RESOURCES

Aquaculture in Maine

Explore the history, species, farming methods, and evolving role of aquaculture along Maine’s coast.

Foundation & Early Innovation

1871-1975

The roots of Maine aquaculture began with public hatcheries, marine research, and the first policies allowing cultivation in shared coastal waters.

1871

Craig Brook Fish Hatchery Established

Craig Brook National Fish Hatchery opens in East Orland as one of the first Atlantic salmon hatcheries in the region.

1972

Darling Marine Center Hatchery Constructed

The University of Maine's Darling Marine Center constructs an aquaculture hatchery as part of the first Sea Grant-funded cold-water marine cultivation project.

1975

Maine’s First Aquaculture Lease Granted

The state grants its first aquaculture lease to Abandoned Farm, Inc. in Clark's Cove, South Bristol.

1903

McKown's Point Hatchery Established

Marine fish and lobster hatchery operations begin at McKnown's Point in Boothbay Harbor.

1973

Maine Aquaculture Leasing Laws Enacted

Maine establishes legislation governing the leasing of public marine waters for aquaculture development.

Industry Formation & Expansion

1976-1999

During the late 20th century, Maine aquaculture expanded rapidly through trade organizations, salmon farming, shellfish hatcheries, and new experimental licensing systems.

1982

First Salmon Farm in Cobscook Bay

Ocean Products becomes the first salmon farming company operating in Cobscook Bay, helping establish the region as the center of Maine’s salmon industry.

1988

Maine Aquaculture Innovation Center (MAIC) Established

Maine Aquaculture Innovation Center is formed with support from the Maine Legislature to promote economically and environmentally sustainable aquaculture development.

1996

Maine’s First Commercial Seaweed Farm

Coastal Plantations Inc. successfully farms Porphyra species for nori production in partnership with researchers from the University of Connecticut.

1998

First Northeast Aquaculture Conference & Exposition (NACE)

The first biennial conference is held to connect producers, researchers, students, and industry professionals across the Northeast.

1976

Maine Aquaculture Associated Formed

The Maine Aquaculture Association becomes the nation’s first trade association representing aquaculture farmers.

1987

Beals Island Regional Shellfish Hatchery Founded

The hatchery pioneers the use of hatchery-reared soft-shell clams for shellfish management and restoration efforts.

1991

MAIC Incorporates as a 501(c)(3)

MAIC transitions from the University of Maine and becomes an independent nonprofit organization.

1998

Experimental Aquaculture Leases Created

Maine authorizes experimental marine lease sites for companies, researchers, and individuals conducting aquaculture trials and innovation projects.

1999

Limited Purpose Aquaculture Licenses (LPAs) Created

Maine creates renewable small-scale licenses allowing growers to test shellfish cultivation sites and techniques.

Research, Collaboration & Workforce Development

2000-2015

Aquaculture research institutions, workforce training, and industry collaboration expanded significantly in the early 2000s.

2002

Shellfish Working Group Established

Led by Dana Morse and Maine Sea Grant, the group creates networking and professional development opportunities for shellfish growers.

2009

Aquaculture Research Institute Created

The University of Maine Board of Trustees establishes the Aquaculture Research Institute to strengthen statewide aquaculture research initiatives.

2014

SEANET Grant Awarded

The Sustainable Ecological Aquaculture Network receives a $20 million NSF grant supporting collaborative research across Maine’s coastline.

2004

Cooke Aquaculture Acquires Maine Salmon Operations

Cooke Aquaculture purchases all commercial salmon farming operations in Maine, becoming the state’s sole commercial salmon producer.

2013

First Aquaculture in Shared Waters Class

The Aquaculture in Shared Waters program launches community-based aquaculture training programs for fishermen and sea farmers in Maine.

2015

First Maine Aquaculture R&D Summit

Industry members and researchers gather to explore emerging challenges, technologies, and innovations in Maine aquaculture.

Modern Growth & Global Recognition

2019-Present

Maine aquaculture enters a period of rapid diversification, international attention, and climate-focused innovation.

2019

Maine Seaweed Week Launches

Maine Seaweed Week begins as a statewide celebration of Maine seaweed harvesters, products, and culinary innovation.

2022

Seagriculture USA Held in Maine

Seagriculture USA hosts its first U.S. conference in Maine, highlighting advances and opportunities in the growing American seaweed industry.

2020

COVID-19 Pandemic Impacts Aquaculture Industry

The global pandemic disrupts seafood markets, labor systems, supply chains, and coastal communities throughout Maine and beyond.

Farmed Species

Oysters

Crassostrea virginica · Ostrea edulis

Oyster farming is one of the fastest growing sectors of Maine’s aquaculture industry. Maine’s cold, clean coastal waters provide ideal conditions for producing high-quality oysters known for their distinctive briny flavor, appearance, and consistency. Oyster farming has expanded significantly over the past few decades, supporting coastal economies and working waterfronts across the state.

Eastern oyster (Crassostrea virginica)
The Eastern oyster is the most widely farmed shellfish species in Maine, forming the foundation of the state’s modern shellfish aquaculture sector. It is characterized by an irregular, elongated shell with a deep cup. Native to the Atlantic coast of North America, wild Eastern oyster reefs were once abundant along the East Coast. Most of these reefs have disappeared due to overharvesting, habitat loss, disease, and declining water quality, although Maine’s cold waters historically did not support large wild oyster reefs. This species is fast-growing, typically reaching market size in 18 to 30 months. Eastern oysters have a wide salinity tolerance, making them suitable for growth in a range of coastal and estuarine environments.

