Hughes Center Blog

New Research Helps Remote Setters Produce Oysters More Efficiently

Every year, billions of oysters are planted in Maryland’s Chesapeake Bay. Most begin their lives in a hatchery and go through a remote setting process where microscopic oyster larvae attach to cleaned oyster shells before the spat on shell are placed on Bay bottom to grow.

Spat on shell producers have long known that the process is unpredictable. Some shells end up with more than 50 oysters attached, while others get none. In addition, larvae settle heavier on shells at the bottom of tanks compared to shells in the top and middle. Because producing one million spat on shell costs $3,500–$5,000 in materials and labor, that variability can become expensive and it can also affect oyster survival once planted in the Bay.

A recent applied research project set out to answer a deceptively basic question: where do oyster larvae settle when conducting remote setting — and can we improve it?

A closer look inside the tank

Funded by the Hughes Center for Agro-Ecology, research was conducted by Alex Golding with Ferry Cove Shellfish and Dr. Jill Bible with Washington College.

Researchers studied large “remote setting” tanks at the Ferry Cove Oyster Hatchery. Each tank holds containers filled with oyster shell. Mature oyster larvae are introduced and given several days to settle, distribute around the tank and transform into juvenile oyster spat.

To understand settlement patterns, scientists placed labeled sample shells throughout the tanks — at the top, middle, and bottom — and tracked how many oyster spat attached in each location.

They also tested two factors that remote setters can easily control: light (covered tanks vs. uncovered tanks) and aeration (high air flow vs. low air flow).

What they found

First, researchers confirmed something that hatchery staff and spat on shell producers had suspected for years: oyster larvae strongly prefer the bottom of the tank.

Researchers found that there are more oysters attached to shells at the bottom than to shells in the middle or top. Larvae naturally sink before setting, which helps explain the pattern — but the team wanted to know if traditional setting practices were making it worse, and what could be done to distribute it more evenly.

Light did not matter

Covering tanks with tarps — to simulate complete darkness, experienced at the bottom of the Bay — did not change where oysters settled. Larvae still concentrated at the bottom.

That finding is still useful. Covered tanks dramatically reduced biofouling (organisms growing inside the tank), meaning less cleaning was required between sets resulting in lower labor costs for growers.

Aeration did matter

Air flow, however, made a difference. In a high aeration environment, oysters still clustered at the bottom. However, in a low aeration environment, oyster larvae distributed much more evenly throughout the tank. The result was a more uniform vertical settlement of larvae across shells, on the top, middle, and bottom.

Why this matters

When too many oysters grow on the same shell, they compete for space and resources, reducing survival and harvest potential. Meanwhile, empty shells represent wasted resources.

By simply adjusting aeration levels, growers or producers may be able to:

• improve survival rates.
• increase harvest production.
• reduce material costs.
• enhance nutrient removal benefits from oysters in the Bay.

Even a modest improvement could save growers up to 20% in production costs.

What comes next?

This is the first time scientists have studied spat distribution in full-scale remote setting tanks, not just laboratory systems. The next step is repeating the trials and testing at other remote setting locations to confirm the results across different tank designs. The researchers will also continue to test other factors that impact oyster spat distribution with funding from the Hughes Center for Agro-Ecology.

Read the project’s final report here.