Pelagic broadcast spawning fish (pelagophil) is a threatened reproductive guild of fishes emblematic of the Great Plains. Dewatering, combined with other forms of fragmentation (e.g., large reservoirs), act synergistically to exacerbate the decline of pelagophils. Stream connectivity is hypothesized to be important for migrations by some pelagophils and downstream drift of eggs and larvae. It is likely that several aspects of the flow regime are important to Great Plains fishes and determining which metrics relate to overall population persistence would be beneficial to support proposed management actions. To improve our understanding of the flow needs for fishes of the Great Plains, we suggest a regional perspective relating flow loss to fish persistence would offer a negotiating point for water- management decisions. Regional flow-ecology hypotheses would support the relationships that exist across a broad range of flows and it would apply to other rivers of the region should restoration or rehabilitation become an option. Identifying flows were connectivity occurs and possible refuge locations at low flows would provide substantial support for a minimum flow needed for population persistence and identify refuge population locations under extreme conditions. Lastly, we need to understand how connectivity relates to movement by these fishes. Our specific study objectives are 1) Develop relationships between flow regime and occupancy by pelagophils, 2) Determine the relationship among habitat connectivity and flow and identify refuge habitats that persist during low-flow periods, 3) determine movement during the non-breeding season when most of our uncertainty is greatest related to movement needs. This project supports two Master’s students in the Department of Natural Resources Ecology and Management (Advisor: Shannon Brewer) and Aerospace Engineering (Advisor: Jamey Jacob).

Globally, human alterations to river systems have resulted in the decline of migratory large-river fish populations. The Red River basin is home to several migratory large-river fishes that are considered species of conservation concern. My research focuseson the movement patterns and population dynamics of Blue Suckers in the lower Red River basin (downstream of Lake Texoma). We used acoustic telemetry to document Blue Sucker movement at a coarse resolution. We found homing to the same tributaries for spawning to be common among our tagged fishes, but when fish strayed, it was common to an undammed tributary. We investigated population dynamics of Blue Suckers below Denison and Hugo dams, and modeled the trajectory of the population. Our models suggest that the populations are declining suggesting the populations near dams are sinks. To better understand the variability of Blue Sucker recruitment, we investigated the relationship between Blue Sucker abundance in each year class and the environmental flow conditions at the time each year class would have been born. Preliminary results suggest that years where adult Blue Suckers encounter natural flow pulses, rather than hydropeaking, result in strong year classes the following year. Additionally, low-flow conditions in the only undammed tributary we examined resulted in stronger year classes. I anticipate completing my dissertation in 2018.

Isolated populations may benefit from different conservation and management activities. The Least Darter is a species of conservation concern that has two isolated populations occupying portions of the Arbuckle Mountain and Ozark Highlands ecoregions. My study objective is to determine what environmental factors are related to Least Darter occupancy, while accounting for detection Our general approach is to assess different environmental factors at multiple spatial scales to determine the relationships among microhabitats, reaches, and stream segments and occurrence of Least Darter and sympatric species. The major benefits will be identification of likely populations that can be used as the foundation for a targeted monitoring program, and 2) it will help identify stream segments that likely contain spring locations. We will also use fiber optics to map thermal patches at a fine scale, within two stream segments, and show how Least Darter distribute themselves in response to fine-scale habitat features (i.e., temperature, depth, velocity).

Changes in weather patterns and anthropogenic disturbance have severely altered stream ecosystems. Stream fishes are declining at an alarming rate largely due to changes to flow regimes. Thus, establishing ecological flow relationships is an important component of stream fish conservation and management strategies. Flow-ecology relationships provide a legal mechanism to balance human water-use needs with the ecological integrity of aquatic ecosystems. However, despite improved theoretical perspectives and analytical advancements, stream fish flow-ecology relationships remain poorly understood. For example, the seemingly simple question of minimum flow requirements for a stream fish species is often unknown, which inhibits effective water management plans. I am using modeled streamflow data and assemblage-level surveys from 1980-2016 to examine flow-ecology relationships of Red River stream fishes. Specifically, I am implementing a hierarchical Bayesian modeling approach to establish relationships between local colonization and extinction of stream fishes and both surface and groundwater flow metrics. In addition to providing important ecological information, the model will be used to predict future Red River stream fish distributions under different climate change and groundwater pumping scenarios. This project will help guide stream fish conservation and management strategies and water-use policies in the south-central United States.