European oyster (Ostrea edulis)
The European oyster is a non-native species, characterized by a round, flat shell with smooth edges. This oyster prefers cooler waters and has a slower growth rate than the Eastern oyster, often taking three to five years to reach market size. Although European oyster aquaculture is limited and subject to strict permitting in Maine, this species occupies a niche in the raw half-shell market.

The European oyster (Ostrea edulis) was the first oyster species farmed in the state. During the 1970s and 80s, companies in Blue Hill and on the Damariscotta River used rafts to culture European oysters. This species is native to Europe but was commercially introduced to the Boothbay region by the US Fish and Wildlife Service in the 1940s. Hatchery-produced seed oysters were reared to market size in Japanese lantern nets, stacked trays, or floating trays suspended in the water. Suspension culture, a technique in which shellfish are grown off bottom, is a labor-intensive form of cultivation that requires continuous tending and cleaning of both gear and shellfish.

In the mid-1980s, growers switched to cultivating our native eastern/American oysters (Crassostrea virginica) due to their greater tolerance for extreme temperatures and salinity. At this time, researchers at the University of Maine initiated a selective breeding program to develop genetic strains of oysters more suited to Maine's growing conditions.

HATCHERY
Oyster production begins in a shellfish hatchery with the ripening of parental broodstock during the off-season winter months. Parents are typically spawned in March and April, with juvenile seed oysters becoming available to industry growers in late May and June. Land-based or floating upwellers are commonly used for the initial growing stage to protect seed and enhance growth by forcing nutrient-rich waters through the growing bins.

GROW-OUT METHODS
After purchasing oyster seed, farmers typically begin growing out oysters in floating bags or cages arranged in lines. Surface cages are regularly flipped to air dry the undersides and thus control the accumulation of biofouling organisms. As oysters grow in size, farmers regularly size-grade, thin, and cull their crop to maintain optimal growing conditions. Once water temperatures start to drop in the late fall and early winter, growth begins to plateau. During this time farmers will typically sink their cages to protect the oysters from harsh surface conditions or overwinter them in a temperature-controlled environment (typically a raft or indoor storage facility).

FLOATING SYSTEMS
In Maine, it is common for farmers to rely entirely on floating systems to grow oysters from seed to market. If farmers have a boat, it is by far the most accessible option. Farms can take advantage of warm surface temperatures and food availability to optimize growth, as well as higher wave action, which can control biofouling and provide natural tumbling.

SUSPENSION SYSTEMS
Suspension systems offer a more 3-D approach to oyster farming, utilizing the vertical water column instead of just the sea surface or seabed. Farming systems with cages that sit raised on the seabed are common in Maine. While highly effective for holding large volumes of oysters, suspension systems require more labor and expensive equipment for raising and lowering cages.

BOTTOM CULTURE
Bottom planting is a common practice on oyster farms worldwide, with significant reductions in labor and equipment costs. Certain markets may also prefer the harder shell and taste of a bottom-grown oyster. In Maine, growers may remove their oysters from floating systems to be bottom planted once they have reached at least 1.5”, at which point their thicker shell can deter predators. This method is not foolproof, however, and farmers should expect to lose some of their crop to predation. Site selection is crucial for this more “hands-off” approach, as oysters are usually left to grow until harvested by a diver or a drag.

INTERTIDAL CULTURE
Growing oysters in the intertidal zone is common across the globe and in certain areas within the United States. The advantage of this approach lies in both access and regular exposure to air, allowing farmers to set and maintain the site without needing a boat. Twice daily tidal exposure helps reduce biofouling and improve the shelf life of the product. Intertidal farming can be done with different gear types, but the most common is a “rack and bag” system in which bags rest on a platform that sits above the seabed. Intertidal culture has been trialed in Maine, however ice coverage has proven a major barrier to success.

PRODUCT HANDLING & QUALITY
Aside from the taste of the oyster, which is largely determined by environmental factors, farmers focus on achieving consistent and appealing product appearance. High-quality oysters are generally characterized by a deep cup, round shape, and consistent size in addition to their flavor profile. Growers often talk about achieving a good “meat-to-shell” ratio, meaning that the meat is plump and fills the shell to the edges. To achieve a quality product, farmers will regularly shake their oyster bags or put their product through a tumbling machine to chip excess shell growth. Oysters will take anywhere from a year to three years to reach market size, during which time farmers should regularly sort and handle them. The consistency and general appearance of the final product is usually a good indicator of how much the product was handled through its lifetime.

PROCESSING
Harvested oysters are sorted and prepared for market based on size, appearance, and shell condition. Processing steps may include washing, sorting, and packaging. During warm summer months, oysters are rapidly cooled to 50℉ or below shortly after harvest to prevent growth of Vibrio bacteria.

The Maine Department of Marine Resources (DMR) is the primary regulator for aquaculture leases, licenses, and rules in coastal waters. DMR reviews lease applications, sets conditions, and administers aquaculture permitting processes.
Growers can apply for a Limited Purpose Aquaculture License (up to 400 square feet, renewable annually), an experimental lease (up to 4 acres, 3 years) or a standard lease (up 100 acres, 20 years).
Key regulations include a 2.5-inch minimum size for American oysters, strict Vibrio control plans (June 1–Oct 15), and mandatory gear marking.
Growers must comply with biosecurity protocols regarding seed sourcing and restricted movement in areas with MSX disease.

