2025 Midwest Fish & Wildlife Conference

AUTHORS: Caitlin Bloomer, University of Illinois Urbana-Champaign; Joel Corush, Illinois Natural History Survey; Mark Davis, Illinois Natural History Survey; Maxwell Hartman, Arkansas Game and Fish Commission

ABSTRACT: The Slenderwrist Burrowing Crayfish, Fallicambarus petilicarpus, is a short-range endemic restricted to the Ouachita River drainage in south-central Arkansas and northern Louisiana. U.S. Fish and Wildlife Service is currently evaluating this species for listing as threatened or endangered under the Endangered Species Act (ESA). Since 2021, teams of inter-agency biologists have been collecting data on this species to inform the listing decision. We used species distribution modeling to identify habitat associations and estimate the total available habitat within the known range of this species. We used Restriction-site associated DNA sequencing (RADseq) to establish effective population size and estimate genetic differentiation between populations. Here we will present an overview of our data collection and how our results support the listing of this species under the ESA. We will also highlight the major data gaps that still exist and how we plan to address them through future field studies.

AUTHORS: Patrick F. Allison Jr., University of Mississippi;
Corey G. Dunn, U.S. Geological Survey, North Carolina Cooperative Fish & Wildlife Research Unit; North Carolina State University;
Susan B. Adams, USDA Forest Service, Southern Research Station, Center for Bottomland Hardwoods Research;
Jesse W. Breinholt, LGC RAPiD Genomics;
Kenneth A. Sterling, USDA Forest Service;
Devin M. Raburn, North Carolina Cooperative Fish & Wildlife Research Unit; North Carolina State University;
Zanethia C. Barnett, USDA Forest Service, Southern Research Station, Center for Bottomland Hardwoods Research;
Ryan C. Garrick, University of Mississippi

ABSTRACT: Recent advancements in morphological data collection and molecular phylogenetics have resulted in numerous updates to crayfish taxonomy. However, there are still problematic taxa among these decapods. The genus Hobbseus is one such group, as the morphological characters traditionally used for species identification can provide ambiguous diagnoses. Given that some Hobbseus species have been petitioned for listing under the Endangered Species Act, this uncertainty is particularly concerning, as it inhibits implementation of effective conservation strategies. We reassess the taxonomy of Hobbseus using an integrative approach to species delimitation that combines morphological and molecular data. We include four complementary datasets: 1) traditional morphometrics; 2) geometric morphometrics; 3) single-locus mitochondrial DNA sequences; and 4) multi-locus hybrid enrichment single copy nuclear DNA sequences. Here, we provide preliminary results from analyses of the DNA sequence datasets.

AUTHORS: ZAchary J. Loughman, West Liberty University; Parker Hildreth, Tennessee Wildlife Resource Agency; Jonathan D. Eisenhour, Office of Kentucky Nature Preserves; Eric Ng, West Liberty University, Kaleb Norris, West Liberty University; Kathryn Schulz, West Liberty University; Michael C. Compton, Office of Kentucky Nature Preserve.

ABSTRACT: Cambarus jezerinaci, the Spiny Scale Crayfish, is a small headwater species endemic to the central Appalachians of Kentucky, Tennessee, and Virginia. Recently C. jezerinaci was petitioned for federal listing, resulting in the need for a Species Status Assessment (SSA). With the exception of C. jezerinaci description, limited surveys have been completed for this taxa. Cambarus jezerinaci has an interesting distribution in Kentucky, with populations known to occur prior to survey efforts in the South Fork of the Kentucky River basin, as well as the Upper Cumberland watershed. In the summer of 2022, a weeklong survey effort procured new C. jezerinaci locations in the Middle Fork of the Kentucky River, as well as the Upper Cumberland. Genetic samples were taken on all animals captured and analyzed with 2 COI genes. Results of this work indicated that multiple lineages existed for C. jezerinaci in Kentucky that differ genetically from type populations, warranting more dedicated work. In the summer of 2024, in accordance with the Kentucky Crayfish Blitz as well as the WLU Crayfish Laboratory, 306 sites were sampled across the entirety of the Kentucky Fork basins, as well as the Upper Cumberland watersheds. Cambarus cf. jezerianci was procured from 28.2% of sites sampled. Genetic samples were acquired from all specimens and will be analyzed using RADSeq methods. Future work will focus on elucidating the conservation genetics and taxonomic standing of C. jezerinaci to support the completion of the SSA.

