The invasion window for warmwater fish in clearwater lakes: the role of ultraviolet radiation and temperature

Aim In clear, cold‐water lakes, ultraviolet radiation ( UV ) and temperature are two important stressors that may prevent the establishment of aquatic invasive species by inhibiting the survival of sensitive early life history stages. In this study, we develop a UV –temperature response model to predict the establishment potential of a warmwater fish, largemouth bass ( M icropterus salmoides ), in a large subalpine lake based on the ability of bass larvae to tolerate UV and temperature stress along a UV –temperature stress gradient. Location L ake T ahoe ( C alifornia/ N evada, USA ). Methods We compared the UV tolerance of largemouth bass larvae to that of the native redside minnow ( R ichardsonius egregius ) in outdoor UV exposure–response experiments. A UV –temperature response model for larval bass was developed that combined the experimentally derived UV exposure response from our outdoor experiments with a temperature response curve derived from the literature. We used the UV –temperature response model to predict reproductive success (i.e. larval survival) over the range of UV exposure and temperature conditions in nearshore Lake Tahoe. The model predictions were validated with in situ incubation experiments at nearshore locations. Results Non‐native bass were significantly less UV tolerant than native redside minnows. The UV –temperature response model predicted that larval bass survival varies seasonally, spatially and over depth gradients in nearshore L ake T ahoe and is constrained by UV and temperature conditions. In situ incubation experiments confirmed model predictions. Main conclusions Our findings provide important insights into the potential for species invasion in clear, cold‐water lakes that are experiencing significant changes in both temperature and transparency. The conceptual model and approach that we employ is a potentially powerful tool for exploring unanswered questions in invasion biology, including the role of alternate stable states in facilitating invasion and the potential for invasive species to promote ‘invasional meltdown’ through their impacts on water clarity and temperature.