Keith D. Koupal

The Nebraska Game and Parks Commission

Prey abundance and size vary seasonally, creating a dynamic connection between predator and prey. The natural complexity related to consuming multiple prey types as fish undergo ontogenetic diet shifts combined with the frequent sampling and substantial laboratory time investment required to investigate seasonal predator-prey dynamics limits unders...

Objective The need to augment of Walleye Sander vitreus populations may increase as these populations face challenges of changing habitats and climatic conditions. Since little has been published outside of agency reports on wild broodstocks, the intent of this study was to describe sex‐specific Walleye spawning participation from a Great Plains br...

Fish stocking continues to be an important and often‐used tool in fisheries management. Mortality of fish may be high in the first few days after stocking due to predation and a lack of appropriate food and habitat. The objective of this study was to develop a conceptual model that may identify stocking locations that can help improve the survival...

Alewives Alosa pseudoharengus are native to the Atlantic Coast but have been introduced to inland waters as forage for sportfish populations. Alewife introductions have benefitted sportfish growth and body condition but have also negatively influenced larval fish survival through predation or competition for zooplankton. In 1986, alewives were stoc...

Estimates of age and growth are important parameters for understanding fish population dynamics. Most studies of age and growth involve recreationally important species, but evaluations of population structure and dynamics are important to managing prey or introduced species. Alewife Alosa pseudoharengus are a prey species native to the Atlantic Co...

Reservoir Walleye (Sander vitreus) populations often experience limited recruitment to the adult stage. Several factors may lead to recruitment bottlenecks, including intra-and interspecific predation and a lack of suitable habitat. Therefore, stocking is often used to sustain populations. Additionally, prey fish species can be introduced to enhanc...

Objective Track cohort survival, individual growth, and PIT tag retention, as well as relative growth rate, from fall to the following spring for age‐0 Muskellunge Esox masquinongy held in an extensive culture pond. Methods A total of 806 age‐0 Muskellunge were provided a 12‐mm PIT tag in October 2021 and placed into a 0.1‐ha pond. Individual tota...

The ratio of female to male Walleye Sander vitreus across the spatial scale of large reservoirs and during non-spawning times receives little attention, even though standardized sampling occurs during this time. This study evaluated whether the proportion of female Walleye collected from seasonal sampling at different spatial areas within a large r...

Stocking is a common management practice to maintain walleye populations where natural recruitment is low or to introduce and sustain walleye populations outside of their native range. Different sizes of stocked fish (e.g., fry versus fingerling) may contribute differently walleye year class strength. Collecting fish following stocking and determin...

Alewives Alosa pseudoharengus are native to the Atlantic Coast and have negatively impacted other fishes directly via consumption of eggs and larvae and indirectly by outcompeting larval fish for zooplankton. In 1986, Alewives were stocked into Lake McConaughy as an alternative prey resource; Many have speculated that this introduction led to reduc...

Juvenile fish growth is dependent on their food habits and can influence their survival through their first winter. Several studies have linked age-0 Walleye Sander vitreus body condition to recruitment, both for stocked and naturally produced fish. In the past few years, the size and condition of fall age-0 Walleyes in Lake McConaughy has varied,...

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 benefi...

Habitats may become unavailable to fish in reservoirs at different water elevations. Coves are particularly vulnerable to habitat loss as these peripheral zones may become isolated from the main reservoir. Quantifying habitat loss at different water elevation reductions and estimating the cost of replacing specific types of habitat or maintaining a...

Sediment berms of various heights have developed in the mouths of several coves within Harlan County Reservoir due to a combination of sediment deposition and lateral drift of eroded sediments. These berms can isolate coves from the main reservoir if the berm height is greater than the water elevation of the reservoir. Previous research in other re...

Coves are part of the mosaic of fish habitats in many U.S. reservoirs, but over time these coves may be disconnected from the main reservoir for varying durations due to the buildup of sediment berms at the mouth that are higher than reservoir elevations. Our four‐year study (2017 – 2020) of five coves of Harlan County Reservoir, Nebraska, across t...

The Aransas-Wood Buffalo population of Whooping Cranes (Grus americana) migrates approximately 4000 km through the central Great Plains biannually, between their breeding and wintering grounds. Whooping Cranes depend on stopover sites to provide secure resting locations and the caloric resources necessary to complete their migration, such as the US...

Water chemistry can vary spatially and temporally within a riverscape (i.e., reservoir, rivers, and tributaries) due to different surficial geologies, groundwater influences, surrounding land use, habitat type (i.e., reservoir or river), and water residence time. Microelemental signatures may be absorbed by calcified structures of fish and have bee...