The Prairie Chub is classified as a pelagic broadcast-spawning cyprinid based on phylogenetic relationships and shared morphological characteristics with other Macrhybopsis spp. Great Plains pelagic-spawning cyprinid populations have undergone substantial population and range declines due to their sensitivity to anthropogenic changes to the natural flow regime. Currently, there is a paucity of information regarding Prairie Chub biology and life history; thus, little is known about specific factors (i.e., discharge magnitudes) that promote successful recruitment in the upper Red River basin. This research will provide a useful ecological metric for informing future water management decisions that will help conserve populations of pelagic broadcast-spawning cyprinids in the upper Red River basin. This project will be completed by a student at Oklahoma State University (PI is Shannon Brewer) and Texas A&M (co-PI is Josh Perkin). The purpose of this project is to improve the conservation and management of Prairie Chub and other pelagic broadcast minnows including members of the Macrhybopsis complex. We will assess movement at several locations to determine the relationship with recruitment. We will also evaluate the importance of flow regime metrics and relationships between hydrology and recruitment.

Limited information is available about movements of riverine Smallmouth Bass (SMB) in landscapes with prevalent river-reservoir interfaces. This is especially problematic for the Neosho subspecies of SMB given the distribution covers an interwoven landscape of rivers and reservoirs. My dissertation research focuses on movement and habitat use of the Neosho SMB. My research focuses on the reproductive and juvenile development periods, and I am studying several aspects of age-0, juvenile, and adult SMB ecology within this framework. I am using radio telemetry to quantify movements and habitat use of adult and juvenile SMB in streams that vary in size, hydrology, and proximity to impoundments in northeast Oklahoma. I am conducting snorkel surveys on a diverse subset of stream reaches throughout the range of the Neosho SMB to understand the multi-scale habitat features and environmental conditions that influence SMB nest and age-0 SMB densities in Ozark streams. Lastly, I am quantifying days since hatch of young-of-year SMB via otoliths to determine the environmental relationships among hydrologic factors and the timing of spawning and subsequent daily growth.

Salmonids may compete for limited resources with other species with broadly similar ecological niches, but these niches may be occupied by overlooked life stages (e.g., juvenile Smallmouth Bass); nevertheless, this may affect the overall recruitment of other important sport fishes or species of conservation concern. Competitive interactions have been shown to be condition specific. For example, competitive interactions are often controlled by water temperatures and thus, may only occur seasonally or under certain environmental conditions. Understanding these differences is beneficial if there is interest in identifying conditions where stocking may be problematic for native fishes. Because competition can only be infered from field-based studies, I will conduct artificial stream experiments to determine short-term growth differences among native fishes and native fishes with trout introduced. Fish densities will be comparable to that observed in the field and fish will be maintained in a artificial riffle/pool complex where prey items will be introduced. We will create two temperature regimes in the test tanks to determine if competition is dependent on thermal conditions to gain insight into what conditions competition is more or less problematic (if either). We will use DNA:RNA ratios to measure differences in short-term growth among species. Because we know that Rainbow Trout feed heavily on crayfish, I will also compare crayfish demographics at locations occupied by trout and those that are not. This will provide additional insight to indirect interations among fish species as crayfish serve as a primary food source for important native sport fishes that prey on specific size classes of crayfish. Collectively, these data will be beneficial to agencies making decisions about stocking of non-native trout populations.