Natural resource professionals from U.S. Army Corps of Engineers and the Missouri Department of Conservation, recreational anglers, and community members formed an action group in 2020, and have collaborated to develop a long-term fisheries habitat management plan for Mark Twain Lake. The group assessed lake conditions, existing natural habitat structure, capabilities of independent entities, available resources, and alignment of long-term goals to establish a five-year management plan for the development of fisheries habitat. Since 2021, this group has successfully established artificial habitat structure at four areas of the lake encompassing 105 reservoir acres and improved the recreational angling opportunities in the affected areas.

There are two distinct goals of this proposed project. The first goal is to continue development of artificial fish habitat structure that will replace what has deteriorated through the natural maturation process of the reservoir, or through the authorized operational requirements imposed upon the reservoir. Proposed is the installation of artificial structural components at a location to restore approximately 35 acres of underwater fisheries habitat, and directly support recreational angling opportunities. The structures will be constructed of materials providing long-term durability, capable of withstanding the stresses of submerged and dry environments and designed to reduce snagging of traditional fishing tackle and equipment. The structures will be placed at differing elevations in the basin of reservoir in a pattern to provide for stability and integrity of development. Furthermore, this project proposes the development of direct shoreline access to the restoration site which will appeal to a broad demographic spectrum, including families, youth, senior citizens, and novice anglers. Though designed and placed as a shoreline fishing resource, the developed site will still be accessible to anglers conveying by boat.

The second goal supports the recruitment and retention of sport fisheries species through the development of littoral zone habitat. Loss of natural structure through the normal maturation of the reservoir has had a definitive impact on its capability to sustain resilient and stable populations of the traditional sports fish that are sought by the angling community. This project proposes developing and placing littoral structures that will directly complement traditional spawning areas of the lake, providing escape and nursery cover for juvenile fish. Area encompassed in the project will be 28 reservoir acres. Execution involves saturating the basin of coves with vertical littoral habitat structure, constructed of hardwood materials, and designed to provide protected interior space. These structures will be placed adjacent to slopes possessing the ideal rocky substrate favored for spawning by many of the fish species of the lake. Though placement of the littoral zone habitat will be habitat-driven, the support to recreational fishing will be realized when the recruitment class matures to a size contributing to the sustainable population present in the reservoir.

Methods

Under this plan, locations for the fish habitat structures are determined utilizing the following criteria:

a. Gradual slope or grade
b. Proximity to existing available parking and shoreline access
c. Lack of habitat structure, or subject to rapid degradation
d. Larger coves or bays with multiple inlets
e. Not exposed to current
f. Not located in traditional boat travel routes
g. Sheltered to secure integrity of habitat development

Under this plan, locations for the littoral zone habitat structures are determined utilizing the following criteria:

a. Gradual slope or grade
b. Adjacent to rocky slopes
c. Lack of habitat structure
d. Not exposed to current
e. Not located in traditional boat travel routes
f. Sheltered to secure integrity of habitat development

The habitat structures proposed for development of this habitat restoration project will include the following:

a. Mark Twain Lake Cubes – 100 “MTL Cubes” will be constructed for placement at the restoration site. Each cube will measure 4 feet height, 4 feet in width, and 4 feet in breadth. The cubes are constructed of 1 ½ inch PVC pipe and are intertwined with 100 feet of 4 inch drain tile tubing. The cubes are designed to standards proven to be extremely effective in similar reservoir environments. Reference Figure 5. The design utilized at Mark Twain Lake accommodates species of game fish that suspend in differing depths, and to provide habitat at varying lake levels. These structures are placed in mass at deeper depths. Structures are weighted with sand/gravel mixed placed on the interior of the pipe components.

b. Spider Blocks – 150 Spider Blocks will be constructed for placement at the restoration site. A standard 9” x 9” x 15”, dual cavity concrete block serves as the foundation of the feature. Concrete is placed in the cavities to secure ½ inch flexible irrigation tube serving as habitat structure. Reference Figure 5. These structures are distributed in mass at shallow depths in proximity to the shoreline providing littoral zone habitat favored by certain species of game fish, while also providing accessibility to shoreline fishing and vessel-oriented angling experiences.

c. MTL Porcupine Cribs – 150 MTL Porcupine Cribs will be constructed for placement at a designated littoral zone restoration site. Averaging three feet in height, and constructed of hardwood materials, the structures are based on proven designs implemented at reservoirs addressing similar conditions that are present at Mark Twain Lake. These structures will be distributed in mass in the basin of a cove that possess adjacent rocky slopes.

As currently being demonstrated in on-going management efforts associated with the Mark Twain Lake Fisheries Habitat Project, structure development activities occur in four distinct phases as outlined in the following:

a. Determination of management areas through collaboration with associated partners in accordance with standards established by the collective – 14 days
b. Trail Access Development – Construct native surfaced trails providing access from established parking locations to specified shoreline location. Timeframe – 10 days
c. Habitat Structure Construction – Procure the required resources, and assemble the 100 MTL Cubes, 150 Spider Blocks, and 150 Porcupine cribs. Timeframe – 60 days
d. Installation – Transport the habitat components to the designated development areas, coordinate vessels and labor with collaborating partners, and install the structures. Timeframe 30 days.

Monitoring Plan

Monitoring the performance of this project will be a multi-faceted process.
a. Periodic maintenance of the trail system and access areas are required to retain a safe and appealing facility.
b. Missouri Department of Conservation will monitor the sites for population vitality through traditional scientific processes.
c. Sonar scans will be performed on the sites to monitor the integrity of the installed structures.
d. Public feedback through customer surveys and social media outlets to monitor visitor use, visitor perception, and incorporate suggested facility improvements deemed appropriate for the facility.

Outreach Plan

Public outreach and education are an important component of this project. Our plan to communicate the project to the public is provided in the following:
a. Develop a single page printed map, easily re-produced, and easily modified, that incorporates the location of existing and proposed development sites. Maps are available in printable forms, and digital downloads through various partner websites.
b. Continue a contribution/involvement program (eg. Cabins for Crappies) where community members and organizations are engaged to support on-going habitat initiatives. To date, the established program has yielded $1500.00 in community contributed funds.
c. Communication through available Corps of Engineers’ social media outlets, and through available communication outlets of associated partners.