The article discerns variable population dynamics as depicted by seasonal sampling within the same reservoir for walleye and channel catfish.

Fish samples collected during different times of the year can be subject to various biases, but the influence of sampling during different seasons on population dynamics and yield metrics in large reservoirs is not well reported. This study compared the age structure, growth, mortality, and yield estimates of Channel Catfish Ictalurus punctatus and...

The plains topminnow (Fundulus sciadicus) is an endemic Great Plains stream fish that has experienced declines in geographic range and local abundance. Due to these declines, the species has been considered for Federal protection and designated with conservation status in states throughout its historic range. The reasons for declines are likely sim...

Freshwater drum (Aplodinotus grunniens) represent one of the most widely distributed fish species in North America. Identifying biotic and abiotic factors that influence larval freshwater drum densities can improve understanding of early life history. Our objective was to investigate correlations between annual peak density of larval freshwater dru...

Sampling is often standardized with regard to time and space to monitor population characteristics. Effective sampling of large reservoirs can be complicated by the inherit bias of habitat variability along the reservoir gradient. Our objective was to assess spatial and seasonal distribution patterns of target and non‐target fish species in a large...

Perrion MA, Kaemingk MA, Koupal KD, Schoenebeck CW, Bickford NA. 2019. Use of otolith chemistry to assess recruitment and habitat use of a white bass fishery in a Nebraska reservoir. Lake Reserv Manage. XX:XX–XX. Managing fisheries that exhibit variable annual recruitment is challenging, and maintenance stockings are often prescribed to minimize in...

Stopover sites provide important forage resources and protection from predators to the Aransas-Wood Buffalo population of Whooping Cranes (Grus americana) as they migrate 4000 km across the Great Plains each spring and fall. Given the Whooping Crane’s expansive migration corridor, sensitivity to human disturbance, small population size, and protect...

Understanding consumption patterns and preferences of particular life stages for fish species can clarify potential dietary overlap and identify energy flow within aquatic communities. Age-0 white bass (Morone chrysops) have been documented to consume a variety of prey items and zooplankton are a common occurrence. The importance of particular zoop...

White Bass (Morone chrysops) and Hybrid Striped Bass (M. saxatillis × M. chrysops) populations often coexist in the same waterbody and are known to achieve different lengths, have differing reproductive success, and provide different opportunities for anglers. However, comparative population dynamics from systems where Moronids are managed with the...

Much attention has been given to describing how abiotic factors impact the population dynamics of Yellow Perch Perca flavescens, especially during early life history; however, the impacts of biotic factors are less understood. In this study, we simplified the community assemblage to reduce interspecific competition and gain a better understanding o...

Dams act as an anthropogenic barrier to fish movement, and these barriers can influence population dynamics, gene flow, and spawning success. Fish passage structures, such as lifts, natural passages, or a series of pools, are often constructed to aid fish movement. However, the success of fish passing through these structures is rarely evaluated, e...

The ontogenetic diet shift to piscivory can be energetically beneficial for fish growth and allows larger, more energetically profitable prey to be consumed. A shift to piscivory may be easier for longer individuals within a cohort due to larger gape size, and an early shift is likely advantageous, potentially leading to increased growth rates and...

Background. The North American prairie biome is considered one of the most endangered ecoregions. Prairie fishes have been affected by many anthropogenic disturbances, including the construction of bridges and culverts as road crossings over streams. The objective of our study was to test fish assemblage characteristics upstream and downstream of s...

Background. The North American prairie biome is considered one of the most endangered ecoregions. Prairie fishes have been affected by many anthropogenic disturbances, including the construction of bridges and culverts as road crossings over streams. The objective of our study was to test fish assemblage characteristics upstream and downstream of s...

The Sandhills of Nebraska are a unique ecotone that is home to hundreds of natural lakes. These water bodies are known to be productive and susceptible to inundation from non-native common carp (Cyprinus carpio). Excessive populations of common carp typically require renovation of the system; however, little background has been published on the rel...

Plains Topminnow (Fundulus sciadicus) populations have experienced large declines throughout the Central Great Plains, with Western Mosquitofish (Gambusia affinis) introductions suggested as a contributing factor. There are limited studies identifying the food habits of Plains Topminnow and the trophic interactions with Western Mosquitofish. This s...

Gizzard shad (Dorosoma cepedianum) are an influential forage fish and driver of zooplankton resources in many reservoirs. The ability to identify the biotic and abiotic factors that influence the timing of elevated gizzard shad densities can be important to better utilize this forage fish and manage sport fish. The objective of this study was to in...

