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Miami study finds key to reducing invasive fish in Lake Tahoe


Sand Harbor, a highly transparent site in Lake Tahoe, is used for fish incubation experiments (photo: Carrie Kissman).
A study by scientists and colleagues of Miami University’s Global Change Limnology Laboratory has demonstrated that maintaining high ultraviolet (UV) transparency in Lake Tahoe may be the key to reducing invasion of warm-water fish, such as bluegill, that threaten the native fish species in the lake.

The study, led by Andrew Tucker, doctoral student in zoology at Miami, is published in the March issue of the journal Ecology.

“The proliferation of invasive species is one of the most important anthropogenic impacts in freshwater systems,” researchers said.

Their study examined how underwater UV radiation (UVR) can regulate warm-water fish invasion. Changes in the UV transparency of the waters of Lake Tahoe, a sub-alpine lake renowned for its deep blue water and high transparency, is allowing warm-water fish species to invade and spread in the lake.

According to the study authors, the transparency of the lake has decreased over the past several decades, and a number of nonnative warm-water fish species have established populations in some portions of the lake.

“For example, invasive bluegill can only nest successfully when human disturbance such as shoreline development reduces UV transparency,” said Craig Williamson, Ohio Eminent Scholar in Ecosystem Ecology and head of the Global Change Limnology Lab. “This creates a UV refuge, an ‘invasion window’, which enables the bluegill to spawn in the surface waters where the temperatures are warm enough for survival of its embryos and larvae.”

The study showed that dissolved organic carbon (DOC) and chlorophyll were important regulators of variation in the UVR in nearshore areas of Lake Tahoe, explained Tucker, suggesting that regulating chlorophyll and DOC inputs could help stem future declines in UVR transparency in Lake Tahoe and in turn help reduce invasion of nonnative fish.

An understanding of the mechanisms underlying UVR transparency in Lake Tahoe could “enable us to better understand how regional and global environmental changes related to the factors that mediate UVR transparency could, in turn, affect habitat invasibility in the large, highly transparent lake,” Tucker said. “We suspect that this framework and our results could be directly relevant to other transparent lakes.”

The study, “Ultraviolet radiation affects invasibility of lake ecosystems by warm-water fish,” is published in Ecology 91(3). Authors are Tucker; Williamson; Kevin Rose, Miami doctoral student; James Oris, professor of zoology and associate dean for research and scholarship at Miami; Sandra Connelly (former Miami doctoral student), lecturer, Rochester Institute of Technology; Mark Olson, associate professor of biology, Franklin and Marshall College; and David Mitchell, professor of carcinogenesis, University of Texas MD Anderson Cancer Center.

Williamson’s research focuses on understanding the role of UV radiation in aquatic systems and the effects of climate change on lakes. For more information about Williamson’s global change limnology laboratory, including photos and video, go to

Related Media

Photos Photos  
Redside Dace Larva.tiff”: Redside dace, a native minnow species in Lake Tahoe, contain pigments to protect them from UV damage. The species is more tolerant of UV than invasive bluegill (photo: Andrew Tucker).
Bluegill larva.tiff”: Bluegill, an invasive species in Lake Tahoe, do not contain pigments to protect them UV damage (photo: Andrew Tucker).


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