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Wednesday, 10 May 2006 00:00

Have you seen this fish? Researchers probe new species called the sicklefin redhorse

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When Dr. Robert Jenkins proclaimed in 1992 that he had discovered a new fish species in the Hiwasee and Little Tennessee rivers, it likely caused a stir among ichthyologists who found their library of fish field guides suddenly out of date and a handful of museum curators who scrambled to correct their collections.

His announcement that a sixth species of redhorse had been lurking undetected in Western North Carolina’s rivers met little skepticism from colleagues, however.

“They believed me because I know what I’m doing,” said Jenkins, a researcher at Roanoke College in Virginia. “I’m Mr. Redhorse.”

Jenkins, who’s devoted his life’s work to the redhorse, noted that this variety was “anatomically distinct,” with a sickle-shaped fin on its back. Jenkins promptly dubbed it the sicklefin redhorse. DNA tests later confirmed that the sicklefin is indeed its own species.

There are several hypothesis for why the sicklefin went undetected by science for so long. But primarily, someone with Jenkins’ passion for the redhorse simply hadn’t come along yet.

“The sicklefin is lucky to have him,” North Carolina State University graduate student Scott Favrot said.

It’s doubtful that the sicklefin redhorse in the Valley River in Cherokee County see it that way, however. Favrot has just launched a two-year study on a select group of sicklefin redhorse with the aim of learning more about this new and elusive species.

In mid-March, 25 unlucky sicklefin were shocked to the surface, scooped out of the river, sedated, slit open — albeit with scalpels sanitized between fish — implanted with a transmitter and dumped back in the river. If that ordeal wasn’t bad enough, a graduate student in a canoe with lots of sticks and rods has taken a supreme interest in the sicklefin, poking and prodding their favorite foraging spots twice a week for the past month now.

While Favrot claims to be an overworked, underpaid grad student, his job consists of floating down the Valley River in a canoe between Andrews and Murphy with a radio antennae picking up the signals of the sicklefin redhorse implanted with the devices. Each time he detects a sicklefin signal, Jenkins promptly pulls his canoe to shore.

“You don’t want to run up on them and spook them,” Favrot said. “You want habitat data from the spot where they were before they were disturbed.” Favrot scrambles about on the bank triangulating the sicklefin’s exact location, reboards the canoe and paddles over to examine the spot.

He measures the depth, samples dissolved oxygen levels, takes the water temperature, calculates the velocity of water, takes GPS readings, measures the distance to the bank, notes any nearby tree trunks or boulders and describes the composition of the river bottom.

“This is the first movement study of the sicklefin redhorse ever,” said Mark Cantrell, a U.S. Fish and Wildlife biologist who was integral in securing funding for the study. “Tracking their day-to-day movements promises to yield a lot of good information.”

The sicklefin are not exactly bastions of family values. Last week, Favrot was privy to one of the first sightings this year of the sicklefin’s unique mating habits. What appeared to be two sicklefin redhorse females were surrounded by about eight males. The sicklefin redhorse spawn in a trio at the least — one female and two males — but often prefer to spawn as a gang, taking no chances that the eggs aren’t fertilized by the time they’re through.

If the process wasn’t complex enough, the sicklefin swim upstream — sometimes great distances — to spawn each year. Favrot’s research will hopefully uncover what triggers the sicklefin to move.

“What are the environmental cues to spawn, when does it spawn, where does it spawn — all the w’s,” Favrot said.

Favrot’s advisor, Dr. Tom Kwak, called spawning the “weak link” in the sicklefin’s survival.

“That’s the bottle neck in their life history, ” said Kwak, the unit leader of U.S. Geological Survey Fish and Wildlife Research Unit at NCSU.

Cantrell predicts rising water temperature and the length of daylight both play a role. But whatever it is, it’s happening right now.

“They were down here by Murphy and boom — within a couple of weeks they had moved 15 miles upstream to the spawning beds,” said Cantrell.

Tracking the sicklefin up and down the Valley River has proved challenging for Favrot, a self-described amateur in the canoe before his research project started. It’s hard to say whether he’s getting better, since he and his research assistant, Hannah Shively, have yet to make a trip down river without capsizing. Unfortunately, the first such mishap cost the team their radio telemetry device. But they have since improved their strategy for dealing with the feisty river. Bungee cords and Rubbermaid tote bins are central to the strategy.

