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Photo Gallery of Aquaculture Techniques Used in Maine

1) Raft culture of blue mussels: Mussel seed is "socked" (wrapped with biodegradable thread) onto lines suspended from the cross beams of a floating raft. As the mussels grow they attach to the lines using their byssal threads. Mussels feed on naturally occurring phytoplankton, while suspended in the water column, until they reach a marketable size.


Casco Bay mussel rafts
mussel rope culture


mussel harvest


2) Long-line culture of blue mussels: Similar to raft culture, mussels are socked onto lines that are suspended in the water column. With long-line techniques, however, back-lines instead of rafts are used to support the socked mussels. As such, mussels are generally more spread out during the growth cycle. Additionally, back lines and the attached long-lines (hung in loops) can be submerged. Smaller surface lines may also be used to collect wild mussel seed or spat.

Blue Hill Bay Long Lines    

3) American and European Oyster Farming: A variety of techniques are used for the culture of oysters. Some of the more popular methods include:

a) Upwellers: Enclosed systems that use electrical or tidal power to pump water through internal silos, increasing food availability to the shellfish contained within. Upwellers are commonly sited off docks or within marina boat slips for ease of access. Once the shellfish reach a size suitable to withstand predation they are often placed in floating ADPI bags or other structures or planted freely on bottom leases to continue growing.

b) Suspended culture using floating ADPI bags: Juvenile oysters are placed in plastic mesh bags and floated at the water's surface. As the oysters grow they are often graded for size. Bags are also routinely rotated to prevent the accumulation of fouling organisms. Some farmers will cultivate oysters to market size using floating ADPI bags whereas others choose to use the bags as nursery sites to contain and protect young oysters until they are able to withstand predation when broadcast over the bottom sediments of a lease.

c) Submerged racks and bags: A shellfish rack can be likened to a chest of drawers - multiple bags of shellfish are stacked within a rack that is sitting on the bottom sediments.

d) Free-planting on bottom: No structures are used. Harvest methods include SCUBA diving, dragging and when shallow enough hand picking.

seed oyster



      Damariscotta River oyster farm
American oysters


4) Net-Pen Finfish Farming:


Polar Circles


         Atlantic salmon


harvesting operations
Steel Cages


Some practices that are not considered aquaculture:

  • Lobster pounds – The objective of a lobster pound is to maintain wild caught lobsters until they can be delivered to market. This is a form of storage rather than aquaculture because the product (lobster) enters the pound at an already marketable size and there is no active investment in its future growth.
  • Wet storage of shellfish – Again, this is a form of temporary storage until there is a market for the product. There is no active fostering of growth.
  • Municipal Shellfish Programs - Many towns along the Maine coast have municipal shellfish programs that are actively seeding clam flats as a supplement to wild stocks. While there is some debate as to whether or not this qualifies as aquaculture, leases are not required at this time.
  • Relaying of shellfish from closed areas – When relaying, shellfish are transferred from closed areas, generally because of pollution, to areas classified as open to the harvest of shellfish for a specified period of time. The purpose of relaying is to allow the shellfish time to purge any pollutants, making them safe for human consumption. Relay permits can be obtained through DMR's Public Health Division.
Photo credits: Tollef Olson, Aqua Farms, LLC.; Carter Newell, Great Eastern Mussel Farms, LLC.; Erick Swanson, Maine Cultured Mussels Inc.; Barbara Scully, Glidden Point Oyster Company and MDMR Staff.