Adult White Bass are piscivorous and therefore available prey is restricted with gape width limitations. Limited information is available about the physical morphometric gape width limitations of this species, particularly related to the consumption of Alewife. Alewives were stocked into Lake McConaughy, Nebraska in 1986 in order to provide a prey...

Plains topminnow Fundulus sciadicus are endemic to the Great Plains (USA), and because of declines in their geographic range and local abundance, are granted protection throughout their native range. Experimental reintroductions were conducted to improve conservation techniques and enhance the long-term outlook for plains topminnow persistence in N...

Regionally proximate waters in the Sandhills of Nebraska are known to have distinctive alkaline conditions. However, little is known about the seasonal variability that exists for abiotic conditions and zooplankton communities within these same waters. Th is study assessed two highly alkaline and four moderately alkaline lakes for seasonal trends i...

Conservation of lotic fishes requires consideration of complex patterns among a changing mosaic of fish assemblage structure at multiple spatial scales. Studies have demonstrated the influence of localized competition and predation among stream fishes, but researchers have been largely unable to determine to what extent interspecific interactions a...

Chemical batch marks with compounds such as oxytetracycline hydrochloride (OTC) can be useful for estimates of stock contribution. However, no information currently exists on the feasibility of marking fingerling White Bass Morone chrysops with OTC. The objectives of this study were to determine the level of mortality on White Bass when immersed in...

Smallmouth bass (Micropterus dolomieu) have been introduced across Nebraska into a variety of waterbodies. However, an estimate of smallmouth bass growth and mortality in Nebraska waters has not been produced. The objectives of this study were to use historic sampling data to describe the growth of smallmouth bass in Nebraska lakes in relation to o...

Humans have baited wildlife such as white-tailed deer (Odocoileus virginianus) for generations with the primary purpose of increasing hunting harvest success. Baiting regulation changes are often considered by state management agencies as they pertain to hunting opportunity, fair chase, and disease risk. Cervids require a variety of minerals to sup...

Abstract Humans have baited wildlife such as white-tailed deer (Odocoileus virginianus) for generations with the primary purpose of increasing hunting harvest success. Baiting regulation changes are often considered by state management agencies as they pertain to hunting opportunity, fair chase, and disease risk. Cervids require a variety of minera...

The popularity of walleye Sander vitreus fishing has resulted in the development of specialized regulations that are designed to protect these fisheries. In the case of Sherman Reservoir, Sherman County, Nebraska, the walleye population provides a sportfishing opportunity and serves as broodstock for the state. In 2009, for the primary purpose of p...

Stream fragmentation can be detrimental to lotic fish species by preventing important life history movements. The maximum swimming speed and jumping ability of 10 stream fish species were evaluated to describe potential water velocity and height barriers to fish movement. A 10-L swim tunnel was used to test maximum swimming performance and an artif...

Catch rates are commonly used to indirectly index population density, e.g., nighttime electrofishing to survey Largemouth Bass Micropterus salmoides populations. However, the relationship between catch rate and population density must be known in order for catch rate to serve as an accurate index. We sought to determine if Largemouth Bass electrofi...

The establishment of nonnative species and subsequent replacement of native species is among the greatest threats to freshwater biodiversity worldwide. However, little is known of the effects that invasive species have on individual species and specific mechanisms by which species displacement occurs. The expansion of western mosquitofish Gambusia...

Movement behaviors attributed to spawning, dispersal, or altered habitat availability are essential to the ecology of many lotic fishes and, although considerable research has described movements of sport fish, little is known about the movement patterns of nongame species. Streams and rivers, wherein plains topminnow Fundulus sciadicus are prevale...

Cobble substrate for walleye (Sander vitreus) spawning was added at Sherman Reservoir, Nebraska, in January 2008. We evaluated changes in relative adult walleye abundance and egg density in response to the cobble substrate and estimated site fidelity of adult walleye during the spawning seasons of 2007, 2008, and 2009. A 15% increase in electrofish...

Harlan County Reservoir, located in south-central Nebraska, entered a drought in 2003, providing an opportunity to monitor the effects of drought on the zooplankton community in this irrigation reservoir. We sampled the zooplankton community at 15 standardized locations every other week from April through the third week of October from 2003-2011. T...

Over 2 years, we examined the survival of stocked advanced fingerling Yellow Perch Perca flavescens involving over 16 stocking events in eight lakes in Nebraska. The survival of stocked fish was estimated with respect to both handling mortality during stocking and predation by Largemouth Bass Micropterus salmoides . Handling mortality during stocki...

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 ch...

The Nebraska Game and Parks Commission would like to establish yellow perch angling opportunities in south central Nebraska through the use of stocking fingerling. Studies have indicated that predation mortality can contribute up to 100% of stocked fish mortality. The predation mortality of stocked yellow perch in eight barrow pits was assessed by...

