Geology topics

Mark A. Pegg

Publications and source records attributed to Mark A. Pegg.

13 recordsLinked to original sources

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↗

USGS2020

Ecosystem-specific growth responses to climate pattern by a temperate freshwater fish

Somatic growth patterns among animal populations are maintained through complex processes that vary among ecosystems. Changes in growth patterns may be concomitant with changes in climate; however, understanding how growth will manifest among ecosystems is limited. Information embedded within fish hard-parts (i.e., otoliths, spines, vertebrae) can account for variation in growth patterns resulting from changing climate conditions. Channel catfish Ictalurus punctatus is a freshwater fish species widely distributed across North America with limited information regarding climate influences on growth and differences in climate-growth relations among ecological systems. We assessed growth (total length) response to changing climate conditions for channel catfish among three waterbody types—pit lakes, irrigation and power-generation reservoirs, and flood-control reservoirs in Nebraska, USA. We used linear mixed-effect models and an information theoretic approach to assess the relative strengths among competing hypotheses. The most supported linear mixed-effect model of channel catfish growth was a function of fish age and an interaction between waterbody type and growing-degree-day (GDD). A positive trend existed in GDD from 1990 through 2008 whereby the predicted increase in GDD among waterbody types ranged from 182 GDD to 189 GDD. The predicted change in channel catfish growth resulting from increased GDD ranged from 1% to 39% among waterbody types. Channel catfish population rate functions, thus, may not respond similarly to climate conditions across ecosystem types. Changes in climate variables may contribute to system-specific responses in population dynamics for channel catfish as well as other similar freshwater species. The establishment of relations between climate and growth variables for a freshwater generalist with a plastic diet and broad temperature tolerance serves as an indication of the breadth of responses possible for freshwater fishes under global changes in climate conditions.

Nebraska↗

USGS2019

Exit here: Strategies for dealing with aging dams and reservoirs

Aging infrastructure is prevalent throughout the world but water control management structures, specifically dams are of growing concern. Dams and their corresponding reservoirs have inherent, but separate, lifespans. The proportion of dams around the world that continue operation beyond their intended lifespans is growing at an alarming rate. Society will not only have to navigate the tradeoffs associated with the deterioration of services provided by reservoirs and dams, but also impending structural failures. Society is nearing a critical pinch point where we will have to decide how to deal with dams and reservoirs at scales that range from a single system to multiple systems in large watersheds. No comprehensive strategy exists to inform both the range of actions that can be applied to such infrastructure and how such actions would influence biophysical, socioeconomic, and geopolitical tradeoffs. The development of proactive exit strategies is a critical first step in ensuring controlled transitions for aging dams and reservoirs. Herein, we present an overview of actions and considerations for aging dams and reservoirs in the USA followed by an initial framework for exit strategy development to launch further discussion on how society could deal with this aging infrastructure.

Aquatic Sciences↗

USGS2017

Estimating the number of recreational anglers for a given waterbody

Knowing how many anglers use a given body of water is paramount for understanding components of a fishery related to angling pressure and harvest, yet no study has attempted to provide an estimate of the population size of anglers for a given waterbody. Here, we use information from creel surveys in a removal-sampling framework to estimate total numbers of anglers using six reservoirs in Nebraska, USA, and we examine the influence of the duration of sampling period on those estimates. Population estimates (N ± SE) of unique anglers were 2050 ± 45 for Branched Oak Lake, 1992 ± 29 for Calamus Reservoir, 929 ± 10 for Harlan County Reservoir, 985 ± 24 for Lake McConaughy, 1277 ± 24 for Merritt Reservoir, and 916 ± 18 for Pawnee Lake during April–October 2015. Shortening the sampling period by one or more months generally resulted in a greater effect on estimates of precision than on estimates of overall abundance. No relationship existed between abundances of unique anglers and angling pressures across reservoirs and sampling duration, indicative of a decoupling of angler abundance and angling pressure. The approach outlined herein has potential to provide defendable answers to “how many are there?”, questions we ask when subjects cannot be marked, which should provide new insights about angler populations and subpopulations.

