Aquaculture and Fisheries Commons^™

Angler Effort And Catch Within A Spatially Complex System Of Small Lakes, Christopher J. Chizinski, Dustin R. Martin, Kevin L. Pope, Tony J. Barada, Jeffrey J. Schuckman

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

Spatial layout of waterbodies and waterbody size can affect a creel clerk’s ability to intercept anglers for interviews and to accurately count anglers, which will affect the accuracy and precision of estimates of effort and catch. This study aimed to quantify angling effort and catch across a spatially complex system of19 small (<100 ha) lakes, the Fremont lakes. Total (±SE) angling effort (hours) on individual lakes ranged from 0 (0) to 7,137 (305). Bank anglers utilized 18 of the 19 lakes, and their mean (±SE) trip lengths(hours) ranged from 0.80 (0.31) to 7.75 (6.75), depending on the waterbody. In contrast, boat anglers utilized 14 of the 19 lakes, and their trip lengths ranged from 1.39 (0.24) to 4.25 (0.71), depending on the waterbody. The most sought fishes, as indexed by number of lakes on which effort was exerted, were anything (17 of 19 lakes), largemouth bass Micropterus salmoides (15 of 19 lakes), and channel catfish Ictalurus punctatus (13 of 19 lakes). Bluegill Lepomis machrochirus, crappie Pomoxis spp., and largemouth bass were caught most frequently across the lakes, but catch rates varied considerably by lake. Of the1,138 parties interviewed, most parties (93%) visited …

Self-Imposed Length Limits In Recreational Fisheries, Christopher J. Chizinski, Dustin R. Martin, Keith L. Hurley, Kevin L. Pope

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

A primary motivating factor on the decision to harvest a fish among consumptive-orientated anglers is the size of the fish. There is likely a cost-benefit trade-off for harvest of individual fish that is size and species dependent, which should produce a logistic-type response of fish fate (release or harvest)as a function of fish size and species. We define the self-imposed length limit as the length at which a captured fish had a 50% probability of being harvested, which was selected because it marks the length of the fish where the probability of harvest becomes greater than the probability of release. …

Panarchy: Theory And Application, Craig R. Allen, David G. Angeler, Ahjond S. Garmestani, Lance H. Gunderson, C. S. Holling

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

The concept of panarchy provides a framework that characterizes complex systems of people and nature as dynamically organized and structured within and across scales of space and time. It has been more than a decade since the introduction of panarchy. Over this period, its invocation in peer-reviewed literature has been steadily increasing, but its use remains primarily descriptive and abstract. Here, we discuss the use of the concept in the literature to date, highlight where the concept may be useful, and discuss limitations to the broader applicability of panarchy theory for research in the ecological and social sciences. Finally, we …

Discontinuities, Cross-Scale Patterns, And The Organization Of Ecosystems, Kirsty L. Nash, Craig R. Allen, David G. Angeler, Chris Barichievy, Tarsha Eason, Ahjond S. Garmestani, Nicholas A. J. Graham, Dean Granholm, Melinda Knutson, R. John Nelson, Magnus Nyström, Craig A. Stow, Shana M. Sundstrom

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

Ecological structures and processes occur at specific spatiotemporal scales, and interactions that occur across multiple scales mediate scale-specific (e.g., individual, community, local, or regional) responses to disturbance. Despite the importance of scale, explicitly incorporating a multi-scale perspective into research and management actions remains a challenge. The discontinuity hypothesis provides a fertile avenue for addressing this problem by linking measureable proxies to inherent scales of structure within ecosystems. Here we outline the conceptual framework underlying discontinuities and review the evidence supporting the discontinuity hypothesis in ecological systems. Next we explore the utility of this approach for understanding cross-scale patterns and the …

Predicted Avian Responses To Bioenergy Development Scenarios In An Intensive Agricultural Landscape, Daniel R. Uden, Craig R. Allen, Rob B. Mitchell, Tim D. Mccoy, Qingfeng Guan