AUTHORS: Dusty Swedberg, Prairie Research Institute - Illinois Natural History Survey; Archis Grubh, Texas Parks and Wildlife Department; Christopher Taylor, Prairie Research Institute - Illinois Natural History Survey

ABSTRACT: Crayfishes are a diverse and ecologically important component in Texas's aquatic ecosystems. Timely information on distribution, abundance, habitat needs, and threats is needed to effectively manage this resource. Texas currently has ten crayfish species of greatest conservation need, five of which were the focus of our sampling: Procambarus brazoriensis, Procambarus nigrocinctus, Procambarus nechesae, Procambarus nueces, and Procambarus texanus. From 2022 to 2024, we sampled almost 100 sites targeting these species and have been able to collect each of the five species. Our collections and the associated habitat data have documented possible range reduction in Procambarus nueces and Procambarus texanus. While also documenting Procambarus nigrocinctus and Procambarus nechesae might be more common than initially perceived.  Procambarus brazoriensis is documented as a highly seasonal crayfish with collections that only occur in early spring. With our collection data, we are able to draw conclusions on range and habitat data to better estimate the conservation status for these five crayfishes and other sympatric species that were collected through our efforts. 

AUTHORS: Eric Ng, West Liberty University; Kathryn Schulz, West Liberty University; Zanethia Barnett, US Forest Service; Zachary J. Loughman, West Liberty University



ABSTRACT: The piedmont region of the southeastern United States, once noted by early European explorers to host wide ranging prairie-like habitat, is now dominated by agricultural practices such as pine plantations. The Piedmont Prairie Burrowing Crayfish [(Distocambarus (Distocambarus) crockeri Hobbs & Carlson 1983)] is postulated to have adapted to a terrestrial environment in the piedmont of South Carolina. Nevertheless, the planting of pine throughout the region has removed important habitat elements, such as an open canopy, needed for other Distocambarus populations to persist. Contrarily, other silvicultural practices, such as complete tree removal, seem to benefit D. (D.) crockeri, a suggested prairie habitat specialist. Land management practices used to create prairie-like, open-canopy habitat in the piedmont region could produce a beneficial situation for the vulnerable Piedmont Prairie Burrowing Crayfish. To test this hypothesis, we compared the burrow densities of D. (D.) crockeri in various managed fields to forests within the Long Cane Ranger District of Sumter National Forest, SC. Burrow densities were quantified in 1m2 quadrats along 100m transects that were placed perpendicular to an ecotonal edge of a field and forest. We discovered that the average burrow densities of managed fields were more variable than the forests. However, the means of both averages were near to one another, indicating that maintaining some degree of habitat heterogeneity is important for the persistence of D. (D.) crockeri on a modern landscape.

AUTHORS: Hannah Holbert, West Liberty University; Zackary Graham, West Liberty University; Zachary Loughman, West Liberty University

ABSTRACT: There is no standard for individual captive husbandry of Cambaridae crayfish species, despite captive propagation being an important factor in reintroduction efforts. The Big Sandy Crayfish (Cambarus callainus) and the Guyandotte River Crayfish (Cambarus veteranus) are recognized under the Endangered Species Act as Threatened and Endangered, respectively. Active propagation projects are underway for C. callainus, but standards are still being developed. In order to set a baseline protocol for these federally listed Cambarus species, a shelter preference study was conducted using the Big Water Crayfish (Cambarus robustus). C. robustus is a large-bodied, tertiary burrowing crayfish species native to the eastern coast of the United States and Ontario, Canada. C. robustus commonly occurs in lotic environments and prefers large slab boulders for shelter. Due to similar life history strategies and habitat preferences, this species serves as a potential surrogate for related species such as C. callainus. 31 individual crayfish took part in two trials each, where shelter choices included a natural rock shelter and a piece of clear acrylic, or a natural shelter and tinted acrylic. Trials were conducted for 24-hours, where shelter usage and behavior were monitored through video recordings. Our results suggest that C. robustus will use all shelter types, although natural shelters were occupied more frequently overall. Sex and size of the individuals had minimal or no influence on shelter use. Future research should continue to investigate optimal husbandry practices and rearing techniques for Cambarus species where propagation efforts are necessary.

