Need more proof of global warming? Try finding a particular fish in a Wisconsin lake by the year 2100.

The cisco, a cold-water and deep-dwelling forage fish, was the subject of a study conducted by the University of Wisconsin-Madison and the Wisconsin Department of Natural Resources to gauge how warm lakes in the state were becoming and the rise in the population of invasive aquatic species.

"By 2100, 30 to 70 percent of cisco populations could be extirpated in Wisconsin due to climate change," said Sapna Sharma, a researcher at the UW-Madison Center for Limnology and the lead author of the study.

"Cisco are much more at risk due to climate change rather than interactions with exotic species."

Cisco are found in about 170 inland lakes in Wisconsin, and were once the foundation for fisheries in the state until its population began to decline due to overfishing and invasive species like the alewife, rainbow smelt and sea lamprey.

"The range expansion of invasive species with climate change could be a problem," Sharma said.

"It could change the composition of species we're familiar with in Wisconsin,” Sharma said. “It may be that just a few species dominate. The species composition wouldn't just be different, there could also be less biodiversity."

Ultimately, cisco are valuable barometers of changes in Wisconsin, for better or for worse.

"Cisco aren't the most important socioeconomic species out there, but they are a good indicator of water quality."

The study used future climate scenarios to map the potential decline in cisco.

The study was published in PloS ONE, on August 10, 2011.