In recent decades, there has been a rapid expansion of oyster aquaculture in Maine, with over 150 small farms now operating along the coast (according to the Maine Oyster Trail). According to the Department of Marine Resources, in 2024, Maine landed around 5.4 million pounds of farmed oysters according to the Department of Marine Resources, earning harvesters and growers nearly $15 million and making the fishery Maine’s third most profitable. Oysters typically earn growers $0.75 to $1.00 apiece.

OPPortunities

Oysters naturally improve water quality through filter feeding and require no feed inputs
Farmed oyster reefs can prevent erosion and act as natural storm barriers
Market expansion into new regions and direct-to-consumer markets
Transitioning to solar-powered equipment and electric workboats as a climate adaptation strategy
Technological advancements in site selection
Expanded selective breeding programs

Challenges

Conflict with coastal landowners desiring unobstructed coastal views and recreational access
Warming water temperatures can increase biofouling and risk of disease
Extreme weather events can damage infrastructure and impact water quality

Mussels

Mytilus edulis

While the majority of mussel landings have historically come from wild blue mussel beds, aquaculture methods such as raft culture and longline systems have expanded opportunities for production and market development. Farmed mussels are increasingly valued for their quality and consistency, making them an important component of Maine’s aquaculture sector.

Blue Mussel (Mytilus edulis)
The primary mussel species farmed in Maine is the blue mussel (Mytilus edulis), a native species well-suited to the cold waters of the Gulf of Maine. Wild blue mussel beds can be found in intertidal areas anchored to hard substrates via strong fibers called byssal threads. In mussel aquaculture systems, these byssal threads anchor mussels to the line during growout and are later removed during processing.

The majority of mussel landings in Maine come from wild blue mussel beds. Wild mussels can be harvested all year, but are commonly harvested in winter months when the quality of the meat is best.

In recent decades, mussel farming techniques have taken hold in Maine in the form of suspended culture (mussels hung from ropes suspended in water column) and bottom culture (mussels planted directly on seabed). Early mussel farmers in Maine faced several challenges, including eider duck predation, poor site selection, lack of technology transfer, insufficient capital, and lack of established markets. Bottom cultured mussels were pioneered by Great Eastern Mussel Farms, Inc. and initially produced 4 million pounds annually for the supermarket trade until the company ceased operations in the mid 2000s. Renewed interest in mussel suspension culture has come as a result of successful culture and sales of mussels in the Canadian Atlantic Provinces, where aquaculture development funding has been a priority.

In 1996, the Maine Aquaculture Innovation Center (MAIC) convened the Mussel Suspension Culture Working Group to help develop mussel raft technology with Maine’s native blue mussel. This group initially consisted of about 75 participants, including mussel draggers, lobstermen, clam diggers, urchin divers, and others interested in farming mussels. In 1997, MAIC gave a grant of $2,000 to the working group to study different types of material for mussel seed collection. In 1998, a private foundation gave the group $10,000 to purchase Spanish graders, socking machines and rope for field trials. This was followed by $100,000 in industry development, which included 3 Scottish raft kits, 4 wooden rafts, and other infrastructure installed at Maine lease sites.

Rafts became the structure of choice for suspension culture because they provided a stable working platform and the ability to produce high volumes in small areas. The addition of large protective nets helped mitigate predation by eider ducks.

HATCHERY
Currently the Downeast Institute operates a small-scale mussel hatchery, producing seeded ropes and eyed larvae. MAIC has convened mussel farmers and hatchery operators from around the state to discuss the feasibility of a commercial mussel hatchery.

GROW-OUT METHODS
Several techniques are used to culture mussels along Maine’s coast. While raft systems remain the most common method, longline systems and bottom culture are also used depending on site conditions and operational needs.

FLOATING RAFT SYSTEMS
Floating raft systems, adapted from designs originating in Ireland and Spain are the most common method of suspension culture in Maine. On average, floats measure 40 square feet and are capable of supporting up to 400 drop lines of up to 45 feet in length. Roughly 40,000 pounds of mussels can be expected in an 18 month cycle from seed to harvest. Raft systems are most appropriate for reasonably protected areas. They have the advantage of providing a stable work platform but are susceptible to damage from harsh weather.

LONGLINE SYSTEMS
Longlines consist of a main horizontal line, anchored at both ends with floatation along the center segment. Dropper lines are then suspended from the main line into the water column. These systems have the advantage of being adaptable to deeper waters, or more exposed tides. However, these systems are more difficult to deploy, more susceptible to predation from ducks, and they often require larger work boats with specialized hauling gear.

BOTTOM CULTURE
Bottom culture is a technique where reduced densities of mussels are grown directly on the sea floor. A farmer must locate an appropriate site to seed with mussels or find an established bed to thin and disperse. Farmers who bottom culture save on the capital and maintenance costs of growout gear like rafts or longlines but generally experience lower meat weights than suspension culture methods. Mussels are harvested with a bottom dredge and purged in a container or tank with high flow of clean seawater.

PROCESSING
Regardless of growout method, declumping, debyssing, and grading steps will always be taken prior to packaging. Each stage requires specialized machinery, often arranged in hydraulically operated conveyor systems. Processing machinery may be mounted on a floating barge near the farm site or located in a land-based facility.

