New research compares effectiveness of common Atlantic sea scallop farming methods

Much of the scallop farming techniques used in the U.S. derive from practices in Japan, where scallops have long been a part of the country’s seafood industry. Researchers from the University of Maine are working to test and adapt those practices to help grow the industry in the Gulf of Maine, where oyster farming is currently the most well known form of aquaculture in Maine’s blue economy. 

Building off a four-year study published in the spring, which compared the effectiveness of two different Atlantic sea scallop farming techniques, UMaine researchers further analyzed the economic advantages and disadvantages of the same two methods of scallop aquaculture. Lead researcher Damian Brady, professor of marine sciences at UMaine, and co-author Chris Noren, a postdoctoral researcher, used their results to develop a user-friendly application that helps interested parties compare the different costs and possibilities associated with building their own scallop farms. 

“Now new farmers can make educated decisions on what option is going to be most viable for them, taking into account their location, timeframe, budget and all the other pieces that go into scallop farming,” Brady said. “Ultimately, our goal is to help Maine grow this industry to its fullest potential and preserve Maine’s working waterfronts — an integral part of the state’s culture and history.”

Published in the journal Aquaculture, the study looked at two of the most common options for scallop farming: lantern net and ear-hanging. Previously, lantern net methods were thought to be more cost-effective, but this study shows the ways in which the ear-hanging method can be more cost-efficient over a longer period of time. 

Researchers concluded that ear-hanging production was more advantageous if the scallops’ life cycles exceeded three years, and lantern-hanging is slightly more profitable when scallops are harvested under three years. They also found that the most optimal time for harvesting, regardless of farming method, was when scallops reached an age of 3.75-4 years.

The Two Farming Methods

Lantern net aquaculture uses tiered, circular nets that attach to a long line and hang vertically in the water column — an easier and less expensive system to set up compared to the ear-hanging method. Scallops sit in each tier of the lantern net, which can cause overcrowding and issues with food resource accessibility. However, research showed that overtime, the overcrowding can make lantern net farming productive over a four-year cycle. 

Developed from Japanese methods, ear-hanging involves drilling holes into the “ear,” or the hinge, of the scallop shells, which are then pinned and hung on vertical lines in the water column. This method allows for individual scallops to have more space and access to resources. While it is more expensive to set up, labor costs significantly drop and overall expenses level out over a four-year period. 

To combat start-up price, Japanese scallop farmers have used a number of different technologies and techniques that could be applicable in Maine. This includes specialized equipment, such as automated drilling and pinning machines, or a multi-partner ownership, in which one partner does the drilling and preparation, while the other does the farming and de-pinning. Cooperative partnerships allow each group to invest and specialize in a fraction of the machinery and equipment. 

Comparing Farming Methods

The study looked at two different scallop metrics over a four-year period: the height of the entire scallop shell in millimeters and the weight of the adductor muscle in grams. Both metrics have applications for the current U.S. market and its potential to expand. 

Generally in the U.S., the adductor muscle is the only part of the scallop that is sold or used. The bigger or heavier it is, the higher the price. The U.S. market for whole scallops, which include other parts of the bivalve along with the adductor muscle, is limited, but methods that increase the size of either part of the scallop have the potential to improve market value. 

Although ear-hanging requires more front-end labor and the equipment is more expensive than the lantern net method, the rate of production is significantly faster over a longer time period. It is also more space efficient, which requires a smaller lease and is less expensive. 

Additionally, the researchers stressed the importance of a working waterfront for doing tasks that do not require being on the water. This allows for less weather-dependent work days and for small farms to grow with less limitations. 

Ear-hanging is not only economically more effective in total labor costs and leases; it also results in ear-hanging scallops growing larger adductor muscles on average, according to the study. Researchers concluded that the long-term benefits of growth size, lease cost and total labor costs make the higher start-up costs of ear-hanging worthwhile for farmers entering the market for longer than three years.