Reconstructing Routes of Inland Invasion by the Rusty Crayfish, Orconectes rusticus, in Michigan.
The rusty crayfish, Orconectes rusticus, is native to the Ohio River basin, but has established nonindigenous populations throughout the United States. The species is of particular concern in the Great Lakes Region, where it has undergone a major range expansion during the 20th century. A strong competitor with native crayfish, O. rusticus has the potential to cause cascading trophic effects on food webs. O. rusticus spread has likely been facilitated by a combination of human-mediated and natural processes. Bait bucket movements, the aquarium trade, and intentional introductions for macrophyte control are all potential vectors of dispersal. We used population genomic data and coalescent modeling to reconstruct O. rusticus invasion dynamics in three inland river systems in Michigan (the Saginaw, Cheboygan, and Au Sable drainages). Results from our analysis provide information on likely sources for inland invasions, estimates of the size of founding populations, and the timing of establishment in these systems. The use of population genomic data to inform demographic models provides a flexible and powerful approach for reconstructing invasion histories in species like O. rusticus. Furthermore, understanding invasion histories then provides insight to resource managers on mechanisms to prevent future invaders with similar invasion potential.
Contact: Nicholas Sard, Michigan State University, Fish and Wildlife Department
Control of Invasive Rusty Crayfish on Lake Michigan Spawning Reefs.
Invasive rusty crayfish can hinder efforts to rehabilitate native fish populations, primarily through egg predation. However, there is not an effective control strategy for rusty crayfish in the Great Lakes. Rusty crayfish are one of the dominant egg predators on spawning reefs in northern Lake Michigan. Although eradication of rusty crayfish in the Great Lakes is unlikely, impacts on egg survival can be mitigated when crayfish population size is reduced. Innovative, temporary crayfish barriers have successfully limited Rusty crayfish movement in the laboratory. We will deploy these barriers on critical native fish spawning reefs to suppress recolonization rusty crayfish while concurrently removing Rusty crayfish from surrounding habitat. We are testing whether this integrated control can provide short term protection for vulnerable life stages of native lake trout, cisco, and lake whitefish.
Contact: Andrew Tucker, The Nature Conservancy
Predicting the Potential Distribution of the Invasive Red Swamp Crayfish in the Great Lakes.
We developed predictive models to anticipate the potential distribution of the invasive red swamp crayfish Procambarus clarkii in the Great Lakes. We combined a database of crayfish species occurrences with GIS data layers to model habitats vulnerable to invasion by P. clarkii using both a machine-learning algorithm and physiological information for this species. We developed a boosted regression tree model of all suitable crayfish habitat across the Great Lakes, then constrained this habitat to areas anticipated to be suitable for P. clarkii based on its known physiology: Procambarus clarkii requires a minimum temperature of 15 C for both copulation and oviposition, with peak reproduction occurring at temperatures of 20-23 C. We identified shallow, nearshore waters of all Great Lakes except Superior as suitable for P. clarkii. We predict where P. clarkii is likely to establish in this important freshwater ecosystem, which can be used to identify and prioritize areas where education and outreach should seek to prevent new introductions of this crayfish, and where surveillance and monitoring should seek to identify newly established populations.
Contact: Eric Larson, University of Illinois
Coordinated Response Efforts to the Red Swamp Crayfish Invasion in Michigan.
Red swamp crayfish are one of the most widespread invasive species worldwide, including the midwestern US. As such, many natural resource agencies throughout the Great Lakes Basin have been active with implementing measures to prevent the introduction and spread of red swamp crayfish. In Michigan, for example, it is illegal to possess red swamp crayfish live regardless of the purpose. Despite taking preventive measures, red swamp crayfish were detected and infestations were confirmed in July 2017 in multiple locations throughout the Lower Peninsula of Michigan. The response efforts, led by the MDNR and Michigan State University, are multifaceted and collaborative. Together, we crafted a response plan that will: 1) Implement and evaluate an early detection monitoring strategy in high-risk areas; 2) Implement and evaluate control measures; 3) Determine the distribution of red swamp crayfish in Michigan; 4) Determine the source and relatedness of red swamp crayfish infestations; 5) Collect baseline biological and physical information. Response actions have benefited from great collaboration, but have not always been seamless. We describe lessons learned that can be applied to future responses for red swamp crayfish in Michigan, but also that can be applied to response activities for other invasive species.
Contact: Brian Roth, Michigan State University
Potential Chemical Control for Invasive Crayfish Infestations.
Few control tools are available to managers who experience infestations of invasive crayfish. Cypermethrin and carbon dioxide (CO2) are being investigated as potential chemicals to be used with integrated pest management programs for invasive crayfish. Adult red swamp crayfish (RSC; Procambarus clarkii) were exposed in the laboratory to either CO2or cypermethrin. A shuttle box was used to determine if crayfish avoided inhabiting an area with CO2-enriched water. Test temperatures were 10 and 24 °C and the response was tested in lit (>180 lux) and dim (<50 lux) conditions. Preliminary results from the cold-water trials suggest that RSC spent about equal time on the right and left sides of the shuttle box during baseline, but avoided the chamber containing CO2-enriched water. Crayfish avoided chambers with a CO2 concentration of about 114 mg/L. Results will be presented for standard acute toxicity tests that are currently being conducted to determine lethal concentrations of cypermethrin in warm and cold water. Based on results of these studies, pilot field trials will be conducted in <0.4 hectare research ponds (CO2), artificial burrows (cypermethrin) and retention basins (cypermethrin) in Michigan and Alabama in summer and fall 2018.
Contact: Ann Allert, U.S. Geological Survey