The Maine Department of Marine Resources (DMR) is the primary regulator for aquaculture leases, licenses, and rules in coastal waters. DMR reviews lease applications, sets conditions, and administers aquaculture permitting processes.
Growers can apply for a Limited Purpose Aquaculture License (up to 400 square feet, renewable annually), an experimental lease (up to 4 acres, 3 years) or a standard lease (up 100 acres, 20 years).
Collecting seed (spat) from the wild for farming requires a spat collection license if done outside the lease site.
A state Aquaculture License is required to harvest and sell cultured mussels from a lease site.

While farmed mussels only accounted for roughly ¼ of total mussel landings in 2024, according to the Department of Marine Resources, they made up almost the entirety of the entire fishery’s value ($4.04 million out of total $4.68 million). Maine grown mussels are prized for their size, meat-to-shell ratio, and quality compared to dominant competitors. Proximity to key markets on the East Coast allows for faster delivery and greater freshness.

OPPortunities

Rising demand for local, sustainably raised seafood
Higher price points for farmed mussels due to superior quality and taste.
Significant potential for expanding farm lease acreage
Investment in new farming techniques is improving efficiency and allowing for higher-density farming

Challenges

Predation by eider ducks and starfish
Harmful algal blooms, which can result in mandatory closures of farms for public health safety
Low market prices in comparison to high labor intensity and costs of production, processing, and transportation

Scallops

Placopecten magellanicus · Argopecten irradians

Scallops are a high-value shellfish with deep roots in Maine’s fishing heritage and growing interest from the aquaculture sector. The Atlantic sea scallop has long supported Maine’s commercial wild harvest fishery, while small-scale scallop farming has taken hold in recent decades thanks to technological adaptations from other regions. While technically challenging, scallop aquaculture represents a promising opportunity to diversify Maine’s local seafood market due to strong market demand and increasing interest from producers.

Atlantic sea scallop (Placopecten magellanicus)
The Atlantic sea scallop is a large, cold-water scallop that tends to grow in deeper offshore waters, although it can be found closer to shore in the Downeast region of Maine, where water temperatures remain relatively low year-round. Sea scallops reach market size in one to three years and are prized for their large adductor muscle. While sensitive to environmental conditions and stocking density, their high market value makes them attractive for aquaculture.

Bay scallop (Argopecten irradians)
Bay scallops are smaller than sea scallops and occur naturally in shallower bays and estuaries. Historically, their distribution extended only as far north as Massachusetts. However, as waters in the Gulf of Maine continue to warm, some aquaculturists in Maine are beginning to explore bay scallops as a potential farming species. Bay scallops grow quickly, are well suited to suspended culture systems, and can be farmed alongside other shellfish. While not yet widely produced in Maine, bay scallops offer potential opportunities for diversification and climate-adapted aquaculture.

The Atlantic sea scallop, once referred to as the “giant scallop”, has long been an important species for Maine’s commercial fishing fleet. Following a sharp decline in catches, landings have increased in recent decades, and there has been a concurrent recognition of the premier quality of Maine scallops. Bay scallops have only been farmed experimentally but are becoming a species of interest due to warming Gulf of Maine waters.

In 1999, with support from the Federal Government and the Maine Department of Marine Resources, MAIC organized and led a study mission to Japan’s Aomori Prefecture, where the Japanese scallop (Patinopecten yessoensis) is intensively grown on longlines and on the seabed. The trip sparked local interest, and by the fall of 1999, several research projects had begun to determine if Japanese scallop spat collection and husbandry methods could increase scallop production in Maine. Local fishermen started experimenting with Japanese spat collectors and found success in waters not too far offshore.

In 2021, MAIC convened a consortium (named the hatchery implementation team, or HIT) of researchers, hatcheries and institutions in Maine and the Northeast U.S. to bring together the best cold water hatchery experience and sea scallop larval research. The HIT was assembled in response to the Maine Scallop Aquaculture Report (Fitzgerald et al. 2021), which identified the lack of sea scallop hatchery technology as a primary barrier to meaningful growth in Maine’s scallop aquaculture industry. MAIC and partners also received funding from Atlantic States Marine Fisheries Commission to develop a community of practice around scallop aquaculture, and perform some limited hatchery trials.

SPAT COLLECTION / HATCHERY
Wild sea scallop spat collectors are typically deployed in late September/early August, after larvae have started to settle. Spat collection bags made of mesh are filled with a settlement substrate and hung from vertical lines in the lower third of the water column. Spat retrieval occurs in late spring, followed by the nursery phase. Baby scallops can be kept in bottom cages, lantern or pearl nets, or floating cages until they are ready to begin growout, after about a year. From there, growout takes one to three years, during which time stocking density and growing conditions are closely monitored. Bay scallop seed, on the other hand, is produced in shellfish hatcheries, where spawning of adult scallops is induced via a series of temperature shocks. Fertilized eggs are transferred to conical tanks, where they are supplied a mixed algae diet through their larval phase.

GROW-OUT METHODS (SEA SCALLOPS)
These growout methods are specific to sea scallops, as bay scallops are still only grown experimentally in Maine..

LANTERN & PEARL NETS
Nets are tiered and suspended vertically in the water column from a longline. Scallops are placed in each compartment and thinned as they grow. Lantern nets are cylindrical in shape while pearl nets are pyramid-shaped. Pearl nets are typically used for early stage scallop growth, while the larger lantern nets are used for the latter stages of growout. Routine husbandry is required to maintain optimal growth and minimize mortality throughout the growout period. Nets can be hauled onto the vessel to be sprayed and brushed to remove biofouling organisms. Growers may use a cylindrical washer to remove debris and dead shells prior to grading. Scallops are then graded to a uniform size before being restocked in clean nets.

