TVA went sport fishing Tuesday in Chickamauga Lake, and what fish experts netted was loads of data.
With an electrofishing boat, teams of TVA fisheries biologists filled net after net with bass and crappie from Wolftever Creek during the utility's annual spring sportfish survey.
This year's catch will be added to 10 years of data that tracks bass and crappie numbers by species, as well as by size and general health, according to TVA fisheries biologist John Justice.
But the exercise is not just to tell ordinary anglers there are fish in water.
"These fish are apex species. They're the top of the [aquatic] food chain, Justice said. "So if they're healthy, that gives you an indication of the water quality."
TVA has been doing these surveys for decades on Tennessee River reservoirs and tributaries. Now, up to 10 years of the data is posted on TVA's website for 31 bodies of water. Older surveys were taken in a different manner, and don't reflect an apples-to-apples comparison with numbers from the past decade, Justice said.
In Chickamauga, fish numbers and sizes have been growing. But the percent of disease and parasites also is up.
"Parasites don't really mean that much" in small percentage numbers, Justice said. "If you had numbers in the 25 to 35 percent range, it would tell us we need to stop and take a look at things."
In 2002, TVA found that 3.3 percent of the fish they caught in Chickamauga were diseased or had parasites. The percent fluctuated up and down until 2008 and 2009 when it hit double digits -- 10 percent and 10.4 percent, respectively. In both 2010 and 2011, the percent of fish with problems has edged down to about 5.8 percent.
Justice and TVA spokesman Scott Brooks said the numbers are cyclical, often depending on the weather and other stresses.
"Those may have been low flow [drought] years," Brooks said.
Low flow and warmer temperatures do help bacteria from waste releases to grow, Brooks said.
The figures indicate trends state officials can use to protect the river fisheries better.
The data can be referenced as regulators develop permits for everything from nuclear cooling water release temperatures to industrial releases to treated sewage outfall allowances, Justice said.
Not every reservoir is sampled each year.
Last year, the spring sportfish survey was conducted on 12 Tennessee River reservoirs from March through May.
Chickamauga that year took the prize for the most largemouth bass and the most crappie. It also tallied the highest numbers of fish in the 3-, 4-, and 5-pound or larger range.
This year, TVA will sample eight lakes.
In addition to Chickamauga, crews will survey Nickajack, Watts Bar, Fort Loudoun, Guntersville, Wheeler, Wilson and Pickwick.
Last year, Watts Bar, which suffered the Kingston ash spill in late 2008, had a 14.4 percent disease/parasite rate. That measure had been below 5 percent until 2008, when it had climbed to 9.6. In the three following years, the survey found 12.06 percent, 8.76 percent and 14.4 percent of the catch had disease or parasites.
Nickajack, in 2011, had the highest electrofishing catch rate of all three local lakes: 75.2 an hour.
Justice says biologists think 60 an hour is good.
Nickajack also had the 2011 highest percent of "harvestable" large mouth bass: 81.96 percent. Harvestable means 10 inches long or more -- the size a fish must be for an angler to legally keep it.
Last year's electrofishing catch rate on Watts Bar was 52.2, according to TVA records.
Like Chickamauga, Nickajack's disease and parasites rate had dropped from a 2009 and 2010 peak in low double digits to 6.4 percent last year.
To complete the Chickamauga survey for 2012, the biologists will spend two more days on the lake, inspecting and counting their catch by species, measuring them for length and weighing them. Then they will release them for another day's splash.
Eventually totals from all three days will be averaged for Chickamauga's final 2012 tally.
But after just six hours of shock and awe on Tuesday, TVA biologists had quite a fish tale:
Tuesday crews caught 431 large mouth bass and 26 other bass. About 82 percent of the large mouth bass were of harvestable size.
The crews also caught 101 crappie.
The catch rate was 76 per hour, and the disease parasite rate was 5.3 percent.
At the end of the day, Justice said, it indicates a healthy lake.
"These are world-class fisheries," he said. "We like to see an average catch of 60 fish an hour. Early on in the first hour we got 131 this morning."
He said many of the fish caught here Tuesday were ready to spawn. That's a week or two early due to the warm and early spring.
"The earlier fish spawn, the longer they have to get ready for the winter," he said.
Joe Turner, of Cleveland, is the treasurer of the Tennessee Bass Federation, and he said he liked what he saw of Chickamauga's decade of surveys.
"I would say the bass counts seem to be very accurate based on my fishing experience in the last two years," he said.
Turner wasn't overly concerned about the ups and downs of disease and parasites.
"I'm certainly not an expert in that, but it seems reasonably controlled now," he said, adding that the spikes might have from drought that caused bacteria in sewage releases to proliferate.
Sportfishing has brought thousands of dollars to the Chattanooga area.
In 1986, the Convention and Visitors Bureau officials said the Bass Masters Classic put the city and its water resources on the map by bringing seven national-level tournaments to the area. Some tournaments drew 300 entrants.
Angler Eric Nelson, of Cleveland, watched some of the electrofishing Tuesday.
He said he recently caught 250 crappie in one day in the Hiwassee River, which in 2008 posted a 62.8 fish per hour electrofishing catch rate.
"It's good fishing up there. It's a little tougher here," Nelson said, motioning to the Wolftever Creek. "But there's some big ones here. I hope I catch one."