Geology topics

Keith D. Koupal

Publications and source records attributed to Keith D. Koupal.

4 recordsLinked to original sources

USGS2023

Waterbody size predicts bank- and boat-angler efforts

Bank- and boat-angler efforts are logistically difficult and costly to estimate, preventing landscape-scale estimates that are required to address current and future challenges (e.g., climate change , invasive species) for inland recreational fisheries. Using a large Nebraska, USA, recreational fishery dataset (N = 67 waterbodies), we demonstrate that waterbody size can be used to predict bank- and boat-angler efforts across a heterogeneous landscape of extra small (< 104 ha) and large (> 647 ha) waterbodies. Bank and boat anglers respond to waterbody size, however these relationships appear to be unique between the two angler types. Boat-angler efforts increased as a function of waterbody size, whereas bank-angler efforts increased as a function of waterbody size for extra small waterbodies but not for large waterbodies. The ability to connect waterbody size and angler effort will be important for continued effective inland fisheries management.

Nebraska↗

USGS2022

Natural resource system size can be used for managing recreational use

Outdoor recreation provides societal benefits that are often measured by the amount of use natural resource systems receive. Still, the amount of resource use natural resource systems receive is often unknown or unstudied. Monitoring and quantifying resource use is often logistically difficult and costly but is paramount to optimize societal benefits. Identifying a simple and readily available metric that can indicate the quantity of recreational use of natural resource systems would benefit natural resource management. Using recreational angler participation data during an 11-year study period from 73 public waterbodies in Nebraska, USA, we developed a resource size-use model that demonstrates the ability of natural resource system size to indicate the quantity of recreational use they receive. We demonstrate how resource size-use models can estimate use for unsampled systems, produce broad-scale estimations of use, guide the allocation of resources, and predict how changes in resource system size may affect use. Resource size-use models provide opportunities to manage recreational use, which has been previously elusive for social-ecological systems.

Nebraska↗

USGS2013

Degree-day accumulation influences annual variability in growth of age-0 walleye

The growth of age-0 fishes influences survival, especially in temperate regions where size-dependent over-winter mortality can be substantial. Additional benefits of earlier maturation and greater fecundity may exist for faster growing individuals. This study correlated prey densities, growing-degree days, water-surface elevation, turbidity, and chlorophyll a with age-0 walleye Sander vitreus growth in a south-central Nebraska irrigation reservoir. Growth of age-0 walleye was variable between 2003 and 2011, with mean lengths ranging from 128 to 231 mm by fall (September 30th–October 15th). A set of a priori candidate models were used to assess the relative support of explanatory variables using Akaike's information criterion (AIC). A temperature model using the growing degree-days metric was the best supported model, describing 65% of the variability in annual mean lengths of age-0 walleye. The second and third best supported models included the variables chlorophyll a (r 2 = 0.49) and larval freshwater drum density (r 2 = 0.45), respectively. There have been mixed results concerning the importance of temperature effects on growth of age-0 walleye. This study supports the hypothesis that temperature is the most important predictor of age-0 walleye growth near the southwestern limits of its natural range.

Nebraska↗

USGS2012

Environmental factors regulating the recruitment of walleye Sander vitreus and white bass Morone chrysops in irrigation reservoirs

Understanding the environmental factors that regulate fish recruitment is essential for effective management of fisheries. Generally, first-year survival, and therefore recruitment, is inherently less consistent in systems with high intra- and interannual variability. Irrigation reservoirs display sporadic patterns of annual drawdown, which can pose a substantial challenge to recruitment of fishes. We developed species-specific models using an 18-year data set compiled from state and federal agencies to investigate variables that regulate the recruitment of walleye Sander vitreus and white bass Morone chrysops in irrigation reservoirs in south-west Nebraska, USA. The candidate model set for walleye included only abiotic variables (water-level elevation, minimum daily air temperature during winter prior to hatching, annual precipitation, spring warming rate and May reservoir discharge), and the candidate model set for white bass included primarily biotic variables (catch per unit effort (CPUE) of black crappie Pomoxis nigromaculatus , CPUE of age-0 walleye, CPUE of bluegill Lepomis macrochirus and CPUE of age-3 and older white bass), each of which had a greater relative importance than the single abiotic variable (minimum daily air temperature during winter after hatching). Our findings improve the understanding of the recruitment of fishes in irrigation reservoirs and the relative roles of abiotic and biotic factors.

Nebraska↗