05-26-2004, 07:05 PM
Wednesday, May 26, 2004 - 12:00 AM |
Scientists tagging carp to keep track of population
Caleb Warnock THE DAILY HERALD
For the dozen or so people who spent Tuesday attempting to wrangle thousands of carp on Utah Lake, the most unforgiving -- and unforgettable -- part of capturing the fish and inserting a plastic tag into the dorsal fin of each with a needle gun was not the blood, nor the cold or the fatigue, but the smell.
"Their gear is saturated with fish slime," said Chris Keleher, of the June Sucker Recovery Implementation Program, about the scientists and volunteers who will spend the next 10 days tagging carp in Utah Lake in an effort to estimate the species' population. "It's a stinky business."
Carp are devastating Utah Lake, Keleher said. Averaging about 2 feet in length and weighing 8.7 pounds, the fish have reduced the lake bed to mud in the 123 years since they were introduced by settlers. They strip vegetation away from the edge of the lake, making it all but impossible for the spawn of the endangered June sucker to hide from predators. And as the carp forage the mud, they churn up years of trapped phosphorus, feeding algae that deplete the water of oxygen.
In February, June sucker recovery program officials requested proposals from the community on how to get rid of the carp. SWCA Environmental Consultants was recently awarded a $130,000 contract to study ways to eliminate the fish. The effort to tag and count carp is the first step.
To catch the fish, a 600-foot-long, 10-foot-wide net is stretched between two boats, said Laura Curry, aquatics ecologist with SWCA. The boats then detach from the net and circle around to scare the fish toward the center of the net before reattaching to the net and drawing it into a circle. Scientists and volunteers in hip waders then stand in the lake, reeling the net into the boat. The largest catch so far has been 1,375 carp and about 1,000 other fish, including walleye, channel catfish, white bass, black bullhead catfish, black crappie and bluegill. Scientists shoot each carp with a needle gun, inserting the anchor of a thin plastic tag between the fish's spines. The carp and all the other fish are then released back into the lake. The process is repeated as many as four times a day.
On Thursday, scientists will begin trying to recapture some of the carp they have tagged, Curry said. The number of tagged carp will be compared to the number of untagged carp in each catch to statistically determine the population of the fish.
"We give six days (after tagging) to allow them to disperse back into the population," she said. "The more carp we can tag, the better we can tell the population estimate."
Scientists also plan to take the opercles bone, which protects the gill, from 1,000 of the fish. The bone forms rings similar to that of a tree trunk, which allows the age of the fish to be calculated. In addition, scientists weighed 500 of the fish to get a statistical sampling of their average weight.
No one knows for sure how many carp are in the lake, but scientists have calculated that the carp are so plentiful that if all of the fish in the lake were weighed, 90 percent of that mass would be carp, Keleher said.
In the 1800s, Utah Lake was home to at least six native species of fish, he said. Today, the June sucker and the Utah sucker are the only two remaining. The June sucker occurs naturally nowhere else in the world. After nine years of study, experts believe Utah Lake has only 450 adult wild June suckers left.
In 1994, the federal government named the June sucker an endangered species, allowing its habitat to be protected by law. Soon thereafter, nine water-user groups with interest in Deer Creek Reservoir formed a 40-year, $40 million plan to save the fish, called the June Sucker Recovery Implementation Program.
This story appeared in The Daily Herald on page D1.
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]) there has to be a use for carp.