of the soils structure

and hydrology of the area (Saucier 1994). 

MR&T Project is a complex, comprehensive water resources project, which provides 

flood risk management within the alluvial valley and navigation improvement of the LMR. The 

primary elements of the MR&T Project include: levees, channel improvement features such as 

meander cutoffs, bank stabilization, dikes, dredging, floodways and diversion structures, and 

tributary basin improvements. The historical, present-day, and future morphology of the LMR 

reflects an integration of all these features combined with natural factors such as floods and 

droughts, hurricanes, tectonic activity, geologic outcrops, climatic variability, and sea level rise 

and other anthropogenic activities such as gravel mining. The geomorphology of present-day 

LMR has been significantly altered from its pre-20th century regime by dams, revetments, and 

levees in three primary ways: (1) channel simplification and reduced dynamism, (2) lowering of 

channel-bed elevation, and (3) disconnection of the river channel from the floodplain (Alexander 

et al. 2012). Notably, channel meandering has been eliminated by revetments, cutoffs have 

significantly altered the energy in the system, secondary channels have been altered by dike 

systems, and floodplains have been constrained by levees. For example, Winkley (1977) 

concludes that the LMR was a stable system between Cairo, IL and Natchez, MS in the precutoff period, whereas stage adjustments followed the cutoffs of 16 bendways between 1933-

1942. Although the morphology of the LMR has been altered significantly, it is important to 

recognize that the LMR, unlike the Upper Mississippi River, the Ohio River, and the Missouri 

River, is not heavily controlled by main channel dams and flow regulation (Biedenharn & 

Watson 1997; Soar et al. 2005). Therefore, the LMR is still a dynamic, open river system where 

morphologic adjustments are still occurring, albeit, within the constraints of a river controlled for 

flood risk management and navigation. Therefore, the impacts to habitat should be viewed within 

the context of an altered, but still dynamic river system. 

Hydrology and Hydraulics

One distinct feature of the LMRV is the formation of natural levees along the banks of rivers

and the associated backwater deposits dominated by dense alluvial clays that historically supported

extensive wetland areas. The banks of the river can be as much as 10 to 15 feet higher than the

lowlandsfarther back from the river. Because of these natural levees, drainage within the floodplain,

frequently flows away from the Mississippi River to lower elevations near the valley walls, except

near tributary confluences. Bottomland drainage is provided by streamsrunning parallel to the river

and joining it through major tributaries or at points where the river meandered close to the valley

wall. The claysthat formed these features have low permeability and limit the ability of rainwater to

infiltrate the ground surface (Kleiss et al. 2000).

In the river proper, mean top bank width is 5,450 ft, while mean width of the low-water 

(3 percentile flow of the discharge, Q) channel is 2,960 ft (Tuttle & Pinner 1982). Water 

velocities vary widely but can exceed 10 ft/s around dike fields. The LMR hydrograph is 

variable, with yearly stage fluctuations of 20-40 ft (mean=22 ft). The river shows two distinct

depth-distribution patterns (Miranda & Killgore 2013). Over its lowermost 248-mi segment, the 

river has been engineered to maintain deep water to support navigation of large container 

vessels, with a mean maximum depth near 66 ft and a maximum mean depth near 131 ft LWRP. 

The Low Water Reference Plane (LWRP) is associated with the discharge that is equaled or 

exceeded 97% of the time taken from flow duration curves. This deep segment is a relatively 
9

homogeneous navigation channel, with limited variability in depths (Coefficient of Variation, 

CV, 40-60). Above river mile 248, mean maximum depth at LWRP is near 26 feet and maximum 

depth can exceed 100 ft below LWRP. Variability in depths in this upper segment of the river is 

higher than in the first 250 mi (CVs about 50-70). April has the highest average monthly 

discharge (947,457 cfs), and October has the lowest average monthly Q (260,844 cfs) (Tuttle & 

Pinner 1982). At Vicksburg, MS, (rm 437) mean Q is 617,000 cfs for the 1944-1994 period and 

mean suspended sediment load is 198 x 106 tons/yr (Moody & Meade 1992). Maximum 

discharge at Vicksburg, MS during the height of the 2011 flood was 2,272,000 cfs (MR&T 

2012). The timing, duration, and frequency of annual low-discharge and high-discharge events, 

however, vary widely among years. 

Although the stability of the LMR reflects the contribution of a variety of factors such as 

levees, cutoffs, dikes, revetments, and dredging, the event that has had the most pronounced 

morphological impact on the LMR was the meander cutoff program of the 1930s and 1940s. 

Biedenharn & Watson (1997) documented the stage adjustments in the LMR during the pre-cutoff (1880s–1930s), and post-cut-off (1943–1994) periods and found that the entire Mississippi 

River, between Natchez, MS, and Cairo, IL, is responding in a manner similar to the response of 

a stream to a single cut-off. Their study identified a degradational regime between Sunflower, 

MS, and Fulton, TN, and an aggradational regime between Vicksburg and Natchez, MS. 

Upstream of Fulton and the reach between Sunflower and Vicksburg were transitioning to 

dynamic equilibrium. It should be recognized that these are long-term decadal trends and that 

short-term reversal of trends, usually in response to major flood events, may occur. Although 

these may be slow, long-term trends, their impact on habitat may be significant, due to changes 

in the hydrologic connectivity between the secondary channels and floodplain. This is 

particularly an issue in the degradational reaches of the river where the stage duration changes 

may cause the diked secondary channels to become more hydrologically isolated from the river. 

The evolutionary trends on the LMR occur over long time periods, and are typically measured in 

multiples of decades. Therefore, an opportunity exists to develop management strategies to 

mitigate the impacts of these long term trends. 

Habitat Classification and Distribution

There have been several aquatic habitat classifications of the LMR. The river is divided 

into the channel and floodplain, and within each of these two broad categories, macrohabitats 

have been defined based on geomorphic, hydraulic, biological, and other descriptors (Baker et al. 

1991). More recently, nine macrohabitats were defined in Table II-1 for the channel environment 

that can be easily identified and mapped (Miranda & Killgore 2011). Channel and sandbar 

habitats are most common in the LMR, revetted banks [Articulated Concrete Mattresses (ACM)] 

occur along outside bends, and natural banks occur along inside bends associated with vegetated 

islands, most secondary channels, and abandoned bendways. There are over 100 island 

complexes, which include a secondary channel, island usually vegetated, and main channel 

border (Williams & Clouse 2003). A more recent study identified 199 chutes, which include 

both vegetated islands identified by Williams and Clouse (2003), and non-vegetated islands 

where flow in the main channel zone is bifurcated by a point bar or mid-channel bar bed forms 

with a crest elevation > +5 ft. LWRP (Guntren et al. 2012). Dike fields are dispersed throughout 

the channel border down to the lower reaches near Baton Rouge, LA (rm 212 to 953.5) and 

average 1.0 dike/rm. Of the 774 dikes constructed since the beginning of the dike construction 
10

effort on the LMR, 225 (29%) have been notched. Overall, there are about 482,418 acres of 

aquatic habitat within the top banks of the river, assuming a bank-full stage (MR&T 2012). 

Table II-1. Type and abundance of macrohabitats in the Lower Mississippi River.

Habitat type Description Abundance

Steep sandbar High sloping sandbar often associated with the downstream reach 

of an island or point bar where the maximum current speeds begin 

to cross the channel forming eddies, deep water, and depositional 

areas along the bank. 

8,649 acres1

Gentle sandbar Low sloping sandbar with moderate to high current. They 

constitute the primary littoral habitat in the river and occur in 

association with point bars, islands, middle bars, and dike systems

70,425 acres2

Island complex Usually include, from the bank outward, a secondary channel, 

island, and main channel. Upper reach is shallow and swift while 

lower reaches become deeper and sluggish. 

25,652 acres at 0 

LWRP; 93->100 

side channels3

ACM/riprap Articulated Concrete Mattress (ACM) is placed over eroding river 

banks with riprap along the top portion. Buckling and variation in 

bottom slopes create large interstitial spaces surrounded by hard 

substrates. Strong currents and deep water are usually associated 

with this habitat.

17,915 acres4

Natural bank Usually occur on the concave side of the river where consolidated 

silts and clays form the primary substrate. Banks are often steep 

and woody debris from fallen trees can accumulate. 

9,266 acres 4

Flooded shoreline At high stages, flooded sandbars and willow trees provide 

temporary habitats usually occurring along the convex side of the 

river. Detritus and terrestrial vegetation become available in 

relatively shallow, low velocity refugia. 

More than 360 mi 

at overbank flows5

Gravel bar Coarse sand and gravel are deposited in bendways usually in the 

upper reaches of point bars or islands where water is shallow and 

swift. Gravel may extend from the shoreline to the channel border. 

At least 76 bars 

with predominately 

gravel6

Channel Includes the main channel and channel border. Water depth can 

exceed 25 m, currents are strong, and substrate is usually sand. 

321,237 acres 4

Dike Constructed with large rocks and extend perpendicularly from the 

bank to the channel border habitat. Some dikes can exceed 900 m 

in length. Large eddies can form below dikes, and depth and 

velocity varies greatly along its longitudinal axis.

Avg. of 1.0

dikes/RM7

1 Analogous to lentic sandbars from Baker et al. (1991)

2 Analogous to lotic sandbars from Baker et al. (1991) 3 Williams and Clouse (2003) 

4 Baker et al. (1991)

5 Derived by dividing the river length between the Ohio River and Baton Rouge by 2 (720 mi/2=360) to represent a 

minimum value for the convex side of the river, which would always be less than the concave side but more than 

360 miles. 6 See Table II-2 7 Based on 774 dikes constructed up to 2012 on the LMR between river miles 212 to 953.5. 

Gravel bar habitats are of particular interest in the Conservation Plan because of their 

importance as spawning substrate for pallid sturgeon as well as other fish species. A recent 

study conducted by ERDC-GSL and the Biedenharn Group identified the general location of 

gravel deposits in the Lower Mississippi River using historical Red Hen imagery, photographs, 

field observations, and historical potamology data. The Red Hen System allows for georeferenced HD videos to be acquired from the helicopter reconnaissance. With this technology, 
11

geo-referenced videos provide latitude and longitude in a continuous fashion along the entire 

flight route, thereby allowing the investigator to accurately locate all pertinent features along the 

stream. This results in a more efficient use of resources, and provides a broader perspective at a 

significantly reduced cost. This analysis divided 138 channel bars between Cairo, IL, and Old 

River into four broad categories as shown in Table II-2. Although the amount of gravel generally 

decreased in the downstream direction, it is significant that gravel was observed throughout the 

study reach. This analysis represented a major first step with respect to identifying gravel 

locations along the river. However, these results are considered preliminary for the following 

reasons:

• The resolution of the Red Hen videos was often inadequate to definitively identify 

the presence of a gravel bar. 

• Gravel deposits may have been under water at the time of the Red Hen flights. The 

recent 2012 Red Hen flight that was conducted at extreme low water following the 

2011 flood, has not been analyzed yet, but preliminary indications are that gravel 

bars may have been more prevalent than in previous flights.

• It is also likely that many gravel deposits may have been covered by sand at the time 

of the Red Hen flights. In fact, analysis of the historical potamology data have 

indicated that these are highly dynamic features, with gravel bars being alternately 

buried in sand and then exposed again through time. 

• At some locations where gravel was observed, it is possible that these were armor 

layers rather than extensive gravel bars.

The LMR leveed floodplain, which includes the floodplain contained between the levees 

(i.e., the batture) and backwater areas, is a dynamic freshwater ecosystem, often changing 

markedly in response to the river’s annual hydrologic regime. The 2.25 million-acre leveed 

floodplain is interspersed with abandoned channels (e.g., oxbow lakes), meander scars (e.g., 

sloughs), levee borrow pits, and large expanses of forested wetlands, and tributary mouths 

(Baker et al. 1991). These areas provide a diverse array of aquatic habitat types and are 

connected to the river at high water. Based on MR&T (2012), the LMR floodplain lying 

riverward of the levees is comprised of about 2.25 million acres and varies in width from 1 to 15 

miles. The land cover in 1992 consisted of about 1,313,090 acres of forests, 371,569 acres of 

agricultural lands, and 127,408 acres of lakes, streams, and man-made water bodies (Table II-3). 

These lands function as the main overflow system of the river and contain a diversity of 

terrestrial habitats and bottomland hardwood forests. Sugarberry/American elm/green ash, 

sycamore/sweetgum/ American elm, black willow and cottonwood/willow forest types make up 

70% of the wooded bottomlands.

Baker et al. (1991) noted a number of distinct changes in the river ecosystem compared to 

the historic unaltered system. The overall floodplain was reduced by 80% due to the levee 

system. Many oxbow lakes are now outside of the levee system, and other waterbodies within 

Table II-2. Classification of channel bars between Cairo IL and Old River.

Classification Number Observed

GS – Predominately Gravel 44

SG – Predominately sand but with considerable gravel 32

SPG –Mostly sand, with possible gravel, but not definitive 49

S – Predominately sand with little to no gravel 13
12

the batture gradually fill due to sediment accretion. Turbidity, sedimentation, and expanded 

agricultural development impact aquatic communities associated with oxbow lakes in the 

Mississippi Alluvial Valley (Miranda & Lucas 2004). Main stem habitats have been altered as 

well. Channel cut-offs reduced the number of bendways, which shortened the river causing a 

major loss in channel habitat including pointbars and gravel bars. Dike fields reduce aquatic 

surface area due to sediment accretion between dikes, although dikes associated with outside 

bends often scour sediments and increase pool habitat. Closure dikes across the mouths of 

secondary channels increase sand deposition that reduces hydraulic connectivity to the main 

channel. Williams &Clouse (2003) reported a loss of 23 secondary channels with vegetated 

islands from the 1960’s to the 1990’s due to sedimentation in the channel, and Guntren et al. 

(2012) reported a similar trend for chutes (non-vegetated secondary channels) continuing into the 

2000’s. Natural steep banks have declined substantially due largely to the construction of 

revetments (Baker et al. 1991). However, channel habitat and transitional areas between the 

thalweg and shoreline (i.e., channel borders) have persisted over time and continues to provide 

habitat diversity in the mainstem LMR. 

Table II-3. Distribution of Major Habitat Types 

Within the Lower Mississippi River Valley1

Habitat Type

Area (acres)

[% total]

Bottom land hardwood forests 981,887 [35 %]

Agricultural Lands 478,345 [17 %]

Open Water (Lakes, borrow pits) 515,656 [18 %]

Backwater Areas (sloughs, ponds) 680,800 [24 %]

Other 137,186 [6 %]

Total 2,793, 874 1 – Mississippi River and Tributaries 2011 Post-Flood Report,

 June 2012, Mississippi Valley Division

Effects of Climate Change on the Mississippi River System

The ability to predict the impacts of climate change on a river system as large as the 

Mississippi River is wrought with significant uncertainties. Ultimately, it would be desirable to 

integrate climate change studies and water resource evaluations to the point where one can

predict changes in river discharges and attribute those changes to either climate variability or 

change. However, at this point in time, efforts remain rudimentary and integration of the 

multitude of driving variables that influence discharge for the Mississippi have not led to 

conclusive predictions of change. For instance, a recent paper by Caldwell et al. (2012) discussed 

that increases in impervious cover by 2060 may offset the impact of climate change during the 

growing season in some watersheds, while in other areas, increased water withdrawals for human 

consumptions, industrial utilization and irrigation could either offset or exacerbate climate 

change impacts. Hirsch and Ryberg (2012) concluded that there was not strong statistical 

evidence relating historic flood magnitudes to changes in global mean CO2 levels. Additionally, 

the Mississippi River basin has had significant annual and inter-annual variability throughout the 

period of historical record. As a recent example, between the flood of the spring of 2011 and 
13

the drought of 2012, water levels at the gage in Memphis, Tennessee varied by 59 feet. Natural 

interannual and inter-decadal variability make it difficult to detect potential climate changes due 

to anthropogenic or other sources. 

Despite these constraints, climate scientists have suggested a few trends for the watershed 

that may be useful to consider. Bonnin et al. (2011) have presented evidence that there will be

an increase in heavy, flood-inducing precipitation events, particularly in the Ohio Basin that 

would have a direct influence in the LMR. Raff et al. (2009) also found that for the James River 

in the Missouri River Basin climate projections result in an increased simulated annual 

maximum flood potential through time. Also, Kunkel et al. (2013) report that although there is 

also large interannual variability in regional temperatures, historical tendencies for the Midwest 

U.S. as a whole are towards increased annual temperatures. Trends calculated from the 

CRUTEM3 data set show a 0.11 ̊F per decade increase in annual mean temperature over the 

Midwest during the 1900-2010 period. Conversely, another predicted outcome is increased or 

prolonged periods of drought (IPCC 2007; GCRP 2009) that may affect in channel habitats 

utilized by pallid sturgeon and other species that are their food items. 