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

Conversion of native prairie to agriculture has increased food and bioenergy production but decreased wildlife habitat. However, enrollment of highly erodible cropland in conservation programs has compensated for some grassland loss. In the future, climate change and production of second-generation perennial biofuel crops could further transform agricultural landscapes and increase or decrease grassland area. Switchgrass (Panicum virgatum) is an alternative biofuel feedstock that may be economically and environmentally superior to maize (Zea mays) grain for ethanol production on marginally productive lands. Switchgrass could benefit farmers economically and increase grassland area, but there is uncertainty as to how conversions between rowcrops, …

Introduction: Social-Ecological Resilience And Law, Ahjond S. Garmestani, Craig R. Allen, Craig Anthony Arnold, Lance H. Gunderson

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

Environmental law is intimately connected to ecological concepts and understanding. The legal instruments, institutions, and administration of law in the United States are predicated on assumptions that nature is globally stable and that the inherent variability in ecological systems is bounded. This current legal framework is based upon an understanding of ecological systems operating near an equilibrium, or if disturbed, moving back toward an equilibrium. Such assumptions make much current environmental law ill-suited for many pressing environmental issues (Ruhl 1999; Garmestani et al. 2009; Craig 2010; Verchick 2010; Benson and Garmestani 2011). Emerging environmental challenges, such as cross-boundary water governance …

Self-Confidence Of Anglers In Identification Of Freshwater Sport Fish, Christopher J . Chizinski, D. R. Martin, K. L. Pope

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

Although several studies have focused on how well anglers identify species using replicas and pictures, there has been no study assessing the confidence that can be placed in angler’s ability to identify recreationally important fish. Understanding factors associated with low self-confidence will be useful in tailoring education programmes to improve self-confidence in identifying common species. The purposes of this assessment were to quantify the confidence of recreational anglers to identify 13 commonly encountered warm water fish species and to relate self-confidence to species availability and angler experience. Significant variation was observed in anglers selfconfidence among species and levels of self-declared …

Toxicity Of Copper Sulfate And Rotenone To Chinese Mystery Snail (Bellamya Chinensis), Danielle M. Haak, Bruce J. Stephen, Robert A. Kill, Nicholas A. Smeenk, Craig R. Allen, Kevin L. Pope

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

The Chinese mystery snail (Bellamya chinensis) is a freshwater snail native to Southeast Asia, Japan, and Russia and is currently classified as an invasive species in at least 27 states in the USA. The species tolerates a wide range of environmental conditions, making management of established populations difficult. We tested the efficacy of two traditional chemical treatments, rotenone and copper sulfate, on the elimination of adult Chinese mystery snails in laboratory experiments. All snails (N=50) survived 72-hour exposure to rotenone-treated lake water, and 96% (N=25) survived 72-hour exposure to pre-determined rotenone concentrations of 0.25, 2.5, and 25.0 mg/L. …

Transdisciplinary Application Of Cross-Scale Resilience, Shana M. Sundstrom, David G. Angeler, Ahjond S. Garmestani, Jorge-H. Garcia, Craig R. Allen

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

The cross-scale resilience model was developed in ecology to explain the emergence of resilience from the distribution of ecological functions within and across scales, and as a tool to assess resilience. We propose that the model and the underlying discontinuity hypothesis are relevant to other complex adaptive systems, and can be used to identify and track changes in system parameters related to resilience. We explain the theory behind the cross-scale resilience model, review the cases where it has been applied to non-ecological systems, and discuss some examples of social-ecological, archaeological/ anthropological, and economic systems where a cross-scale resilience analysis could …

Status Of Native Stream Fishes Within Selected Protected Areas Of The Niobrara River In Western Nebraska, Jonathan J. Spurgeon, Richard H. Stasiak, George R. Cunningham, Kevin L. Pope, Mark A. Pegg

