Lower Mountain Fork River Habitat Enhancement


Tailraces often lack suitable fish habitat due to reduced inputs of sediment and woody debris coupled with frequent scouring flows. These habitat deficiencies have significant impacts on fish populations and subsequent management of tailrace fisheries. For example, reductions in usable area limits the amount of productive stream for anglers because fish are concentrated in few suitable areas. Fish movement and dispersion is also limited because necessary habitat is not available throughout the stream continuum. The absence of overhead cover increases fish susceptibility to predation and warming of stream water. Further, the lack of hydraulic checks limit flow dynamics and flow-related habitat alternatives necessary for fish feeding, resting and moving.

Similar to other tailrace fisheries, the lower Mountain Fork River trout fishery in McCurtain County, Oklahoma is characterized by the habitat limitations described above. Significant habitat improvements within this stream are necessary to improve physical and hydraulic habitat conditions and the angling potential of the system.

In-stream habitat enhancement techniques using native materials can improve habitat deficient streams by providing dynamic and suitable conditions for fish. Depending on stream type and bed materials, a variety of structures may be used to improve habitat quality and availability. Some of the structures appropriate for use in the lower Mountain Fork River include check dams, weirs, log and rock veins, cross veins, boulder clusters and flow constrictors. All of these structures improve hydraulic characteristics within the channel as a dynamic mix of current vectors, eddies and slack water are formed from their interaction with flow.

For example, check dams deepen shallow reaches of stream above the structure by impounding water and below by creating plunge pools. Useable area increases longitudinally while fish movement potential is maintained.

Weirs increase habitat quality, diversity and availability across the channel cross-section. Advanced weir designs enable adjacent positioning of pool and riffle habitat which increases hydraulic diversity, cover and carrying capacity.

Log and rock vanes stabilize laterally eroding banks, restore natural channel geometry and increase trout habitat. This occurs by decreasing erosional sediment supply and facilitating hydraulic creation of small scour holes associated with the end of vanes which provide deeper refuges for trout.

Cross vanes reduce stream bank erosion and retain proper channel width to depth ratios regardless of discharge by continuously placing the deepest portion of the channel in the center of the stream. Deepened stream reaches created by these structures significantly increase fish carrying capacity and movement potential.

Boulder clusters offer hydraulic relief from water current and strategic feeding zones for fish.

Lastly, flow constrictors decrease width to depth ratio which creates deeper channels with higher carrying capacity, movement and refuge benefits.

The completion of a habitat enhancement project requires many steps. First, on-site stream survey techniques are used to choose strategic areas for fish habitat improvements. Next, the proposed structures are designed using standard stream rehabilitation and in-stream habitat improvement protocols. Necessary permits covering the scope of work are then acquired prior to beginning work. Project funding is then solicited and, after these steps are complete, the work to improve the stream can begin.