An evaluation of research on crayfish invasion pathways in the Great Lakes region

Invasive crayfish species have become a significant ecological concern in the Laurentian Great Lakes Basin, adversely affecting native biodiversity and ecosystem functions. This review synthesizes 24 years of peer-reviewed literature to elucidate crayfish invasion pathways in the Great Lakes. Over this period, the literature has highlighted natural dispersal and bait release as dominant invasion pathways for crayfish in this region, accounting for over half of reported cases. Emerging pathways, including the retail trade and accidental releases, underscore the evolving nature of invasion pathways. Research efforts have concentrated geographically in Wisconsin, Michigan, and Illinois, with limited studies addressing other Great Lakes states, revealing significant gaps to understand the full scope of invasion pathways. This review identified rusty crayfish ( Faxonius rusticus ) and red swamp crayfish ( Procambarus clarkii ) as the focus of much of this work while other species were not as prevalent in introduction pathways research. While historical studies have provided foundational insights, reliance on historical pathways data has limited our understanding of newer mechanisms, such as aquarium trade releases and species misidentifications in retail markets. To address these challenges, we recommend broadening the research focus of future work to encompass underrepresented regions and species, enhancing collaborative efforts among stakeholders, and improving regulatory oversight of retail trade practices. Public engagement is a critical component for mitigating the impacts of invasive crayfish through responsible consumerism and pet ownership practices. This comprehensive synthesis aims to inform future research efforts, policy development and surveillance initiatives, foster coordinated responses to invasive species threats, and contribute to the preservation of the Great Lakes Basin’s ecological integrity.