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

Lotic systems within the Great Plains are characterized by highly fl uctuating conditions through both space and time. Fishes inhabiting these systems have adopted specifi c life- history strategies to survive in such environments; however, anthropogenic disturbance to prairie streams has resulted in declines and extirpation of many native stream fi shes. Terrestrial protected areas (i.e., parks and reserves) are designated to support native fl ora and fauna and, it is assumed, to provide protection to native fi shes. We assessed the presence and relative abundance of stream fi sh populations within protected areas along the Niobrara River in western …

Assessing Resilience In Stressed Watersheds, Kristine T. Nemec, Joana Chan, Christina Hoffman, Trisha L. Spanbauer, Joseph A. Hamm, Craig R. Allen, Trevor Hefley, Donald Pan, Prabhakar Shrestha

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

Although several frameworks for assessing the resilience of social-ecological systems (SESs) have been developed, some practitioners may not have sufficient time and information to conduct extensive resilience assessments. We have presented a simplified approach to resilience assessment that reviews the scientific, historical, and social literature to rate the resilience of an SES with respect to nine resilience properties: ecological variability, diversity, modularity, acknowledgement of slow variables, tight feedbacks, social capital, innovation, overlap in governance, and ecosystem services. We evaluated the effects of two large-scale projects, the construction of a major dam and the implementation of an ecosystem recovery program, on …

Habitat Structure And Body Size Distributions: Cross-Ecosystem Comparison For Taxa With Determinate And Indeterminate Growth, Kirsty L. Nash, Craig R. Allen, Chris Barichievy, Magnus Nyström, Nicholas A. J. Graham

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

Habitat structure across multiple spatial and temporal scales has been proposed as a key driver of body size distributions for associated communities. Thus, understanding the relationship between habitat and body size is fundamental to developing predictions regarding the infl uence of habitat change on animal communities. Much of the work assessing the relationship between habitat structure and body size distributions has focused on terrestrial taxa with determinate growth, and has primarily analysed discontinuities (gaps) in the distribution of species mean sizes (species size relationships or SSRs). The suitability of this approach for taxa with indeterminate growth has yet to be …

Consuming Fire Ants Reduces Northern Bobwhite Survival And Weight Gain, P. Evans Myers, Craig R. Allen, Hannah E. Birge

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

Northern bobwhite quail, Colinus virginianus (L.) (Galliformes: Odontophoridae), population declines are well documented, but pinpointing the reasons for these decreases has proven elusive. Bobwhite population declines are attributed primarily to loss of habitat and land use changes. This, however, does not entirely explain population declines in areas intensively managed for bobwhites. Although previous research demonstrates the negative impact of red imported fire ant (Solenopsis invicta Buren) (Hymenoptera: Formicidae) on northern bobwhites, the mechanisms underlying this effect are largely unknown. To meet the protein demands of early growth and development, bobwhite chicks predominantly consume small insects, of which ants are …

Quantifying Spatial Scaling Patterns And Their Local And Regional Correlates In Headwater Streams: Implications For Resilience, Emma Göthe, Leonard Sandin, Craig R. Allen, David G. Angeler

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

The distribution of functional traits within and across spatiotemporal scales has been used to quantify and infer the relative resilience across ecosystems. We use explicit spatial modeling to evaluate within- and cross-scale redundancy in headwater streams, an ecosystem type with a hierarchical and dendritic network structure. We assessed the cross-scale distribution of functional feeding groups of benthic invertebrates in Swedish headwater streams during two seasons. We evaluated functional metrics, i.e., Shannon diversity, richness, and evenness, and the degree of redundancy within and across modeled spatial scales for individual feeding groups. We also estimated the correlates of environmental versus spatial factors …

Review Of The Negative Influences Of Non-Native Salmonids On Native Fish Species, Kelly C. Turek, Mark A. Pegg, Kevin L. Pope

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

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 influence species of concern. The objective of this paper is to review known interactions between non-native salmonids and native fishes, 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 influence species of concern (e.g., reduce abundance and alter behavior) via different mechanisms (e.g., predation and competition). …

Degree-Day Accumulation Influences Annual Variability In Growth Of Age-0 Walleye, Christopher S. Uphoff, Casey W. Schoenebeck, W. Wyatt Hoback, Keith D. Koupal, Kevin L. Pope

