Choosing Your Farm Site

Where to Farm

With an understanding of what seaweed you plan to farm, the next key piece in planning your seaweed farm is site selection. Before we dive into how to pick a good location for a seaweed farm, however, let’s think a bit about what a seaweed farm actually looks like. For this section we will focus on a long-lineType of aquaculture system where the cultured species is suspended in the water column from a floating line that is anchored to the seafloor at different points. seaweed farm, which is standard for sugar kelp, skinny kelp, and winged kelp in Maine.

What does a kelp farm look like?

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Mooring system including a yellow buoy with "sea farm" written on it and an anchor

Kelp long line roughly two meters below the ocean surface with kelp growing on it.

Dropper buoys (different from the mooring system) spaced along the long-line to keep the kelp at the appropriate depth.

Here is a simple schematic of a single kelp long-line. The equipment introduced here is revisited in greater detail in the next unit of this module. Being able to visualize what your seaweed farm might look like and having a basic design before you start looking for sites is helpful because it can help you to pick appropriate locations that will meet ecological, practical, and social needs of the farm.

From an ecological standpoint, you will need to think about a number of factors that impact the health of kelp (or any seaweed) when siting your farm. Some of these factors may also impact your choices in farm equipment, which makes them especially important to take into consideration. 

Beyond the environmental factors needed for healthy kelp to grow on a farm, it is also critical to consider practical elements when siting your farm. Perhaps most importantly, you should take into account the seasonality of farming seaweed in Maine. Kelp is a winter crop; it goes in the water starting in October and November, does most of its growing from December through April, and is harvested from April to late May. This means that nearly all of the time you spend working on your kelp farm the weather will be below 50 degrees F– not including wind chill– and can reach dangerous lows and produce hazardous winter conditions. Since winter is the off-season for Maine’s working waterfront, ocean access and access to your site is another key consideration, especially if docks and landings aren’t available in the winter. Ice may also become a factor for farms, especially if they are located near freshwater inputs to the ocean. Understanding the full picture of seasonal conditions and access to your site is critical to deciding where to farm, farming successfully, and staying safe on the water.

Physical and environmental site selection for kelp farms

Videos featuring the late Seth Barker talking about site selection for seaweed aquaculture. Video Credit: Maine Aquaculture Innovation Center.

In Maine, three species of kelp are currently farmed commercially and a couple of companies are experimenting with growing horsetail kelp and dulse. All of the commercial kelp farming in the state happens on long-lines, and the growing environments for each species are considered interchangeable. Because long-lines need to be appropriately positioned seven feet below the surface without kelp blades dragging on the seafloor at low-tide, there must be sufficient depth at a location in order to have a kelp farm. 

When it comes to site selection for seaweed farming, there are a couple of factors that differ substantially from site selection for bivalve farming. First, since seaweeds are primary producers rather than secondary producers, seaweed growth depends on light, carbon dioxide, and the presence of inorganic nutrients (NPK) rather than food and dissolved oxygen. That means sites which are best suited for seaweed are not necessarily optimal for growing bivalves. 

Next, commercially farmed Maine seaweeds are a fast-growing winter crop that can reach harvest size in a period of five to seven months. Due to this seasonality and rapid growth, farms are in the water during cold months and can be almost completely removed during the summer when boat traffic increases. Therefore, site selection for kelp farms must pay close attention to where ice formation happens, but they may avoid some of the conflict of use issues that other farmers encounter. 

Physical site selection characteristics for kelp (sugar, winged, skinny)

As kelps are cold water species, temperature is the biggest factor in having a successful kelp farm. Without appropriately cool water, kelps may appear “blonde,” which indicates that the kelp blades are not experiencing optimal growth. Nutrients are also crucial to farming kelp, but coastal waters in the Gulf of Maine rarely experience conditions where lack of nutrients are a problem. Below is a chart that outlines the optimal ranges for various water quality measures for the three kelps grown commercially in Maine (Saccharina latissima, Alaria esculenta, Saccharina angustissima) and the one kelp grow experimentally (Laminaria digitata).

