Mississippi Valley Division Engineer Research and Development Center

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))

Mississippi River Geomorphology and Potamology Report No. 4

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

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

of endangered and threatened species. Since the early 2000s, the U.S. Army Corps of 

Engineers (USACE), Mississippi Valley Division (MVD), has worked with the U.S. Fish 

and Wildlife Service (USFWS), the Lower Mississippi Conservation Committee, and 

state conservation agencies to identify and resolve endangered species and ecosystem 

management issues. The goal was to protect listed species without impacting the USACE 

civil works missions of managing flood risks and facilitating navigation in the Lower 

Mississippi River (LMR). The Conservation Plan was prepared collaboratively by 

USACE and the USFWS, submitted to USFWS as USACE’s Biological Opinion, and 

followed by issuance of a non-jeopardy Biological Opinion by USFWS. The Plan 

provided the programmatic mechanisms by which the Channel Improvement Program 

(CIP) of the Mississippi River and Tributaries (MR&T) project was being utilized to 

implement conservation measures without major impacts on USACE’s primary mission.

These measures will maintain and improve habitat values within the LMR for recovery 

of endangered and other sensitive species inhabiting the river channel. 

Endangered Species in the LMR

There are three species in the LMR listed as “Endangered” under the Endangered 

Species Act: the Interior Least Tern (Least Tern or ILT), the Pallid Sturgeon, and the Fat 

Pocketbook Mussel. Least Terns are fish-eating birds that nest on open sandbars in the 

LMR. Annual nesting season tern counts 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. Pallid Sturgeon occupy the bottom of the LMR — usually in deep, fast-flowing 

water — and can live more than 25 years in their southern range. Historical records of 

Pallid Sturgeon in the 20th century are extremely rare, and the USFWS was able to 

document only 28 records of the fish from the LMR prior to its listing in 1990; none 

were documented in the Atchafalaya River. Today, more than 500 subadults and adults 

have been documented in the LMR and more than 600 in the Atchafalaya River. The Fat 

Pocketbook Mussel is a freshwater pearly mussel native to the Ohio River system and 

Mississippi River drainage. This species is relatively large, with adults sometimes 

reaching over five inches in length; it is aptly named for its valve morphology, which is 

highly inflated and obovate. The Fat Pocketbook Mussel was never considered abundant 

in the LMR channel, but it does occupy depositional areas in oxbow lakes, sloughs, 

secondary channels, and dike fields.

Components of the Conservation Plan

As part of the MR&T, the CIP provides low-water navigation in the main channel using 

river training structures. Over the years, there has been a gradual loss of off-channel 

habitat that threatened populations of the endangered species. It became apparent that 

the very programs significantly affecting the river are potentially the most important and 

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

accomplished by preparing a Conservation Plan that incorporates ecological engineering 

opportunities during the design phase of channel improvement and channel maintenance 

projects under the authority of Section 7(a)(1) of the ESA. There are six primary 

components of the Plan: environmental setting, authorized project description, 

endangered species accounts, LMR environmental baseline, effects analysis, and 

management and conservation measures in the LMR. 
For More Information

To access the full version of 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)), click the following link: 

http://acwc.sdp.sirsi.net/client/search/asset/1040663.

Additional MRG&P reports, historic reports, and MRG&P 

information can be accessed from the MVD Publications and 

Technology Transfer website: 

http://www.mvd.usace.army.mil/mrgp_pubs.

Points of Contact

Dr. Jack Killgore

Jack.Killgore@usace.army.mil

Dr. Barb Kleiss

Barbara.A.Kleiss@usace.army.mil

Conservation Measures

The Mississippi Valley Division and Districts in the LMR identified strategies and actions — also referred to as 

conservation measures — to avoid and minimize adverse effects of the CIP and to continue diversifying habitat: 

 Avoid adverse impacts directly associated with CIP engineering practices, including compliance with seasonal 

restrictions for construction and dredging; avoid closure of secondary channels; and avoid impacts of dikes on 

gravel bars.

 Develop and implement channel construction and maintenance operational guidelines to diversify habitat. This 

strategy has been ongoing and includes notching dikes, reestablishing connectivity of secondary channels, and 

using innovative river training structures such as chevrons and hardpoints as conservation tools. 

 Develop cost-effective monitoring programs, as funding allows, to document habitat preferences and population 

trends of the listed species in response to channel operations and maintenance. 

 Share restoration, research, and monitoring responsibilities and costs by maintaining strong partnerships with other 

federal and state agencies and NGOs. 

Future

The Conservation Plan ensured that all future channel operations and maintenance activities would be in compliance with 

the Endangered Species Act. The Plan also demonstrated that a collaborative, cost-effective approach to using Section 

7(a)(1) of the Act can successfully protect endangered species; additionally, the Plan can serve as a model for future ESA 

actions undertaken by USACE. 

Summary of Significant Findings

 Section 7(a)(1) of the Endangered Species 

Act can be used to collaboratively define 

needs and measures to protect listed species, 

and reach full compliance with the Act. 

 A concerted effort lasting over a decade was 

necessary by USACE and partners to 

determine status and trends of the listed 

species and to develop final conservation 

measures.

 USACE can use their own authority and 

expertise to avoid and minimize impacts of 

channel construction and maintenance in the 

LMR — including application of innovative 

river engineering techniques.

 Collaboration with other federal and state 

agencies early in the planning process 

resulted in cost-effective, discretionary 

conservation measures agreeable to all 

parties.

 Conservation Plans offer greater 

predictability and efficiency in ESA 

compliance and streamline the Biological 

Opinion process under 7(a)(2) of the Act.