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

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 …

The Feasibility Of Producing Adequate Feedstock For Year-Round Cellulosic Ethanol Production In An Intensive Agricultural Fuelshed, Daniel R. Uden, Robert B. Mitchell, Craig R. Allen, Qingfeng Guan, Tim D. Mccoy

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

To date, cellulosic ethanol production has not been commercialized in the United States. However, government mandates aimed at increasing second-generation biofuel production could spur exploratory development in the cellulosic ethanol industry. We conducted an in-depth analysis of the fuelshed surrounding a starch-based ethanol plant near York, Nebraska that has the potential for cellulosic ethanol production. To assess the feasibility of supplying adequate biomass for year-round cellulosic ethanol production from residual maize (Zea mays) stover and bioenergy switchgrass (Panicum virgatum) within a 40-km road network service area of the existing ethanol plant, we identified ∼14,000 ha of marginally productive cropland within …

Fecundity Of The Chinese Mystery Snail In A Nebraska Reservoir, Bruce J. Stephen, Craig R. Allen, Noelle M. Chaine, Kent A. Fricke, Danielle M. Haak, Michelle L. Hellman, Robert A. Kill, Kristine T. Nemec, Kevin L. Pope, Nicholas A. Smeenk, Daniel R. Uden, Kody M. Unstad, Ashley E. Vanderham, Alec Wong

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

The Chinese mystery snail (Bellamya chinensis) is a non-indigenous, invasive species in freshwater ecosystems of North America. We provide fecundity estimates for a population of these snails in a Nebraska reservoir. We dissected 70 snails, of which 29 were females. Nearly all female snails contained developing young, with an average of 25 young per female. Annual fecundity was estimated at between 27.2 and 33.3 young per female per year. Based on an estimated adult population and the calculated fecundity, the annual production for this reservoir was between 2.2 and 3.7 million young.

Survival And Behavior Of Chinese Mystery Snails (Bellamya Chinensis) In Response To Simulated Water Body Drawdowns And Extended Air Exposure, Kody M. Unstad, Daniel R. Uden, Craig R. Allen, Noelle M. Chaine, Danielle M. Haak, Robert A. Kill, Kevin L. Pope, Bruce J. Stephen, Alec Wong

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

Nonnative invasive mollusks degrade aquatic ecosystems and induce economic losses worldwide. Extended air exposure through water body drawdown is one management action used for control. In North America, the Chinese mystery snail (Bellamya chinensis) is an invasive aquatic snail with an expanding range, but eradication methods for this species are not well documented. We assessed the ability of B. chinensis to survive different durations of air exposure, and observed behavioral responses prior to, during, and following desiccation events. Individual B. chinensis specimens survived air exposure in a laboratory setting for > 9 weeks, and survivorship was greater among adults …

Enamel-Based Mark Performance For Marking Chinese Mystery Snail Bellamya Chinensis, Alec Wong, Craig R. Allen, Noelle M. Hart, Danielle M. Haak, Kevin L. Pope, Nicholas A. Smeenk, Bruce J. Stephen, Daniel R. Uden

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

The exoskeleton of gastropods provides a convenient surface for carrying marks, and in the interest of improving future marking methods our laboratory assessed the performance of an enamel paint. The endurance of the paint was also compared to other marking methods assessed in the past. We marked the shells of 30 adult Chinese mystery snails Bellamya chinensis and held them in an aquarium for 181 days. We observed no complete degradation of any enamel-paint mark during the 181 days. The enamel-paint mark was superior to a nail-polish mark, which lasted a median of 100 days. Enamel-paint marks also have a …

Mortality Estimate Of Chinese Mystery Snail, Bellamya Chinensis (Reeve, 1863) In A Nebraska Reservoir, Danielle M. Haak, Noelle M. Chaine, Bruce J. Stephen, Alec Wong, Craig R. Allen

