– Hatchery –

Soft-Shell Clams


We take orders for cultured soft-shell clam (Mya arenaria) juveniles in the late winter and spring each year. Orders are placed during this time to help us understand what the demand is for cultured clams so that we can produce enough each year.

Clam prices are based on the size of the seed clams produced. Larger clams require more time and handling on our part so they cost more than small clams.

If you are interested in ordering small clams (for growing in an upweller or floating trays), sizes up to 2 mm can be shipped to you between May and June.

Call us anytime if you have a special order.

For Delivery Inside Maine

Size (mm) Size (in) Price per 1,000
1 mm 0.04 in $5.30
1.5 mm 0.06 in $7.60
2 mm 0.07 in $10.15
5-7.9 .20-.31 $19.00
>8 mm >.32 $25.00

For Delivery Outside Maine

Size (mm) Size (in) Price per 1,000
1 mm 0.04 in $5.30
1.5 mm 0.06 in $7.60
2 mm 0.07 in $10.15
5-7.9 .20-.31 $24.00
>8 mm >.32 $30.00

Size is shell-length.

To place an order for soft-shell clam seed, call Kyle at 207-259-5048 or e-mail: kyle.pepperman@downeastinstitute.org.

Clam Pick Up and Planting

You are encouraged to pick up your clams sometime in April, but prior to May 1. After May 1 we cannot guarantee that your order will be filled. Planting clams during April or May ensures that the animals will reach their maximum shell length by the time that growth ceases in the fall.

For more information on increasing your clams survival in the clam flats and hatchery culture, check out DEI’s Manual on the Culture and Grow-Out of Soft-Shell Clams: A Practical Guide for Growing Clams in the Intertidal.

Transplant Permit Required in Maine

For Maine communities and individuals ordering DEI soft-shell clam seed, remember that you will need to obtain a transplant permit from the Maine Department of Marine Resources.  Please follow this link to find a transplant/relay permit application and instructions as well as contact information for the area biologists in your region.


Growing seed clams is a labor-intensive process that begins in January when soft-shell clam broodstock are collected from local flats. Hatchery staff culture algae (single-celled plants, or phytoplankton), and feed the algae to clam broodstock for approximately two months before inducing them to spawn. The larval (swimming) clams that result are microscopic. For their first two weeks of their life, the larval clams live in large circular tanks where they grow from 1/600th of an inch to 1/50th of an inch, or a little bit smaller than a grain of sand.

Microalgae are used to condition broodstock, and to feed clam larvae and juveniles. DEI rears a combination of diatoms and flagellates.

The first step in growing algae at the hatchery begins with stock culture in small 125mm flasks.
Cultured phytoplankton is then held in algal tubes (25-gallon fiberglass containers) required to feed millions of clam seedlings.
Clam broodstock are held in the facility for several months prior to spawning. We use a thermal shock technique to induce clams to spawn. This involves keeping the clams at 10-15oC (50-60oF) for several weeks prior to shocking them with 23-24oC (73-75oF) seawater.
Here, a male clam has been induced to spawn using the thermal shock technique.
A soft-shell clam pediveliger (ca. 14-days old). This is a swimming clam larvae, and is approximately 180-microns, or nearly 1/125th of an inch.

The tiny clams are then transferred to trays with fine mesh screening and floated on the surface of water-filled rectangular “set” tanks. (The tanks are referred to as set tanks because the clams which have been swimming in the water “settle” out to land on the surface of the screens that have been placed in the set tanks.) From that point on, the animals feed on cultured algae that hatchery staff grow in large, 25- and 50-gallon fiberglass tanks that surround the periphery of the hatchery.

Hatchery-reared soft-shell clam seed at DEI resting on window screening.
Tank used for raising soft-shell clam larvae.

Cleanliness is critical to the survival of tiny clams, and hatchery workers drain and refill the set tanks every other day, spraying off the clams and moving them to increasingly larger screens as they grow. When the clams attain a size of two millimeters in length, hatchery staff use a graduated cylinder to measure out 15,000 to 20,000 animals, which are placed in trays constructed of wood and window screening. Each tray receives a handful of periwinkles before being moved to a nearby ocean nursery site.

Seed clams being prepared for floating nursery trays. A handful of periwinkles is added to each side of the tray, and these help keep the window screen meshes clear of fouling macroalgae and other debris that would reduce water flow to the clam seed.

There the trays float on the surface of the water until November, which is the end of the clams’ natural growth cycle. During this time, the periwinkles act as marine vacuum cleaners and help keep the screens free of fouling material. By the end of the growing season, the juvenile clams are 1/4 to 1/2-inch in length.

Floating trays with black plastic covers to keep seagulls from poking through the mesh and preying on the growing clams inside the tray.
Soft-shell clam seed have grown from 2.5 mm to 12-15 mm from June to late October.
Close-up of soft-shell clam seed in late fall prior to overwintering.

Although the clams are large enough to seed, staff return them to our facility rather than expose them to winter mortality on the flats. The seed clams are transferred from the trays into mesh bags, which are stacked into modified lobster traps and submerged in circulating seawater until spring.

Off-loading nursery trays at DEI during November 2010.
Bags of clams inside overwintering cages at DEI. These will be submerged in running seawater from November until the following April/May.

The following spring, clams are stocked onto flats in communities that are interested in enhancing their flats with cultured clam seedlings.

A spring seeding on flats in Hampton, New Hampshire. Nets (1/4-inch aperture) are used to deter predators such as green crabs.

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