EAR HANGING
Ear hanging is the process of drilling a small hole into the ear of individual scallops and pinning them in pairs to dropper lines. Although labor and space intensive, this technique allows for ample nutrients and minimal crowding, thought to result in faster growth rates and larger meats.

BOTTOM CULTURE
Bottom culture is a farming method where sea scallops are grown directly on the seafloor. It is a relatively simple and economical approach but success depends on the quality of the seabed and requires careful site selection. Scallops are placed in bottom cages made of wire mesh or molded plastic. Husbandry is done by bringing cages to the surface, where stocking, grading, thinning, and harvest can be accomplished. To clean cages, some farmers air dry, powerwash, or dip the cage in a hypersaline or hot water bath. While highly effective for holding large volumes of scallops, their cost may be an issue.

PROCESSING
Harvested scallops are typically cleaned using a high-pressure sprayer to remove algae, barnacles, and other fouling organisms. A specialized knife, and in some cases automated machinery, is then used to open the shell and extract the adductor muscle. The adductor muscles are cleaned, graded by size, and inspected for quality.

The Maine Department of Marine Resources (DMR) is the primary regulator for aquaculture leases, licenses, and rules in coastal waters. DMR reviews lease applications, sets conditions, and administers aquaculture permitting processes.
Growers can apply for a Limited Purpose Aquaculture License (up to 400 square feet, renewable annually), an experimental lease (up to 4 acres, 3 years) or a standard lease (up 100 acres, 20 years).
Seed used in aquaculture must originate from within the same Health Zone as the lease/LPA site, or a special permit must be acquired.
A state Aquaculture License is required to sell cultured scallops.

The vast majority of scallop landings in the state (>99%) still come from wild harvest, but sea scallop aquaculture has taken hold with several small commercial farms operating along the coast. Bay scallops have only been farmed experimentally in the past but are becoming a species of interest due to warming coastal waters.

In 2024, farmed scallops represented only a small fraction of the total fishery value, accounting for just over 5,000 pounds of more than 4 million pounds of scallops landed in Maine, according to the Department of Marine Resources. Despite the challenges with growing scallops at scale, several Maine farms are actively refining culture techniques. Operations such as Vertical Bay are experimenting with scaling sea scallop production, while other farms are testing the feasibility of bay scallop aquaculture.

OPPortunities

Strong domestic demand and high price point
Well suited to Maine’s cold-water marine environment
Proven culture techniques and technologies from Japan and other regions
Expanded domestic market for live and roe-on scallops

Challenges

Low tolerance for crowding; sensitive to temperature and salinity changes
Limited large-scale seed production due to lengthy larval phase, larval sensitivity, and hatchery expenses
Careful site selection required
Labor-intensive husbandry that can be difficult to scale

Algae

Saccharina latissima · Saccharina angustissima · Alaria esculenta

Maine has played a leading role in the modern farmed algae industry for over 15 years. The state’s cold, clean coastal waters, long maritime tradition, and strong research infrastructure have supported the development of a sustainable, innovation-driven sector.

Algae are a diverse group of photosynthetic organisms that range from from single-celled microalgae to multicellular macroalgae. They play an important role in global carbon, nitrogen, and phosphorus cycles by taking up carbon dioxide and nutrients during photosynthesis. This process can help reduce excess nutrients in the water and alleviate localized ocean acidification. Around the world, algae are both cultivated and wild harvested for food and non-food uses. In Maine, the term “kelp farming” refers to the cultivation of native, cold-tolerant brown seaweeds using longline systems.

Microalgae, or phytoplankton, are microscopic organisms that form the base of most aquatic food webs. They can be cultivated in tanks or photobioreactors and commonly used as dietary supplements, livestock feed, and hatchery feed for shellfish and urchins. Microalgae species cultivated for hatchery and research purposes include Isochrysis, Tetraselmis, and Chaetoceros.

Macroalgae— commonly called “seaweed”— are multicellular algae that attach to a substrate, providing habitat for marine organisms and contributing to ecosystem structure. Edible macroalgae are often referred to as “sea vegetables” and are gaining popularity as nutritious and sustainable food sources. Macroalgae (seaweed) species commonly farmed in Maine include sugar kelp (Saccharina latissima), skinny kelp (Saccharina angustissima), and winged kelp (Alaria esculenta).

Seaweed has long been part of Maine’s coastal culture through Indigenous and working waterfront wild harvest traditions. Commercial cultivation, however, is relatively recent. In the late 20th century, researchers and early entrepreneurs began adapting Asian and European kelp-farming techniques to the cold, nutrient-rich waters of the Gulf of Maine.

Pilot projects in the 2000s and early 2010s—led by the University of Maine, Bigelow Laboratory for Ocean Sciences, and industry partners—established reliable hatchery and longline grow-out methods for native species such as sugar kelp. These efforts laid the foundation for Maine’s modern seaweed industry and positioned the state as a national leader in farmed seaweed.

Over the past 10–15 years, Maine’s seaweed industry has grown from small pilot farms into a large, integrated network of small- and mid-scale farms, established seed-production nurseries, and a growing value-added processing sector.

