For most of four decades, Andy DePaola’s job was to keep people safe from what lurks in raw oysters. Now, on a pier in Coden, he is growing them — and the machines that grow them. The retired federal microbiologist operates Depe Oysters, an oyster farm on Portersville Bay that raises more than 200,000 oysters at a time using equipment he invented himself, run alongside partners who plan to sell them chargrilled and raw from a food truck.
The story is a window into how the Gulf’s oyster business is changing. The wild-caught oysters that once filled skiffs in Mobile Bay have grown scarce as the historic reefs have been depleted, and the region’s answer has been a new generation of oyster farms — operations that apply serious science and engineering to grow oysters from seed to harvest in the bay’s own waters.
The Scientist Behind the Farm
DePaola grew up pier fishing with his father, Depe, on the North Carolina coast, and earned BS and MS degrees in food science, microbiology and marine biology at North Carolina State, followed by a Ph.D. at the University of Florida. He then spent his entire 37-year career in public service at the FDA’s Gulf Coast Seafood Laboratory on Dauphin Island, where he became the agency’s leading expert on Vibrio — the naturally occurring estuary bacteria that makes raw oysters risky — serving as lead seafood microbiologist and national Vibrio policy coordinator from 2013 until his retirement in 2015.
His work underpins national and international control plans for reducing the risk of illness from raw seafood. He remains active as a food safety consultant to industry, universities and international organizations, and serves on the executive board of the Shellfish Growers Climate Coalition.
When he retired, he named the farm after his father. The tinkering began years before the official 2017 launch, and it produced the invention that defines the operation: the Shellevator, a patented device that pneumatically automates shellfish transport from the seafloor to above the water’s surface — and moves seamlessly around the farm to escape hazards to the shellfish or the people growing them.
Why the Wild Reefs Are Struggling
DePaola is unusually well placed to explain why Mobile Bay’s natural oyster grounds have fallen on hard times, and his explanations run from ecology to weather. Oysters spawn by broadcasting eggs and sperm into the water in late May, when water temperatures approach 80 degrees; one animal’s release triggers its neighbors, which is why a critical mass of adults is required for successful fertilization. Larvae drift for about three weeks before settling onto hard substrate — a rock, a piling, another oyster. Settle into mud, and the animal dies.
But the population has dropped below the threshold where natural spawning reliably succeeds, and nature keeps raising the stakes. “These mass mortality events have occurred more frequently in recent years and often occur when tropical storms stall over the Mobile Bay watershed,” DePaola says. “A 90-degree heat anomaly in March 2020 woke oysters early from their winter hibernation before the rainy season ended and wiped out an entire crop in less than a week. It seems like Mother Nature is inventing new ways to kill oysters.”
Upriver rainfall is part of the problem too: heavy freshwater inflow pushes salinity below what oysters can tolerate, closing harvest areas and stressing the reefs. Since he moved to Mobile Bay in 1980, DePaola says the water has grown markedly more turbid — starved of the light submerged grasses need — and runoff laden with pathogens and nutrients has brought frequent harvest closures and harmful algal blooms.
Jubilees, Bull Sharks and a Rising Bay
The changes show up in strange ways for anyone who spends time on the water. Mobile Bay’s famous jubilees — low-oxygen events that drive sea life to the shoreline in summer — were once rare on the bay’s west side, and have become more common, typically after calm, overcast July and August mornings. Stingrays surfacing and crabs dying in traps are the early warning; a ship’s wake, crashing a wave ashore, can end a jubilee in minutes. DePaola says bay waters deeper than three feet have become so hypoxic in recent years that populations of brown shrimp, blue crabs and oysters no longer support commercial harvest there.
The shoreline itself is changing. According to figures from the Dauphin Island Sea Lab, tidal surge on the bay has risen about a foot since DePaola moved to the area — and it keeps rising about an inch every two years. Ship wakes and seawall-protected shorelines compound the erosion and turbidity. The nightly lantern lights of flounder giggers and soft-shell crabbers, once a fixture of the west shore, have largely disappeared.
The species that has adapted best? Bull sharks, DePaola says — hunters that find prey by sound and smell rather than sight, and face little competition in a murkier bay. He would know: he and his wife Dianne caught 160 juvenile bull sharks off their Mon Louis Island pier in three days, winning $7,500 for first place in the Guy Harvey Foundation catch-and-release shark division of the 2016 Alabama Deep Sea Fishing Rodeo.
Inside the Farm
At the Coden operation, the numbers run past 200,000 oysters in the water at a time. The process starts in a bottle nursery on the pier, where oyster spat purchased from Auburn University sit in inverted bottles flushed with water pumped from Portersville Bay. The flow keeps the tiny shellfish suspended and feeding as they grow, before they are screened and moved into progressively larger mesh bags — every two weeks or so — until they are ready for the grow-out stage.
That is where the Shellevators line up around the end of the pier, each one stacked with four levels of oyster bags and plumbed with independent lift tanks, valves and a compressed-air manifold. Opening and closing valves in sequence floats the apparatus to the surface or sinks it to the bottom. The mobility matters: oysters are raised out of the water weekly for a day of drying to keep barnacles and other fouling organisms from colonizing the shells and gear, and the lift-and-move design lets waves tumble the oysters into the deep cups and polished shells that half-shell customers pay for. Predators still require hands-on work — the oyster drill, a snail with a taste for oysters, has to be picked off by hand, and research teams from the Dauphin Island Sea Lab visit the farm to study the pest.
Ready for Market
DePaola continues to refine the Shellevator — he patented it in 2017 and has begun leasing improved versions to other oyster farms through a third-party contract — while his focus shifts to expanding Depe Oysters and bringing its product to market. “We are ready,” he says. His partners, Daryl and Christina Steiner, and their son Crawford tend the operation, and much of the crop is destined for The Roaming Oyster, the Steiners’ food truck, to be served raw on the half shell or chargrilled.
On Mon Louis Island, just south of the mouth of Fowl River, the DePaolas keep a living shoreline growing along their own stretch of the bay — one more experiment in a life spent on the water. The man who wrote national Vibrio policy now grows the oysters he once regulated, in the bay he has watched change for 45 years, with the patience of someone who knows that oysters, like the bay itself, reward whoever pays attention. For anyone who loves a Gulf oyster, that patience is worth rooting for.