Wildlife biologists are in the midst of an unprecedented effort to release about 750,000 young spotted seatrout into Charleston waterways.

Scientists released more than 200,000 trout fingerlings into Charleston Harbor this month and plan to release another 250,000 into the Ashley River and yet another 250,000 into the Wando River in August.

This massive trout stocking, funded by the sale of saltwater fishing licenses, follows the release of 4,000 cobia fingerlings into the Colleton River in mid-July.

“We’ve been very busy,” said Mike Denson, assistant director of the Department of Natural Resources’ Marine Resources Institute at Fort Johnson.

The baby cobia will be legal sized (33-inch fork length) in two to three years, and they are expected to return to the Port Royal Sound. The baby seatrout are expected to grow quickly and could be catchable in a year, Denson said.

But whether the massive trout-stocking effort actually leads to better fishing remains uncertain. Figuring that out is one of the project’s goals.

“We’ve never stocked trout, and there’s no good information on the impacts of stocking trout, so we have no idea what to expect,” Denson said.

After decades of stocking red drum and cobia in Lowcountry waters, scientists have established that these efforts have huge impacts on recreational fisheries.

An earlier cobia-stocking study, for example, showed that almost half the 2007-year-class cobia caught in the Broad River were among 50,000 3-inch fish released into the river by DNR researchers.

In the latest stocking program, a joint effort between the DNR and federal Fish and Wildlife Service, scientists raised the cobia and seatrout in ponds at the Waddell Mariculture Center in Bluffton.

Raising nearly a million baby seatrout is no easy task. Not only are trout very fragile fish, they’re also voracious eaters and highly cannibalistic when kept in captivity. If feedings weren’t properly calibrated, the scientists at Waddell could have started with a half-million fish but quickly wound up with a pond filled with just 50,000.

What’s more, they’ve managed to raise distinct “families” of trout, all genetically fingerprinted offspring of brood stock taken from the areas where the young will be released. In other words, only Ashley River seatrout will go back into the Ashley, only Charleston Harbor fish will go back into the harbor, and only Wando River fish will go back into the Wando.

“We don’t want to negatively impact wild populations in any way,” Denson said. “That goes the same for cobia.”

Releasing site-specific fish isn’t just a precautionary measure; it’s the focal point of the scientific research.

“When we come back and sample fish next year, we can determine which fish were wild, which are stocked, and which fish are from each family,” Denson said. “That way, we can determine how much they move and whether they mix through the whole harbor system.”

Charleston, it turns out, is a great place to conduct such ground-breaking research on seatrout.

“We have a monitoring group that goes out every month of the year, and have been for 20 years, to get a good data set using trammel boats,” Denson said. Pairing such a massive amount of information with new genetic identification methods allows scientists to better understand the natural ups and downs of fish populations and gauge the effects of stocking programs.

“We’ve gotten pretty high-tech,” Denson said.

Reach Matt Winter, Tideline magazine editor, at 843-937-5568 or matt@tidelinemagazine.com.