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Sometimes an environmental issue needs a face - even an unattractive one - so that people can relate to it. Ecologists have made the sucker-mouthed, plate-covered Gulf sturgeon the sentinel species of the Suwannee River.
"Sentinel species implies something like a canary in the coalmine," Randy Edwards of the University of South Florida told LiveScience. "If you can keep sturgeon in the river, you have protected the river."
The sturgeons make their presence known by jumping six feet out of the water on summer evenings. With adults reaching eight feet long and 200 pounds, they make quite a splash. Edwards and is colleagues once counted more than 1,000 jumps from various sturgeon on a single day.
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Ancient creatures
From the fossil record, sturgeons have been traced back 200 million years.
"They found a plan that worked," Edwards said, "and they are sticking with it." The fish seem strangely dinosaur-like with their sharp, bony plates - called scutes - that serve in place of scales.
But the reason that Gulf sturgeons are so indicative of the health of the Suwannee is that they utilize almost the entire length of the river by returning to their birthplaces to mate and lay eggs.
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The sturgeon spawning grounds on the Suwannee are 140 miles (220 kilometers) upstream from the mouth. Unlike salmon, which die after spawning in freshwater, sturgeons - which can live to be 25 years old - swim back down the river to winter in the Gulf.
"Sturgeons are probably migrating out of the Suwannee right as we speak," Edwards said last week.
The summer fast
The adults need to get back to the Gulf because they typically do not eat while they are in the river - losing somewhere around 20 percent of their body mass.
Because of this extended fast, Edwards wonders why the fish would waste energy jumping out of the water so much. He guesses that the breaching is a form of communication in the coffee-colored waters of the Suwannee.
When they do eat, Gulf sturgeons are bottom feeders. They have barbles - catfish-like whiskers - that help them search sediments for prey, which they vacuum up with their sucker mouths.
Despite their long history, Gulf sturgeons were listed as threatened under the Endangered Species Act in 1991. This put a stop to the commercial fishing that had cut into their numbers, but the fish have been slow to recover.
Proactive approach
Edwards said that there are currently about 8,000 Gulf sturgeons that make the Suwannee their summer home, with far fewer numbers in the six other major U.S. rivers that have spawning grounds.
The Suwannee River, which flows from the Okefenokee Swamp in southeastern Georgia down through northern Florida, is one of the most pristine rivers in the country - with no dams for returning sturgeons to contend with.
"The Suwannee is a fairly healthy ecosystem," Edwards said. There are concerns about high nitrate concentrations and threats from cities to siphon off more freshwater, but Edwards said that calling the Gulf sturgeon a sentinel species was a way to be "proactive" and not wait until bigger problems developed.
"If we can keep the river the way it is," he said, "we would be happy."
Michael Schirber began writing for LiveScience in 2004 when both he and the site were just getting started. He's covered a wide range of topics for LiveScience from the origin of life to the physics of Nascar driving, and he authored a long series of articles about environmental technology. Over the years, he has also written for Science, Physics World, andNew Scientist. More details on his website.
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