AUTHORS: Calvin R. Rezac, Mississippi Museum of Natural Science, Mississippi Department of Wildlife, Fisheries, and Parks

ABSTRACT: In 2020, a genetic and morphological evaluation of the Rusty Gravedigger (Lacunicambarus miltus) by Glon et al. supported the elevation of two new species, the Banded Mudbug (L. freudensteini) and the Lonesome Gravedigger (L. mobilensis). Based on the published study by Glon et al., both species occur only in Mississippi and Alabama and were thought to be confined between the Pascagoula and Mobile Rivers. The reported range of both species is currently less than 1,000 km2 and are among the most-narrow ranged species within the state of Mississippi. With only 5 known localities for each species in the state, further efforts to determine the status and complete distribution were needed. Herein, we report on the results from a burrowing crayfish survey at novel sites within and outside the known range of both focal species in Southeastern Mississippi. Surveys took place between January-August 2024, and at each site we collected crayfish using hand excavation, slurp guns, and dip nets. Additional notes on habitat, burrow abundance, and soil composition were also recorded. In total, 104 sites (22 via boat) were surveyed and 21 species were captured including both target species. Banded Mudbug was capture at 11 sites within the known range of the species; however, we failed to expand the species into notable areas outside its range. Lonesome Gravedigger was found at 16 sites, but was notably found in areas more north and west than previously reported. The results of the survey help to improve the understanding of Mississippi burrowing crayfish distribution and status in the state. Notes on other newsworthy crayfish research at the Mississippi Museum of Natural Science may also be discussed.

AUTHORS: Kathryn Schulz, West Liberty University; Eric Ng, West Liberty University; Michael Kendrick, South Carolina Department of Natural Resources; Zanethia Barnett, USDA Forest Service; Nicole Garrison, West Liberty University; Zachary Loughman, West Liberty University



ABSTRACT: Species distribution modeling (SDM) is becoming an increasingly common tool for rare species detection. SDMs analyze and predict the habitat variables driving the distribution of the target species, which can provide useful insight into potential habitats for endemic taxa. Burrowing crayfish often have a patchy distribution on the landscape, making detection difficult. The primary burrowing crayfish genus Distocambarus (Decopoda: Cambaridae) is represented by five taxa, four of which are located within the Piedmont region of South Carolina. All species are narrowly endemic and globally rare, often occurring in fragmented habitats. The distribution of the genus has not been thoroughly delimited, making management efforts difficult. Two species are of greatest conservation need in South Carolina (D. youngineri and D. carlsoni), raising interest in a formal revision of the distribution of the genus within the state. We employed an SDM driven by habitat variables from sites with positive Distocambarus spp. presence to predict potential occurrences outside their current range. We validated the model by visiting predicted locations and confirming species presence or absence. The SDM method successfully expanded the range of the four species residing in South Carolina and led to novel habitat observations, which indicates greater plasticity among the genus than previously documented.

AUTHORS: Montana Fonner, West Liberty University; Zachary Loughman, West Liberty University


ABSTRACT: Cambarus veteranus (Guyandotte River Crayfish) has been in severe population decline since their description in 1914 by Faxon. In 2016 the species was listed as endangered under the Endangered Species Act due to a widespread range reduction. The major contributing factor to this decline is siltation caused by both historic and current logging and mining operations. C. veteranus occupies the interstitial spaces between slab boulders and the benthos. Siltation fills the interstitial space both, smothering live crayfish and reducing habitat availability by cementing slab boulders into the stream bed. C. veteranus is endemic to the Upper Guyandotte River Basin. Historically C. veteranus was found in 8 tributaries of the mainstem of the Upper Guyandotte River. Today C. veteranus is only found in one historic tributary, Pinnacle Creek. More recently, another stream, Clear Fork/Laurel Fork, was found to harbor populations of C. veteranus. Despite the conservation standing of C. veteranus a comprehensive habitat study on the mainstem of the Upper Guyandotte River has not been conducted. This study aims to investigate the mainstem of the Upper Guyandotte River and Lower Pinnacle Creek to determine habitat quality. We recorded observations of anthropogenic degradation, such as siltation, bank instability, and pollution. Data collected will be used towards mitigation efforts in restoring habitat suitability within the study area for C. veteranus. In addition, habitat data collected along the mainstem was integrated in crayfish collection surveys, at possibly overlooked locales, which were determined to have potentially suitable habitats for C. veteranus.