Water quality site selection characteristics for kelp (sugar, winged, skinny)

Seaweeds other than kelp are not currently farmed in Maine. This is in part due to how new seaweed aquaculture is to the United States and in part due to how complicated obtaining seaweed seed can be. However, dulse is farmed across the Atlantic in Ireland, and several manuals on dulse farming are available from there. Given that folks in Maine are beginning to experiment with dulse cultivation, we will include information about dulse site selection in the chart below:

Physical and water quality site selection characteristics for dulse

Seasonality and site selection: kelp considerations

Harbor Access

Some harbors close in the off season. You will want to make sure that your intended access point to the ocean for farming remains open and has adequate resources to keep your vessel up and running.

Winter Work & Transit

With freezing winter temperatures, you may want to consider how long you will spend in transit to your farm and how exposed your route is. Wind and waves may become an issue for accessing the farm on many winter days, so you will want to make sure your site is practically accessible year round.


Ice can cause major problems for your kelp farm. If your gear gets tangled in an ice flow, it could be dragged out of place, damaged, or even destroyed. Ice can ruin an entire crop of kelp in a couple of days, especially when combined with wind if you’re not careful with your farm placement.

Digital tools for site selection

A video (58:19) about digital site selection tools available for prospecitive farmers. Video Credit: Maine Aquaculture Innovation Center. Available on YouTube:

After seasonality, the next relevant concern for seaweed farm site selection is proximity to processing. Remember in the last section when we mentioned wet weight and dry weight prices for seaweed? Those numbers are directly relevant to seaweed processing. For seaweed to go from a long-line in the ocean to a consumer, it often must be processed first. The most common methods for processing and stabilizing seaweed include drying and blanching followed by freezing (see Unit 3, Section 2: Harvesting and Processing). 

When deciding on a farm site, it’s actually important to think all the way down the line to processing your product. There is a relatively short time window between when seaweed is harvested and when it must be processed before the quality begins to decline. This means you need to know how long it is going to take to get your seaweed from the line to the processing location. Whether you choose to process your seaweed in house or work with another company to do it, locating near the facility where you will be processing can facilitate production of the highest quality product. 

In addition, end markets might impact where you choose to farm. If you hope to certify and sell your seaweed as organic, certain site considerations and practices must be followed in order to be eligible, and prospective organic farmers should be aware of these before siting their farm.

Maine Organic Farmers and Gardeners (MOFGA)

MOFGA is Maine’s organic certification service. More information about MOFGA can be found on the MOFGA website and the MOFGA Certification Services website. below you can find MOFGA’s guidelines for organic sea vegetable certification. (Published in 2015).

The final crucial piece of the site selection puzzle for your seaweed farm is how your farm will impact the local community. This community includes everyone from coastal landowners near your farm to fishermen that share the waterways to other aquaculture farmers in close proximity. Maintaining support for your farm within the local community (termed social license to operate) is key to successful aquaculture operations in Maine, and the relationships you have with community members should start well before your farm ever enters the water. Information and strategies for establishing good rapport within your community and maintaining social license to operate can be found on the Maine Aquaculture Innovation Center website and in the learning module TITLE.

Social License to Operate

Social license to operate, a term describing the informal, ongoing support for a project granted by the community, is gaining traction in the aquaculture industry. Farmers have recognized the importance of gaining community support for the success of their own farms and the broader industry. Social license is also a community empowerment tool. Having the power to withhold or grant social license gives community members more of a say in how companies operating in shared waters act– this puts pressure on aquaculture farmers to prioritize their community’s well-being in an effort to become better neighbors. This way of thinking creates a more socially sustainable industry.

Text from the MAIC website.

Between taking water quality measurements at potential farm sites, examining digital data resources, and speaking with various community members about your potential farm, the process of choosing a site is much more involved than just pointing your finger at a map. However, paying attention to these details is foundational in building a successful business. Taking the time to do your homework on site selection before you put in a lease application pays off every time you get a great harvest at an ecologically ideal location or have community members supporting your farm within their networks. 

Having selected a seaweed species to grow, planned where to put your farm, and applied for/been approved for an aquaculture leaseA lease of an area in, on, or under coastal waters including the public land beneath the water for the purpose of cultuvation of aquatic organisms such as algae, shellfish, finfish, or crustaceans for food., it is nearly time to get your equipment in the water and your seaweed on the lines. Which brings us to the next thing you need to think about: how are you going to get the ‘seed’ for your seaweed farm?