Nebraska↗

USGS2016

Using standardized fishery data to inform rehabilitation efforts

Lakes and reservoirs progress through an aging process often accelerated by human activities, resulting in degradation or loss of ecosystem services. Resource managers thus attempt to slow or reverse the negative effects of aging using a myriad of rehabilitation strategies. Sustained monitoring programs to assess the efficacy of rehabilitation strategies are often limited; however, long-term standardized fishery surveys may be a valuable data source from which to begin evaluation. We present 3 case studies using standardized fishery survey data to assess rehabilitation efforts stemming from the Nebraska Aquatic Habitat Plan, a large-scale program with the mission to rehabilitate waterbodies within the state. The case studies highlight that biotic responses to rehabilitation efforts can be assessed, to an extent, using standardized fishery data; however, there were specific areas where minor increases in effort would clarify the effectiveness of rehabilitation techniques. Management of lakes and reservoirs can be streamlined by maximizing the utility of such datasets to work smarter, not harder. To facilitate such efforts, we stress collecting both biotic (e.g., fish lengths and weight) and abiotic (e.g., dissolved oxygen, pH, and turbidity) data during standardized fishery surveys and designing rehabilitation actions with an appropriate experimental design.

Nebraska↗

USGS2016

Fishing for ecosystem services

Ecosystems are commonly exploited and manipulated to maximize certain human benefits. Such changes can degrade systems, leading to cascading negative effects that may be initially undetected, yet ultimately result in a reduction, or complete loss, of certain valuable ecosystem services. Ecosystem-based management is intended to maintain ecosystem quality and minimize the risk of irreversible change to natural assemblages of species and to ecosystem processes while obtaining and maintaining long-term socioeconomic benefits. We discuss policy decisions in fishery management related to commonly manipulated environments with a focus on influences to ecosystem services. By focusing on broader scales, managing for ecosystem services, and taking a more proactive approach, we expect sustainable, quality fisheries that are resilient to future disturbances. To that end, we contend that: (1) management always involves tradeoffs; (2) explicit management of fisheries for ecosystem services could facilitate a transition from reactive to proactive management; and (3) adaptive co-management is a process that could enhance management for ecosystem services. We propose adaptive co-management with an ecosystem service framework where actions are implemented within ecosystem boundaries, rather than political boundaries, through strong interjurisdictional relationships.

Journal of Environmental Management↗

USGS2015

The global status of freshwater fish age validation studies and a prioritization framework for future research

Age information derived from calcified structures is commonly used to estimate recruitment, growth, and mortality for fish populations. Validation of daily or annual marks on age structures is often assumed, presumably due to a lack of general knowledge concerning the status of age validation studies. Therefore, the current status of freshwater fish age validation studies was summarized to show where additional effort is needed, and increase the accessibility of validation studies to researchers. In total, 1351 original peer-reviewed articles were reviewed from freshwater systems that studied age in fish. Periodicity and age validation studies were found for 88 freshwater species comprising 21 fish families. The number of age validation studies has increased over the last 30 years following previous calls for more research; however, few species have validated structures spanning all life stages. In addition, few fishes of conservation concern have validated ageing structures. A prioritization framework, using a combination of eight characteristics, is offered to direct future age validation studies and close the validation information gap. Additional study, using the offered prioritization framework, and increased availability of published studies that incorporate uncertainty when presenting research results dealing with age information are needed.

Reviews in Fisheries Science & Aquaculture↗

USGS2015

Reservoir rehabilitations: Seeking the Fountain of Youth

Aging of reservoirs alters the functions, and associated services, of these systems through time. The goal of habitat rehabilitation is often to alter the trajectory of the aging process such that the duration of the desired state is prolonged. There are two important characteristics in alteration of the trajectory—the amplitude relative to current state and the subsequent rate of change, or aging—that ultimately determine the duration of extension for the desired state. Rehabilitation processes largely fall into three main categories: fish community manipulation, water quality manipulation, and physical habitat manipulation. We can slow aging of reservoirs through carefully implemented management actions, perhaps even turning back the hands of time, but we cannot stop aging. We call for new, innovative perspectives that incorporate an understanding of aging processes in all steps of rehabilitation of reservoirs, especially in planning and assessing.

Fisheries↗

USGS2015

Accuracy or precision: Implications of sample design and methodology on abundance estimation

Sampling by spatially replicated counts (point-count) is an increasingly popular method of estimating population size of organisms. Challenges exist when sampling by point-count method, and it is often impractical to sample entire area of interest and impossible to detect every individual present. Ecologists encounter logistical limitations that force them to sample either few large-sample units or many small sample-units, introducing biases to sample counts. We generated a computer environment and simulated sampling scenarios to test the role of number of samples, sample unit area, number of organisms, and distribution of organisms in the estimation of population sizes using N -mixture models. Many sample units of small area provided estimates that were consistently closer to true abundance than sample scenarios with few sample units of large area. However, sample scenarios with few sample units of large area provided more precise abundance estimates than abundance estimates derived from sample scenarios with many sample units of small area. It is important to consider accuracy and precision of abundance estimates during the sample design process with study goals and objectives fully recognized, although and with consequence, consideration of accuracy and precision of abundance estimates is often an afterthought that occurs during the data analysis process.