AUTHORS: William G. Wells, University of the South; Marley G. Barton, University of the South; Katie E. McGhee, University of the South: Graham E. Nystrom, University of the South

ABSTRACT: In this preliminary study, we measured and compared effectiveness of electrofishing and kick seining sampling methods for crayfishes from four headwaters streams on the Domain of the University of the South. The University of the South is located on the southern Cumberland Plateau ecoregion in Sewanee, Tennessee. Specifically, we examined how many individuals were captured between gears, and carapace length differences between capture methods during March—April 2024. Focal species were Cambarus sphenoides (Triangleclaw Crayfish) and Faxonius placidus (Bigclaw Crayfish). Four times as many crayfish were captured on average with the electrofishing method (13.5 ± 4.1 crayfish) compared with the kick seining method (3 ± 1 crayfish) across all four streams. Captured crayfish were of similar sizes using both methods. The higher catch rate from electrofishing method compared to kick seining method demonstrates that electrofishing is the best sampling method for headwater streams tested on the southern Cumberland Plateau for Triangleclaw and Bigclaw crayfishes.

AUTHORS: Cameron Haeffner, Southern Illinois University; Dr. Greg Whitledge, Southern Illinois University

ABSTRACT: Naturally occurring chemical markers in calcified structures, such as otoliths and fin rays or spines, have been commonly used in the study of fish environmental history, including identifying natal environments of wild fish, distinguishing stocked from wild fish, and inferring sources of invasive species. There are a few examples of the use of natural chemical markers in aquatic invertebrates, but this technique has not been used for crayfishes. Eye stalks have been used to estimate age of some crustaceans and may contain a microchemical record of crayfish environmental history, although this has not been tested. The objectives of this study are to determine whether crayfish eye stalks reflect microchemical (Sr:Ca, Ba:Ca) signatures of water, whether water-eye stalk microchemistry relationships differ among species, and whether this structure retains microchemical signals of previously occupied environments following crayfish transfer or molting. Four species of crayfish (Faxonius virilis, F. illinoiensis, F. luteus, and F. punctimanus) were collected from several streams in Missouri and Illinois with different water microchemical signatures. A laboratory study was also conducted in which crayfish were transferred between waters with different Sr:Ca ratios to assess signature retention. Eye stalks were sectioned and analyzed using laser ablation-ICPMS. If eye stalks contain a microchemical record of crayfish environmental history as anticipated, this technique could potentially be used to reconstruct environmental history (e.g., origin, movement) of crayfishes in the wild and may also be useful for inferring sources of non-native species.

AUTHORS: Anna Raney, University of Missouri and Florida Fish and Wildlife Conservation Commission; Jacob Westhoff, U.S. Geological Survey, Missouri Cooperative Fish and Wildlife Research Unit, School of Natural Resources

ABSTRACT: Crayfish invasions are among the top global threats to native crayfish populations. In Missouri, cross-basin introductions have impacted multiple endemic species. The Saint Francis River crayfish (Faxonius quadruncus) and Big Creek crayfish (F. peruncus), endemic to the upper Saint Francis River (USFR) drainage in Missouri, are currently under threat of extinction due to introductions of Woodland Crayfish (F. hylas) from nearby drainages. Previous research has documented reduced abundances and range reductions for both native species in reaches invaded by Woodland Crayfish. However, the entire ranges of the native species have not been systematically sampled prior to this study, and past survey data documenting the invasion are over 15 years old. Management agencies need updated information to create an informed recovery plan for the two threatened species. Using a stratified random sampling design, we conducted a basin-wide distribution survey at 96 sites across the USFR drainage in 2022-2023. We incorporated presence-absence data from this survey with coarse-scale environmental variables into random forest, boosted regression, and spatial stream network models to create species distribution models for the two endemic species and the invasive Woodland Crayfish population. Additionally, we used targeted, intensive sampling to locate the leading edges of invasion in six streams. During these efforts, we discovered and mapped additional invasions in two major tributaries to the USFR drainage and documented a 1.4 km range expansion upstream from the 2009 leading edge in Orr Hollow Creek. The Woodland Crayfish is now present in most major tributaries on the left side of the basin as well as multiple locations in the mainstem river. Despite these range expansions, small impoundments at multiple locations appeared to harbor refuge populations of endemic crayfish based on survey data. Results from this study can be used to identify refugia for native species and locate barriers to further invasion.