 

Under the radar

The elusive sicklefin shares its turf with five other species of redhorse, namely the silver, black, golden, small mouth and river redhorse.

“This is a very unique place with this many distinct species of redhorse still intact and living together in the same river,” Cantrell said.

For more than a century, it appears the sicklefin was posing as one of these other five.

“People had looked at them before,” Jenkins said. “Some specimens were even in museums, but they were misidentified.”

But in reality, the sicklefin doesn’t look like the other redhorses anymore than a basset hound looks like a dachshund — cursory similarities but notable differences nonetheless.

“It is a pretty distinct looking fish,” said Kwak. “I think it was just overlooked by the ichthyologists because it is so restricted in its distribution.”

Local fishermen probably knew there was a redhorse with a curvy fin on its back, but weren’t much help passing the word to the ichthyologists.

“To most people, any sucker is a sucker. They don’t distinguish between the species,” Jenkins said. The term sucker refers to a type of fish that spends the day snuffing along the river bottom. They’re not only hard to catch, but have lots of small bones that are irritating to anyone who decides to eat one.

 

Back in time

How one river ended up with six different species of redhorse who all bump into each other regularly as they go about their daily routine requires a long walk back in time, possibly millions of years.

One likely scenario is that the ancestors of the sicklefin redhorse got isolated from the rest of their species — possibly by a waterfall or by a flood that created a new river channel.

“Once a population is isolated, it can have mutations and genetic natural selection for those mutations,” Jenkins said. The group of isolated fish evolved into a new species that no longer resembled the fish they got separated from.

The sicklefin’s sickle fin makes it a particularly streamlined fish.

Although a couple of Favrot’s redhorse tend toward the lazy side and lounge about in slower water, the rest gravitate toward swifter water.

“It’s less taxing for a sicklefin to be in a habitat like this than other fish,” Favrot said of the swift water habitat.

Whether they adapted the fin in response to suddenly swifter water or whether they plotted the fin as a route to a less crowded area of the river, it’s proven advantageous regardless.

“They can exploit the food and spawning habitats of swifter water better that the other redhorse,” Cantrell said.

 

Saving the sicklefin

A true river groupie, Cantrell wears a black leather belt studded with small silver trout.

“There’s not a market yet for a sicklefin redhorse belt, but if they ever make one, I’ll buy it,” Cantrell said.

Cantrell’s belt dilemma captures the problem faced by researchers who wanted to study the sicklefin.

“For years there wasn’t money to study them because they weren’t considered a game fish,” Kwak said.

This study on the Valley River is the first since Jenkins identified the sicklefin as its own species 14 years ago. It is being funded by the U.S. Fish and Wildlife Service, the U.S. Geological Survey and the World Wildlife Fund.

“It is such an important project,” said Kwak. “We talk about all the fungi and plants and insects in the rainforests of South America that have been discovered and here’s a fish that gets up to seven pounds in our backyard that hasn’t been described. That’s phenomenonal to me, and we are excited to learn all we can about the fish and ensure its long-term survival.”

The sicklefin is only found in the Valley River, a small section of the Little Tennessee, and an even smaller section of the Oconaluftee and Tuckasegee rivers.

“It’s geographic range is tiny. It’s minute,” Cantrell said. “This is the stronghold of the sicklefin redhorse in the world.”

Such a small territory makes it particularly vulnerable to extinction.

“If anything happens to this river, there goes a major part of this species’ only habitat,” Favrot said.

Jenkins hypothesizes the sicklefin evolved here and largely stayed put, but that it’s territory has probably shrunk somewhat. Dams that keep the sicklefin from spawning likely played a hand in reducing its range. Sedimentation is now one of the biggest threats, since it covers the river bottom where the sicklefin finds its food.

Favrot’s already started to find patterns in where the sicklefin hang out. They like swifter, shallower water flowing over a rocky riverbed free of silt. He can also see how much they move from one day to the next.

“We are also intersted in how habitat changes might affect them so we can avoid making those mistakes,” Kwak said. “The fish is performing some kind of balancing ecological function in this system and we may not necessarily understand it, but if the fish is lost it could become apparent.”

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