At this time, it is difficult to say whether any of these potential climate-induced changes 

are likely to have any measurable impact on the three species that are the subject of this report.
14

Part III: AUTHORIZED PROJECT DESCRIPTION

Channel Improvement Program

In response to the 1927 flood, the MR&T Project was authorized by the Flood risk 

management Act of 1928, which has been modified numerous times to provide the present 

project authority. The MR&T Project along the main stem of the Mississippi River includes an

extensive, 2,216-mile levee system; three floodways to divert excess flows past critical reaches;

and channel improvement and stabilization features to protect the integrity of flood reduction 

measures and to ensure proper alignment and depth of the navigation channel. The Channel 

Improvement Program of the MR&T project provides for a low-water navigation channel nine 

feet deep (authorized to 12 feet) and 300 feet wide from Baton Rouge, LA to Cairo, IL and for 

stabilization of river banks to protect the flood risk management levees from Head of Passes, 

LA. to Cairo, IL. and on the lower 9 miles of the Ohio River. This Conservation Plan applies to 

the Channel Improvement Program (CIP).

The CIP consists of the construction of river engineering structures, including stone 

dikes, foreshore protection dikes, articulated concrete mattress (ACM), and trench fill 

revetments; and maintenance dredging to maintain the channel depth and width in the main stem 

of the Mississippi River. Construction dredging has also been used in a few instances. As of 

September 2012, there were approximately 355 miles of stone dikes, 145 miles of foreshore 

dikes, and 1,055 miles of operative revetment on the LMR. Stone dike work is about 91 percent 

physically complete, with 35 miles of dikes remaining to be constructed. ACM revetment work 

is approximately 97 percent physically complete, with 36 miles to be built in the future. The CIP

is scheduled to be finished in 2020. Continued maintenance beyond 2020 will be required.

River Engineering Structures

Three main types of river engineering structures are used in CIP: Revetments, dikes, and 

bendway weirs. In addition, hard points, roundpoints, and chevron dikes are used in some 

instances. A combination of these structures work synergistically in a river reach to achieve both 

flood risk management and navigation objectives. The effects of these structures on endangered 

species habitats are discussed in Part V.

Revetments

Revetments are placed on riverbanks to arrest bank caving and protect levees and other 

structures, and to maintain an efficient channel alignment. Caving banks of the LMR are 

typically stabilized with ACM. ACM is comprised of concrete blocks 46.5 inches long, 17.75 

inches wide, and three inches thick spaced one inch apart and tied together with corrosionresistant wire to form a continuous mattress. 

In the 1980s, ACM design was modified for environmental enhancement. ACM is now 

constructed with longitudinal grooves over the surface of each block to reduce current velocity 

and increase surface area for the attachment of macroinvertebrates (Way et al. 1995). ACM is 

placed on the graded bank slope from just above the water surface at the time of construction and 

extended to a prescribed point in the channel not necessarily to the bottom. The upper bank area 

is graded to a typical slope of 1 vertical to 3 horizontal and paved with riprap stone; asphalt was 
15

used prior to the early 1960's. ACM is flexible, strong, and durable and ensures complete 

coverage of the bank. About eight percent of the ACM surface is comprised of spaces between 

the individual blocks. Trench fill revetment is also occasionally used in the LMR for major 

channel realignment or when some continued erosion of the river bank is required to provide a 

desired channel alignment. A trench is excavated on the land or island along the design channel 

alignment and filled with quarry stone. When the river migrates laterally into the filled trench, 

the stone launches and stabilizes the bank.

Pokrefke (2012) describes Off-Bankline revetments as an environmental enhancement 

alternative, providing slack water habitat compared to traditional On-Bankline revetments. 

According to Pokrefke (2012), the Off-Bankline revetment is a row of stone, typically “A” stone, 

and is placed 5 feet to 15 feet riverside of the existing bankline at an elevation of the existing 

bank height. Notches are typically left in the revetment to allow fish to access the slack water 

areas. 

Between 2003 and 2012, linear feet of revetment placed averaged (± standard deviation) 

48091.9 ± 9853.9 (Table III-1). The majority of revetment laid was to repair revetment damaged 

by floods. Annual variability is due to funding, magnitude of flood damage and length of low 

stages conducive for construction activities. As of 2012, there is 1055 miles of revetment along 

the banks in the LMR. 

Table III-1. Linear feet of revetment laid over the past ten calendar years in the Lower Mississippi River.

District 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012

New

Memphis 5554 6077 1893 5829 3552 5305 2276 1392 01 0

Vicksburg 6105 9159 12855 6610 9726 6669 7374 9581 0 1950

New Orleans 0 0 0 0 0 0 0 0 0 0

Maintenance

Memphis 14983 14667 14350 12793 13952 9192 17020 13071 01 342182

Vicksburg 6802 9196 9984 7315 11132 10002 8502 10094 6512 27468

New Orleans3 10401 12057 8361 26818 11175 12370 15248 10688 7849 n/a

Total 43845 51156 47443 59365 49537 43538 50420 44826 14361 63636

1 – No ACM placed due to flood

2 – All flood-damaged ACM

3 – Combined maintenance and reinforcement

Dikes

Dikes have been used intermittently on the Mississippi River for over a hundred years; 

however, beginning in the 1960s, a comprehensive dike program was initiated in an effort to 

reduce dredging costs, and establish improved navigation alignments. Stone dikes are 

constructed in the river channel to develop a self-maintaining (minimal maintenance dredging), 

low-water navigation channel with authorized project dimensions and alignment. Dike systems 

function, in conjunction with revetments, to modify and stabilize channel alignment, reduce 

discharge through secondary channels, and decrease width and increase depth of the low-water 

(navigation) channel through bed degradation, mainly in channel crossings (Fenwick 1969; Cobb 

& Magoun 1985). 
16

The morphological response to the construction of dikes is site specific and depends upon 

a number of factors such as dike type (permeable or impermeable), dike elevation, configuration 

(level crest, sloping crest, and stepped up or stepped down), dike angle and length, sediment 

characteristics (size and concentration) of the channel, and the hydraulic and hydrologic 

characteristics of the channel. However, there are some general trends associated with dikes that 

typically occur. First it should be recognized that the hydraulic effects of dikes will vary with 

stage. The top elevation of a dike is often designed well below the top bank elevation to 

minimize impacts of dike construction at higher flows. Secondly, it must be recognized that the 

hydraulic and sedimentation impacts of dikes also change with time. When first constructed, the 

cross-sectional area of the channel will be reduced due to the presence of the dikes. However, 

this reduction in area is insignificant at high water stages. With time, the dikes will typically 

induce sediment deposition in the area between the dikes, and increase the area and depth in the 

main channel due to erosion. 

Design of stone dike systems is variable and depends on purpose, site conditions, and 

economics (Pokrefke 2012). Spacing of dikes is based on experience and local factors, but is 

typically one to two times the length of the next upstream dike. Dikes comprising a system may 

be stepped-up, i.e., dike crown elevations increase downriver, or stepped down, i.e., dike 

elevations decrease downriver. Stepped-down dike systems tend to increase deposition between 

dikes during high discharges which successively overtop each dike as stages rise, while steppedup systems tend to promote scour between successive dikes (Franco 1967; Fenwick 1969). 

However, studies of dike systems on the LMR have shown that sedimentation was higher in level 

and stepped-up systems than in stepped-down systems. This may be due to the large channel 

width and wide spacing of dikes.

Transverse stone dikes, also called spur dikes, are linear structures that range in length 

from 1,000 to 12,000 feet (mean = 2,000 ft.) and are built of large quarry-run stone. They extend 

from the bank into the channel and are oriented normal to flow or are angled as much as 30 

degrees downstream or upstream, depending on local conditions and objectives. Stone dikes are 

trapezoidal in cross-section, generally with a crown width of 5-14 ft and a longitudinal profile 

that slopes from the riverbank towards the channel. A sloped dike profile enables the structure to 

affect channel alignment over a range of low to mid-bank stages. Dike length is based on total 

channel width and the design width or trace of the navigation channel, i.e., the required amount 

of channel contraction and conveyance. Crown elevations are based on the degree of channel 

control required, existing bed elevations, and costs. For example, a dike that traverses a deep 

secondary channel may have a relatively low crown elevation because construction cost 

increases exponentially as a function of dike height. A trail or L-head section may be constructed 

at a right angle and extend downstream from the channelward tip of a transverse dike to increase 

channel control at reduced cost or to simulate bank alignment. Rootless dikes are also used to 

provide habitat diversity. This type of dike has an offset typically 100 feet or more from the river 

bank (Pokrefke 2012). The rootless section provides environmental diversity by altering flow 

and sediment transportation, and multiple dikes can be left rootless and in a line to create a 

secondary channel for environmental enhancement (Pokrefke 2012). 

As a result of the MR&T dike program, dredging costs on the LMR have been reduced 

dramatically. However, the associated deposition of sediment within the dike fields reduces 

aquatic surface area, degrading the quality of these valuable aquatic habitat areas. In response to 
17

these concerns, a detailed data collection program was established by the Mississippi Valley 

Division (MVD) in order to quantify the sedimentation trends in these dike fields. Utilizing these 

data, Biedenharn et al. (2000) conducted a detailed study of the sedimentation trends of 28 

individual dike fields on the Lower Mississippi River. For this study, the channel was divided 

into three distinct areas (main channel, pools, and sandbars) based on the classification scheme 

developed by Cobb and Magoun (1985). The pools are basically the area between the dikes as 

defined by the area circumscribed by the bank line and a line connecting the channel-ward tips of 

the dikes. The sandbar areas were defined as the bar area between the pool boundary and the -10 

foot Low Water Reference Plane (LWRP) contour. The boundary of the main channel is the 

remainder of the channel up to the -10 foot LWRP contour. Although there was considerable 

uncertainty and variability in the individual dike-field trends, some general trends were observed. 

According to their report:

• The largest impacts of the dikes occur in the initial response period (first 5 to 

15 years following dike construction) after which the response decreases 

significantly.

• The pool (area between the dikes) response is dominated by decreases in 

surface area, volume, and depth. However, these filling trends are affected by 

a number of factors. The filling trends are most pronounced in the tighter 

bends (Radius of Curvature/Width < 5), with the impacts being lessened as the 

bend radius increases. Filling is also the dominant process in the straight 

reaches, but the trends are less consistent, with a number of reaches actually 

exhibiting enlargement. The most significant filling appears to occur in the 

initial 5 to 10 years following dike construction. These filling trends continue 

through time, but at a reduced rate.

• The main channel response was dominated by increases in surface area, 

volume, and depth. The most significant enlargement of the main channel 

occurs during the initial period immediately following dike construction. 

• The sandbar area (identified as a transition area between the main channel and 

the pools) was highly variable, experiencing both scour and fill. The sandbars 

appear to represent a transition zone between the filling trends in the pools 

and the scouring trends in the main channels.

• The volume trends for the overall reaches (combined main channel, pools, and 

sandbars) indicate that the overall reaches have either enlarged or experienced 

no significant change, while the surface area showed no significant change or 

minor decreases. Thus, it appears that the dikes have either produced a larger, 

more efficient channel, or had no significant impact on the overall channel 

cross section at all.

In recognition of the potential loss of habitat resulting from sedimentation in the dike 

fields, the Corps began a dike notching program on the Lower Mississippi River in the late 

1980s. A dike notch is a weir section in the dike that is designed to maintain flow through the 

dike fields at low river stages, thereby minimizing the adverse sedimentation impacts in the 

secondary channels. The size of the weir section depends on local site conditions, but typically 

the top width varies from about 100 to 300 feet, with a weir invert of about +5 feet above the 

LWRP. Not all dikes are subject to notching, either because of location and minimal 
18

environmental benefits, or because a notch would reduce their integrity of purpose (e.g., short 

dikes). 

Hubbard et al. (2006) conducted a limited analysis of pre and post notching surveys 

within the Memphis and Vicksburg Districts. This was not a comprehensive assessment of dike 

notching, but rather was a limited investigation based on five dike fields with a short post-notch 

time period ranging from 5 to 11 years. Because of the limited data, this study did not produce 

any conclusive trends that could be extrapolated to dike notching in general. However, the study 

did provide useful insight into the behavior of the five dike fields studied. Specifically, the study 

showed that the spatial and temporal scour and fill trends in the dike fields were extremely 

dynamic. The response to notching was observed to be site specific, with locations of scour and 

fill varying from year to year with the dike fields. These findings are important because they 

document that the dike fields are not static environments, but rather are temporally and spatially 

highly dynamic systems.

A total of 774 dikes, averaging 1.0 dike/rm, have been constructed between river miles 

212 to 953.5 since the beginning of the dike construction effort on the LMR (Table III-2). Of the 

774 dikes constructed, 225 (29%) have been notched to diversify bathymetry below the dike. 

Notching closing dikes of secondary channels may be most effective in diversifying habitat 

conditions by maintaining flows in secondary channels for extended periods during low river 

stages. To date, the combined efforts with LMRCC have cost-efficiently rehabilitated nine

secondary channels totaling almost 40 miles of in-channel habitat and enhanced hundreds of 

acres of seasonally flooded habitats without impacting the COE’s primary missions of flood 

damage reduction and provision of a safe, stable commercial navigation channel. 

Table III-2. List of river training structures, excluding revetment, constructed up to 

2012 or proposed for the Lower Mississippi River.

River Training 

Structure

Memphis 

District

Vicksburg 

District

New Orleans 

District

Total

Total Dikes Constructed

Dikes 467 293 141 774

Notched Dikes 147 78 0 225

Hardpoints 209 28 0 237

Chevrons 4 3 0 7

Bendway Weirs 6 2 0 8

Proposed for 5-year Plan

Dikes 28 16 0 44

Notched Dikes 14 4 0 18

Hardpoints 20 0 0 20

Chevrons 0 0 0 0

Bendway Weirs 10-13 4-6 0 14-19 1 – Dikes occur down to RM 212 in the New Orleans District

Bendway Weirs

Bendway weirs are linear stone structures, similar to transverse stone dikes, except for 

where they are placed in the channel. Originally designed by Derrick et al (1994), these 
19

structures are placed from the concave bank across the main or navigation channel. A series of 

weirs are constructed in a bend to form a functional system. These structures typically have 

elevations 20 feet or more below the LWRP, thereby allowing passage of navigation traffic, and 

are variously angled upstream depending on site conditions. Bendway weir systems are designed 

to increase uniformity of flow, to lower velocities, and to reduce shoaling in a bend. These 

effects are accomplished by widening the low-water channel and making it shallower, resulting 

in a more rectangular, as opposed to a triangular, channel cross-section. The number, length, 

elevation, angle, and spacing of bendway weirs are based on site conditions and physical model 

tests. Bendway weirs were first constructed by the St. Louis District, and are now used in the 

MMR and the LMR. As of 2012, Vicksburg and Memphis Districts have constructed a total of 8

bendway weirs in the LMR (Table III-2). 

Hardpoints

Hardpoints were designed to stabilize river banks as a cost-effective alternative to 

revetment. Hardpoints consist of stone fills spaced along an eroding bank line, protruding only 

short distances into the channel. Based on a description by Lagasse et al. (2009), a root section 

extends landward to preclude flanking. Hardpoints are most effective along straight or relatively 

flat convex banks where the streamlines are parallel to the bank lines and velocities are not 

greater than 10 ft/s within 50 ft of the bank line. Hardpoints may be appropriate for use in long, 

straight reaches where bank erosion occurs mainly from a wandering thalweg at lower flow rates. 

They would not be effective in halting or reversing bank erosion in a meander bend unless they 

were closely spaced, in which case spurs, retarder structures, or bank revetment would probably 

cost less. Hardpoints are most commonly placed in lieu of revetment along the concave bank in 

secondary channels in the LMR. Compared to revetment, hardpoints conserve natural river bank, 

diversify riverine habitat through deposition and scour, and provide velocity refugia for aquatic 

organisms. As of 2012, Vicksburg and Memphis Districts have constructed a total of 237 

hardpoints in the LMR (Table III-2). 

Roundpoints

Multiple Roundpoint Structures (MRS) are alternating rows of rock mounds within the 

footprint of a typical dike. According to Pokrefke (2012), this structure is built to a two-thirds 

bankfull stage with the spacing of the rock mounds a function of the structure height. MRS are used 

like a dike to maintain the navigation channel and to create flow and bathymetric diversity within a 

dike field; therefore, the main benefit of these structures is to create diverse flow and scour patterns 

for aquatic improvement (Pokrefke 2012). 