AUTHORS: Eric R. Larson, University of Illinois; Caitlin C. Bloomer, University of Illinois; Don Eaton, Minnesota Department of Natural Resources; Denver Link, University of Minnesota; Reagan Oller, University of Illinois; Gretchen J.A. Hansen, University of Minnesota

ABSTRACT: The signal crayfish (Pacifastacus leniusculus), native to the Pacific Northwest of North America, is among the most invasive crayfish species globally, with populations widely established throughout Europe and Japan. Signal crayfish have never been detected from eastern North America, although previous research has identified the Upper Mississippi and Great Lakes watersheds as environmentally suitable for this invasive species. In October of 2023, ten signal crayfish individuals were trapped from a lake in west central Minnesota by a commercial bait harvester. We report here molecular surveillance of this possible, incipient signal crayfish invasion. Mitochondrial DNA (mtDNA) barcoding identified the collected crayfish as P. leniusculus, resembling non-native populations of the species known from the Lake Tahoe area of California and Nevada. We collected environmental DNA samples in summer and autumn of 2024, including through sampling kits distributed to lake association volunteers, and used quantitative PCR with a signal crayfish-species primer and probe assay to survey for evidence of this species in the original lake and neighboring freshwater ecosystems. Our preliminary results are relevant to management responses for this novel, potentially impactful invasive species in the Midwest.

AUTHORS:  Caden J. Jungbluth, Wisconsin Cooperative Fishery Research Unit, Molecular Conservation Genetics Lab; Amy L. Springer, Wisconsin Cooperative Fishery Research Unit, Molecular Conservation Genetics Lab; Stephen F. Spear, U.S. Geological Survey, Upper Midwest Environmental Sciences Center; Jared J. Homola, U.S. Geological Survey, Wisconsin Cooperative Fishery Research Unit

ABSTRACT:  Prevention of new invasive species often hinges on early detection and quick removal. Aquatic invasive species can be especially difficult to detect without extensive sampling due to habitat complexity and low initial abundances. Point-of-use biomolecule detection methods provide a possible solution via near real-time identification of DNA or other biological materials. Loop-mediated isothermal amplification (LAMP) provides a user-friendly approach for environmental (e)DNA detection that can be easily deployed in the field and yield diagnostic results within 40 minutes. Water can be filtered and the eDNA can be rapidly extracted with a Chelex resin and a portable heat block. We are developing a LAMP assay for red swamp crayfish (Procambarus clarkii) to enable identification of introductory pathways (e.g. the pet trade) and monitoring of the spread of established invasion sites. We generated 36 candidate primer sets that we evaluated in silico for red swamp crayfish specificity using the program BLAST to identify DNA sequence alignments to other species in the NCBI database. Sixteen species-specific candidate primer sets were then optimized for temperature of the LAMP reaction and brand of master mix. The optimal set of conditions were then used to further evaluate species-specificity through test amplifications of extracted DNA of related species (i.e. other Procambarus crayfish). Finally, we performed limit of detection testing down to a concentration of 1 copy/μL of target DNA, with consistent detections present at 100 copies/μL. Field collection of eDNA water samples from known infested waterbodies is underway to identify potential environmental inhibitors to our ability to detect red swamp crayfish presence. This tool could be implemented to detect—and possibly prevent—invasions through rapid field-based monitoring in areas where red swamp crayfish are a concern for introduction and spread.

AUTHORS: William Ota, Michigan State University; Aaron Sullivan, Michigan State University; Sarah Walker, Michigan State University; Brian Roth, Michigan State University

ABSTRACT: Red swamp crayfish (Procambarus clarkii) are the planet's most widely distributed invasive crayfish. They are a keystone species that can alter shoreline stability, macroinvertebrate communities, trophic interactions, water quality, and macrophytes in invaded ecosystems. This species became established in Michigan in 2017 within ponds and lakes, initiating an adaptive management plan to monitor, mitigate, and/or eradicate invasive populations. From 2021-2023, we tracked red swamp crayfish using radio telemetry in seven ponds in Southeast Michigan. Crayfish from 32 - 42 mm were tagged and tracked weekly for 5-6 months per individual over 2 years. A total of 235 crayfish were tagged and successfully tracked. Red swamp crayfish home range size was significantly affected by pond size (p

