Research about Lower Mountain Fork River

USGS2019

Winter and spring diet of the orangebelly darter, Etheostoma radiosum, among tributaries of the Lower Mountain Fork River

Little is known about prey use by the orangebelly darter, Etheostoma radiosum , and what is known has been described from relatively large river systems. We examined prey use by orangebelly darters from first- and second-order tributaries in the Lower Mountain Fork River of southeastern Oklahoma. Adult darters ( n = 141) were captured from five tributaries in 2015, and stomach contents were examined to determine prey use. Aquatic isopods were the most frequently consumed organism. This differs notably from previous reports that insects, primarily dipterans, were the predominant prey for the species.

Oklahoma↗

USGS2018

Assessing wild juvenile trout ecology in the lower Mountain Fork

Reservoir tailwaters can be valuable fisheries for Rainbow Trout ( Oncorhynchus mykiss ), which is commonly stocked as mitigation for the altered habitat because it performs well as a put-and-take species in these thermally depressed systems. These fisheries are usually sustained by stocking due to flow fluctuations and lack of suitable spawning habitat that may limit natural reproduction. The Lower Mountain Fork River (LMFR) below Broken Bow Dam in southeastern Oklahoma is one of two year-round trout fisheries in the state and wild, juvenile Rainbow Trout were documented beginning in 2006, prompting speculation about the potential for a self-sustaining population. To determine this potential, we searched several sites over two years throughout the LMFR for wild, juvenile Rainbow Trout to estimate several parameters related to their population status (e.g., age, growth, time of spawning and hatching, and prey use). We also assessed the availability of macroinvertebrate prey to determine how food resources may affect trout sustainability. We found wild, juvenile Rainbow Trout each year, but only at sites within the first 4.5 km of the 19-km tailwater. Juvenile trout were the result of spawning that took place from late January through mid-April. Growth and body condition were variable between years, but similar to other systems. Weekly survival estimates using catch curves were low (<80%), suggesting limited potential for recruitment; however, declining catchability of larger juvenile fish likely biased these estimates. Wild, juvenile Rainbow Trout ate a variety of food items, but selected for Amphipoda and Diplostraca and against Trichoptera. Overlap in diet with adult Rainbow Trout was low (Bray-Curtis dissimilarity = 0.70). Macroinvertebrate prey resources available to trout varied among management zones, being most abundant in Zone 1 and Zone 3. Potential for a wild fishery may exist in the upper portion of the LMFR but additional research on recruitment to adulthood would be required to provide a more definitive answer.

Oklahoma↗