Chevrons

Chevrons were originally used by the St. Louis District in the Middle Mississippi River 

as a river training structure for nose protection for islands and habitat restoration tool (Davinroy 

1996). Only a few chevrons have been built in the LMR. Chevrons are typically used in wider

reaches of the river where a flow split is desired. A C-shape rock dike is constructed and aligned 

to split flow while protecting the existing shoreline. A series of chevrons are usually required to 

obtain the desired effect. The split flow scours the substrate along the outside trailing edges of 

the chevron. Scour also occurs within the interior of the chevron and can form small islands 

immediately downstream as sand deposits in more slackwater areas. Chevrons can 
20

simultaneously assist or aid bank protection, channel scour, and habitat diversity. As of 2012, 

Vicksburg and Memphis Districts have constructed a total of 7 chevrons in the LMR (Table III2). 

Dredging

One of the primary missions of the USACE is to maintain the channel depth and width 

for commercial navigation. Between Cairo, IL and Baton Rouge, LA in the LMR, the USACE 

maintains a 9-foot deep channel (12 foot authorized) that is 300-feet wide and a 9-foot deep 

channel in the ports and harbors. Dredging occurs mostly at crossings, of which there are 

approximately 200 between the mouth of the Ohio and Baton Rouge, LA (Baker et al. 1991). 

However, only a few of the 200 crossings are regularly dredged. Dredging can be substantial 

below Baton Rouge at low river stages to maintain the deep draft 45-foot channel, however this 

work is not done under the MT&T authority. Dredged material from the LMR is usually 

deposited directly in flowing water where it disperses throughout the channel or in existing dike 

fields. This method is referred to as within-banks or flow-lane disposal and is used above and 

below Baton Rouge. This type of disposal also has environmental benefits by maintaining 

sediment within the channel to build sandbars, reduce erosion, and provide material to build or 

replenish island habitats and coastal wetlands. In some cases, dredge material is pumped through 

a pipeline to nearby fields or other off-channel locations to build landforms, although this type of 

disposal has not been used in many years.

Different types of dredges (cutterhead, dustpan, and hopper) are used depending upon the 

area. In the LMR, large dustpan dredges (e.g., Jadwin, Hurley, and Potter) are most commonly 

used by the USACE. The suction head, approximately the width of the dredge, is lowered to the 

face of the material to be removed. High velocity water jets loosen the material which is then 

drawn by pump as slurry through the dredge pipe and floating pipeline where the material is 

deposited outside of the navigation channel. Hopper dredges (e.g., Wheeler, Essayons,, and 

McFarland) are also operated where dredged material must be moved greater distances. Hopper 

dredges stores dredged material onboard and transport it to an approved disposal site. Hopper 

dredges are only used below Baton Rouge to maintain the 45-foot navigation channel. 

Cutterhead dredges (e.g., Thompson) are equipped with a rotating cutter apparatus surrounding 

the intake end of the suction pipe. Cutterheads can efficiently dig and pump up to a mile all types 

of alluvial materials and compacted deposits, such as clay and hardpan. Using booster pumps, 

cutterhead dredges have the capability of pumping dredged material longer distances, but can be 

cost-prohibitive and limited by available lengths of discharge pipe. 

Over the past ten years, a total of almost 431,000,000 cubic yards of sediment have been 

dredged from the main channel of the Mississippi River, including the deep draft channel below 

Baton Rouge (Table III-3). This represents an average of 43,000,000 ± 12,000,000 cubic yards 

dredged each year. Annual variation in dredging amounts is due to river stage; low water years 

require more dredging to maintain the navigation channel. From 1948 - 2008, the total linear 

feet of dikes constructed has drastically reduced the amount of annual dredging required to 

maintain minimum depth of the navigation channel, excluding the deep draft channel below 

Baton Rouge (Figure III-1).
21

Table III-3. Cubic yards of maintenance channel dredging, excluding harbors, over the past ten 

years in the Lower Mississippi River.

Year Memphis 

District

Vicksburg 

District

New Orleans District Grand 

Total

Baton Rouge 

to Old River

New Orleans 

to Baton 

Rogue

Gulf of 

Mexico to 

New Orleans

New Orleans

District 

Total

2003 6,073,352 1,030,475 623,692 13,728,125 9,381,050 23,732,867 30,836,694

2004 4,953,282 1,422,200 452,464 8,656,512 13,010,523 22,119,499 28,494,981

2005 10,838,046 982,968 824,628 19,368,940 13,616,139 33,809,707 45,630,721

2006 5,883,104 3,102,696 441,035 9,953,606 7,245,234 17,639,875 26,625,675

2007 7,504,241 4,260,200 623,878 11,762,086 10,556,543 22,942,507 34,706,948

2008 5,814,028 1,851,804 325,695 28,773,375 13,406,342 42,505,412 50,171,244

2009 7,116,535 860,587 579,040 26,661,826 18,477,845 45,718,711 53,695,833

2010 7,126,552 1,318,424 366,180 22,994,560 23,055,732 46,416,472 54,861,448

2011 7,001,328 1,315,100 814,478 21,826,412 14,431,080 37,071,970 45,388,398

2012 12,706,518 3,323,993 1,926,194 24,523,153 17,626,336 44,075,683 60,106,194

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0

10000

20000

30000

40000

50000

60000

70000

46485052545658

1960196219641966196819701972197419761978198019821984198619881990199219941996199820002002200420062008

DIKE LENGTH (1000 LINEAR FEET)

DREDGING QUANTITY (1000 CY)

YEARS

DIKES TOTAL

NEW ORLEANS DREDGING

MEMPHIS DREDGING

VICKSBURG DREDGING

Figure III-1. Relationship between cumulative dike lengths and dredged quantities in the 

Lower Mississippi River, upstream of Baton Rouge and the deep draft channel and excluding 

harbors. Figure developed by Mississippi Valley Division
22

PART IV: ENDANGERED SPECIES ACCOUNTS

Interior Least Tern

The life history of least terns (Sternula antillarum) has been described in great detail 

many times, in many different environments (Hardy 1957; Massey 1974; Wolk 1974; USFWS 

2003, 2005a) and synthesized during the exhaustive literature review associated with the Birds of 

North America account for this species (Thompson et al. 1997) (which includes, in detail, 

distribution, habitat, food habits, demographics, and other life-history characteristics). 

Additional life-history information, as well as a detailed accounting of the Endangered Species 

Act, Section 7 Consultation process as it related to the USACE (Omaha District) is detailed in 

the 2003 USFWS Biological Opinion for the operation of the Missouri River (USFWS 2003). 

Management challenges for least terns also have been described in great detail (USFWS 1985; 

1990a; 2003; 2005a, b; 2006). Research and monitoring needs have been articulated several 

times in collaborative settings (Guilfoyle et al. 2004; Lott & Pashley 2006; Martin et al. 2009; 

Guilfoyle & Fischer 2012). Hundreds of research papers, technical reports, Master’s theses, and 

PhD dissertations have been written on a huge variety of topics in locations and environmental 

contexts spanning the entire geographic range (see the bibliography link at http://leasttern.org). 

Also, population models have been applied in numerous contexts (Kirsch 1996; Akçakaya et al. 

2003; National Research Council 2004; Lombard et al. 2010; Lott & Wiley 2012). These topics 

are detailed below.

Life History

Least terns are fish-eating birds that nest in open sandy areas and other bare ground areas 

along rivers and coasts. The population of least terns that nest on large rivers in the central 

United States is known as the Interior Least Tern (ILT) (Figure IV-1). Sandbars are the primary 

habitat component used for ILT nesting. When sandbars become covered in vegetation, they are 

no longer suitable for tern nesting. New habitat is formed when high water removes existing 

vegetation or deposits new sand, or when sand is deposited properly during the dredged-material 

disposal process to create sandbars. 
23

Figure IV-1. 2005 breeding distribution of the Interior Least Tern (ILT). See legends for colony 

types and river types. Numbers correspond to geographic segment numbers (From Lott 2006).

The ILT is found from the LMR, north to Montana along the Missouri River. The largest 

breeding populations occur on the LMR; along large Southern Great Plains rivers, particularly 

from the Arkansas, Cimarron, Canadian, and Red rivers; southern portions of the Upper Missouri 

River and its tributaries – the Platte and Niobrara Rivers; and in Illinois, Kentucky and Indiana 

along the Wabash and Ohio Rivers. 

The interior population is one of two geographically-defined populations of least tern 

listed under the U.S. Endangered Species Act (ESA) as Federally endangered (the other being 

the California Least Tern). The interior population was Federally listed as 

endangered in 1985 because of suspected low numbers and concerns about breeding season 

habitat loss and degradation on large rivers of interior North America (USFWS 1990a). A 

recovery plan for ILT was published in 1990 that provided a summary of the known population 

size, identified suspected threats, and detailed delisting criteria (USFWS 1990a). This plan also 

outlined recovery strategies to increase the ILT population to approximately 7,000 adults 

throughout its range, and to maintain drainage basin-specific target populations for 10 years 

(Table 1). This number was quickly reached, possibly due to more intensive surveys, improved 

survey techniques, and a better understanding of tern colony locations, especially on the LMR 

(Kirsch & Sidle 1999). However, concern has persisted about population size goals for other 

drainages as set in the recovery plan, as well as chronic threats to ILT (see below). The USFWS 

is currently conducting an assessment of the current status of the ILT (5-year review).

Distribution 
24

Little is known about the historical distribution and abundance of ILT breeding along 

interior U.S. rivers. Least terns exploit early-successional habitats along rivers for breeding, 

nesting, and brood-rearing, and then migrate long distances to winter mostly outside of the 

United States. The dynamic nature of rivers, which may flood during the nesting season one 

year, and experience drought the next, provide a highly variable set of nesting conditions for 

terns upon return from wintering grounds. This environmental variability necessitated that terns 

develop life-history strategies to cope with such stochasticity. These strategies include their 

relative longevity (with total lifespans as long as long as 20 years), reproductive life-spans 

ranging from age 2 or 3 to death (Thompson 1982, Thompson et al. 1997), their ability to re-nest 

after nest failure (which can increase recruitment following flooding and/or egg/chick predation), 

and a diet that can include a variety of fish species.

Today, there is much more extensive information regarding ILT distribution and 

abundance (Figure IV-1). A wide variety of Federal and state agencies, universities, and nongovernmental organizations have all conducted a myriad of research and monitoring activities 

throughout the range that provides a much clearer range-wide picture, much more so than even 

10-15 years ago. In addition, tools such as the Cornell Laboratory of Ornithology eBird 

(www.eBird.org) portal are providing new information on least tern distribution from throughout 

the range that otherwise has been unavailable.

As a species, the least tern has a broad breeding distribution, with nesting records in 37 

different US states (Thompson et al. 1997, Pyle et al. 2001, Lott 2006, Marschalek 2010), along 

both coasts of Mexico and northern Central America (Howell & Webb 1995), and many islands 

throughout the Caribbean (Thompson et al. 1997, Bradley & Norton 2009). Least tern breeding 

populations are nearly continuously distributed (with a few exceptions) from the Missouri River 

in Montana south through the Mississippi Valley (and its large western tributaries) along the 

entire Gulf of Mexico coast, west to Belize and east to Florida, up the Atlantic Coast from

Florida to Maine, and throughout the Caribbean. Aside from California, coastal Least Terns are 

not Federally listed under the ESA, although they are on several state lists of conservation 

concern (Thompson et al. 1997).

There are several ecological factors that likely have influenced the contemporary 

distribution and abundance of ILT. First, frequent flooding events, which either create habitat, or 

set back plant succession on sandbars (where the majority of nesting attempts take place), 

strongly influences ILT distribution (Sidle et al. 1992, Leslie et al. 2000). Second, ILT tend not 

to nest in proximity to tall vegetation (i.e., riparian forest) or other high features (USACE 2011aAppendix B), or where channels become narrow (Jorgensen et al. 2012). Third, reduced 

availability of small fishes as forage throughout the breeding season may result in very low chick 

survival and render breeding habitat as poor quality. Fourth, changes to river systems both 

above and below reservoirs due to dam construction have resulted in hydrologic and sediment 

delivery alterations that have fragmented habitat, and subsequently, ILT populations. Finally, in 

some locations, engineering practices have influenced distribution and abundance in a positive 

manner. For example, dike fields created by the USACE along the LMR designed to trap 

sediments and facilitate a self-regulating navigation channel have created habitat conditions 

(large sand accumulations behind dikes) that support the largest ILT population (by an order of 

magnitude) within their range (Lott 2006). Other types of nesting areas that were not historically 

available to ILT have also been exploited by the bird, such as reservoir shorelines, industrial 
25

sites, and dredged material deposition islands (Boylan et al. 2004; USACE 2011a,b; Fischer 

2012).

The most comprehensive review of ILT distribution and population size was prepared by 

Mr. Casey Lott, American Bird Conservancy (ABC) under contract with USACE. Lott (2006) 

organized and synthesized the results of the only synchronized range-wide survey of ILT to date. 

Most recently he has summarized changes in knowledge of the distribution during a range-wide 

ILT workshop in Alton, IL, April 2012. In brief, a 25-year data set strongly suggests ILT range 

expansion within and outside of areas occupied at the time of the 1985 listing; invasion and 

occupation of a number of types of anthropogenic habitats (i.e., reservoirs, rooftops, sand mines, 

industrial sites); and expansion of range-wide bird population estimates, from a low of ~2,000 at 

time of listing, to >17,500 in 2005 (Lott 2006). The synthesis also demonstrates that the ILT has 

met or exceeded range-wide numerical recovery criteria identified in the 1990 recovery plan 

(7,000 adult birds) for at least 18 years (1994-2012). ILT numbers essentially doubled from 1995 

to the 2005 range-wide count (e.g., Lott 2006: 17,591 ILT range-wide).

Breeding and Nesting

Sandbars are the primary habitat component used for ILT nesting. Sandbars generally are 

not stable features of the natural river landscape, but are formed, enlarged, eroded, moved, or 

destroyed, depending on the dynamic forces of the river. New habitat is formed when high water 

removes existing vegetation or deposits new sand, or sand is deposited properly during the 

dredged-material disposal process to create sandbars. When sandbars become fully vegetated, 

birds will not select them for nesting (Thompson et al. 1997). Flooding can scour some 

vegetation from sandbars and convert them back to suitable nesting habitat, but, at multi-year 

scales, if perennial woody vegetation becomes well-established and high flows can no longer 

remove vegetation, sandbars succeed to forest and permanently lose habitat value (Friedman et 

al. 1998, Johnson 2000, Wiley & Lott 2012).

Throughout much of the ILT range, the USACE is responsible for maintaining navigation 

along rivers through practices such as dredging, dike construction, dredged-material disposal, 

and variable dam discharge actions (Fischer et al. 2004, Guilfoyle et al. 2004). These actions can 

have varying positive or negative effects on sandbar nesting habitat. Stabilization of major rivers 

for navigation, hydropower, irrigation, and flood risk management has destroyed, in large part, 

the dynamic nature of natural river processes (Smith & Stucky 1988). Many of the natural 

sandbars within the ILT range are unsuitable for nesting because of vegetation encroachment or 

are too low and subject to frequent inundation. On the three major lock and dam navigation 

systems within the ILT range (McClellan-Kerr Navigation System on the Arkansas River, the 

Lower Ohio River Navigation System, and the J. Bennett Johnston Navigation System on the 

Lower Red River), ILT nesting occurs most frequently where regular dredging to maintain 

navigation depths results in dredged material disposal within dike-fields or confined disposal 

facilities (USACE 2005, 2011b) or on mid-channel dredged material sites. While vegetation is 

often removed from dike-field disposal sites in AR due to flooding or large inter-annual stage 

differences that inundate bare sand areas for months at a time, dredged material sites with less 

dynamic flow regimes require regular vegetation control to persist (USACE 2011b). ILT also 

have nested on a variety of intentionally restored mid-river sandbars (usually in response to 

regional habitat loss), such as those on the Platte, Missouri, and Canadian Rivers (Hill 1993, 

Plettner & Jenniges 1999, USACE 2011a- Appendix B, 2011b), and reproductive success has 
26

been highly variable on many of these sites (USACE 2011a- Appendix B, 2011b). On the 

Missouri River, the extremely long-duration floods of 1995-1997 created large amounts of bare 

sandbar nesting habitat, which quickly was degraded due to erosion and/or vegetation 

succession. Subsequently, sandbar construction below Gavins Point dam began in 2004, leading

to the creation of significant nesting areas for the regional ILT population. On the LMR, sand 

island ILT nesting habitat has been maintained by a natural flood hydrograph. While dike 

construction on the LMR was previously considered a potential threat to ILT (by increasing 

connectivity of islands to banks), higher elevations of the islands due to effects of the dikes has 

apparently benefitted the species. These benefits are being maintained and enhanced, where 

appropriate, by the USACE dike notching program.

Wintering

 

Though much is known about the life-history of least terns during the breeding season in 

North America, comparatively little is known about life-history and threats during the nonbreeding season when most individuals migrate to wintering areas outside of the United States. 

