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Researchers Find Salmon Vital To Biodiversity in California

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(Sacramento, CA)
Thursday, October 27, 2011
(click on images for larger view)
In a rowboat on Butte Creek near Chico, I'm about to plunge into chilly water to snorkel with spawning salmon. I'm accompanied by someone who has done this a lot, U.C Davis fish biologist Lisa Thompson.

THOMPSON: "When you see them in the water, they're in their environment. Its three dimensional, they can swim so well. We may startle them, but they really have the upper hand. We are just in there with our masks and snorkels trying to get by."

As I try to navigate the rushing water in a puffy diving suit I get glimpses of these magnificent fish.  It's clear Thompson is right. The salmon do have the upper hand here, for now.  But Thompson says climate change may determine the ultimate fate of these fish.

She helped lead a study by UC Davis and the Stockholm Environment Institute which found that climate change, is likely  to warm Butte Creek by more than two degrees.
Water that warm is lethal to salmon. Under those conditions, the roughly 5,000 salmon that typically spawn here would die before they ever made it upstream.
The study looked beyond the fish as well, to understand what might be the effect of  a salmon  extinction on the overall biodiversity of the area around the creek.

UC Davis Biologist Melanie Truan explains.

1027JR SALMONII BEARCUBTRUAN: "One of the primary research goals of this project was to look at tipping points. And if the salmon disappear would that create a tipping point, a threshold at which the ecosystem would be irrevocably changed and never recover or be a different system then it is today."

When we think of salmon in a stream  a classic image comes to mind. Bears plucking the salmon out of the water. Truan wanted to understand how important the salmon might actually be to the  bears. For clues she turned to a tree near the stream where bears like to scratch themselves.  

1027JR Hair on TreeTRUAN: "We pulled about two or three years worth of hair off this tree and analyzed it for stable isotopes. Marine and fresh water isotope ratios. And determined that during the spawning season, the bears, at least the ones that we sampled,  have about  forty percent of their body tissues is derived from marine sources."

"Marine sources" means the ocean. Because salmon don't eat on their way up stream  after leaving the sea, the nutrients in their system are the ones they have brought with them from the salt water. 
The study also sought to determine what other species might be dependent on salmon. For that answer, Truan  turned to another piece of technology.

1027JR Stealth CameraTRUAN: "We set up remote cameras. They're digital cameras that are motion activated and they work both at night and during the day, they have infrared flashes so they take pictures at night.  So we have daytime nighttime."

"We have about forty to fifty photographs of bears and most of them unique bears, We're not seeing the same ones over and over again. So there must be a pretty substantial number of bears coming down."

Truan expected to see the bears and  creatures like turkey vultures. But what surprised her was the range of other species her cameras captured dining on salmon; Skunks, deer, small rodents and most surprisingly ringtail cat

1027JR SALMONII RINGTAILTruan:. "In fact they didn't even know that there were ring tail cats here in the valley until the photos showed the ringtail eating the salmon. So it was kind of a way to show that there were ring tales here."

Truan's photos are fun and fascinating, but she says the implications of research suggesting the spring run Chinook might go extinct, are sobering.

TRUAN: The bears would lose forty percent of their nutrient source this time of year. And studies have show that bears that consume  salmon go into hibernation in better condition, they have more cubs, sort of a nutrient boost to them. And clearly it probably has that effect on other organisms as well.

With all the creatures we now know depend on salmon for their nutrition, the researchers say it becomes more urgent to manage Butte Creek in a way that keeps it  cold, free flowing and salmon-friendly.


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