Comparable temperature-dependent predatory impacts of two invasive crayfish, Pontastacus leptodactylus and Pacifastacus leniusculus

Abstract Narrow-clawed crayfish ( Pontastacus leptodactylus ) are an emergent invasive species in the UK and Europe, with limited data regarding their potential ecological impacts. Predicting ecological impact in current and future climate conditions is essential to inform policy and management actions. Therefore, we determined temperature-dependent predation of P. leptodactylus compared to the well-studied Signal crayfish ( Pacifastacus leniusculus ) on native prey Gammarus pulex , along a seasonal gradient (9℃, 12℃, 17℃, and 22℃) using functional response. P. leniusculus are wide-spread global invaders and are included as a well-known damaging invader reference species. Both species exerted strong predatory impact on G. pulex at all temperatures, however, when field abundance was considered P. leptodactylus have a higher relative impact driven by higher field abundance for our sampled populations. P. leptodactylus relative impact potential will increase with temperature up to ~ 17℃ and was exacerbated when prey ( G. pulex ) response to temperature change was incorporated, due to decreased prey abundance at higher temperatures. Our findings indicate P. leptodactylus overlooked potential as a damaging invader, both currently and in the future, and highlight the importance of considering resource and consumer response to changing climate in impact assessments. We recommend that stakeholders consider renewed management appraisals for populations of P. leptodactylus to reduce spread and population size to minimise ecological harm.