Report: Warming Waters Will Harm Freshwater Fish and Thousands of Jobs

Habitats that meet the climate requirements for freshwater fish will be cut in half by 2100.

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Habitats that meet the climate requirements for freshwater fish will be cut in half by 2100.

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Warmer water brought on by climate change has begun threatening freshwater fish that thrive in cooler environments, and may cut the number of suitable habitats in half by the end of the century, according to a new report from the National Wildlife Federation.

[READ: Ocean Acidification May Amplify Global Warming]

The advocacy group released a report on Thursday examining the effects hotter summers and shorter, warmer winters will have on freshwater fish and the thousands of jobs that depend on them. Unless society does more to curb carbon pollution and invest in clean energy, the report says, the decline in habitat for cold-water fish will be accompanied by an annual decline of as much as $6.4 billion in lost revenue from outdoor recreation and fishing jobs.

"More extreme heat and drought are already causing big problems for fish that rely on cold, clean water – and the warming we've seen so far is just the tip of the iceberg," Doug Inkley, a National Wildlife Federation senior scientist and co-author of the study, said in a released statement.

As extreme weather conditions like heat waves, droughts and wildfires become more common, the lakes, rivers and streams that are home to certain game fish also become warmer – and less habitable – for the species that need cold water to survive.

"As water temperatures move away from a species' optimal temperature range, growth and survival rates decline, reproductive success declines and the fish become more susceptible to pollution, parasites, and disease," the report says.

The warmer waters can also open the door for more warm-water species to move in.

[SLIDESHOW: 10 Animals Threatened by Global Warming]

"Temperature increases of even a few degrees can have dramatic impacts, harming iconic game fish ... and giving a leg up to destructive invaders like sea lamprey," said co-author Jack Williams, in a released statement. "We need to manage our water resources in a way that ensures that both people and fish have the clean, cool, and abundant water they need to survive."

And as cold-water fish are either killed or forced out of increasingly warming waters, there becomes less opportunity for the $26 billion fishing business known as angling, according to the report. A decline in angling could cause destination fishing locations to close, with "major economic implications," the report says. Fishing opportunities in Yellowstone National Park alone, for example, can generate between $67.5 million and $385 million annually.

"Guides, outfitters, fly shops, and rural communities depend on these waters to feed their families and pay the bills," said Land Tawney, executive director of the conservationist group Backcountry Hunters & Anglers, in the report.

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