Early leaders such as Atlantic Sea Farms helped establish commercial markets for Maine-grown kelp, while companies like Maine Coast Sea Vegetables continue to bridge wild harvest and cultivation traditions through multi-species research and product development.

HATCHERY
The process begins in a hatchery, where reproductive tissues from mature kelp are induced to release spores. These spores settle onto spools of twine and develop into juvenile kelp plants, creating “seeded” lines ready for deployment on farms.

Microalgae are cultivated in indoor tanks, carboys, or photobioreactors under controlled light, temperature, and nutrient conditions. These systems allow hatcheries to produce dense, clean cultures of algae that serve as essential feed for oyster, mussel, and clam larvae. While not typically grown at commercial volumes for consumer products, microalgae research in Maine contributes to biotechnology, climate studies, and innovations in aquafeed.

GROW-OUT METHODS
In the fall, when water temperatures have dropped, farmers deploy seeded lines onto larger horizontal growout lines anchored to the sea floor. These horizontal longlines are typically suspended about 6-8 feet below the water surface to ensure adequate sunlight and nutrient exchange. During late winter and early spring, the kelp seed grows rapidly, relying only on natural sunlight and nutrient-rich waters. Farmers periodically check gear, remove fouling organisms, and monitor plant growth before harvesting in spring, when quality and yield peak.

PROCESSING
Harvested seaweed is transported to shore as quickly as possible to maintain freshness. After being washed, the seaweed is either chilled, cut, blanched, dried and/or frozen, depending on the final product and available processing infrastructure. Processed seaweed is most commonly used for food products, animal feed additives, and agricultural biostimulants.

The Maine Department of Marine Resources (DMR) is the primary regulator for aquaculture leases, licenses, and rules in coastal waters. DMR reviews lease applications, sets conditions, and administers aquaculture permitting processes.
Growers can apply for a Limited Purpose Aquaculture License (up to 400 square feet, renewable annually), an experimental lease (up to 4 acres, 3 years) or a standard lease (up 100 acres, 20 years).
Site proposals are reviewed for impacts on navigation, existing fishing and aquaculture operations, and environmental sustainability.
Local communities and stakeholders are notified of lease applications and may participate in the decision-making process.
Anyone harvesting over 50 pounds/day or commercially must have a DMR Seaweed Harvesting License.
Leaseholders must submit monthly landing reports and are limited in the number of LPAs they can hold.

Maine continues to expand both seaweed farming capacity and market development. In 2024, roughly 18.7 million pounds of farmed and wild-harvested seaweed were landed in Maine, valuing just under 2.5 million USD according to the Department of Marine Resources. The value of the seaweed industry has more than doubled since 2020, when it represented roughly 1 million USD. Farmed seaweed still only represents a small fraction of all harvested seaweed—less than 1 of nearly 19 million pounds landed in 2024. The value of the industry is growing, though, from $339,000 in 2021 to $592,000 in 2024.

OPPortunities

Unique opportunity for fishermen and aquaculture operators to diversify income in off-season
Potential for co-location with shellfish and/or finfish farms
Future expansion of in-state processing and post-harvest infrastructure
New market and product development
Climate resilience research

Challenges

Limited in-state processing infrastructure
Rapid post-harvest handling needed to maintain product quality
Limited consumer familiarity with products and need for new product development and branding
Markets are still developing compared to more established seafood industries

Finfish

Multiple species

Finfish aquaculture in Maine focuses on the farming of cold-water fish species in both clean, productive coastal waters and land-based recirculating systems. Finfish farming has played a role in Maine’s aquaculture sector for decades and continues to contribute to food production, employment, and innovation on our working waterfronts. Today, the industry operates in cooperation with wild fisheries and other forms of aquaculture. This work is supported by advances in fish health, environmental monitoring, and farming technology. Research, collaboration, and adaptive management remain central to the sector’s development.

Atlantic Salmon (Salmo salar)
Aquaculturists have been raising Atlantic salmon in the Gulf of Maine since the 1970s. Because commercial fishing for Atlantic salmon in the United States is prohibited, all Atlantic salmon sold in U.S. markets are farm-raised. Salmon farmers in Maine were among the first globally to develop comprehensive Best Management Practices (BMPs) to minimize environmental impacts. Developed collaboratively with state and federal regulators and environmental organizations, these BMPs establish environmental performance goals that exceed regulatory requirements and rely on third-party audits for verification. Salmon farms in Maine are regulated by the Maine Department of Marine Resources, the Department of Environmental Protection, and the U.S. Army Corps of Engineers.

Cooke Inc. is a Canadian-based seafood company that has been operating salmon farms in Maine for over 20 years. Cooke now maintains a fully integrated operation with several inland hatcheries, 24 lease sites, and a salmon processing facility in Machiasport. As new technologies have enabled Atlantic salmon to be raised in freshwater, several companies have proposed land-based farming projects. Great Northern Salmon is currently developing a moderate scale salmon farm in Millinocket at the site of an old paper mill. The project is doubling as a clean-up for the sludge that was deposited in the lagoons located on the property and is partially funded by the U.S. Environmental Protection Agency. The farm is projected to produce 7,500 metric tons of salmon a year relying on 100% renewable local hydropower.

Trout (multiple species)
Maine has one of the oldest and most productive hatchery programs in the United States. Established in 1895, the Maine Department of Inland Fisheries and Wildlife (MDIFW) operates eight hatcheries that collectively produce more than one million brook trout, brown trout, lake trout, splake, landlocked salmon, and rainbow trout a year. These facilities are supplied by lake water, springs, and underground wells, resulting in efficient operations with a low carbon footprint. Fish are stocked into more than 800 lakes, streams, rivers, and ponds across the state according to species-specific management guidelines.

