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.