Development and application of a UV attainment threshold for the prevention of warmwater aquatic invasive species

Abiotic factors are important regulators of biological invasion and a recent study in Lake Tahoe (CA/NV, USA) showed that ultraviolet radiation (UV) can play a role in mediating warmwater fish invasion. In this study we highlight field and laboratory experiments that indicate strong species related differences in UV-induced stress between native and non-native fish species inhabiting the nearshore environment in Lake Tahoe. We use this differential UV sensitivity to develop a UV Attainment Threshold (UVAT) that if realized could be used to reduce susceptibility to warmwater fish invasion in nearshore environments. The UVAT is a target value for water transparency based on: (1) incident solar UV exposure levels during peak spawning season, and (2) experimentally derived UV exposure levels lethal to larval warmwater fish. We suggest that this value can be easily measured, monitored, and targeted to reduce the establishment and spread of invasive fish species. We also discuss how the UVAT increases the cost effectiveness of invasive species management. This approach could be relevant for any aquatic invasive species that is UV sensitive and constrained to relatively shallow water environments by, e.g. requirements for warmer spawning temperatures. Because many aquatic systems are threatened by both invasive species and declining water transparency we suggest that this research could have important applications in many systems, particularly in colder more UV transparent waters found in regions such as western North America.