In addition to state hatcheries, several private farms raise trout using land-based recirculating aquaculture systems (RAS). Mi’kmaq Farms in Aroostook County raises brook trout in a 3,000-square-foot hatchery. The hatchery was developed to strengthen food sovereignty within the Mi’kmaq Nation and is incorporated with agricultural production. Outflow from the system irrigates crops and fish waste is captured for plant fertilizer. Small-scale operations such as Shy Beaver Trout in Hollis and Spectrum Trout Farm in South Paris specialize in producing trout for pond stocking, restaurants, resorts, and private landowners.

Other Species
Kingfish, Maine, Inc. has proposed a land-based recirculating aquaculture system in Jonesport designed to eventually produce 8,500 metric tons of yellowtail kingfish annually. The project, which has undergone multiple permit appeals since 2022, would operate using sea water and 100% renewable energy. Farm-raised yellowtail kingfish are certified by Aquaculture Stewardship Council (ASC) and Best Aquaculture Practices (BAP). Additional finfish species farmed in Maine at smaller scales include tilapia (Springworks Farm) and ornamental species (Sea and Reef Aquaculture).

Finfish aquaculture has been part of Maine’s coastal economy since the late 20th century. Commercial salmon farming in marine waters took off in the 1980s following 1973 legislation that permitted the leasing of public marine waters. Early development was driven by suitable environmental conditions and preexisting working waterfront infrastructure across the state. Over time, the industry has evolved in response to environmental, biological, and regulatory challenges, as well as shifting market conditions. Today, finfish aquaculture is an established component of Maine’s broader aquaculture landscape, contributing to employment and innovation in the sector.

HATCHERY
Spawning season and egg collection for salmonid broodstock occur in the fall. Fertilized eggs are incubated in a freshwater hatchery, where juvenile fish are then raised under controlled conditions with close monitoring and frequent size grading. After 18 months juveniles will undergo smoltification, a complex physiological and behavioral transformation that prepares them for marine survival. In the spring, as water temperatures are warming, farmers transport Atlantic salmon smolt to saltwater farms. Other hatchery-raised finfish, such as the trout raised in the state’s hatchery program, are released into the wild, while others may spend their entire lives in a land-based farm.

GROW-OUT METHODS

MARINE NET-PEN SYSTEMS
Marine net-pen systems are typically located in sheltered, high-energy coastal areas such as bays, which provide sufficient water exchange. Site approvals are managed by the Maine Department of Marine Resources. A typical marine net-pen farm typically consists of multiple floating pens secured by large anchors and mooring lines. Each pen is designed with several layers of protection, including a primary containment net that extends 30 to 50 feet below the surface, a secondary predator net to deter seals and other wildlife, and a top cover to prevent fish escapes and bird predation.

The state of Maine limits stocking densities for salmonid species to a maximum of 30 kilograms per cubic meter to reduce stress on fish and minimize environmental impacts. Salmon raised in net pens are generally fed dry, nutrient-dense pellets made from fish meal and plant-based proteins. The grow-out period typically lasts between 12 and 24 months, depending on water temperature and site conditions.

LAND-BASED, RECIRCULATING AQUACULTURE SYSTEMS (RAS)
Recirculating Aquaculture Systems (RAS) are land-based aquaculture facilities designed to minimize water use while supporting high-density fish production. These systems continuously treat and recycle water through a combination of mechanical filtration, biofilters, and UV treatment, allowing operators to carefully manage water quality and oxygen levels. Stocking densities are determined by the system’s capacity to remove excess nutrients and maintain optimal conditions. Essential husbandry practices include daily monitoring of water quality, automated feeding, rapid waste removal, and strict biosecurity controls. Because RAS operate in a fully controlled environment, they can support optimized, year-round growth. Potential benefits include increased biosecurity, water efficiency and environmental control. However, high capital and operational costs remain a barrier, and most land-based systems in Maine are still in an experimental or pilot stage.

PROCESSING
Harvested finfish are rapidly cooled to below 40°F to ensure quality. Fish are brought to processing facilities, where they are typically gutted, filleted, and vacuum-sealed before being flash-frozen. Processing facilities must adhere to strict regulations involving waste management, records maintenace, and sanitation standards.

The Maine Department of Marine Resources (DMR) is the primary regulator for aquaculture leases, licenses, and rules in coastal waters. DMR reviews lease applications, sets conditions, and administers aquaculture permitting processes.
A Maine Pollutant Discharge Elimination System permit is required from the Department of Environmental Protection to manage potential waste.
The U.S. Army Corps of Engineers regulates infrastructure in navigable waters.
Regular health checks and vaccinations are mandatory for minimizing disease and parasite transmission.

Finfish aquaculture in Maine is currently limited in scale compared to shellfish farming but remains an important component of the state’s aquaculture sector. Atlantic salmon production supplies domestic markets and contributes to year-round employment in coastal communities. The industry continues to adapt to environmental change, evolving technology, and market dynamics.