Ecological Modelling↗

USGS2014

Potential population and assemblage influences of non-native trout on native nongame fish in Nebraska headwater streams

Non-native trout are currently stocked to support recreational fisheries in headwater streams throughout Nebraska. The influence of non-native trout introductions on native fish populations and their role in structuring fish assemblages in these systems is unknown. The objectives of this study were to determine (i) if the size structure or relative abundance of native fish differs in the presence and absence of non-native trout, (ii) if native fish-assemblage structure differs in the presence and absence of non-native trout and (iii) if native fish-assemblage structure differs across a gradient in abundances of non-native trout. Longnose dace Rhinichthys cataractae were larger in the presence of brown trout Salmo trutta and smaller in the presence of rainbow trout Oncorhynchus mykiss compared to sites without trout. There was also a greater proportion of larger white suckers Catostomus commersonii in the presence of brown trout. Creek chub Semotilus atromaculatus and fathead minnow Pimephales promelas size structures were similar in the presence and absence of trout. Relative abundances of longnose dace, white sucker, creek chub and fathead minnow were similar in the presence and absence of trout, but there was greater distinction in native fish-assemblage structure between sites with trout compared to sites without trout as trout abundances increased. These results suggest increased risk to native fish assemblages in sites with high abundances of trout. However, more research is needed to determine the role of non-native trout in structuring native fish assemblages in streams, and the mechanisms through which introduced trout may influence native fish populations.

Nebraska↗

USGS2014

Experimental evaluation of rainbow trout Oncorhynchus mykiss predation on longnose dace Rhinichthys cataractae

Laboratory and in-stream enclosure experiments were used to determine whether rainbow trout Oncorhynchus mykiss influence survival of longnose dace Rhinichthys cataractae . In the laboratory, adult rainbow trout preyed on longnose dace in 42% of trials and juvenile rainbow trout did not prey on longnose dace during the first 6 h after rainbow trout introduction. Survival of longnose dace did not differ in the presence of adult rainbow trout previously exposed to active prey and those not previously exposed to active prey ( = 0.28, P = 0.60). In field enclosures, the number of longnose dace decreased at a faster rate in the presence of rainbow trout relative to controls within the first 72 h, but did not differ between moderate and high densities of rainbow trout ( F 2,258.9 = 3.73, P = 0.03). Additionally, longnose dace were found in 7% of rainbow trout stomachs after 72 h in enclosures. Rainbow trout acclimated to the stream for longer periods had a greater initial influence on the number of longnose dace remaining in enclosures relative to those acclimated for shorter periods regardless of rainbow trout density treatment ( F 4,148.5 = 2.50, P = 0.04). More research is needed to determine how predation rates will change in natural environments, under differing amounts of habitat and food resources and in the context of whole assemblages. However, if rainbow trout are introduced into the habitat of longnose dace, some predation on longnose dace is expected, even when rainbow trout have no previous experience with active prey.

Ecology of Freshwater Fish↗

USGS2014

Status of native stream fishes within selected protected areas of Niobrara River in western Nebraska

Lotic systems within the Great Plains are characterized by highly fluctuating conditions through both space and time. Fishes inhabiting these systems have adopted specific life-history strategies to survive in such environments; however, anthropogenic disturbance to prairie streams has resulted in declines and extirpation of many native stream fishes. Terrestrial protected areas (i.e., parks and reserves) are designated to support native flora and fauna and, it is assumed, to provide protection to native fishes. We assessed the presence and relative abundance of stream fish populations within protected areas along the Niobrara River in western Nebraska based on data collected during 1979, 1989, 2008, and 2011. The spatial extent of protection, landscape changes resulting in degraded physiochemical parameters, and introduced species may reduce the effectiveness of these terrestrial protected areas in protecting native fishes in Great Plains stream environments.

Great Plains Research↗

USGS2013

Review of the negative influences of non-native salmonids on native fish species

Non-native salmonids are often introduced into areas containing species of concern, yet a comprehensive overview of the short- and long-term consequences of these introductions is lacking in the Great Plains. Several authors have suggested that non-native salmonids negatively inflfluence species of concern. The objective of this paper is to review known interactions between non-native salmonids and native fifishes, with a focus on native species of concern. After an extensive search of the literature, it appears that in many cases non-native salmonids do negatively inflfl uence species of concern (e.g., reduce abundance and alter behavior) via different mechanisms (e.g., predation and competition). However, there are some instances in which introduced salmonids have had no perceived negative inflfl uence on native fifi shes. Unfortunately, the majority of the literature is circumstantial, and there is a need to experimentally manipulate these interactions.

Great Plains Research↗