The rains of Hurricane Florence dumped so much fresh water into the Waccamaw and Pee Dee rivers that the wash plumed into the Atlantic Ocean, pushing all the saltwater out of the vast Winyah Bay.

Three months later, the salinity is still near zero in the bay off Georgetown.

What that means for fish in the rich estuary isn't known. But a few families of red drum are about to give researchers a few clues. The results could decide the future of managing the catch that's so sought after by anglers and consumers that studies suggest it's severely overfished.

S.C. Department of Natural Resources scientists stocked the bay with genetically distinct "families" of drum just before and after the September storm. A third family will be stocked in the spring. About 500,000 young drum overall will be stocked.

Over the next three years of surveying, researchers will check DNA of captured drum to try to find out what happened to the three rounds of stocked fish, said DNR wildlife biologist Justin Yost.

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The S.C. Department of Natural Resources boats regularly stock juvenile red drum in Winyah Bay in other coastal locations. Justin Yost/SCDNR Inshore Fisheries Research Section/Provided

What researchers learn could help the department in the future target stocking efforts across the coast, based on rainfall and storms that are becoming more extreme as air and seas warm.

The red drum, the state's most popular saltwater game fish, isn't an easy fish to figure out.

Among the complexities of assessing the stock are that they are long-lived fish that appear to go through periods of strong spawning years followed by weaker years without any real long-term consequences for the species. Also, that the drum can range from not-so-brackish to saltwater.

But any answers would be important.

In South Carolina alone, the red drum (also known as spot-tails) fishery is one of the most popular inshore and nearshore catches of everyday anglers and charter boat customers. It has been estimated to be worth $600 million per year.

More than 500,000 people hold saltwater licenses in the state, and the number of licenses issued is growing two to three percent each year.

After the storm, as flood waters swelled, the DNR sampling came away with fewer fish than usual overall but did find good numbers of drum, said Joey Ballenger, DNR assistant marine scientist.

No mass die-offs have been spotted or reported since the flood, but the fish would be expected to move to saltier water.

"The only thing we noted is that fish were more heavily concentrated in water around the jetties, as salinities were higher there," Ballenger said. 

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Hauling trailers carry juvenile red drum to be stocked by the hundreds of thousands in coastal locations. Erin Weeks/SCDNR Inshore Fisheries Research Section/Provided

"Given natural variability of red drum recruitment in the system, the general state of red drum across South Carolina and life history of the fish, we never may be able to identify particular impacts of this event," he said.

In recent years, more anglers have said they've seen a decline in the fishery.

While a 2015 federal assessment of the entire Atlantic coast suggested red drum have not been overfished, a 2017 assessment by DNR found the red drum are overfished here. State legislators reduced the bag, or personal catch limit from three fish to two per trip and boat limit to six per trip.

The red drum fishery in the state is now predominantly catch and release, with more than 80 percent of the fish released alive, said Mel Bell, DNR fishery management director.

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An adult red drum. Justin Yost/SCDNR Inshore Fisheries Research Section/Provided

The drum, also called redfish and spot-tail bass, has been fished so relentlessly that as far back as 1981 DNR began putting limits on the catch. In the 1990s, the coastal population began to grow rapidly and technology advanced with it, bringing more sports boats and more successful fishing.

By 2000, the survey numbers had fallen so alarmingly that the catch limit was dropped from five to two fish per trip and a “slot” of fish sizes that could be kept was established. Red drum populations rebounded, which led to recreational fishing groups pushing for the limit being loosened in 2006 to three fish per trip and the slot adjusted.

The findings from the Florence study will be compared with preliminary findings from hurricanes Joaquin in 2015 and Matthew in 2016, Yost said.

The flood rains from Joaquin two years ago diluted the saltwater to a weak brackish far upstream in the bay, but some of the stocked young drum moved back there anyhow, he said.

Reach Bo Petersen Reporter at Facebook, @bopete on Twitter or 1-843-937-5744.

Science and environment reporter. Author of Washing Our Hands in the Clouds.