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

The Chinese mystery snail (Bellamya chinensis) is an aquatic invasive species found throughout the USA. Little is known about this species’ life history or ecology, and only one population estimate has been published, for Wild Plum Lake in southeast Nebraska. A recent die-off event occurred at this same reservoir and we present a mortality estimate for this B. chinensis population using a quadrat approach. Assuming uniform distribution throughout the newly-exposed lake bed (20,900 m2), we estimate 42,845 individuals died during this event, amounting to approximately 17% of the previously-estimated population size of 253,570. Assuming uniform distribution throughout all …

Scenarios Of Bioenergy Development Impacts On Regional Groundwater Withdrawals, Daniel R. Uden, Craig R. Allen, Rob B. Mitchell, Qingfeng Guan, Tim D. Mccoy

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

Irrigation increases agricultural productivity, but it also stresses water resources (Huffaker and Hamilton 2007). Drought and the potential for drier conditions resulting from climate change could strain water supplies in landscapes where human populations rely on finite groundwater resources for drinking, agriculture, energy, and industry (IPCC 2007). For instance, in the North American Great Plains, rowcrops are utilized for livestock feed, food, and bioenergy production (Cassman and Liska 2007), and a large portion is irrigated with groundwater from the High Plains aquifer system (McGuire 2011). Under projected future climatic conditions, greater crop water use requirements and diminished groundwater recharge rates …

Rainwater Basin Wetland Inundation Decision Support System Guide, Christopher F. Jorgensen, Andy A. Bishop, Daniel R. Uden, Roger Grosse

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

The Rainwater Basin region of south-central Nebraska, U.S.A., is a critical stopover location for migratory waterfowl, waterbirds and shorebirds traveling along the Central Flyway. The ephemeral playa wetlands in the region serve as spring staging areas, providing critical habitat for migrating birds to rest, feed and establish pairs before resuming their northward migration to the breeding grounds. Collectively, the playa wetlands found in the region form the Rainwater Basin Wetland Complex, encompassing a 6,150 square-mile area of rolling loess plains that extend over 21 counties. Analyses of the State’s historic soil surveys (1910-1917), National Wetland Inventory (NWI; 1980-1982; U.S. Geological …

Effects Of Simulated Angler Capture And Live-Release Tournaments On Walleye Survival, John H. Loomis, Harold L. Schramm Jr., Bruce Vondracek, Patrick D. Gerard, Christopher J. Chizinski

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

We examined the effects of acclimation water temperature, live-well (LW) water temperature, and LW dissolved oxygen (DO) concentration on survival of adult Walleyes Sander vitreus subjected to simulated tournament conditions (angling, LW confinement, and weigh-in procedures) under controlled laboratory conditions. We tested three acclimation temperatures (12, 18, and 24◦C), and three LWtemperature differentials (Delta T=−4, 0, and +4◦C) were tested at each acclimation temperature. Survival was monitored after 8 h of LW confinement and during a 5-d retention period in 1,700-L tanks. None of the Walleyes that were acclimated to 24◦C and subjected to simulated tournament procedures survived the 5-d …

Predictors Of Regional Establishment Success And Spread Of Introduced Non-Indigenous Vertebrates, Criag R. Allen, Kristine T. Nemec, Donald A. Wardwell, Justin D. Hoffman, Mathew L. Brust, Karie L. Decker, Daniel Fogell, Jennifer Hogue, Aaron Lotz, Thaddeus Miller, Marcy Pummill, Luis E. Ramirez-Yañez, Daniel R. Uden

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

Aim To provide the first analysis of predictors of both establishment and spread, both within and across taxa, for all vertebrate taxa within a region.We used Florida, USA, as our study system because it has a well-documented history of introduction and invasion, and is a hotspot for biological invasions.

Location Florida, USA.

