Aquaculture 101

What is Aquaculture?

Aquaculture is the practice of cultivating seafood in a controlled environment rather than harvesting it from wild populations. Think of it as farming in the sea — except instead of corn and cattle, aquaculturists raise sea vegetables, fish, and shellfish.

Aquaculture is rapidly growing in popularity. Today, it accounts for nearly half of global seafood production, a figure that continues to rise as it outpaces the production rate of wild harvesting.

Species Farmed

A variety of marine species can be farmed, including species of mollusks, fish, and sea vegetation. Like traditional farming, farmable species depend on the region. In Asia, countries like China farm mainly freshwater fish (specifically carp), while countries that have fjords of sheltered sea water like Norway mainly farm finfish in sea cages. In the Southern United States, the most prevalent form of aquaculture is freshwater farming, specifically farming catfish, but in ocean-based farms in the Northeast, the cold, low-salinity estuary water leads to the most popular species being oysters.

Aquaculturists in the Northeast specialize in cultivating species such as sea vegetables like kelp, mollusks including oysters and mussels, and finfish like salmon. The industry also continues to explore new species for farming, including eels, sea scallops, soft-shell clams, hard-shell clams, and various marine algae.

Environmental and Economic Benefits and Challenges

The most common challenge that aquaculturists face is finding a suitable location to set up their farm. Aquaculture farms require boating infrastructure, and also must comply with local regulations. In Maine specifically, the process to get an aquaculture site approved for farming is quite rigorous, and is commonly the largest obstacle that new farmers must overcome. While these regulations can be challenging for aquaculture businesses, they are an important way to ensure that sea farming remains sustainable and responsible. To help farmers navigate these regulations we created our own essential start guide that outlines the process while providing insight into the best practices to streamline the process.

How farms affect surrounding ecosystems is also an important factor to consider. It's this reason why there are so many strict rules and regulations in place when it comes to site location and how cages are monitored.

Despite these challenges, aquaculture can strengthen local economies while offering significant environmental benefits when done responsibly. Aquaculture provides a consistent, dependable source of seafood, making it a great supply source for restaurants. It also has a much smaller carbon footprint than traditional farming while simultaneously avoiding pollutants such as pesticides, making it an increasingly popular choice with climate-conscious farmers. Our Aquaculture Program Manager Carissa Maurin sees this firsthand when talking to sea farmers.

In the Gulf of Maine, shellfish and sea vegetables — the most commonly farmed species — play a crucial role in maintaining ecosystem health. Shellfish are natural filter feeders, actively cleansing the water and reducing the risk of harmful algal blooms, which helps keep the Gulf of Maine pristine. Additionally, both shellfish and sea vegetables, such as kelp, absorb carbon as they grow, reducing the carbon footprint of aquaculture farms and contributing to climate resilience through carbon sequestration.

Farming shellfish and sea vegetables is also environmentally friendly due to the low maintenance required to farm them. Shellfish and sea vegetables don’t require aquaculturists to feed them, instead feeding on what is already present in the water they are grown in. This not only makes the water cleaner, but also avoids the use of things like antibiotics.

Regional Focus: Aquaculture’s Role in New England’s Blue Economy

Fishing is central to New England’s identity and a vital source of employment for Gulf of Maine residents. Aquaculture provides a vital entry point for those looking to join the working waterfront, whether through launching new farms or offering fishermen a valuable source of supplemental income. Maine’s historic fishing industry plays a key role in driving aquaculture growth, giving the state a distinct advantage over other regions in expanding the sector.

Further expanding aquaculture practices creates new jobs within the region’s seafood industry — a commitment we actively support through initiatives like the Maine Aquaculture Apprenticeship, developed in partnership with the Maine Aquaculture Association. A key limit to aquaculture expansion is a lack of skilled workers, and the Maine Aquaculture Apprenticeship is a direct response to that issue. The program provides skills and experience necessary to succeed in the aquaculture industry to people of any experience level, which connects farms with a source of skilled labor.

An Inside Look at a Maine Oyster Farm

To understand how aquaculture farms in Maine operate, we’re going to look at how one oyster farm in Maine operates — Bar Harbor Oyster Co. The first step to growing oysters is to buy seed. Oyster seed is bought in the form of small, young oysters, ranging in size from smaller than a fingernail to roughly a third of an inch. The smaller seed is cheaper, but takes longer to reach maturity and is more fragile.

Once the seed gets to the farm, they are placed in oyster cages and put into the water. These cages keep the oysters separate from the rest of the ecosystem, but still allow water to flow through so that the oysters can filter feed. During warm months, these cages float near the top of the water, but come winter they are sunk to the ocean floor to protect the oysters from the ice and cold.

As the oysters grow, they take up more space in their cage, and can become crowded. To accommodate the growth, the oysters are taken out of the water and put through a machine called a grader, which sorts the oysters by size and cleans them. After grading, the oysters are put back into cages with the space they need to continue growth. This process happens once or twice a year to every oyster.

After three years, the oysters have grown enough to be sold. After a final grading, the oysters big enough for market are put back into the water until an order is received, at which point the oysters are retrieved, washed, bagged, and then put into a refrigerated truck for delivery.

If you’d like to learn more about Bar Harbor Oyster Co. and aquaculture operations in Maine, be sure to check out our series of videos starring the business owner Joanna Fogg which highlights different aspects of aquaculture in Maine, and shows you the oyster farm in action.

Our Role in Supporting Aquaculture

At GMRI, we focus on fostering healthy ocean ecosystems, supporting sustainable seafood, strengthening the blue economy, and addressing climate change. Aquaculture sits at the intersection of all these challenges, making its responsible growth part of the solution.

As the sustainable aquaculture sector expands in the Gulf of Maine, its role in bolstering our region’s blue economy becomes increasingly clear. To ensure this growth benefits both the environment and local communities, we collaborate with industry leaders, farmers, researchers, businesses, and nonprofits. By working together, we can help the industry meet rising workforce demands, provide essential business planning and training resources, and support long-term profitability for sea farmers across Maine.

It’s important to recognize that aquaculture is not meant to replace the wild harvesting of Gulf of Maine fisheries. For over a decade, GMRI has worked to maintain the Gulf of Maine’s rich and productive ecosystem—one that supports both wild fisheries and the coastal communities that rely on them. Aquaculture doesn’t compete with wild fisheries; rather, the two industries complement each other. Both depend on clean water, a deep understanding of the marine environment, thoughtful management, and forward-thinking leadership. By balancing responsible aquaculture with well-managed wild fisheries, our region can strengthen its seafood industry, ensure food security for growing populations, and adapt to a changing climate.