OPPortunities

Strong domestic and global market demand for finfish
High protein yield and efficient feed conversion compared to many terrestrial livestock species
Culture of native species whose growth is compatible with Maine’s cold-water environment
Potential for continued innovation in farming systems and fish health management
Workforce training and retention in aquaculture operations

Challenges

Sensitivity to environmental conditions, including temperature and water quality
Fish health and disease management
Public perception and social license concerns
Regulatory complexity and siting constraints
High capital and operational costs

Clams

Mya arenaria · Mercenaria mercenaria

Clam harvesting has been part of Maine’s coastal culture for hundreds of years, merging local food systems, municipal management, and working waterfronts. Today, clam aquaculture is emerging as a complement to wild harvesting as mud flats face declining productivity due to predation and environmental change. Through hatchery production, seeding, and experimental grow-out techniques, farmers and researchers in Maine are exploring ways to rebuild wild populations and diversify shellfish aquaculture.

Soft-shell clam (Mya arenaria)
The soft-shell clam can be found in intertidal mudflats along the East Coast of North America and has long been a seafood staple of New England. As the name suggests, soft-shell clams have a brittle calcium carbonate shell that cannot close completely, requiring them to burrow deep in mud or sand to protect themselves from predation. They are characterized by a long siphon, which allows them to filter feed from deep burrows.

Hard clam / Northern Quahog (Mercenaria mercenaria)
The hard-shell clam thrives in shallow, sandy or muddy saline waters along the Eastern seaboard of the United States. These clams have thick, robust shells that close tightly to protect against predation. They are particularly abundant between Cape Cod and New Jersey, although their distribution is expected to shift northwards due to warming temperatures, making them an emerging species of interest in Maine. Quahog aquaculture is a well-established industry in Massachusetts, with an extensive network of municipally-managed hatcheries, nurseries, and growout sites.

Other Species of Interest: Atlantic surf clam (Spisula solidissima), Atlantic razor clam (Ensis leei), Arctic surf clam (Mactromeris polynyma)

Clam digging dates back hundreds of years in Maine, with ancestors of both the native Wabanaki people and early European settlers harvesting clams from intertidal flats. Since the 1800s, towns in Maine have maintained the authority to issue harvest licenses, open and close areas for digging, and set harvest limits. In recent decades, wild clam populations have declined in many areas due to increased predation by green crabs and ribbon worms, as well as other ecological and environmental pressures. Clam aquaculture has emerged in response to these declines, with efforts focused on seeding historically productive mudflats and exploring new farming approaches.

HATCHERY

SOFT-SHELL CLAMS
The Downeast Institute for Applied Marine Research and Education’s hatchery produces millions of seed soft-shell clams every year. Broodstock are shocked into releasing eggs by being moved from 50℉ to 70℉ water. Fertilized eggs are then collected and moved to large tanks. Once seeds have reached 1/15” in length, they are placed in floating trays at a density of 15,000 per tray and transported to a mudflat near the hatchery. The young clams are left to grow in trays until they reach transplant size (⅛-½”).

HARD-SHELL CLAMS
Quahog larvae are bred in hatcheries and fed algae until they reach 1mm in size. After the larvae have developed their shell and lost their swimming ability (usually 7-14 days), they are moved to mesh containers, where they are supplied with seawater. One of the biggest farming challenges is this nursery phase, as it can be difficult to keep 1mm seed contained while maintaining sufficient water flow. Once they reach 2-5mm, they continue their nursery stage in an upweller or mesh bags in the water.

GROW-OUT METHODS

SOFT-SHELL CLAMS
Hatchery-raised soft-shell clams are often transported to historically productive but underpopulated mudflats during the spring. The population of a particular mudflat may be low due to overharvesting, natural predation, or poor recruitment, so seeding and management may be adjusted based on these factors. The seeded area is covered with nets to limit predation and transplanted clams are left to grow until they reach market size.

HARD-SHELL CLAMS
For their final growout, hard shell clams can be placed in trays, pens, or bags that are planted on intertidal or subtidal mud flats. The bags/trays should be routinely pulled out of the mud to prevent them from getting buried. They have been experimentally grown beneath floating oyster farms with mixed success.

The Maine Department of Marine Resources (DMR) is the primary regulator for aquaculture leases, licenses, and rules in coastal waters. DMR reviews lease applications, sets conditions, and administers aquaculture permitting processes.
Growers can apply for a Limited Purpose Aquaculture License (up to 400 square feet, renewable annually), an experimental lease (up to 4 acres, 3 years) or a standard lease (up 100 acres, 20 years).
Key regulations include a 2-inch minimum size for soft-shell clams, mandatory native species usage, and mandatory gear marking.
Many towns have conservation ordinances that require residents to obtain municipal licenses to farm or harvest

Soft-shell clams remain one of Maine’s most valuable wild shellfish industries. In 2024, approximately 5.7 million pounds of soft-shell clams were landed in Maine according to the Department of Marine Resources. Soft-shell clams generated $15.6 million in market value, making it the second most profitable Maine fishery after lobster. Hard-shell clam landings totaled approximately 1.9 million pounds, with a value of $3.4 million. While most clam production remains wild-harvested, aquaculture and enhancement efforts are increasingly viewed as tools to stabilize supply and support coastal communities.

OPPortunities

Growing demand for small clams in raw half-shell markets
Expansion of clam seeding and wild population enhancement programs
Development of quahogs as a secondary crop for shellfish farmers
Selective breeding and hatchery advances to improve survival

Challenges

High predation pressure from crabs, worms, birds, and fish
Labor-intensive seeding and predator management
Sensitivity to temperature and sediment conditions