AUTHORS: Sarah Walker, Michigan State University; Brian Roth, Michigan State University; William Ota, Michigan State University; Colin Assenmacher, Michigan State University; Aaron Sullivan, Michigan State University

ABSTRACT: Red swamp crayfish (Procambarus clarkii) are global invaders that negatively affect ecosystems worldwide through bank erosion, trophic interactions, and competition. There is limited research about their habitat preferences in invaded areas inside North America or in lentic ecosystems. Our study evaluates habitat selectivity by red swamp crayfish in southeastern Michigan ponds where red swamp crayfish were first found in 2017. We used radio telemetry to track the movement and habitat characteristics of confirmed locations for 46 crayfish at 4 sites in June through September of 2022. We used remotely sensed habitat characteristics from 2022 NAIP aerial imagery and determined macrophyte cover, terrestrial vegetation cover, and shore use of each detection. We then analyzed these classifications for selectivity using Ivlev’s Electivity Index. We gave further context to these classifications and selectivity by analyzing them with our field habitat observations in a logistic regression. Our index indicated a strong avoidance of shore areas, an avoidance of no cover areas, and a non-selective use of macrophyte areas. We also demonstrated slightly more selectivity for areas with terrestrial cover in male I crayfish and less avoidance of terrestrial vegetation cover areas in ponds with less macrophytes. Field observed deep water habitat characteristics significantly (p-value

AUTHORS: Colin Assenmacher, Michigan State University; William Ota, Michigan State University; Kathleen Quebedeaux, Michigan Department of Natural Resources, Fisheries Division; Brian Roth, Michigan State University

ABSTRACT: Procambarus clarkii are the world’s most widespread invasive crayfish species established in Michigan since 2017. P.clarkii is of high concern due to their extensive burrowing behavior, which can damage human infrastructure through bank erosion and decreased bank stability. Our research aimed to investigate how soil and environmental characteristics of pond banks relate to P.clarkii burrow density. We measured key soil characteristics and potentially influential environmental variables from July to August of 2024 at 74 sites invaded by P.clarkii in Southeast Michigan to quantify which physical properties influence variations in burrow density within a waterbody and across multiple waterbodies. These sites were spread across 13 invaded waterbodies at three golf courses with varying burrow densities. Calculated burrow density was based on surveys conducted during the 2023 and 2024 field seasons and ranged from 0 to 8.42 burrows per square meter across sample sites and targeted waterbodies. We collected soil cores at each site to determine particle size, percent organic matter, penetration resistance, bulk density, and profile soil horizons. Bank slope, percent vegetation cover, and canopy cover were measured at each coring location. Preliminary analysis indicates regions of low burrow density are associated with steeper pond banks, particularly in the first 50 cm from the waterline. Mean vegetation cover ranged from 80 to 84% across burrow density classes and 35 to 99% over all sites. Penetration resistance was highest in areas of no burrow activity. We found less variation in soil bulk density and percent canopy cover in areas with high burrow density. This indicates that P.clarkii has preferred soil and environmental characteristics when burrowing. These findings help to identify the physical characteristics of high burrowing areas, which will be used to assist in the development of preventative management strategies against P.clarkii establishment and burrowing.

AUTHORS: Dalton Clayton, Department of Natural Resource Ecology and Management, Iowa State University;

Dr. Michael Moore, USGS Iowa Cooperative Fish and Wildlife Research Unit;

Dr. Michael Weber, Department of Natural Resource Ecology and Management, Iowa State University;