Least terns of unknown populations/subspecies are found during the winter along the Central 

American coast and the northern coast of South America from Venezuela to northeastern Brazil 

(USFWS 1990a). 

Abundance

Since the initial listing of this species, knowledge and understanding of the range and 

population demographics of ILT has grown considerably. Increased monitoring efforts have 

revealed larger population numbers and a greater extent of overall distribution of this species 

than previously thought. In November 2005, ERDC-EL sponsored a regional workshop in Tulsa, 

Oklahoma on monitoring programs for the ILT. Discussions focused on: 1) defining goals and 

objectives for local, regional, and range-wide monitoring programs; 2) deciding what 

information to collect during monitoring programs; 3) standardizing data collection and analysis 

protocols among programs; 4) integrating local efforts into regional or range-wide approaches; 

and 5) evaluating the effects of management actions on ILT within the context of regional or 

range-wide recovery (Lott & Pashley 2006). Repeated efforts to standardize count protocol and 

data reporting since this meeting have mostly failed, although data reporting has increased in 

some areas. This failure has been driven, largely, by the need for individual monitoring programs 

to continue to supply data to local USFWS field offices in the format that was originally

requested of them for Section 7 compliance. Since most ILT monitoring programs in Districts 

and/or drainage basins have evolved independently, in the absence of communication among 

programs, and without any incentive for collaboration, it has been difficult to encourage change 

among disparate monitoring programs, who most often stick to their unique regional protocols to 

be in compliance with biological opinions. 

Although many ILT counts were conducted prior to 2005, regular survey coverage was 

incomplete across the large breeding range of ILT, limiting the ability to assess the conservation 

status or trends for this population. Because of the large number of programs collecting 

independent data on ILT (at least 29, reviewed in Lott [2006]), the ERDC-EL and ABC took the 

initiative to coordinate a range-wide survey during the last two weeks of June in 2005. Over 140 

participants contributed to this survey, and ABC/ERDC raised additional funds, from the Tulsa 

District, to ensure counts were conducted in areas that are not covered by annual monitoring 
27

programs (Lott 2006). The primary objectives of this survey were 1) to provide a minimum count 

of the number of adult ILT occurring in North America during the breeding season, 2) to 

document the range-wide distribution of nesting colonies, and 3) to describe the types of habitats 

that are being used for nesting. Survey crews covered ~4,700 river miles, 22 reservoirs, 62 sand 

pits, 12 industrial sites, 2 rooftop colonies, and over 16,000 acres of salt flats, counting a grand 

total of 17,591 ILT in association with 489 different colonies. Just over 62 percent of all adult 

ILT were counted on the LMR (10,960 birds on 770+ river miles). Four additional river systems 

accounted for 33.3% of the remaining ILT, with 11.6% on the Arkansas River system (including 

the Canadian and Cimarron Rivers and the Salt Fork of the Arkansas River), 10.4% on the Red 

River system, 6.9% on the Missouri River system, and 4.4% on the Platte River system. Lesser 

numbers of terns were counted on the Ohio River system (1.0%), the Trinity River system in 

Texas (1.0%), the Rio Grande/Pecos River system in New Mexico and Texas (0.8%), the 

Wabash River System (0.6%), two reservoirs in East Texas (0.3%), and the Kansas River system 

(0.3 percent). A majority of adult terns were counted on rivers (89.9%), with much smaller 

numbers at sand pits (3.6%), reservoirs (2.5%), salt flats (2.3%), industrial sites (1.4%), and 

rooftops (0.3%). 

Within the LMR, the USACE initiated annual nesting season tern counts between Cape 

Girardeau, MO, and Greenville, MS, following the 1985 listing. The survey reach was extended 

downstream to Vicksburg, MS, in 1988, and to Baton Rouge, LA, in 2004. These counts have 

documented a persistent increase in the number of ILT known to utilize the LMR, from 

approximately 300 birds in 1985, to over 12,000 in 2011 (Jones 2011) (Figure IV-2).

After the 2005 range-wide survey ABC and ERDC developed a flexible on-line data 

entry system for ILT surveys and encouraged partners collecting information on ILT to 

contribute their data. This database became the standard data entry platform for the Tulsa

District’s monitoring program (covering a large portion of the range of ILT), and resulted in the 

reporting of enough ILT counts in different areas to increase the understanding of range-wide 

distribution and abundance of ILT, beyond what was learned during the 2005 range-wide survey. 

The ILT range-wide numerical recovery criterion (7,000 birds) (USFWS 1990a) has been 

met or exceeded each of the past 18 years (1994–2012). Using range-wide seasonal count data 

of adult ILTs from 1984 (722 terns) to 1995 (8,859 terns), Kirsch and Sidle (1999) demonstrated 

achievement of the numerical recovery criterion, and a positive range-wide population growth 

trend. They noted, however, that most of the ILT increase had occurred on the LMR, observed 

that population increases were not supported by available fledgling success estimates, and 

hypothesized that ILT increases were possibly due to immigration surges from a more abundant 

Eastern Gulf Coast least tern population. 

Range-wide ILT counts doubled between 1995 and 2005 (e.g., Lott 2006: 17,591 adult 

ILT range-wide), and the majority of birds continue to be reported from the LMR (Lott 2006; 

~62% of the 2005 range-wide count occurred in the LMR). Counts now equal or exceed 

population estimates for least tern along the U.S. Gulf Coast (Lott 2006). Lott (2006) noted 

marked declines in Gulf Coast least tern populations in recent years, hypothesized a wider least 

tern metapopulation that includes Gulf Coast and ILT subpopulations, and the potential for 

significant immigration from the Gulf Coast inland due to high human disturbance along the 

coast and presence of better nesting conditions on the LMR. However, there are no data or 

observations directly supporting either the Kirsch and Sidle (1999) or Lott (2006) immigration 
28

hypotheses as a factor in the 20+ year increase in ILT counts, either in the LMR or range-wide. 

Recent studies, however, have shown high genetic connectivity among groups of ILT inhabiting 

different drainage basins, as well as between interior and coastal populations (Draheim et al. 

2010).

Recovery Status

The 1990 delisting recovery criteria for ILT specified protection and management of 

essential breeding habitats, a range-wide population of 7,000 birds, and population targets for 

five river drainages - Missouri, Mississippi, Arkansas, Red, and Rio Grande Rivers. 

Habitat protection and management programs have been established across the ILT range 

over the past 20 years, primarily under section 7(a)(2) consultations. Current range-wide 

population estimates exceed 17,000 birds. USFWS is currently conducting a review of the 

recovery status of ILT.

Pallid Sturgeon

The pallid sturgeon (Scaphirhynchus albus) is a benthic, riverine fish that occupies the 

Mississippi River Basin, including the Mississippi River, Missouri River, and their major 

tributaries (i.e. Platte and Yellowstone Rivers), and the Mississippi’s major distributary, the 

Atchafalaya River (USFWS 1990b). Pallid sturgeon (PS) belong to the family Acipenseridae 

(Actinopterygii: Acipenseriformes) and members of this order are often referred to as “living 

fossils” because of their prehistoric appearance and representation in the fossil record from the 

Cretaceous period of geological history (Hilton & Grande 2006). North American Acipenserids 

are represented in the fossil record from the pre-Pleistocene period (Hilton & Grande 2006). The 

PS was first described in 1905 by Forbes and Richardson as Parascaphirhynchus albus, but was 

later placed in the genus Scaphirhynchus (Forbes & Richardson 1905; Bailey & Cross 1954). In 

1990, the PS was listed as an endangered species under the Endangered Species Act of 1973 

(USFWS 1990b). Its decline was attributed to several anthropogenic impacts, including habitat 

modification and commercial harvest of the fish (USFWS 1990b). More recent studies have 

added water contamination, entrainment, and hybridization to the list of impacts (Divers et al. 

2009; USFWS 2009a; Blevins 2011; Schrey et al. 2011). A recovery plan, which listed 

recommendations and policy changes, was issued by the USFWS in 1993, and included a 

recovery date of 2040. The shovelnose sturgeon (S. platorynchus) is a sibling species to the PS 

and shares much of its range. The two species are morphologically similar, although the 

shovelnose sturgeon is more abundant than the PS (Kallemeyn 1983; Killgore et al. 2007a). To 

further protect the PS, the shovelnose sturgeon was listed as a threatened species under the 

Similarity-of-Appearance Provisions of the Endangered Species Act in 2010 (USFWS 2010b). 

This listing bans the commercial harvest of shovelnose sturgeon in areas where PS are known to 

occur (USFWS 2010b). 

Life History

Pallid sturgeon occupy the benthos of large, turbid rivers in North America, particularly 

the main channel (Kallemeyn 1983). Much of the natural habitat throughout the range of PS has 

been altered by humans, and this is thought to have had a negative impact on this species 
29

(USFWS 1993). Habitats were once very diverse, and provided a variety of substrates and flow 

conditions (Baker et al. 1991; USFWS 1993). Extensive modification of the Missouri and 

Mississippi rivers over the last 100 years has drastically changed the form and function of the 

river (Baker et al. 1991; Prato 2003). Today, habitats are reduced and fragmented and much of 

the Mississippi River basin has been channelized to aid in navigation and flood risk management

(Baker et al. 1991). The impact of habitat alteration on pallid sturgeon throughout its range is 

unknown, but recent studies have shown that in the un-impounded reaches, suitable habitat is 

available and a diverse aquatic community exists (USFWS 2007). River restoration plans in the 

Missouri and Mississippi rivers are currently in place, although it is unclear how much progress 

has been made (USFWS 2007). 

Habitat - PS are thought to occupy the sandy main channel in the Mississippi, Missouri, 

and Yellowstone Rivers most commonly, but also are collected over gravel substrates (USFWS 

1993; Bramblett & White 2001; Hurley et al. 2004; Garvey et al. 2009; Koch et al. 2012). 

Several studies have documented PS near islands and dikes, and these habitats are thought to 

provide a break in water velocity and an increased area of depositional substrates for foraging 

(Garvey et al. 2009; Koch et al. 2012). Increased use of side channel and main channel islands 

has been noted in spring, and it is hypothesized that these habitats may be used as refugia during 

periods of increased flow (Garvey et al. 2009; Koch et al. 2012). Recent telemetry monitoring of 

PS in the LMR indicate use of most channel habitats, including dikes, revetment, islands, 

secondary channels, etc. (Kroboth et al. 2013).

PS occur within a variety of flow regimes (Garvey et al. 2009). In their upper range, adult 

PS are collected in depths that vary between 2-48 ft with bottom water velocities ranging from 2 

ft/s and 3 ft/s (USFWS 1993; Bramblett & White 2001; Gerrity 2005). PS in the LMR have been 

collected at depths greater than 65 ft with a mean value of 33 ft, and water velocities greater than 

6 ft/s with a mean value of 2 ft/s (ERDC unpublished data, Kroboth et al. 2013). Turbidity is 

thought to be an important factor in habitat selection by PS, which have a tendency to occupy 

more turbid habitats than shovelnose sturgeon (Blevins 2011). In the LMR, pallid sturgeon have 

been collected in turbidities up to 340 NTU’s with a mean value of 90 NTU’s (ERDC 

unpublished data). 

Movement - PS, like other sturgeon species is a migratory fish species and moves

upstream annually to spawn (Koch et al. 2012). Movements are thought to be triggered by 

increased water temperature and flow in spring months (Garvey et al. 2009; Blevins 2011). 

Garvey et al. (2009) suggested that PS remain sedentary, or remain in one area for much of the 

year, and then move either upstream or downstream during spring. It is possible that because 

movement in large, swift rivers requires a great amount of energy, this relatively inactive period 

may be a means to conserve energy (Garvey et al. 2009). Most active periods of movement in the 

upper Missouri River (RPMA2) were between 20 March and 20 June (Bramblett & White 2001). 

In one study, individual fish traveled an average of 3.73 mi/day and one individual traveled over 

9.94 mi/day (Garvey et al. 2009). PS in the Missouri River have been reported as traveling up to 

5.90 mi/hour and 13.30 mi/day during active periods (Bramblett & White 2001). PS may 

undertake long-distance, multi-year upstream based on recaptures of shovelnose sturgeon in the 

Missouri River originally tagged in the LMR. Upstream distances approaching 1245 mi have 

been recorded (ERDC unpublished data) and similar distances have been recorded for 

downstream movements (USFWS unpublished data, Kroboth et al. 2013). 
30

Aggregations of PS have been reported in several locations in the middle Mississippi 

River, particularly around gravel bars, including one annual aggregation at the Chain of Rocks 

Dam, and this is thought to be related to spawning activities (Garvey et al. 2009). Aggregations 

of PS in the lower 8.70 mi of the Yellowstone River are thought to be spawning areas of 

sturgeon from the Missouri River (Bramblett & White 2001). PS have been found to have active 

movement patterns during both the day and night, but move mostly during the day (Bramblett & 

White 2001). 

Feeding - Sturgeon are benthic feeders and are well adapted morphologically (ventral 

positioning of the mouth, laterally compressed body) for the benthic lifestyle (USFWS 1993; 

Findels 1997). Adult PS are primarily piscivorous (but still consume invertebrates), and are 

thought to switch to piscivory around age 5 or 6 (Kallemeyn 1983; Carlson et al. 1985; Hoover et 

al. 2007; Grohs et al. 2009). In a study of PS in the middle and lower Mississippi River, fish 

were a common dietary component and were represented primarily by Cyprinidae, Sciaenidae, 

and Clupeidae (Hoover et al. 2007). Other important dietary items for PS in the Mississippi 

River were larval Hydropsychidae (Insecta: Trichoptera), Ephemeridae (Insecta: 

Ephemeroptera), and Chironomidae (Insecta: Diptera) (Hoover et al. 2007). PS diet varies 

depending on season and location, and these differences probably are related to prey availability 

(Hoover et al. 2007). In a Mississippi River dietary study, Trichoptera and Ephemeroptera were 

consumed in greater quantities in winter months in the lower Mississippi River, while the 

opposite trend was observed in the middle Mississippi River (Hoover et al. 2007). Hoover et al. 

(2007) also found that in both the middle and lower Mississippi River, dietary richness is greatest 

in winter months. 

Spawning - Freshwater sturgeon travel upstream to spawn between the spring equinox 

and summer solstice, and it is possible that either a second spawn or an extended spawning 

period may occur in the fall in southern portions of the range (i.e., Mississippi River) (USFWS 

2007; Wildhaber et al. 2007). These spawning migrations are thought to be triggered by several 

cues, including water temperature, water velocity, photoperiod, presence of a mate, and prey 

availability (Keenlyne 1997; DeLonay et al. 2007; DeLonay et al. 2009; Blevins 2011). Gamete 

development is completed during the upstream migration and sturgeon are thought to spawn near 

the apex of their migration (Bemis & Kynard 1997). It is thought that female Scaphirhynchus 

spp. do not reach sexual maturity until ages 6-17 and spawn every 2-3 years and that males do 

not reach sexual maturity until ages 4-9 (Keenlyne & Jenkins 1993; Colombo et al. 2007; Stahl 

2008; Divers et al. 2009). PS and shovelnose sturgeon at lower latitudes (e.g., lower Mississippi 

River) may begin spawning at an earlier age than those in upper portions of the range (e.g., 

Upper and Middle Mississippi and Missouri Rivers) because they are thought to have shorter 

lifespans and reach smaller sizes (George et al. 2012). Also, LMR PS may be more highly 

fecund than those in northern portions of their range (George et al. 2012). It is thought that PS, 

like shovelnose sturgeon spawn over gravel substrates, but spawning has never been observed in 

this species (USFWS 1993; DeLonay et al. 2007; DeLonay et al. 2009). 

Rearing - PS hatch when they reach a total length of approximately 1⁄4-inch, and larvae 

feed on yolk reserves and drift downstream for 11-17 days, until yolk reserves are depleted 

(Snyder 2002; Braaten et al. 2008; DeLonay et al. 2009). Length of drift and rate of yolk 

depletion are dependent on several factors, including water temperature, photoperiod, and water 

velocity (Snyder 2002; DeLonay et al. 2009). Larval drift is not completely understood and the 

impacts of artificial structures, as well as the role of eddies, are unknown (Kynard et al. 2007; 
31

Braaten et al. 2008). During drift, sturgeon repeat a “swim up and drift” pattern, in which they 

swim up in the water column from the bottom (<10 in) and then drift downstream (Kynard et al. 

