Survivor: Chesapeake
An Oyster Reality Show
Standish Allen checks a bag of his best-performing seed oysters by Michael W. Fincham
Standish Allen leads the Aquaculture Genetics and Breeding Technology Center, one of the few long-term oyster-breeding programs in the world. Here Allen checks a bag of his best-performing seed oysters, a line named “Lola” that is a crossbreed between oysters from low salinity waters in the Chesapeake Bay and oysters from Louisiana that carry resistance to Dermo. These Lola oysters survive and grow well in the Yeocomico River near Kinsale, Virginia, but no single line of crossbreeds does well everywhere in the Bay. Credit: Michael W. Fincham.

SOME OYSTERS SURVIVE DISEASE and some don't. When survivors mate with survivors, their offspring tend to survive even longer. Natural selection, nature's long-running reality show, will over time pick winners among the oyster tribes of the Chesapeake Bay and vote losers right out of the estuary. Eventually the Bay would hold an oyster population of winners, animals largely impervious to MSX and Dermo, the two diseases that devastated oysters in this estuary for more than 50 years.

Standish Allen wants to speed up the process of picking winners, at least for oyster farmers. A dozen years ago he began growing oysters on the tidal flats in front of the Virginia Institute of Marine Science, an area at the mouth of the York River where disease usually flourishes. Working with the Chesapeake's native oyster, Crassostrea virginica, he would wade out on the flats and pick out the hardiest survivors, both males and females. To make sure the survivors hooked up with each other, he would spawn them in his hatchery at the Aquaculture Genetics and Breeding and Technology Center. Their offspring would then head out to the flats to take their chances with disease.

Two to three years later, Allen would wade out again and start picking the winners among the offspring so they could also hook up together in his hatchery. "It's a little simplistic," says Allen. "It's just weeding out the ones that can't tolerate disease until you have just the right ones." By finding the right ones, generation after generation, Allen was hoping to amplify the trait of disease resistance. So far it's working: the oysters in each generation survive better than their parents.

Breeding begins with a simple concept — pick the right oysters — but it immediately gets more complicated. The right oysters for the tidal flats of the York River, for example, may not be the right oyster for other areas to the south or the north. So Allen now puts his oysters out on three different farm sites: the high salinity waters of the Lynnhaven Inlet down near the mouth of the Bay, the moderate salinities of the VIMS tidal flats, and the lower salinities of the Yeocomico River up near the state's northern border.

It gets more complicated again when you're also trying to breed resistance to two very different diseases at very different sites, all at the same time. MSX, Allen discovered, was the easier disease problem to solve. Since this disease attacks oysters at any age, young or old, MSX creates an immediate selective pressure, picking winners and losers as soon as new oysters go into the water. As a result, according to Allen, it takes only four to five generations to breed a line of oysters that are fairly resistant to MSX disease. Sometimes, apparently, you can speed up natural selection.

And sometimes you can't. Since Dermo strikes oysters later in their life cycles, often at three years, Allen found it much more difficult to quickly create a Dermo-resistant oyster line. Thinking outside the box, he went outside the Bay and brought in oysters from the Gulf of Mexico where Dermo has been attacking oysters for much longer. He's hoping to tap into their hard-earned natural resistance by crossbreeding Louisiana survivors with Chesapeake Bay survivors.

First, of course, he had to expose the Gulf oysters to MSX, a disease new to them, and find which oysters could survive and which could not. Since he needed different oysters for different places, he created two lines of these crossbreeds. He calls his low-salinity Louisiana line Lola, and he named his high-salinity Louisiana line hANA.

His latest strategy for defeating Dermo seems, at first, counterintuitive. Two years ago Allen decided to stop selective breeding for disease resistance. "We have reached a level, a plateau of disease resistance that I think is acceptable for commercial purposes," he says. His alternative strategy for Dermo: breed for speed. Since Dermo attacks oysters in their third year, he wants to grow an oyster you can harvest at two years — or earlier. "You are doing an end run around the disease," he says. Disease becomes a moot point.

How fast are his oysters?Starting from seed phase, his natural oysters can already reach market size in 18 months — at least when grown in off-bottom floats or cages. "Our goal is to get it down to around a year," he says, "so that you put out an oyster, and in a year you can have a crop."

He's already reached that kind of fast growth rate with his triploid oysters, an invented oyster designed to carry three sets of chromosomes. Because they are sterile, non-spawning oysters, triploids grow faster, and they can be eaten year-round. To create triploids, Allen takes natural diploid oysters that carry two sets of chromosomes and breeds them with tetraploid oysters that carry four sets. His tetraploids all carry disease resistance — and so do their triploid offspring. Oyster hatcheries in Virginia and elsewhere can acquire tetraploid brood stock from the VIMS breeding center and then create their own triploids.

Disease and fast growth are only two of the numerous traits Allen has focused on with his breeding strategies. Oyster farmers, like oyster eaters, also want traits like meat weight, oyster size, shell shape. As a result, Allen has created more than 15 oyster lines, using natural selection, generation after generation, to nail down each specific trait.

His latest move may seem counterintuitive again, but now he is collapsing those lines, crossbreeding lines with specific traits in hopes of getting a couple lines that carry all those traits. "I hesitate to call them 'superlines,' " he says, "because that sets expectations too high." But that's what he calls them, at least among friends and reporters. In short: the final survivor in Standish Allen's reality show should be the perfect half shell oyster.

vol. 9, no. 2
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