AURORA (CBS) — Extreme heat and low water levels in area rivers are creating a dangerous combination.

As CBS 2’s Derrick Blakley reports, the long-term effects could spell big trouble.

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All along the Fox River, the story is the same: Low water levels caused by drought and heat are hampering recreational uses–and endangering fish and wildlife.

At the Montgomery dam in Aurora, rocks in the river that would normally be submerged are fully visible.

Fishermen are taking advantage by fishing from the rocks, but they know their prey are suffering.

“We find a lot of dead ones where we normally go,” said fisherman Mark Sendzimer. “We think they’re not getting enough oxygen and food in my mind.”

The river is currently four feet below where it normally flows, judging from the watermarks on a nearby bridge pylon.

Stifling heat, combined with less water flow, triggers more algae. That reduces nighttime oxygen for fish.

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“There have been fish die-offs both in the Fox River and the lakes in Lake County,” said fisheries biologist Leonard Dane.

Dane found a typical casualty of the river drought: dead clams.

“Either they were in that hole and the water drained out, or they were in shallower water and picked up by a raccoon, skunk or blue heron,” he said.

Farther downriver, at the Geneva Kayak Center in Yorkville, a lower river means less business. Parts of the river are too dangerous for rental kayaks and canoes.

A whitewater festival, scheduled for this weekend, has been canceled.

We didn’t want to deter anyone from the sport by getting hurt on exposed rocks that are now not underwater,” said Patrick Croke of the Geneva Kayak Center.

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The river’s woes won’t be solved quickly. Experts say it would take days and days of steady rain to bring water levels on the Fox even close to normal.