Methods We analysed non-indigenous species (NIS) data from peninsular Florida – which included both successful and unsuccessful introductions from all vertebrate classes – to determine the best predictors of both establishment and spread for fish (65 species), herpetofauna (63 species), birds (71 species) and mammals (25 species). We …

The Feasibility Of Switchgrass For Biofuel Production, Rob Mitchell, Kenneth P. Vogel, Daniel R. Uden

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

Switchgrass research has been conducted cooperatively by the US Department of Agriculture and the University of Nebraska since the mid-1930s, with a primary focus on bioenergy since 1990 at several institutions. Progress has been made in switchgrass breeding and genetics, molecular genetics, establishment, fertility management, production economics, production energetics, harvest and storage management, ecosystem services and ethanol yield. A complete field-validated biomass production system has been developed for the Midwest and Central Plains. Even with favorable economic and sustainability results from field trials, switchgrass for bioenergy has not been adopted on a large scale. Lack of adoption is likely due …

Population Estimate Of Chinese Mystery Snail (Bellamya Chinensis) In A Nebraska Reservoir, Noelle M. Chaine, Craig R. Allen, Kent A. Fricke, Danielle M. Haak, Michelle L. Hellman, Robert A. Kill, Kristine T. Nemec, Kevin L. Pope, Nicholas A. Smeenk, Bruce J. Stephen, Daniel R. Uden, Kody M. Unstad, Ashley E. Vanderham

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

The Chinese mystery snail (Bellamya chinensis) is an aquatic invasive species in North America. Little is known regarding this species’ impacts on freshwater ecosystems. It is believed that population densities can be high, yet no population estimates have been reported. We utilized a mark-recapture approach to generate a population estimate for Chinese mystery snail in Wild Plum Lake, a 6.47-ha reservoir in southeast Nebraska. We calculated, using bias-adjusted Lincoln-Petersen estimation, that there were approximately 664 adult snails within a 127 m² transect (5.2 snails/m²). If this density was consistent throughout the littoral zone (depth) of …

Variation In Native Micro-Predator Abundance Explains Recruitment Of A Mobile Invasive Fish, The Common Carp, In A Naturally Unstable Environment, Przemyslaw G. Bajer, Christopher J. Chizinski, Justin J. Silbernagel, Peter W. Sorensen

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

Why certain species of fish become invasive is poorly understood and a key obstacle to restoring many of the world’s ecosystems. In this study we tested whether variation in biotic resistance exerted by native predators might explain the reproductive success of the common carp, a large and fecund invasive species that typically spawns in outlying and unstable shallow habitat. An initial three-year study of the relative abundance of youngof- year (YOY) carp in interconnected lakes in the Upper Mississippi River Basin discovered that YOY carp are only found in shallow waters that experience winter hypoxia (winterkill) and have low densities …

Implications Of Community Concordance For Assessing Stream Integrity At Three Nested Spatial Scales In Minnesota, U.S.A., Christine L. Dolph, David D. Huff, Christopher J. Chizinski, Bruce Vondracek

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

1. Fish and invertebrate assemblage data collected from 670 stream sites in Minnesota (U.S.A.) were used to calculate concordance across three nested spatial scales (statewide, ecoregion and catchment). Predictive taxa richness models, calibrated using the same data, were used to evaluate whether concordant communities exhibited similar trends in human-induced taxa loss across all three scales. Finally, we evaluated the strength of the relationship between selected environmental variables and the composition of both assemblages at all three spatial scales.

2. Significant concordance between fish and invertebrate communities occurred at the statewide scale as well as in six of seven ecoregions and …

Using The Judas Technique To Locate And Remove Wintertime Aggregations Of Invasive Common Carp, P. G. Bajer, Christopher J. Chizinski, P. W. Sorensen

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

Radio- and acoustic telemetry in three Midwestern lakes demonstrated that common carp, Cyprinus carpio L., aggregate as water temperatures descend below 10C. Particularly dense aggregations formed at temperatures <5 >C, and once located, these aggregations could be removed with an efficiency of up to 94% using seine nets. Carp aggregated just below the surface of the ice (approximately 1.5 m) and rarely descended to warmer waters, which extended down to 10 m. Although aggregations consistently formed close to shore, their locations could not be explained by temperature or dissolved oxygen. The aggregations also moved frequently, making radio-tagged fish invaluable to locate …