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Vibratory Screener Helps Raise Little Neck Clams

BRIGANTINE, NEW JERSEY—Clam Daddy's (www.clamdaddysnj.com), a family owned and operated business located in Brigantine, NJ, has been selling hard shell little neck clams (Mercenaria mercenaria) since 1984. Initially, only clams growing naturally in Brigantine Bay were harvested, but as demand increased while yields did not keep pace, the company began to breed and grow its own fresh clams in a temperature controlled hatchery. Today, the company focuses on upscale outlets such as gourmet restaurants in nearby Atlantic City and seasonal produce markets that demand top quality rather than mass markets that buy primarily on price.

The clams begin their lives in late March as microscopic organisms invisible to the naked eye, growing to the size of a grain of sand in about 17 days and gradually increasing to market size over a period of three to four years. As they grow, they are moved from the breeding tank through a series of smaller vessels where they are fed with specially grown algae. Once the water in the bay warms to a temperature between 50°F (10°C) and 60°F (15°C), they are transferred outdoors to vessels called upwellers, through which the bay water, which contains naturally occurring algae, is continuously circulated. Once the clams reach a sufficient size, they are transferred to long, shallow structures, called raceways, through which bay water is also continuously circulated. The raceways are arranged on a pier in order of the size of the clams they contain, with those designated for the largest clams closest to the bay.

"As the clams continue to grow, the larger ones are transferred to a different raceway," says Bill Mayer, owner of Clam Daddy's. "If we didn't do this, the larger ones would consume all of the nutrients, leaving the smaller ones to starve. Originally, we separated the larger clams by placing several handfuls in a manual shaker screen—a wooden box with a mesh screen bottom—and shaking it until all of the smaller clams passed through the mesh. This, however, was not only time consuming but also resulted in a lot of sore arms."

As sales continued to grow, manual separation became increasingly burdensome. So in 2010, the company automated its screening process by installing a 36 in. (914 mm) diameter Vibroscreen® circular vibratory screener manufactured by Kason Corporation of Millburn, NJ.

"Our Kason screener eliminated the need for a time-consuming, repetitive task," says Mayer. "It not only does in minutes what used to take hours, but allows me to deploy my staff to perform more important operations."


Vibratory screener automates classification by size

The circular vibratory screener consists of two screening decks, one above the other, with an imbalanced-weight gyratory motor that causes them to vibrate. "When the time comes to remove the larger clams from a raceway, we scoop several handfuls of them into the top deck of the screener, which has a slightly larger mesh than the lower one," Mayer explains. "For example, we might have a 3/8 in. (9500 micron) screen on top and a 1/4 in. (6300 micron) screen on the bottom. As the clams move toward the periphery, the smaller clams fall through onto the bottom screening deck. Those small enough to pass through the tighter mesh of the lower screen are ejected through a discharge spout into a collection pan. Those too large to pass through the smaller mesh are ejected through another discharge port into a separate collection pan. The largest clams, those that failed to pass through the larger mesh of the upper screen, remain on that screen."

"Once all the clams in a raceway have been screened, the smallest ones are returned to the raceway from which they were originally taken, Mayer explains. "Those slightly larger are placed in the next raceway with clams of their own size, while the largest clams are placed in the next raceway after that. The process continues until the largest clams from the last raceway are removed and placed in special leased areas of the bay, where they continue to feed and grow until harvested to fill an order."


From birth to harvesting takes 4-5 years

The process of growing clams begins with growing algae, the food on which clams thrive from birth through final harvesting. Algae culture starts in test tubes. Each week, the cultures are transferred to larger containers, first to flasks, then to carboys. At the same time, large vessels called kalwalls are filled with UV-filtered sea water to kill any harmful bacteria that may prevent the algae from growing. Nutrients are added, and the kalwalls are inoculated with cultures from the carboys. In a week to ten days, the algae cells begin to divide and multiply until ready to feed to the clams.

Simultaneously, brood stock clams are brought indoors in February. The temperature of the water is gradually increased and they are fed twice daily. After about a month and a half, the brood clams are full of eggs and sperm. About 60 female clams can produce millions of eggs. Gradually increasing the temperature of the water triggers the clams to release both eggs and sperm, and the eggs are fertilized in separate tanks. The first larval stage, called veligers, swims in the tank for about 10 to 15 days before eventually settling to the bottom. At this stage, they can be seen only under a microscope.

As the clams grow, their shells begin to harden and they are measured and checked to ensure they are healthy. The water is changed and the tanks cleaned to make sure they are free of harmful bacteria. At 16 days old, growth rings become evident and at 17 days, the hatchlings look like grains of sand. After about two weeks, the clams are transferred to vessels called downwellers, in which warmed sea water is circulated from the top down. They are fed by naturally occurring algae in the sea water.

Once the bay warms to the desired temperature, the clams are brought outside and transferred to upwellers, in which bay water circulates from the bottom up. The upwellers are drained daily, allowing the clams to be checked for growth and rinsed. When large enough, the clams begin their progression through the raceways, sorted by size by the circular screener. When the largest clams reach the last raceway, they are ready to be planted in the bay.


Protected areas of the bay reserved for seed clams

The seed clams are planted in shallow areas of the bay leased from the State of New Jersey and covered with special nets so they will not be eaten by birds, crabs, skates or other predators. During the summer and fall, built-up algae must be cleaned from the nets using special rakes to prevent the clams from suffocating. The nets remain on the hatchery areas until winter, when they are removed.

The leased areas of the bay are marked with plastic or cedar stakes and remain off limits to boats and personal watercraft. The areas stay under constant surveillance, not only by Conservation officers but also by local residents, to prevent theft. Different areas are reserved for different size clams and as they grow, they are moved from area to area. When they reach their full size after 4 to 5 years, they are harvested, rinsed, sorted by size, counted, bagged and refrigerated, ready for delivery.

"The reason upscale restaurants and farm markets prefer our clams is that they are never gritty with sand because we use special rakes to clean the nets and harvest the clams," Mayer says proudly. "We also don’t harvest them until they are needed to fill an order, so they are the freshest clams that you will find anywhere."

Vibratory Screener Helps Raise Little Neck Clams
 


Vibratory Screener Helps Raise Little Neck Clams
 

A 36 in. (914 mm) diameter circular vibratory screener automatically sorts the seed clams by size in minutes, replacing the slower, labor-intensive manual shaker screen shown at right.


Vibratory Screener Helps Raise Little Neck Clams
 

Smaller seed clams are ejected through a discharge spout into the collection pan on the left, while larger ones are ejected into the pan on the right.


Vibratory Screener Helps Raise Little Neck Clams
 

Clam Daddy's delivers freshly harvested clams to upscale outlets such as gourmet restaurants in nearby Atlantic City and seasonal produce markets that demand top quality.


 



Eggs just after fertilization


 

Clams start growing as they are fed with algae, which is produced in the laboratory and can be seen in their gut.


Vibratory Screener Helps Raise Little Neck Clams
 

Algae is grown in kalwalls in the hatchery to feed the clams.


Vibratory Screener Helps Raise Little Neck Clams
 

Unloading clams at Brigantine Bay.


Vibratory Screener Helps Raise Little Neck Clams
 

Clams ready to be sorted and counted.

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