2002; Kynard et al. 2007). A hatchery series of shovelnose sturgeon from Louisiana (J. Dean, 

Natchitoches National Fish Hatchery, unpublished data) reports complete yolk sac absorption at 

days 8-9 post-hatch, which is several days sooner than shovelnose sturgeon from Gavins Point 

National Fish Hatchery in South Dakota, so there could be a latitudinal difference in yolk 

absorption and larval maturation rates throughout the range of PS (Snyder 2002). Exogenous 

feeding begins when yolk reserves are depleted and drifting has ceased, and timing can differ 

latitudinally (DeLonay et al. 2009). The switch from endogenous to exogenous feeding is known 

as the “critical period”, because mortality is likely if sturgeon do not find adequate food (Kynard 

et al. 2002; DeLonay et al. 2009). PS begin exogenous feeding around 11-12 days post-hatch in 

upper portions of their range, but exogenous feeding was observed in fish as small as 0.70 inches

TL in the lower Mississippi River (Harrison et al., unpublished data), which could be as young as 

6-8 days post hatch based on unpublished age and growth data from Natchitoches National Fish 

Hatchery (Braaten et al. 2007). The diets of young of year and juvenile PS and shovelnose 

sturgeon in upper portions of their ranges are much like those of the adult shovelnose sturgeon, 

and are primarily composed of aquatic insects and other benthic macroinvertebrates (Braaten et 

al. 2007; Wanner et al. 2007; Grohs et al. 2009). Young of year and juvenile PS in the LMR feed 

primarily on Chironomidae over sand in channel habitats (Harrison et al. 2012, unpublished data 

Kynard et al. (2002), found larval PS to be photopositive and showed little preference to 

substrate color, except for a slight preference for light substrates when exogenous feeding began. 

It is thought that PS become increasingly photonegative starting around day 11 post-hatch 

(Kynard et al. 2002). In this same study, larval sturgeon swam in open habitats, seeking no cover 

under rocks in the swimming tube, and aggregated in small groups around days 3-5 posthatching (Kynard et al. 2002). The black tail phenotype of young sturgeon is thought to aid in 

recognition and aggregation (Kynard et al. 2002). PS have been observed swimming and drifting 

at a wide range (2-118 in) above the bottom depending on water velocities (although most fish 

are thought to say in the lower 20 in of the water column), and drift velocities are thought to 

range from 1-2 ft/s (Kynard et al. 2002; Kynard et al. 2007; Braaten et al. 2008). Drift distance of 

larval sturgeon is thought to be between 86-329 mi (Kynard et al. 2007; Braaten et al. 2008). 

Juvenile PS have been found in water depths ranging an average of 8 ft in the upper Missouri 

River (Gerrity 2005). Maximum critical swimming speeds for juvenile PS range from 0.3 ft/s to 

0.8 ft/s depending on size with larger juveniles (6-8 in TL) able to withstand higher water 

velocities than their smaller counterparts (5-6 in TL) (Adams et al. 1999). 

Distribution and Abundance

PS occur in parts of the Mississippi River Basin, including the Mississippi River south of 

the Missouri River, and the Missouri, Atchafalaya, Yellowstone, and Platte rivers, where it is 

adapted to pre-modification habitats of these systems (Kallemeyn 1983; Killgore et al. 2007a). 

Recovery efforts have divided the extensive range of PS into four management units (Figure IV3a) [previously six recovery management priority areas (RPMAs) (Figure IV-3b)] (USFWS 1993

& 2013). These areas were selected as areas of high importance for recovery task 

implementation based on population variation (i.e., morphological, genetic) and habitat 
32

differences (i.e., physiographic regions, impounded, unimpounded reaches) throughout the

extensive range of the PS (USFWS 1993). The Great Plains Management Unit (GPMU) extends 

from Great Falls of the Missouri River, Montana, to Fort Randall Dam, South Dakota, and 

includes the major tributaries thereof (Yellowstone, Marias, Milk Rivers). The Central Lowlands 

Management Unit (CLMU) includes the Missouri River from Fort Randall Dam, South Dakota, 

to the confluence of the Grand River, Missouri, and includes the major tributaries thereof (lower 

Platte, lower Kansas Rivers). The Interior Highlands Management Unit (IHMU) includes the 

Missouri River from the confluence of the Grand River, Missouri, to the confluence of the 

Mississippi River, Missouri, and the Mississippi River from Keokuk, Iowa, to the confluence of 

the Ohio River, Illinois. The Coastal Plain Management Unit (CPMU) includes the Mississippi 

River from the confluence of the Ohio River, Illinois, to the Gulf of Mexico, Louisiana, and 

includes the Atchafalaya River distributary system, Louisiana. 

Figure IV-3a. Map depicting pallid sturgeon management units
33

PS differ in body size, age to sexual maturity, and population size throughout their range 

(Murphy et al. 2007; USFWS 2007). PS from the CPMU reach much smaller total lengths 

(typically <39 in TL) than do PS from the GPMU, which are commonly reported as reaching 

lengths of >39 in TL (Brown 1955; Kallemeyn 1983; Keenlyne & Maxwell 1993; Bramblett & 

White 2001; Killgore et al. 2007b; USFWS 2007). This latitudinal difference in size has been 

attributed to shorter growing seasons in cooler water and the need for sturgeon in cold climates 

to allocate more energy (i.e., larger bodies) for survival in a harsher environment (Killgore et al. 

2007b). Conversely, some studies indicate that increased temperatures in the southern range of 

PS may shorten the growing season (Power & McKinley 1977; Conover 1990). Alternatively, it 

has been suggested that PS may use southern reaches of their range (i.e., middle and lower 

Mississippi River) for feeding habitat and as a growth period, and then migrate to more northern 

reaches (i.e., Missouri River and major tributaries) as adults for spawning habitat (Killgore et al. 

2007b). PS in the GPMU are also genetically distinct from PS in the CLMU and IHMU and the 

Atchafalaya River distributary (included in the CPMU) (Campton et al. 2000; Tranah et al. 

2001). These differences highlight the importance of thorough research throughout the entire 

range of the PS. 

Figure IV-3b. Map depicting PS range. Outlined areas correspond with 

approximate locations of RPMAs as designated in the initial PS Recovery Plan 

(USFWS 1993). Map not to scale. Source: Pallid Sturgeon 5-year Review 

(USFWS 2007)
34

GPMU

The most recent available estimates suggest there are approximately 45 wild PS

remaining in the most upstream portion of the GPMU (previously RPMA 1), which includes the 

Missouri River from the confluence of the Marias River to the headwaters of Fort Peck 

Reservoir, Montana, and of those, all are thought to be older adults (USFWS 2007). Natural 

recruitment is not thought to have occurred in this area over the last 20 years (Gerrity et al. 

2008), so stocking of juveniles and larvae began in 1997 and continues today (USFWS 2007). In 

this region, PS are hatchery-reared from broodstock captured in the region at the Gavins Point 

National Fish Hatchery until age-1 and subsequently released (Gerrity et al. 2008). Recent 

collection data reveal that stocking efforts are working to alleviate extirpation of the species in 

this section of the GPMA (USFWS 2007). Although historical population demographics from 

pre-altered habitats are unknown, the PS population from downstream of Fort Peck Dam to the 

headwaters of Lake Sakakawea, North Dakota, and from the Yellowstone River below the 

confluence of the Tongue River, Montana (Previously RPMA 2), is thought to have declined by 

40%-58% since the 1960s (Keenlyne 1989; USFWS 2007; Braaten et al. 2009). Latest estimates 

suggest that there are around 160 wild sturgeon remaining in this section of the GPMU, and that 

there is little to no natural recruitment (Klungle & Baxter 2005; USFWS 2007). Population 

estimates and forecasts suggest that natural populations in this section of the GPMU will be 

extirpated between 2016 and 2018 (Kapuscinski 2002; Klungle & Baxter 2005). Stocking efforts 

are currently in place and hatchery-reared juvenile PS are being released until a population size 

of 1,700 individuals is reached (Braaten et al. 2009).

CLMU

There are no naturally occurring wild PS remaining in the most upstream portion of the 

CLMU, including the Missouri River downstream of Fort Randall Dam to Lewis and Clark Lake 

(formerly RPMA 3), so the entire population is made up of hatchery-reared fish and translocated 

wild PS (USFWS 2007). Stocking in this region began in 1997 and continues presently, and 

sturgeon sampling efforts have collected five out of six age classes that were stocked in this 

study area (Shuman et al. 2005).

A recent PS study conducted in a 50-mile reach of the lower Missouri River downstream 

from the confluence of the Platte River estimated a population size much higher than those in the 

GPMU (Steffensen et al. 2012). In this reach, 492 individuals (38 were recaptures) were 

collected between 2008-2010 (Steffensen et al. 2012). Of those, 93 were wild PS, and 399 were 

hatchery-reared PS (Steffensen et al. 2012). This count is slightly lower than the records from 

1990-2005, which reported 117 unique wild PS from the Missouri River below Gavins Point 

Dam to the confluence of the Mississippi River (formerly RPMA 4)(USFWS 2007). It is 

currently unclear whether or not natural recruitment occurs in this study area (USFWS 2007).

IHMU

It is still unclear if there is any natural recruitment in the lower Missouri River, from 

Gavins Point Dam to the confluence of the Mississippi River (Steffensen et al. 2010; USFWS 

2007). Between 1994 and 2008, nearly 80,000 hatchery-reared PS had been released into the 

lower Missouri River, and as of 2008, only 1% had been recaptured (Steffensen et al. 2010). 
35

Wild PS are more frequently captured in the middle Mississippi River (MMR), which extends 

from the confluence of the Missouri River to the confluence of the Ohio River, than in the 

GPMU and CLMU. In a collaborative sampling effort between 2002 and 2005, researchers from 

the USACE, Missouri Department of Conservation, and Southern Illinois University, captured 

148 PS, with only 12 fish of hatchery origin (USFWS 2007). In the MMR, the pallid : 

shovelnose sturgeon ratio ranges from 1:36 to 1:77 pallid : shovelnose (Killgore et al. 2007a).

Age-0 PS have been collected in the MMR, although it is unknown where spawning occurs 

(Hrabik et al. 2007).

CPMU

Between 1996-2006, 162 PS were collected in the LMR, and >500 individuals have been 

captured to date (Killgore et al. 2007a, USFWS database 2013). Pallid : shovelnose ratios vary 

between 1:6 to 1:30 pallid : shovelnose (Killgore et al. 2007a). There is a relatively large 

population (1:6 ratio of pallid : shovelnose) of PS in the Atchafalaya River distributary than in 

other parts of the pallid sturgeon range, although it is still unclear whether or not natural 

recruitment occurs in this area (Killgore et al. 2007a; USFWS 2007). More than 600 PS have 

been captured and marked in the Atchafalaya to date (USFWS database 2013). Age-0 PS have 

been captured in the LMR, although it is unclear exactly where and when spawning occurs 

(ERDC, unpublished data; Hartfield et al. 2013). 

Recovery Status

The USFWS (1993) criteria to down list PS from endangered to threatened include a 

population structure with at least 10% sexually mature females, and sufficient numbers in the 

wild to maintain population stability. USFWS (2007) conducted a 5-Year Review of the 

conservation status of the PS, including an assessment of status in each identified RPMA 

throughout its range. They identified a lack of adequate information on population size, 

recruitment, and trends exists in RPMAs 5 and 6 (Mississippi and Atchafalaya rivers, 

respectively), and the continued need for artificial supplementation efforts in RPMAs 1, 2, 3, and 

4 (reaches of the Missouri River), concluding that the PS did not meet criteria for downlisting to 

threatened status or for delisting in any portion of its range. The 5-Year Review recommended 

revision of the PS Recovery Plan and criteria for recovery. A draft revision has been released by 

USFWS (2013), which notes significant genetic structure through the range, redefines 

management units, and identifies the potential of delisting by management area. The primary 

strategy for recovery of pallid sturgeon is to: 1) conserve the range of genetic and morphological 

diversity of the species across its historical range; 2) fully quantify population demographics and 

status within each management unit; 3) improve population size and viability within each

management unit; 4) reduce threats having the greatest impact on the species within each 

management unit; and, 5) use artificial propagation to prevent local extirpation within

management units where recruitment failure is occurring. Pallid sturgeon recovery will require

an increased understanding of the status of the species throughout its range; developing

information on life history, ecology, mortality, and habitat requirements; improving our

understanding of some poorly understood threat factors potentially impacting the species; and

using that information to implement management actions in areas where recovery can be

achieved.
36

Fat Pocketbook Mussel

The fat pocketbook mussel Potamilus capax is a freshwater pearly mussel native to the 

Ohio River system and Mississippi River drainage (Watters et al. 2009). Fat pocketbook mussels 

(FPM) belong to the family Unionidae, which is one of two families of pearly mussels that occur 

in North America (Watters et al. 2009). This species was originally described as Unio capax

Green 1832, but was later placed in the genus Potamilus Rafinesque (Watters et al. 2009). This 

species is aptly named for its valve morphology, which is highly inflated and obovate (MMNS 

2001; Watters et al. 2009). This species is a relatively large species, with adults sometimes 

reaching over 5-inches in length (USFWS 1989). The FPM was listed as endangered throughout 

its range by the U.S. Fish and Wildlife Service in 1976, and a recovery plan was issued in 1989 

(USFWS 1976; USFWS 1989). The decline of the FPM has been attributed to several 

anthropogenic impacts, including water contamination and loss of habitat, particularly to 

perturbations associated with river navigation and flood risk management (USFWS 1989). 

Because its shell is too thin for use, this species is of no commercial value (Harris & Gordon 

1990). An updated 5-year review reported that the FPM species status is improving based on 

increases of site records throughout its range (USFWS 2012b).

Habitat

FPM occupy depositional areas of large, slow moving rivers, and museum records 

suggest that this species requires flowing water and stable substrates (USFWS 1989; Watters et 

al. 2009). This species is typically found in sand and silt substrates, but has also been collected in 

mud, clay, and fine gravel substrates in depths ranging from a few inches to ten feet in depth 

(Baker 1928; Parmalee 1967; Harris & Gordon 1987; USFWS 1989; Harris & Gordon 1990; 

USFWS 2012b). The FPM, which in some populations has a very thin shell, is able to survive in 

deep depositional areas of silt, and it has been suggested that prior to anthropogenic habitat 

alteration, this species was probably common in oxbows and sloughs (Miller & Payne 2005). In 

the lower Mississippi River, FPM have been found in sand in secondary channels and in a 

mixture of sand, silt, and mud in side channels (USFWS 2012b).

Movement

Freshwater mussels generally follow two movement patterns, vertical and horizontal, 

and movement is thought to be seasonal and/or related to reproduction or habitat suitability (Peck 

2010). Relocation has been used to move FPM populations threatened by habitat modification 

(e.g., dredging, channel maintenance, road/bridge construction) to more suitable habitats (Peck 

2010). After relocation, this species has a tendency to move less than do non-relocated 

individuals (Peck et al. 2007). FPM have an average range of approximately 21 yds, but some 

individuals have been noted to move >165 yds (Peck et al. 2007). A 25 month study of the 

movement patterns of the FPM in Arkansas using telemetry demonstrated that the average home 

range of this species is 117.0 yds, and most movements are downstream in unimpounded reaches 

(Peck 2010).
37

Feeding

Like other freshwater mussels, the FPM feeds by circulating water through its gills, 

removing particulate organic matter (Miller & Payne 2005; EPA 2007). It has been demonstrated 

that different bivalve species filter different sized particulate matter, although the specific diet of 

this species is unknown (Silverman et al. 1995).

Reproduction

Gravid FPM have been found between June and December and this species is likely 

bradytictic (Baker 1928; Oesch 1984; USFWS 1989; Roe et al. 1997; Watters et al. 2009). 

Fertilization occurs in spring after sperm are released upstream of female mussels and are 

siphoned into the gills (Baldridge et al. 2007; USFWS 2012b). The posterior portion of the outer 

gills is the marsupial region in this species (Watters et al. 2009). Glochidia are packaged in 

white, fragile conglutinates (Utterback 1916). Glochidia are axe-head or hatchet-shaped with 

hooks along the lateral margin of the ventral flange and measure 0.105 x 0.185 mm (Utterback 

1916; Oesch 1984). The only known host species for FPM is freshwater drum Aplodinotus 

grunniens Rafinesque, but the method of glochidial attachment remains unknown (Watters et al. 

2009; USFWS 2012b). It has been suggested that glochidial attachment may occur upon 

ingestion of the gravid adult by the molluscivorous host (Dillon 2000; Barnhart et al. 2009). 

FPM less than 5 years in age have been collected in the St. Francis system, Arkansas, and in the 

LMR system, indicating successful reproduction and recruitment (W.T. Slack, pers. comm.; 

USFWS 2012b).

Distribution and Abundance

Historically, the FPM occurred in the upper Mississippi and Ohio rivers and the major 

tributaries thereof, but this range has declined by >70% (Harris & Gordon 1987; NatureServe 

2012). There are museum records of FPM from the upper Mississippi River from the confluence 

of the Minnesota and St. Croix rivers to the White River, but this species has not been found 

there since the 1980s and is thought to have been extirpated from many of those sites (EPA 

2007; NatureServe 2012; USFWS 2012b). At the time of listing, the FPM was only known from 

one locality, the St. Francis Floodway in Arkansas, and in 1989, an updated recovery plan was 

published with additional records from the St. Francis River and several small drainage ditches 

and tributaries (USFWS 1989, 2012b). Since 1989, additional FPM populations have been found 

in the St. Francis system, LMR, White, Ohio, Wabash, lower Tennessee, and Cumberland Rivers 

(USFWS 2012b).