ABSTRACT: The introduction of aquatic invasive species can have negative ecological impacts on invaded ecosystems. Rusty Crayfish (Faxoninus rusticus), a species native to the Ohio River Basin, has extended its range into 28 US states, 3 Canadian provinces, and Western Europe. Rusty Crayfish can displace native crayfishes through competition, destabilize aquatic food webs, alter habitat through bioturbation and consumption of aquatic vegetation, and predate on fish eggs, presenting management challenges. Managers currently lack information on Rusty Crayfish distribution and habitat selection in shallow lakes and wetlands in the glaciated, agriculturally dominated landscapes found near the southern and western margins of their introduced range. Thus, our objective is to determine the habitat associations of Rusty Crayfish in Storm Lake, IA, to help understand Rusty Crayfish habitat selection in a novel habitat on their invasion front and its relationship to native crayfish habitat selection. To explore our objective, we deployed 708 baited minnow traps to sample crayfishes from June through August of 2023 and 2024, across three depths bins (~0-1.5m, 2-3m, 3+m). We also collected habitat data, including dissolved oxygen, pH, water temperature, dominant substrate, and presence of cobble and macrophytes at each trap location. We captured 85 invasive Rusty Crayfish and 47 native Virile Crayfish (Faxonius virlis). Rusty crayfish capture probability increased with cobble substrate, macrophytes, and earlier in the summer. Virile Crayfish capture probability was positively associated with macrophytes, they were more likely to be captured later in the summer and were more likely to captured in the medium and deep depth bins. Our results suggest that Rusty Crayfish and Virile Crayfish are not overlapping in habitat usage, which may suggest competition or niche partitioning.

AUTHORS: John F. Bieber, Loyola University Chicago; Ivàn Beck, Colorado College; Reuben Keller, Loyola University Chicago

ABSTRACT: The Chicago River represents a system that is at the edge of several invasion fronts; two of which are the invasive crayfish P.clarkii and F. rusticus. For years, these populations have remained in distinct areas of the Chicago River with little overlap, however; the factor(s) that limits their spread is not known. This project used complimentary field and lab experiments to investigate how stress levels (measured via hemolymph glucose) differed among the populations along a gradient in the Chicago River to inform where populations are in the river.

For the field study, we trapped crayfish in the Chicago River and immediately drew hemolymph from captured individuals. We hypothesized that stress would be the greatest for P.clarkii near Lake Michigan, where populations have not yet been found, and simultaneously would be the lowest for F.rusticus as they are established in Lake Michigan.

In the lab study, we collected P.clarkii along with water from the area where they were captured for holding in lab. Crayfish acclimated in lab before the tanks were filled with Lake Michigan water, and hemolymph was collected after a 90 min period. We hypothesized that P.clarkii populations near Lake Michigan would show lower relative stress to immersion in lake water compared to individuals further downstream and compared to individuals that were not flushed with lake water.

Interestingly, we found that individuals further downstream exhibited elevated glucose compared to individuals closer to Lake Michigan, and our lab studies showed that immersion in Lake Michigan water reduces stress compared to individuals without immersion. Collectively, our results suggest environmental contaminants may be driving the distribution of crayfish. Additionally, this work highlights the importance of considering physiology when managing an invading species.

AUTHORS: Cheyenne E. Stratton, Missouri Department of Conservation; Donald C. Behringer, University of Florida; Jamie Bojko, Teesside University; Margaret L. Taylor, University of Florida; Lindsey S. Reisinger, University of Florida

ABSTRACT: Parasites can affect their hosts’ ecological impacts by reducing host density and altering host traits such as behavioral traits. Most research focuses on density-mediated impacts, but trait-mediated impacts may be equally or more important as they control the interactions among organisms. Parasites can act as top-down forces in ecosystems and can trigger trophic cascades through density- or trait-mediated effects. We investigated how a parasite alters the well-documented ecological impacts of the invasive rusty crayfish (Faxonius rusticus). In 2019, we discovered a significant decline in the F. rusticus population in a Wisconsin lake corresponding to an outbreak of a microsporidian parasite, Nosema rusticus, which reduced infected crayfish activity levels. We hypothesized that infected crayfish, due to reduced activity and lethargy, would have lesser impacts on lower trophic levels including macrophytes and leaf litter (i.e., a trait-mediated trophic cascade). We also predicted that N. rusticus would increase crayfish mortality. To test this, we conducted a 4-week mesocosm experiment in which we varied parasite prevalence to test the trait-mediated indirect effects of the microsporidium on resource biomass and abundance. We also varied crayfish density to compare the strength of trait-mediated effects to a reduction in crayfish density. In support of our hypothesis, we found that less macrophytes and leaf litter were consumed in mesocosms with infected crayfish. Our results also suggest that this parasite is likely to cause density-mediated effects because crayfish infected with N. rusticus had higher mortality rates. These results suggest that parasites can mitigate the impacts of invasive species through both trait- and density-mediated trophic cascades.