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Grass carp (Ctenopharyngodon idella), an invasive cyprinid within the Laurentian Great Lakes, is naturally reproducing in several Lake Erie tributaries, which has raised concerns of the species' spread throughout Lake Erie and the other Great Lakes. Knowledge of the recent invasion extent outside of the western basin of Lake Erie, particularly in eastern tributaries and nearshore waters, is limited. Understanding the invasion extent would improve the efficacy of ongoing coordinated multi-agency control efforts. Molecular tools, such as environmental DNA (eDNA), have shown promise for early detection of aquatic invasive species. In this study, water samples (N = 476) were collected for grass carp eDNA monthly between May and November in 2018 and 2019, at three sites in the Michigan waters of Lake Erie and the Detroit River. We fit Bayesian multi-scale occupancy models to determine differences in eDNA capture and detection probability among grass carp qPCR assays, sampling sites, and across time. To determine whether grass carp were physically present, and to validate eDNA samples, we quantified recent grass carp presence in sampled areas using an existing acoustic telemetry and field sampling framework. Our results indicate that grass carp eDNA capture probability differed among sites, but there was no difference among months. Positive grass carp eDNA detections were observed across multiple months at each site, with 69% of sitespecific sampling events testing positive for grass carp eDNA on at least one assay and replicate. The majority (65%) of weeks where positive eDNA sampling detections occurred also concurrently had one or more grass carp detected via acoustic telemetry 1-6 days prior. Our results highlight the potential utility of using eDNA to monitor the invasion extent of grass carp within the nearshore waters of Lake Erie. However, further evaluation of the factors that influence grass carp eDNA characteristics among sites within Lake Erie are needed to determine its efficacy for surveillance protocols by natural resource management agencies. [ABSTRACT FROM AUTHOR]

Management agencies are tasked with difficult decisions for conservation and management of natural resources. These decisions are difficult because of ecological and social uncertainties, the potential for multiple decision makers from multiple jurisdictions, and the need to account for the diverse values of stakeholders. Decision analysis provides a framework for accounting for these difficulties when making conservation and management decisions. We discuss the benefits of the application of decision analysis for these types of issues and provide insights from three case studies from the Laurentian Great Lakes. These case studies describe applications of decision analysis for decisions within an agency (management of double-crested cormorant), among agencies (response to invasive grass carp), and among agencies and stakeholders (sustainable fisheries harvest management). These case studies provide insight into the ways that decision analysis can be useful for conservation and management of natural resources, but we also highlight future needs for decision making for these resources. In particular, applications of decision analysis for conservation and management would benefit from enhanced integration of both ecological and social science, inclusion of a broader base of stakeholders and rightsholders, and better educational opportunities surrounding decision analysis for undergraduates and graduate students of natural resources management programs. Specific lessons from our experiences include the importance of establishing trust and transparency early through the formation of a working group, collaboratively defining objectives and evaluating uncertainties, risks, and tradeoffs, and implementing participatory modeling processes with an independent facilitator with appropriate quantitative skills. History: This paper has been accepted for the Decision Analysis Special Issue on Decision Analysis to Advance Environmental Sustainability. Funding: This study was supported by Great Lakes Restoration Initiative funding provided to the Michigan Department of Natural Resources [Grant F16AP01094] from the U.S. Fish and Wildlife Service and sub-awarded to Michigan State University. [ABSTRACT FROM AUTHOR]

Trapping and removing invasive crayfish is one of the most common forms of control, however gear-specific biases can limit effectiveness of such methods. We evaluated five trapping gears (Gee's minnow traps [GMT], pyramid traps [PYR], artificial refuge traps [ART], additional partition refuge traps [APART], and juvenile traps [JUV]) for their effectiveness in a Procambarus clarkii Girard, 1852 (red swamp crayfish) removal effort among four Southern Michigan ponds between May and October 2019. Our objectives were 1) determine which gear(s) produce the highest catch per unit effort (CPUE); 2) assess gears for body size and sex biases; 3) ascertain the degree of seasonality in gear-specific catches and biases. We found that baited GMT and PYR traps substantially outperformed the ART, APART, and JUV traps with respect to CPUE. However, catches of refuge-style traps trended positively over the season. Body size biases were prevalent, with GMT and PYR traps consistently recording individuals > 30 mm carapace length. The ART and APART traps caught relatively smaller individuals but trended towards capturing larger individuals later in the season. We observed no sex biases or biases between Form 1 and Form 2 males among the gears. Our findings support employing multiple gears for crayfish removals but demonstrated that baited traps can remove more crayfish than unbaited traps (on a CPUE basis) and both can capture body size trends by accounting for the timing of capture. Further, the lack of sex bias suggests any of these commonly used traps can be used to broadly sample females or male reproductive forms. Based on our results and recommendations, the Michigan adaptive response strategy has adopted a combination GMT-APART strategy to maximize CPUE while also targeting a wide range of crayfish sizes. [ABSTRACT FROM AUTHOR]

Aim: Our goal was to use eDNA metabarcoding to characterize fish community diversity, detect aquatic invasive species (AIS) and assess how measures of community (or AIS) diversity are influenced by lake physical and environmental covariates, measures of hydrological connectivity and human accessibility. Location: Michigan, USA. Methods: eDNA samples collected from 22 lakes were sequenced using two mitochondrial gene regions (12S and 16S rRNA). Metabarcoding data were compared to traditional fisheries survey data for a subset of lakes, and data from all 22 lakes were combined with environmental information to identify significant associations with community diversity and AIS relative abundance. Results: Occupancy modelling indicated that detection probabilities were generally higher with eDNA than traditional fisheries gear. Measures of connectivity with upstream aquatic habitats were positively associated with both AIS relative abundance and fish species diversity. We also demonstrate the use of spatial interpolation methods to map distributions of species diversity and AIS relative abundance within lakes. Main conclusions: eDNA metabarcoding methods provided information on the composition and diversity of fish assemblages and the presence of AIS in freshwater lakes that varied greatly in drainage connectivity and anthropogenic development. Our case study identified associations between environmental covariates and fish diversity or AIS relative abundance across lakes. This information is of particular importance given increasing anthropogenic disturbance, invasive species spread and associated declines in aquatic biodiversity. Incorporating eDNA metabarcoding as a supplement to traditional fisheries surveys will permit managers to identify greater numbers of taxa, including early detection of AIS, with less field effort and fish mortality. Further, eDNA methods may more accurately identify physical and biological features that correlate with diversity and abundance and allow agencies to more effectively direct AIS management activities. [ABSTRACT FROM AUTHOR]