Recovery Status

Recovery criteria require protection of the St. Francis River population of FPM, and 

location and protection of at least two additional viable populations in two other river systems 

within the historical range of the species. The Ohio River population has expanded in recent 

years, and a population has been discovered in the LMR. Both new populations are considered 

viable, based on the presence of juvenile and subadult specimens. Neither range nor population 

size of FPM have been defined or quantified in the Ohio and LMR, however, both populations 

are being considered by state and Federal agencies during project planning, and are protected to 

some degree through formal and informal consultations.
38

PART V: LMR ENVIRONMENTAL BASELINE

Historical and Current Species Baselines in the LMR

Interior Least Tern

The historical distribution and abundance of ILT is poorly documented. Hardy (1957) 

reported the few documented ILT historical records of occurrence and nesting on the LMR, but 

surmised that the birds nested at many localities along the river. Downing (1980) reported 300 

birds in 11 colonies during an aerial survey of the Mississippi River, and noted the greatest 

concentration of birds occurred between Osceola, Arkansas, and Cairo, Illinois. These primary 

historical sources of information were used to quantify a 1985 estimated population size of 350 

to 400 adult ILT in the listing rule (50 FR 21789). The 1990 Recovery Plan utilized data from 

Sidle et al. (1988) and increased minimum LMR population estimate to ~2,300 adults (U.S. Fish 

and Wildlife Service 1990).

 Nesting colonies have been monitored in the LMR for over 25 years (Figure V- 1) and 

data have shown a significant increase in ILT numbers since initiation of the Lower Mississippi 

River Environmental Program (LMREP) in 1982. ILT are currently distributed along an 800 

mile reach of the LMR between the confluence of the Ohio River and Baton Rouge, LA. The 

population level has ranged from 8,000 – 18,000 birds over the past 9 years, and the drainage 

basin recovery goal has been exceeded for more than 20 years. Some proportion of the increase 

in adult ILT numbers has been attributed to improved survey efforts and efficiency (Lott 2006). 

Changes in survey methods utilized in the LMR, and extending survey reaches correspond to 

some degree with higher ILT counts (Figure V-1). The occurrence of large numbers of ILT 

within the LMR un-impounded navigation system has also been attributed, in part, to higher 

elevation sand and gravel bars associated with channel training dikes (Lott 2006).

USACE analyses indicate that habitat quantity has remained relatively stable and 

underutilized by breeding/nesting ILT for the past two decades (USACE 2008). USACE is 

finalizing a habitat trend analysis of islands for the LMR (Guntren et al. 2012). The LMR 

recovery goal (2,500 birds) has been exceeded every year since 1990. The range-wide ILT 

numerical recovery goal (7,000 birds) has been annually exceeded on the LMR alone since 2003 

(Figure V-1).
39

 

 Figure V-1: ILT Population Survey Results in the Lower Mississippi River, 1985-2012 (Mike

 Thron, USACE).

Pallid Sturgeon

The PS historical baseline in the LMR is undocumented. Prior to listing, collection

records of PS in the LMR were extremely rare, and the USFWS was able to document only 35 

observations of the species from the entire Mississippi River (Keenlyne 1989), 28 of these from 

the LMR and none from the Atchafalaya River. PS population size has not been quantitatively 

defined within the LMR, particularly considering the scope and scale of the available habitat to 

sample. However, in 2001, USACE initiated efforts to develop sampling methods for PS in the 

LMR, as well as studies on abundance, distribution, demography, and habitat use (e.g., Killgore 

et al. 2007a,b; Hoover et al. 2007, etc.). These and other collections, as well as telemetry 

monitoring of sonic tagged individuals have shown that PS occur throughout most of the 950 

mile reach of the LMR (Bettoli et al. 2009, Killgore et al. 2007a, Kroboth et al. 2013, USFWS 

database 2013), and the 200 mile reach of the Atchafalaya River (Constant et al. 1997, Dean in 

litt. 2005-2009, Herrala & Schramm 2011, USFWS database 2013). Collections of PS in the 

LMR include almost 500 individuals collected between the mouth of the Ohio River and New

Orleans, LA (Figure V-2)(Killgore et al. 2007a; USFWS database 2013), ranging in age from 0 –

21 years (50 to >1,000 mm fork length (FL)) (Killgore et al. 2007b, USFWS database 2013). No 

PS or shovelnose sturgeon have been collected below RM 85 (Killgore et al. 2007a; Hartfield, in 

litt. 2001-2010; Kroboth et al. 2013) Over 600 PS ranging from 400 to >1000 mm FL have been 

collected from the Atchafalaya River distributary of the LMR (USFWS database 2013).
40

Figure V-2: Capture and telemetry locations of PS in the LMR and Atchafalaya Rivers. 

Collection and telemetry records by ERDC, USGS, and USFWS. Map developed by Mississippi 

Field Office, U.S. Fish and Wildlife Service.

Although PS population size in the LMR has not been quantified, available data suggest a 

substantial population when compared to fishing effort and fish species composition. Killgore et 

al. (2007a) found that PS comprised 2.2% of fish captured on winter set trotlines, and ranked 5th

in frequency of capture out of 22 species collected. During two years of trotline sampling at 

Vicksburg and Tunica, MS, PS comprised 2.4 and 2.5%, respectively, of fish collected at both 

locations, and ranked 4th in frequency of capture out of 11 species collected (Aycock et al. 2012)

Recaptures of PS are also rare in the LMR. Killgore et al. (2007a) reported only five PS

recaptures over seven years. In another study that conducted two years of monthly PS collection 

and telemetry efforts in a 30-mi reach of the Mississippi River, only a single PS recapture 

occurred out of >60 PS collected, tagged, and released, even though telemetry results indicate 

most PS remained within the sample reach (Kroboth et al. 2013). 
41

There is also evidence that the LMR PS population can sustain removal of substantial 

numbers of individuals from the population. Bettoli et al. (2009) conservatively estimated that 

2% of the commercially harvested sturgeons in the Tennessee reach of the LMR were PS (169 

females over two seasons). Commercial harvest for sturgeon caviar has occurred annually in the 

Tennessee and Missouri reaches of the LMR for more than two decades. While baseline data on 

LMR PS is lacking, the persistence of the species following more than two decades of harvest 

pressure on mature PS females, suggests the population is relatively robust. 

Additional evidence of population size has recently been developed in association with 

evidence of persistent and periodic entrainment losses of LMR PS. During an emergency 

opening of the Bonnet Carre Spillway in 2008, the USACE and USFWS estimated up to 92 PS

were injured or killed due to entrainment (USFWS 2009a). Bonnet Carre has been opened four 

times since the species was listed (1994, 1997, 2008, and 2011). Pallid sturgeon are freshwater 

fish, and once entrained, their only choice is to move into the brackish waters of Lake 

Pontchartrain where they likely perish or move up to the structure as the water recedes where 

they may be rescued as was done in 2008 and 2011. Other diversion structures that have been 

operating for one to five decades (Old River Control Complex, Davis Pond) are also known to 

entrain PS. Pallid sturgeon entrained at Old River Control Complex enter the Atchafalaya River, 

but it is unknown if these fish can spawn in the relatively short reach (137 river miles) between 

the structure and the Gulf of Mexico near Morgan City, LA. It is also unlikely that pallid 

sturgeon can swim from the Atchafalaya River back into the Mississippi River due to head 

differential through the diversion structures. While episodes of commercial harvest or 

entrainment constitute substantial periodic or continuous localized loss of individuals to the PS

population within the specific river reaches, scientific collection efforts indicate the species has 

persisted within the commercially harvested and diversion reaches of the LMR (e.g., Killgore et 

al. 2007 a, b; Kroboth et al. 2013).

LMR PS population demographics have been poorly defined but recruitment has been 

documented by capture of multiple age classes (Figure V-3, Killgore et al. 2007a) and capture of 

larval PS at several locations between the confluence of the Ohio River and Vicksburg, MS. 

Adult PS annual mortality is low (<12%) in the LMR, compared to the Middle Mississippi River 

(>35%) (Killgore et al. 2007b) where commercial fishing was just recently banned (USFWS 

2010b). There are latitudinal morphometric variation and length-at-age differences across the 

range (Murphy et al. 2007), suggesting that management goals should be reach-specific. Specific 

spawning and rearing habitats for PS are poorly known but surmised to include gravel bars 

(spawning), and secondary channels and flooded sand islands (larval and juvenile recruitment). 

Telemetry studies in the LMR have shown use of multiple channel habitats by larger size classes 

of pallid sturgeon, including point bars, secondary channels, crossovers, wing dikes, island tips, 

natural banks, and revetted banks (Kroboth et al. 2013).
42

Fat Pocketbook Mussel

There are no historical records of FPM from the CIP footprint (i.e., active channel) in the 

LMR (Figure V-4). Recent collections of FPM from the LMR indicate a widespread population 

(Figures V-4, V-5), but intense sampling efforts are needed to assess abundance in this region. 

Most of the LMR collection records are from secondary and side channels along the river, 

particularly Gilliam Chute, in Jefferson County, Mississippi (Figure V-6) (USFWS 2012b). 

Specimens have also been collected at St. Catherine’s Creek National Wildlife Refuge. A single 

young individual was collected in a trawl sample below a chevron dike, Bolivar County, 

Mississippi (W.T. Slack, pers. comm.). Live and fresh dead specimens have been collected from 

secondary channels between River Miles 410 – 800, but sampling has been insufficient to 

determine if and where viable populations occur in the river.

0

1

2

3

4

5

6

7

8

9

Number of Individuals

3 5 7 9 11 13 15 17 19 21

Age, years

LMR

MMR

Figure V-3. Age distribution of PS captured in the Lower (LMR) 

and Middle (MMR) Mississippi River (Killgore et al. 2007b).
43

Figure V-4. Historical and present-day distribution of 

Potamilus capax. Collection records, both published and 

unpublished, provided by Mississippi Museum of Natural 

Science, Jackson, MS, USACE Memphis District, Memphis, 

TN, Arkansas Game and Fish Commission, Little Rock, AR, 

USACE-ERDC, Vicksburg, MS, and NatureServe Explorer.
44

Figure V-5. Collection sites of Potamilus capax in the lower 

Mississippi River. Collection records provided by Mississippi 

Museum of Natural Science, Jackson, MS, USACE Memphis 

District, Memphis, TN, USACE-ERDC, Vicksburg, MS, and 

Arkansas Game & Fish Commission, Little Rock, AR.
45

0

50

100

150

200

250

0

8040

960

920880840800760720680640600560520

480440

400360320280240200160120

Main channel

Side channel or secondary 

channel

River mile

Number of specimens

Gilliam Chute (RM 387-381.5)

St. Catherine’s Creek NWR (RM 348)

Canadian Reach (RM 799-800)

Choctaw Bar Island (RM 558.5-565)

Figure V-6. Collections of Potamilus capax in the Lower Mississippi River including specimens 

collected in the Mississippi River main channel, side channels, and secondary channels. 

Factors Affecting Species

Several concerns have been identified for the priority species in the LMR (USFWS 1989, 

2007, 2012c). These include: habitat loss and modification for all three priority species, human 

disturbance to ILT nests and chicks, commercial harvest of PS, dredge entrainment of PS, sand 

and gravel mining entrainment and spawning habitat degradation, entrainment of PS through 

water control structures, effects of pollution and contaminants on all three species, and 

hybridization of PS with shovelnose sturgeon. Ongoing and proposed actions required to fully 

assess these factors are identified below.

Habitat Loss and Modification

While it is likely that habitat modification has the potential to seriously affect all three 

priority species, there is little evidence of direct impacts in the LMR, i.e., knowledge and 

numbers of PS and ILT have increased relative to historical pre-modification conditions, and the 

occurrence of FPM was first documented from the LMR post-modification. 

Appropriate habitat for PS is generally characterized as large, deep, turbid, fast, and freeflowing rivers, with spawning migration and success linked to seasonal high flow events 
46

common to a natural hydrograph. These characteristics are common in the LMR throughout 

nearly all of its length. The LMR appears to contain the most extensive and possibly the best 

quality habitat within the species’ range, including complex channel habitats, numerous 

secondary channels and islands, and widespread gravel bars suitable for spawning. While, the 

location and complexity of channel habitats has been modified over time by river engineering

under the CIP, the potential adverse effects on PS recruitment are poorly documented or 

understood. 

Habitat loss and modification does not appear to be a factor affecting either ILT or FPM 

in the LMR. As noted previously, potential LMR nesting habitat for ILT currently exceeds use 

by the species. The expansion of the FPM range into LMR secondary channels appears to result 

from recent exploitation of developing habitat conditions created within USACE dike fields, 

however, this is poorly documented and understood. 

Maintenance Dredging 

Maintenance dredging of the navigation channel is required in the LMR navigation 

channel, particularly within crossovers and harbors at low river stages. Dredging has been 

shown to take shovelnose sturgeon in the Middle Mississippi River (MMR), suggesting some 

level of take of PS may be occurring through dredge entrainment in the LMR. However, location 

is important because entrainment risk may be reduced in the LMR due its larger channel and 

complexity compared to the MMR. Furthermore, entrainment risk varies depending on type of

dredge (cutter head, hopper, mechanical), the habitat being dredged, and size-dependent 

swimming capability of sturgeon (Hoover et al. 2009; Hoover et al. 2011). Dredging near 

nesting sandbars can disrupt ILT nesting activities. Although mussels can be subject to dredge 

entrainment, habitats where FPM have been found in the LMR are not subject to dredging, and 

dredge entrainment is not considered a threat to FPM in this system. 

Water Diversion Entrainment

Entrainment of PS through water control and floodway structures (i.e., Bonnet Carre 

floodway, Davis Pond, and the Old River Control Complex (ORCC)) is known to occur in the 

LMR. Water control and floodway structures are separate issues from the CIP, and are not 

covered under this conservation plan. The USACE has consulted with the USFWS over the 2008 

spillway operation of Bonnet Carre and the proposed construction of two new diversion 

structures, White Ditch and Convent/Blind River. Biological Opinions have authorized take 

resulting from the emergency operation of Bonnet Carre, as well as possible future take of PS at 

the two planned structures (USFWS 2009a, 2009b, 2010a). Emergency consultations for 

Morganza and New Madrid floodways that were operated during the 2011 flood were also 

completed. The USACE and USFWS need to complete formal consultations over entrainment of 

this species at Davis Pond, Caernarvon, ORCC, and other proposed structures. Entrainment 

studies at LMR diversions, excluding ORCC but including Bonnet Carre and Davis Pond, have 

been completed by ERDC. The final report will document sturgeon entrained through existing 

diversions, document sturgeon occurring in the Mississippi River near the vicinity of existing 

diversions, and present population viability models for risk analysis. Results of these studies will 

be used to quantify entrainment of PS and shovelnose sturgeon at diversions over the project life. 

Localized entrainment losses will be weighed against population size and recruitment levels of 

PS throughout the LMR. USACE is working to identify engineering designs to minimize 
47

entrainment losses through water control structures and has conducted rescue and recovery 

efforts to minimize PS population impacts due to floodway operations. 

Sand and Gravel Mining

Regulatory branches of the USACE issue permits for sand and gravel mining dredging in 

the LMR. Regulatory issues are not directly related to the CIP and are not addressed under this 

conservation plan. The USFWS has expressed concerns that permitted commercial mining 

dredges in the Mississippi River can entrain PS and degrade gravel bars where sturgeon spawn. 

ERDC has conducted multiple studies on sturgeon susceptibility to sand and gravel dredges 

(ERDC-EL 2009) and provided the following information: 

1) A chronology of sturgeon life history stages was compiled by sampling the temporal 

occurrence of larvae, juvenile, and adults using Missouri trawls. Application of these data 

can establish operating windows when dredges would have minimal impacts on spawning 

adults and young-of-year. 

2) Entrainment of sturgeon was directly assessed during dredging operations by sampling 

dredged material and overflow, and field sampling for sturgeon in the vicinity of an 

active dredge. No sturgeons were collected. 

3) Measurements of swimming performance by different size-classes of sturgeon were 

conducted and compared to suction velocities created by dredges. Data provided 

quantitative assessment of risk for young-of-year sturgeon of different sizes. 

An initial survey of gravel bars in the LMR was conducted by ERDC (D. Biedenharn and M. 

Corcoran) and maps developed of their locations. Further potomological studies are necessary to 

fully evaluate effects of sand and gravel dredging on protected species. Currently, special 

conditions are applied to the permits to avoid potential impacts to the species and can be 

modified as new information becomes available.

