Habitat use and movement by fishes using shallow-water habitats in three scenic rivers in Oklahoma.

The Cooperator Science Series was initiated in 2013. Its purpose is to facilitate the archiving and retrieval of research project reports resulting primarily from investigations supported by the U.S. Fish and Wildlife Service (FWS), particularly the Wildlife and Sport Fish Restoration Program. The online format was selected to provide immediate access to science reports for FWS, state and tribal management agencies, the conservation community, and the public at large. Environmental flows are important for the conservation of stream biota. Although a range of flows are necessary for the persistence of aquatic species, minimum-flow standards are often the most basic component. It is well recognized that stream drying disproportionately affects the shallow-water habitat availability in streams. The two objectives of this study were: 1) determine diel habitat use during baseflow conditions by fishes using shallow-water habitats of three scenic rivers in Oklahoma, and 2) assess movement by a subset of stream fishes and relate those movements to environmental parameters. Habitats most susceptible to loss of area varied by stream but collectively, riffles, runs, and backwater habitats experienced the greatest loss of area. Some linear declines in habitat were observed with some habitat losing up to 60% area over measured discharge conditions. The most shallow-water channel units (riffles, runs, vegetated edgewaters) structured much of the fish assemblage in Barren Fork Creek, particularly benthic fishes. Likewise, benthic fishes in Flint Creek and the Illinois River were positively associated with shallow channel units, but more so higher-velocity habitats. These assemblages had the addition of other fluvial specialists (e.g., cardinal shiner). Diel shifts in habitat use occurred in all streams suggesting movement between channel units to be an important component of the shallow-water fish assemblage. Maximum mean daily water temperatures were: 31.63 ˚C and 29.55 ˚C for the Illinois River and Flint Creek, respectively. A 50% modeled reduction in discharge resulted in a 0.32 ˚C and 0.13 ˚C decrease in maximum water temperature in each of the two streams. Temperature modeling of Barren Fork Creek was difficult to reconcile likely because of a breakdown in the stream width-discharge equation at low flows. Increasing discharge in the Illinois River and Flint Creek showed only minimal reductions in risk of exceeding critical thermal maximum (CTM) for fishes. Flint Creek, however, appears to offer thermal refugia for many species, rarely exceeding published CTM values. Continuous recaptures over about 50 days of four PIT-tagged species in Flint Creek were analyzed using a multistate model in MARK. Survival probability of cardinal shiner and orangethroat darter was related to daily discharge. More importantly, transition probability was also related to daily discharge for three species (cardinal shiner, orangethroat darter, and slender madtom). Transition probability was near zero at approximately 15-20 cfs for several species suggesting movements between channel units were inhibited below this level. Management can use the range of flows provided to prevent habitat loss for targeted species or habitats. A follow-up analysis identifying the natural frequency of these flow events would be beneficial and allow a means for targeting natural variation in minimum flows. Critical low flow where some fish species are restricted to particular habitats appears to be approximately 20 cfs. Keywords: Environmental Flows; Minimum Flow