Fisheries managers applied rotenone to Mormon Island West in August of 2010 to renovate a fish community that was hypothesized to be unbalanced (i.e., dominated with gizzard shad and common carp) based on standardized survey results. We estimated species-specific biomass following the lake renovation to provide a baseline biomass estimate for a san...

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 pos...

A technique for mass-marking fish was evaluated that forces fluorescent pigment into dermal tissue with compressed air. A five month trial was conducted where mark retention, readability, and marking mortality were evaluated with six fish species that represent a variety of taxonomic groups. Approximately 100 of each species were marked; a percenta...

The plains topminnow Fundulus sciadicus appears to be experiencing reductions in geographic range and local abundance, which has led to regional protection throughout its native range. Conservation of this species may require introductions to reestablish populations at known historic locations. Therefore, a pond was constructed during September 200...

The U.S. Fish and Wildlife Service has adopted two different pitfall trap protocols to survey the endangered American burying beetle, Nicrophorus americanus. One protocol uses a transect of eight pitfall traps that prohibit bait contact over the course of three trap nights. The other protocol uses buckets that allow for bait contact over a five nig...

Globally, riverine fishes are affected by degradation of habitat, stream alterations, lost stream connectivity and introduction of non-native species. The plains topminnow Fundulus sciadicus, a small stream-dwelling fish, currently does not have a federal conservation status in the USA; however, anecdotal reports have suggested its decline for the...

A new gear for sampling walleye Sander vitreus eggs, egg sampling disks, is described, and the ability of these disks to estimate walleye egg density on mud, cobble, and rip‐rap substrates is demonstrated. Each egg sampling disk was a concave steel disk covered with outdoor carpet. The ability of the disks to estimate walleye egg density and total...

During certain times of the year high densities of larval fish can impact the aquatic community. The specific role of freshwater drum (Aplodinotus grunniens) is not known but larval freshwater drum can be abundant in some systems and have been shown to feed on zooplankton. To assist with understanding the role larval freshwater drum play in reservo...

Many aquatic organisms survive by filter feeding from the surrounding water and capturing food particles. We developed a laboratory exercise that allows students to measure the effects of filtering by fresh water mussels on water turbidity. Mussels were acquired from Wards Scientific and exposed to a solution of baker's yeast. Over a period of one...

Gizzard shad (Dorosoma cepedianum) are prolific spawners that can influence reservoir communities. Larval gizzard shad may compete with larval recreational fish for zooplankton resources. Therefore, it is necessary to determine larval gizzard shad dynamics and food habits to better understand their potential for competition with larval recreational...

Understanding the extent and depth of rotenone impacts on all trophic levels is essential to effective aquatic management. We examined changes in water quality tenets and zooplankton communities following the establishment of 3 ppm rotenone concentration in a Nebraska barrow pit. Dissolved oxygen initially decreased 57% and subsequently increased 2...

The objective of this study was to determine the horizontal and vertical distribution of zooplankton in Harlan County Reservoir in order to assist in developing an appropriate zooplankton sampling regime for this and similar Nebraska irrigation reservoirs. Samples were collected at 16 sites distributed across 3 zones of the reservoir monthly in Apr...

In this study we will examine the intrapopulation variability in growth of age-0 walleye in Harlan County Reservoir. Growth can be an important indicator of recruitment as the length of age-0 fish after that first growing season may influence over-winter survival. Similar to other irrigation reservoirs in Nebraska, Harlan County Reservoir has a low...

Increased anthropogenic disturbance to watersheds and rivers is exacerbating the effects of oscillating wet-dry periods common in the Midwestern United States, consequently impacting the maintenance and health of lake and reservoir systems. A change in flow regime should affect water quality parameters in reservoirs, but few data exist to document...

Cobble substrate for walleye (Sander vitreus) spawning was added at Sherman Reservoir, Nebraska, in January 2008. We evaluated changes in relative adult walleye abundance and egg density in response to the cobble substrate and estimated site fidelity of adult walleye during the spawning seasons of 2007, 2008, and 2009. A 15% increase in electrofish...

Note: Out results suggested that mature male walleye electrofishing CPUE was a better indicator or where eggs were deposited that mature female walleye gill net CPUE.

Cottonmill Lake, a 17.4 ha impoundment located in Buffalo County, Nebraska, was a fishery dominated by common carp (Cyprinus carpio). As a result of the poor sportfish populations, angler participation in May and June of 1993 was low (503 ± 210 angler hours) and angler catch rates for all fish species (0.5 ± 0.4 fish/angler hour) was less than desi...