Commercial Harvest of Pallid Sturgeon

Commercial harvest of sturgeon for caviar and smoked flesh has occurred to various 

degrees in the LMR since the 1800s. Harvest for shovelnose sturgeon has been closed for over a 

decade in the Arkansas, Mississippi, and Louisiana reaches of the LMR; however, harvest of 

shovelnose sturgeon for caviar has increased in the LMR reaches of Tennessee, Kentucky, 

Missouri, and Illinois where they co-occur with pallid sturgeon. Based on data that indicated 

significant numbers of mature female pallid sturgeon were being taken during commercial 

harvest of shovelnose sturgeon in the Tennessee reach of the LMR (Bettoli et al. 2009), and high 

mortality of PS in reaches where commercial harvesting was still legal (Killgore et al. 2007b), 

USFWS listed the shovelnose sturgeon within the sympatric range of PS as threatened due to 

similarity of appearance (USFWS 2010b). This action effectively eliminated the loss of PS to 

commercial caviar harvest in the LMR and Middle Mississippi River.

Pollution and Contaminants

Pesticides and heavy metals have been detected in the tissues of sturgeon throughout the 

United States and could potentially affect all three priority species to varying degrees. These 

contaminants cause reproductive failure and population declines, and pose potential health risks 
48

to consumers of sturgeon meat and caviar. Shovelnose sturgeon in the Mississippi and Missouri 

Rivers have been found with high levels of DDT and chlordane and hermaphroditic individuals 

have been observed (Ruelle & Keenlyne 1993), suggesting that contaminants could impact PS to 

some degree. While water quality has improved in the LMR since implementation of the CWA, 

historical and recent water quality data for the LMR needs to be analyzed to determine the 

significance and trends of pollution and contaminants in the LMR. Pollution and contaminants 

are not directly related to the CIP, however, under some conditions contaminants may be resuspended by dredging activities in contaminated sediments. The LMR is a dynamic channel 

constantly moving and mixing large quantities of sediment through the system. There is no 

indication that sediments within crossovers frequently dredged by USACE under the CIP contain 

contaminant levels above those considered safe by EPA. 

Hydrokinetics

Applications have been made to utilize the LMR for power generation using hydrokinetic 

technology. Effects of hydrokinetic turbines on PS are currently undefined; however, there is 

potential of injury or mortality from turbine blade strikes, as well as potential behavioral effects 

due to electromagnetic fields and noise. USACE Mississippi River fishery data, as well as 

USFWS/USGS telemetry data are being used by hydrokinetic developers to identify potential 

impacts to PS and other fish resources. ILT and FPM are unlikely to be directly affected by 

hydrokinetic turbines; however, infrastructure sighting has the potential to affect these species or 

their habitats. Hydrokinetic turbines are not part of CIP, and their potential effects are the 

responsibility of the applicant.

Hybridization of Pallid and Shovelnose Sturgeon

Hybridization with shovelnose sturgeon has been identified as a threat to PS in the LMR. 

This hybridization was initially believed to be caused by a loss of species isolating mechanisms 

due to river engineering and habitat modifications. However, neither the mechanisms nor the 

essential habitat features have been identified. There is morphological and genetic evidence that 

some proportion of these “hybrids” are morphological variants of both species and have been 

misidentified due to allometric growth of PS (Murphy et al. 2007). There is also evidence that 

morphological and genetic variation interpreted as hybridization existed in LMR sturgeon 

populations prior to, and are unrelated to, engineered modification of the LMR (Hartfield & 

Kuhajda 2009, Schrey et al. 2011). Genetic and morphological studies are in progress to 

improve and standardize identification of river sturgeon in the LMR, and determine the 

significance and possible trends of hybridization as a threat to PS in the LMR (USFWS in litt. 

2011). 
49

PART VI: EFFECTS ANALYSIS

Effects of the Program

Bendway cutoffs constructed between 1929 and 1960 under the MR&T shortened the 

river by >150 mi (Winkley 1977). Since 1960, channel engineering conducted under the CIP has 

resulted in a loss of secondary channels and associated habitats (Williams & Clouse 2003). 

Therefore, the primary environmental effects of the MR&T and CIP have been the physical loss 

of LMR channel habitat quantity, a growing disconnect with the relict floodplain during low to 

moderate river stages, and a general loss of riverine habitat complexity (i.e., diversity). The 

responses of ILT, PS, and FPM to the effects of the CIP are evaluated below.

Interior Least Tern

There are currently no data that indicate habitat loss due to the CIP has adversely affected 

the ILT. In fact, the data suggests that overall the ILT response to the conditions resulting from 

the CIP has been positive. ILT population size has increased from a historical baseline of fewer 

than 500 birds, to a current baseline of ~10,000 or more breeding birds per season (see Figure V1, above). Direct causes of the population increase are not understood; however, they may be 

related, at least in part, to: 1) Earlier and extended breeding potential due to more efficient 

movement of flood flows through the system (including effects of tributary impoundment and 

engineering) (e.g., Schramm 2004; see Figure VI-1); 2) Higher sandbars associated with dike 

fields (e.g., Lott 2006); 3) Dike notching and avoidance work windows implemented by the 

USACE under the LMREP; and/or 4) Migration of coastal breeding colonies due to better 

nesting and forage conditions along the LMR (e.g., Lott 2006).

Human activities near nesting sandbars can disrupt ILT nesting activities. The USACE 

maps ILT nesting sites and maintains 1,500 ft buffers between dredging sites and nesting 

sandbars during CIP construction activities in the nesting season. This distance exceeds most 

recommendations for buffers between waterbirds and human activities (Valente & Fischer 2011).

Terrestrialization of islands and sandbars associated with dike fields has been identified 

as a negative factor affecting ILT. However, actions such as dike notch construction under the 

CIP, are being increasingly utilized to sever land-based routes used by ATV recreationists and 

terrestrial predators to access ILT nesting colonies. 

While habitat quantity and condition is not currently considered to be negatively affecting 

ILT in the LMR, USACE-MVD and Districts have been actively working with partners to 

restore degraded secondary channels and their associated islands and bars. These activities are 

protecting, and enhancing ILT habitat quantity and quality throughout the LMR.
50

Pallid Sturgeon

Consisting of only a few collection records, the historical population baseline of PS in the 

LMR is unknown. Attempts to determine the population status were implemented in 2001 (see 

account under Historical and Current Species Baselines in the LMR, above). Since that time, 

evidence of recruitment has been documented and the number of individual PS records has 

increased proportionately with collecting effort. The identification of the LMR PS population 

trend (i.e., increasing/decreasing) will require several years of continued collection efforts and 

monitoring. Therefore, at this time, we cannot directly determine PS response to habitat changes 

induced by the CIP. However, current information indicates that the PS is widely distributed 

throughout the LMR and suggests the species is not uncommon. 

As noted under Factors Affecting the Species, above, there is documentation of 

entrainment of shovelnose sturgeon by maintenance dredging in the MMR, suggesting the PS are 

also vulnerable. However, risk of entrainment in the LMR during dredging may be reduced due 

to the larger channel size, depth, and complexity compared to the MMR. 

Channel maintenance dredging locations are mapped by the USACE and are considered 

relative to all locations where protected species occur and their seasonal habitat use. Spawning 

and early rearing habitats of sturgeon are protected by seasonal restrictions of dredging. 

Telemetry monitoring of sonic-tagged PS in the LMR by USFWS/USGS has shown little use of 

crossovers by large size classes of PS, particularly in relation to use of other habitats in the LMR 

(e.g., Kroboth et al. 2013). PS telemetry relocations are also most frequently associated with 

1 Jan

1 Feb

1 Mar

1 Apr

1 May

1 Jun

1 Jul

1 Aug

1 Sep 

1 Oct 

1 Nov

1 Dec

30 Dec

0

2

4

6

8

10

12

14

16

0

5

10

15

20

25

30

35

1900-1925 (Y1)

1940-2001 (Y1)

Temp (Y2)

Figure VI-1: Example of the change in average River 

stage resulting from river engineering providing 

prolonged periods for ITL nesting. Dashed line 

represents +10 LWRP. 
51

water depths greater than 18 ft (Kroboth et al. 2013), and a recent study of fish depth distribution 

in the LMR reported minimum depth utilized by PS was 15 ft (Miranda & Killgore 2013), well 

below the authorized depth of the CIP. 

Fat Pocketbook Mussel

The FPM was not historically known to survive in the active channel of the LMR. 

Recent collections of live individuals and fresh dead shells are primarily associated with 

secondary channels stabilized by notched dike fields. It is likely that the dike fields created 

conditions appropriate to the survival of FPM (P. Hartfield, U.S. Fish and Wildlife Service, 

Jackson, MS, pers. comm. 2012). Therefore, it appears that FPM has responded positively to the 

effects of the CIP. Construction and maintenance activities within dike fields and secondary 

channels are considered annually by USACE and partner agencies for potential negative effects 

to FPM and, if present, avoidance measures are identified (see below).

Avoid and Minimize Components of the CIP

Potential effects of annual CIP channel construction and maintenance activities to PS, 

ILT, and FPM habitats, along with potential avoidance and minimization actions, are discussed 

and considered during annual partnership meetings hosted by Memphis and Vicksburg Districts

(see Management and Conservation Measures in the LMR, below). Channel maintenance 

and restoration programs are currently focused on maintaining and enhancing overall channel 

habitat complexity through dike design and notching, restoration of secondary channels, and use 

of value engineering techniques such as hard points and chevrons that provide river training and 

habitat benefits simultaneously. Priority species and their LMR habitats will continue to be 

quantified and monitored by USACE and other participating agencies. These data are used to 

determine the extent and significance of habitat modification to the priority species, quantify 

habitat benefits of creative engineering, project future habitat trends, identify habitat 

improvement opportunities, modify channel management programs as necessary, and monitor 

long-term habitat trends and responses. 
52

PART VII: MANAGEMENT AND CONSERVATION MEASURES IN THE LMR

Long-term conservation of the three priority species, as well as other components of the 

LMR channel ecosystem, requires a multi-partner and multi-faceted scientific and engineering 

approach utilizing water and sediment to maintain and enhance aquatic habitat complexity, 

particularly associated with secondary channels and seasonally flooded/exposed habitats. Under 

the CIP, water and sediments are manipulated through channel engineering in order to maintain 

flood protection and a safe and efficient 9’ deep x 300’ wide navigation channel in the LMR 

from Cairo, Illinois, to Baton Rouge, Louisiana. Channel engineering, including channel 

structure maintenance, therefore, provides opportunities to utilize flows and sediments to 

improve or restore in-stream habitats outside of the navigation channel at little to no extra cost, 

and without impacting navigation activities or flood risk management. Dike notching and other 

river training structures have been successfully used for more than a decade for this purpose. 

Several restoration projects unrelated to navigation, have been designed by the USACE, funded 

by state and Federal partners, and constructed by private contractors. Restoration projects 

constructed in recent years include weirs to prevent dewatering of floodplain oxbow lakes and 

channels, and retrofitted dike notches to restore flow through more than 40 miles of secondary 

channel habitat. This collaborative approach to using the CIP construction and maintenance 

projects as primary tools to manage and conserve the LMR ecosystem by the USACE, along 

with a better understanding, mapping, and avoidance of important habitat areas has resulted in 

significantly improved habitat for the PS, ILT, FPM, as well as numerous other channeldependent species.

Partnerships

Key partnerships and guidelines have been developed over the last 10 years that facilitate 

this Conservation Plan. In 2001 the USACE-MVD LMR districts (New Orleans, Vicksburg, 

Memphis), Southeastern Region USFWS, and Lower Mississippi River Conservation Committee 

(LMRCC), which consists of 12 state natural resource management and environmental quality 

agencies, began conducting annual meetings to discuss LMR conservation issues and 

maintenance and construction projects. Key components of these Partnership meetings include 

updates on locations and habitat use by endangered species in the LMR channel, the 

identification and consideration of using environmental engineering principles in the design and 

construction of river training structures, and improving communication and coordination among 

partners for the benefit of all trust species in the LMR. 

 In 2002, the USACE introduced Environmental Operating Principles (EOP) to provide 

direction in all aspects of USACE activity for improved stewardship of land, water and air. EOP 

implementation guidelines were subsequently adopted to identify ways USACE missions can be 

integrated into environmental laws, values, and practices (ER 200-1-5). USACE-MVD has been 

applying EOPs into the CIP feature of the MR&T, as well as O&M activities in the LMR with 

varying success. Although the CIP is almost complete, remaining components, as well as ongoing and future O&M activities provide opportunities to cost-effectively utilize EOPs to 

improve ecosystem responses to the programs that have affected channel habitat quantity and 

quality in the LMR. Annually the USACE invites state and Federal natural resource biologists 

familiar with river-dependent species, multiple-use management of the LMR, and commercial 

navigation to meet and review proposed CIP actions for the year as well as for out years, and 

identify conservation actions that can be incorporated into USACE channel maintenance 
53

activities. USACE has developed and periodically updates a Mississippi River Channel 

Improvement Master Plan which shows constructed and proposed channel training features, as 

well as environmental improvement features, and priority species locations.

The USACE has developed resources and information vital to strategic management of the LMR 

ecosystem. Aquatic and terrestrial habitats have been mapped within the 2.8 million-acre LMR 

leveed floodplain ecosystem. Aquatic habitat maps of the river’s channel for 1880, 1915, and for 

ten-year intervals from the 1930s to the 1990s have been completed and are being used to assess 

historic habitat trends, conduct habitat spatial analyses, and evaluate project effects on Federally 

endangered species as well as other aquatic resources. Terrestrial habitat and land cover maps 

prepared using 1982 and 1992 data have been used to delineate jurisdictional wetlands, plan 

levee construction to avoid and minimize adverse environmental impacts, and maximize 

beneficial conservation effects. In addition, investigations under the LMREP sponsored by 

MVD have been conducted on fish and wildlife populations and habitat values of levee borrow 

pits, effects of in-channel stone dikes, and articulated concrete mattress revetments. In 2001, the 

MVD initiated informal consultation with the USFWS under section 7(a)(1) of the Endangered 

Species Act to use LMREP designs and additional measures to conserve and manage listed 

species associated with the LMR navigation channel.

In 2000 the LMRCC developed an Aquatic Resource Management Plan (ARMP) for the 

954 river-mile long LMR reach (http://www.lmrcc.org/ARMPstrategies.pdf). The ARMP 

provided a 10-year operational plan to address several factors adversely affecting wetlanddependent natural resources in the LMR active floodplain and backwater areas. As mentioned 

previously, during the period 2001–2004 the Partnership conducted the Mississippi River 

Conservation Initiative (MRCI), which consisted of a series of planning meetings in the six 

LMRCC-member states (AR, KY, LA, MS, MO, and TN) that were designed to identify specific 

aquatic habitat restoration and public access opportunities (http://www.lmrcc.org/MRCI.htm). 

The MRCI was a landscape-scale effort that ultimately resulted in six state-specific lists 

consisting of 239 potential projects. In 2006 the LMRCC, under the auspices of the Partnership, 

began compiling the MRCI projects into a landscape-scale plan – Restoring America’s Greatest 

River (RAGR). The RAGR plan comprises the implementation phase of the Partnership’s fiveyear planning effort to rehabilitate the LMR leveed floodplain ecosystem 

(http://www.lmrcc.org/). Working cooperatively with the Partnership, the LMRCC has 

developed a comprehensive Geographic Information System comprised of spatial databases 

covering the LMR ecosystem and the Mississippi Alluvial Valley to support the implementation 

of the MRCI. Data holdings include vector files of roads, hydrology, river training features 

(dikes, revetments, levees, ports, etc.), public lands boundaries, satellite imagery, digital 

orthophotos, low water video, and raster data including soils, land cover/land use, Digital 

Elevation Models, and bathymetry. These projects raise the habitat and environmental baseline 

of priority species, offsetting and mitigating actions which may be essential to flood risk 

management and the maintenance and safety of the LMR commercial navigation channel.

Since 2005, USACE has collaborated with LMRCC and other partners to: 1) conduct 

synoptic studies of PS population status and habitat restoration benefits; 2) obtain georeferenced video during low water periods to evaluate status of river training structures, and to 

determine habitat quality in secondary channels and other areas of the LMR; 3) quantify longterm changes in depth, volume, and status of secondary channels in the LMR; 4) begin studies of 

gravel bars used by sturgeon and other riverine species as spawning sites; and 5) continue 

planning restoration projects. Information derived from these efforts is shared annually at the 
54

lower basin pallid sturgeon recovery meeting and the channel improvement meetings sponsored 

by the Memphis and Vicksburg Districts. Most recently, the USACE is working with partners to 

execute the Lower Mississippi River Resource Assessment (LMRRA). 

