Fish Live After Niagara Falls, but Don't Survive Yosemite

Q: I visited Yosemite National Park in California recently where I saw rivers that poured over cliffs, becoming thousand-foot-tall thundering waterfalls before continuing on their courses at the bottoms of valleys. Do fish get carried over these waterfalls? Or do they know to stay away from the edge???
Juliet, Toronto, Canada

Q: Do fish go over Niagara Falls? Do they live?

A: It's a cold November day on the Niagara River, barely above freezing. A steady rain beats upon the rushing water. A rainbow trout stirs deep in the river, her red band dark in the depths. Fierce river currents push her to cliff's edge, and she falls to a pool 170 feet (50 m) below. Luckily it's Horseshoe (where 90% of the water falls). No rocks greet her, only a pool whose bottom is 150 feet down. She plunges into the air-bubble-cushioned pool, bobs up and swims slowly away, stunned but alive.

About 90% of fish swept over Niagara Falls survive, estimates Niagara-River expert Wes Hill, who pulled about 400 human bodies from the river over the course of his 76-year life. Fish bodies, unlike humans, are built to withstand great underwater pressures, so such a fall is survivable, for a fish.

Yosemite Falls, however, is far greater — one of the highest in the world. Fish don't make it down alive. Yosemite Creek cascades over a 2400-foot (730-m) cliff to form Yosemite Falls. The water descends in three stages:

1430-foot (425-m) Upper Falls
675-foot (205-m) Cascades (a series of smaller plunges)
320-foot (97-m) Lower Falls

"I presume fish avoid the falls, but sometimes go over," emails Daniel R. Dawson, director of the Sierra Nevada Aquatic Research Laboratory in response to my question, "but I really don't know the answer."

"I have seen fish in Yosemite Creek, above the falls," says photographer Dave Fant of Log Cabin Wilderness Camp, a Boy Scout camp that offers backpacking trips through Yosemite's Wilderness Area. Dave has never actually seen any fish go over the falls, but thinks they well could. "If fish were to go over, they would surely die," he emails. Water thundering over Upper Falls crashes into a rock shelf that "would instantly kill any fish." If any fish "miraculously" survived the first big fall, the jagged rocks at the base of Lower Falls would end its life. No fish could survive both falls.

Further Reading:

Log Cabin Wilderness Camp

Yosemite Fall Facts

World waterfalls database

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(Answered Nov. 12, 2007)