The LMRRA was authorized in WRDA 2000, Sec. 402, and funding was initiated in 

FY09. The reconnaissance level report was approved March 5, 2010. The purpose of the study 

is to develop recommendations for: 1) the collection, availability, and use of information needed 

for river-related management; 2) the planning, construction, and evaluation of potential 

restoration, protection, and enhancement measures to meet identified habitat needs; and 3) 

potential projects to meet identified river access and recreation needs. The Nature Conservancy 

(TNC), along with LMRCC and other partners, including National Audubon Society, 

Delta F.A.R.M., and the American Land Conservancy, have joined this effort as cost-share 

partners on a feasibility level watershed study with the signing of the USACE – TNC cost share 

on January 11, 2012.

These partnerships and actions have provided opportunities to develop, test, and 

implement engineering modifications that fulfill USACE missions while simultaneously 

protecting and enhancing channel habitat values. 

Conceptual Model

The USFWS now considers the USACE partnership and engineering process outlined 

above as the primary strategic approach to maintain river channel habitat values in the LMR, as 

well as for the management and recovery of listed species associated with the channel (USFWS

2012a). This strategic approach can be modeled as follows:

Figure VII-1. Conceptual model employing the CIP as for 

conservation and management of CIP Trust resources.
55

Conservation Plan Outline

The goal of this USACE-MVD conservation plan is to maintain the CIP while 

implementing or improving appropriate habitat conditions necessary for robust, resilient, and 

self-sustaining populations of ILT, PS, and FPM in the LMR. The objectives of this conservation 

plan are to utilize reasonable, prudent, and cost-effective channel maintenance and management 

practices to maintain and improve LMR channel habitat values for listed species and other native 

species. 

The USACE-MVD and LMR Districts have identified the following strategies and 

actions to minimize adverse effects of the CIP, and to mitigate for past and potential future loss 

of LMR channel habitat quantity and complexity. These strategies and actions have been 

implemented, and tested for more than a decade under the channel ecosystem management 

partnership described above. Herein, the USACE-MVD and LMR Districts incorporate the 

following strategies and actions as Standard Operating Procedures and Best Management 

Practices under the CIP to conserve the endangered species associated with the LMR channel, as 

authorized and required under section 7(a)(1) of the Endangered Species Act . This conservation 

plan also complies with procedures and mandates under the USACE Environmental Operation 

Principles, the Civil Works Ecosystem Restoration Policy (USACE ER 1165-2-501), and 

Executive Order 13186 under the Migratory Bird Treaty Act.

Agency conservation programs developed under section 7(a)(1) of the Endangered 

Species Act are intended to assist Federal agencies and their potential partners in planning and 

implementing actions to protect and recover endangered or threatened species affected by the 

agencies activities. These conservation measures are a guide for meeting the goal and objective 

outlined above, and do not obligate any party, including the USACE to undertake specific 

actions at specific times. Implementation of the actions outlined below is contingent upon 

opportunity and annual appropriations and other budgetary constraints.

Strategy 1: Avoid adverse impacts directly associated with CIP engineering practices.

Actions:

a. Comply with seasonal restrictions for construction when appropriate and/or possible.

Seasonal restrictions, or “windows,” have been or may be established by state and 

Federal resource agencies to minimize nesting, spawning, or juvenile disturbance during 

all construction and maintenance activities. Currently, construction is prohibited from 1 

April to 1 August on the LMR, a 5-month window. As new information is developed, 

these restrictions may be modified to reduce impacts on construction activities while 

protecting endangered species and their habitats. However, any changes to these 

seasonal restrictions could potentially impact the navigation mission of the CIP and will 

be carefully considered by all agencies involved.

b. Avoid closure of secondary channels. Loss of secondary channel habitat, and decline of 

Trust species habitat value, has occurred through the construction of secondary channel 

closure structures under the CIP. In recent years, alternatives such as strategic dike 
56

placement, chevrons, etc. have been successfully used in place of closure structures to 

maintain appropriate depth and width of the navigation channel.

c. Avoid impacts of dikes on gravel bars. Gravel bars are typically found at the upstream 

reach of islands and near crossings where water depth is shallow and dikes are required 

to maintain the navigation channel. Efforts are underway to identify established gravel 

bars and avoid construction activities that may result in accretion of sand over welldeveloped gravel substrates. Notching existing dikes impacting gravel substrates has

also been targeted.

Strategy 2: Develop and implement channel construction and maintenance operation 

guidelines that conserve and restore LMR habitat for all three species, are subject to 

adaptive management, and can and will be continued should the species become fully 

recovered. 

Actions:

a. Identify and implement dike construction and maintenance designs that maximize habitat 

complexity. Dike notching is the primary mechanism to increase habitat complexity. 

Most ILT colonies on the LMR are associated with dike fields, which create higher 

sandbars with less exposure to flooding during the summer nesting season. Notches are 

created by removing rock toward the landward end during maintenance work on an 

existing dike or by leaving an open, low section when a new dike is built (Guntren et al.

2012). Water flowing through the notch scours substrates below the dike increasing 

bathymetric diversity and allowing flow to isolate nesting sandbars through most of the 

nesting season. Dike notching and other alternative designs of river training structures

(e.g., round points, chevrons, off-bankline revetment, as described by USACE (2006) and 

Pokrefke (2012), that increase habitat diversity and/or reduce impacts to endangered 

species and other native fauna will only be considered when there is minimal effect on 

the purpose and intent of the authorized project (i.e., navigation/flood risk reduction). 

b. Restore connectivity to the main channel whenever possible. Restoration of secondary 

channels by notching or removing closure dikes, was identified as one of the top 

restoration priorities (Boysen et al. 2012) and an evaluation procedure has been 

developed to rank the habitat value of over 50 secondary channels for planning purposes 

(Killgore et al. 2012). In recent years, secondary channel restoration actions have 

required collaboration of multiple partners, and are expected to continue to do so.

c. Utilize chevrons instead of dikes where conditions are appropriate. Dikes fields form 

large, homogenous sandbars that become exposed at moderate to low discharges. 

Chevrons will be constructed in selected areas to increase hydraulic diversity in 

homogenous sandbar habitat while maintaining appropriate flow conditions for 

navigation and bank protection.

d. Continue to create longitudinal grooves in ACM. Armoring riverbank with ACM to 

protect the river channel is critical to both flood risk management and navigation. 

USACE has designed deep grooves in ACM to increase surface area, reduce surface 

current speed, and allow greater opportunity for attachment of invertebrates. This practice 
57

increases the biomass of invertebrates consumed by PS and by prey species for PS and 

ILT.

e. Utilize hardpoints in lieu of revetment where conditions allow. In some erosional areas, 

hardpoints are an alternative to ACM. They function to prevent bank erosion with less 

impact to natural riverbank. Hardpoints will be considered where practical.

f. Continue to strategically place large woody debris removed from banks during revetment 

construction or repair into the channel. Large woody debris removed from the bank 

during construction and maintenance activities will be strategically placed in the channel, 

to provide habitat for attached macroinvertebrates, as well as shelter for forage fish.

g. Minimize impacts of dredging. Dredging activities will avoid or minimize impacts on 

gravel bars, tributary mouths, and backwater habitats. The USACE will continue to abide 

by terms and conditions established by the USFWS. Beneficial placement of dredged 

material will be utilized where appropriate and authorized.

Strategy 3: Develop cost-effective monitoring program, as funding allows, to document 

habitat and species response to channel operations. 

Actions:

a. Collaborate with USFWS and LMRCC to periodically monitor and measure habitat 

complexity and channel response to river training structures. Habitat complexity will 

be measured using existing capabilities including bathymetric surveys, Red Hen georeferenced video, Lidar, ground truthing including gravel bar surveys, and aerial 

photography. GIS maps using REGIS will be updated with new habitat information.

b. Utilize ILT and PS as surrogate species to monitor ecosystem response to 

management. Unless future information suggests otherwise, USACE will utilize 

these two endangered species as surrogates to document ecosystem function, quality, 

and response to USACE channel management, regardless of future status under the 

ESA. FPM is not recommended as a surrogate species at this time due to limited 

data.

c. Conduct targeted monitoring and analysis of habitat utilization and preference of the 

three endangered species. Field surveys and telemetry will be conducted to evaluate 

habitat use of listed species and their responses to USACE construction and 

maintenance activities in the LMR.

d. Collaborate with USFWS to develop and implement a more statistically rigorous 

monitoring program to track ILT population trends on the LMR. Over the next 1-2 

years, the ERDC-EL will be coordinating with USFWS, ABC, and the USGS to 

develop a range-wide monitoring program for the ILT, which will serve to (1) 

streamline and standardize existing monitoring techniques, and (2) provide a robust 

means of assessing range-wide population status into the future. Ideally, the 

monitoring protocol will rely upon sub-sampling rather than complete counts of 
58

adults throughout the range. Should ILT be delisted, monitoring on the LMR will be 

part of a required range-wide post-listing monitoring plan.

e. Monitor population size and trends of PS in the LMR. Periodic monitoring of PS

populations will continue using standardized collection methodologies. Key 

population attributes, including young-of-year survival, recruitment, adult survival, 

and density, will be evaluated using Population Viability Analysis models. Population 

size and trends will be compared among southern, middle, and upper reaches of the 

LMR. Information will be shared with partners at annual meetings and used to 

evaluate and modify conservation actions.

f. Conduct periodic surveys for presence/absence of FPM. Densities of FPM are 

naturally low in LMR, and it is not historical habitat. Therefore, measurements of 

population size trends are currently not practical. However, low-water surveys of 

FPM in proposed or existing construction sites in main and side channel habitats may

be conducted to evaluate presence/absence as budget and authority allows.

Strategy 4: Share restoration, research, and monitoring responsibilities and costs through 

maintaining strong partnerships with other Federal and state agencies and NGOs. 

Actions:

a. Continue to sponsor annual meetings with partners to discuss and implement Actions 

1 and 2 as part of regular program and project efforts. 

b. Continue to work with LMRCC, The Nature Conservancy, and other partners to share 

restoration and funding responsibilities as budget and authority allows. 

c. Promote the Lower Mississippi Resource Assessment as a means to identify and 

implement conservation and restoration measures. 

The conceptual model (Figure VII-1) and objectives and actions outlined above have 

been developed in consultation with USFWS to comply with the ESA section 7(a)(1) statutory 

requirements to utilize USACE authorities to establish and carry out programs for the 

conservation of endangered species associated with CIP river operations, and for management 

and restoration activities to mitigate for impacts on listed species caused by river operations. 

They also comply with the intent and directives outlined under the USACE Environmental 

Operating Principles, and the Civil Works Ecosystem Restoration Policy (ER 1165-2-501), and 

support the conservation intent of EO 13186 Responsibilities of Federal Agencies to Protect 

Migratory Birds.

Implementation

Implementation of the tasks identified above by USACE-MVD and districts will 

commence immediately. In fact, all of these actions have been at least partially implemented for 

more than a decade, and many have become standard operating procedure by USACE-MVD. 

For example, to date almost 30% (230) of the dikes in the LMR (774) have been constructed or 

retrofitted with notches to increase channel border and seasonally flooded habitat diversity. More 
59

are in the planning process. Additionally, collaborative restoration projects between the 

USACE-MVD, LMRCC, and USFWS have cost-efficiently rehabilitated nine secondary 

channels. Combined, these projects have restored flow to almost 40 miles of in-channel habitat 

and enhanced hundreds of acres of seasonally flooded habitats. These projects have shown no 

negative effect to the USACE’s primary missions of flood damage reduction and provision of a 

safe, stable commercial navigation channel. Seasonal work windows are employed by USACE 

contractors, and are conditions in permits issued by USACE in the LMR. USACE-MVD has 

conducted analyses of secondary channels and completed a comprehensive secondary channel 

assessment (Williams & Clouse 2003; Guntren et al. 2012) that will guide decisions on future 

restoration sites. To date, seven chevrons and 247 hard points have been constructed, resulting 

in preservation of several miles of natural bank habitat. Limited research (and extensive 

monitoring) by USACE-ERDC, USFWS. USGS, and other partners on ILT, PS, and FPM has 

been conducted for more than a decade, and is on-going. Research funding has been provided by 

USACE-MVD, USACE districts, USFWS, USGS, Arkansas Game and Fish, and others. 

Geomorphic and species research information is shared with all partners at annual meetings 

conducted by and at the LMR districts.

Elements of Adaptive Management

Adaptive management is a collaborative, multidisciplinary approach which treats actions 

and policies as testable hypotheses from which learning derives, which in turn provides the basis 

for changes in subsequent actions and policies (Stankey et al. 2005). Developing a sensu stricto

adaptive management program for the three listed species relative to the CIP is not a realistic 

option for many reasons. These include: 1) lack of basic life history and habitat information for 

the target species, 2) a lack of dedicated funding for research and monitoring, 3) practical 

constraints due to maintaining public safety and infrastructure integrity, 4) high levels of 

uncertainty in predicting or measuring species responses, 5) high levels of uncertainty in 

predicting or measuring local channel response, 6) the duration of the management program, etc. 

The strategies and actions outlined above, however, provide for incorporating many 

useful elements of adaptive management into the CIP. Information gathered through channel 

monitoring and priority species research and monitoring has been used to modify/improve river 

engineering and other river regulation activities to avoid or minimize impacts to listed species 

and improve their habitat and population baselines in the LMR (see Conceptual Model, above). 

For example, 1) large gravel bars have been assigned a high priority for research and protection 

because PS larvae have been consistently collected below them and they are assumed to function 

as spawning substrates; 2) telemetry results are being used to provide insight into the possible 

effects of timing and location of channel maintenance activities on PS habitat use; 3) ILT nesting 

survey data have been used in the dike maintenance program to protect and improve nesting 

sites; 4) identification of secondary channels occupied by FPM has been used to modify inchannel and levee construction projects and improve methods to avoid/reduce impact to the 

species; and 5) agencies and NGOs are collaborating in GIS documentation of species records, 

existing engineered structures, and engineering modifications to benefit trust species and 

ecosystem complexity. New information is, and will continue to be considered during annual 

meetings between cooperating partners and agencies. At these meetings, data gaps, needs, 

engineering designs, and monitoring plans, all elements of adaptive management, are

collaboratively identified, prioritized, and modified if necessary. 
60

This collaborative and adaptive approach to management and conservation of the LMR 

has cost-effectively and significantly improved the scientific knowledge base of the three 

endangered species; improved LMR habitats for them and numerous other game and nongame 

species; and provided substantial savings of conservation and channel maintenance funding. 

Continued interagency trust and cooperation are integral to continuing and fully implementing 

the USACE-MVD conservation plan, and to ultimately achieving the conservation goals of all 

agencies involved in the Partnership.
61

PART VIII: CONTRIBUTORS/REVIEWERS

Contributor/Reviewer Agency Contributor/Reviewer Agency

David Biedenharn Biedenharn Group, LLC Christopher Koeppel USACE - Vicksburg

Richard Boe USACE – New Orleans James Merritt USACE - MVD

Darian Chasteen USACE - Memphis Dennis Norris USACE - MVD

Brian Chewning USACE - MVD Kent Parrish USACE – Vicksburg

Rob Davinroy USACE – St. Louis Freddie Pinkard USACE - Vicksburg

Paul DuBowy USACE-MVD Don Rawson USACE - New Orleans

Joan Exnicios USACE – New Orleans Stephen Ricks USFWS

Rich Fischer ERDC-EL Rick Robertson USACE - MVD

Jim Gutshall USACE - MVD Todd Slack ERDC-EL

Paul Hartfield USFWS Mark Smith USACE - Memphis

Audrey Harrison-Lewis ERDC-EL Derrick Smith USACE- Memphis

Jan Hoover ERDC-EL Andrew Smothers USACE - Memphis

Carol Jones USACE - Memphis Mike Thron USACE - Memphis

Edward Lambert USACE - Memphis David Vigh USACE - MVD

Jack Killgore ERDC-EL Rayford Wilbanks USACE - MVD

Barb Kleiss USACE - MVD Gary Young USACE-Vicksburg
62

PART IX: LITERATURE CITED

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sturgeon, Scaphirhynchus albus. Copeia 1999:802-807.

Akçakaya, H. R., J. L. Atwood, D. Breininger, C. T. Collins, and B. Duncan. 2003. 

Metapopulation Dynamics of the California Least Tern. The Journal of Wildlife 

Management 67:829-842.

Alexander, J.S., R. C. Wilson, and W. R. Green. 2012. A brief history and summary of the

effects of river engineering and dams on the Mississippi River system and delta: U.S.

Geological Survey Circular 1375, 43 p.

Aycock, N., J., Brown, D. Hardesty, D. Henke, R. Jones, and J. Williams. 2012. Investigation of 

sturgeon population demographics in the Lower Mississippi River. Annual Report for 

2011 - 2012 submitted to U.S. Fish and Wildlife Service, Jackson, MS. Mississippi 

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