A team of Maine and New England researchers is working on a project to develop the best ocean “scuzz” for hungry sea urchins, and to rebuild Maine’s stock of the once-prolific spiny sea critters. 

Though sea urchins may seem an unlikely focus for Maine’s burgeoning aquaculture industry, “uni,” also known as urchin roe or gonads, is considered a delicacy in many Asian and some European markets. Steve Eddy, director of the University of Maine Center for Cooperative Aquaculture Research, believes urchin could become a valuable economic driver for the Northeast region.

The team, which includes researchers from the University of Maine, Maine Sea Grant, University of New Hampshire and University of Rhode Island, received a $100,000 grant from the U.S. Department of Agriculture’s Northeast Regional Aquaculture Center to improve hatchery production of the green sea urchin and engage prospective urchin farmers on how to grow farms in the Gulf of Maine and coastal northern New England, the University of Maine said in a statement. 

Eddy has been studying sea urchin aquaculture for over 15 years, working to grow urchin seed stock in the hatchery with varying degrees of success. Some years, the 100,000 to 200,000 urchin seeds will yield a harvest of 60,000 urchins, but most years they average between 5,000 and 10,000 of the creatures.

While the yield has varied greatly, Eddy said the hatchery has had success in growing the urchins to market size rapidly.

A sea urchin harvested by the University of Maine’s Center for Cooperative Aquaculture Research as part of a project to determine the best environment for raising the creatures, which fetch a high price on the Asian market. Photo courtesy of University of Maine

With high-protein diets and a steady temperature, the urchins have been raised to market size in two years instead of the three to eight years it can take in the wild, he said.

Sea urchin larvae – small, bell-shaped babies with four to eight arms depending on their age – are known as echinopluteus and drift with the current, feeding on phytoplankton. When they grow their eighth arm, they also grow an internal structure attached to their stomach called a rudiment, Eddy said.

The rudiment will then metamorphose into a microscopic urchin. It can take anywhere from 25 to 45 days to reach that stage. 

Then, Eddy said, the echinopluteus attaches to a hard structure, and the rudiment continues to grow while the rest of the body dissolves. The urchin develops a mouth and jaws over the next few weeks and then starts grazing on biofilm, or what Eddy refers to as “scuzz.” At about 5 millimeters in diameter, they can start eating macroalgae. 

The pace of growth from metamorphosis depends on the composition of the biofilm and the macroalgae, he said, and that is the stage their research will focus on.  

Getting through the first phase has been relatively easy, he said, but after around 25 days, when the urchins turn from larvae to micro-urchins, they tend to struggle.

“The trick is to grow the right kind of scuzz,” Eddy said. “We think we haven’t had the right kind of biofilm (in years when the production has been lacking.) We’re trying to standardize that.”

Part of the project also will involve increasing the urchin stock and reaching out to prospective growers about the creature’s potential.   

“Urchin farming has generated a lot of interest in Maine, but nobody’s really nailed it down yet to where urchins are a profitable crop to grow,” Dana Morse, a Maine Sea Grant associate based at the Darling Marine Center, said in a news release. “To allow us to take advantage of the creativity and ingenuity that prospective growers have – our best chance for developing economically viable systems – they need access to seed stock, and that’s where we are starting.”

At its height in 1995, Maine’s sea urchin fishery, then primarily wild harvest, was worth $35.6 million with 34 million pounds landed, according to the Maine Department of Marine Resources

The population explosion, popularity of uni and relative ease of harvesting – “They don’t run away,” Eddy noted – caused a “free-for-all” and the fishery collapsed due to overfishing. 

The stocks have remained relatively stable over the past few years, but are only a shadow of what they were. In 2019, the fishery was worth $5.8 million, and 1.7 million pounds were landed.

While the state’s sea urchin fishery is no longer booming, global demand for the creatures continues to increase. 

According to Eddy, the quality of roe, which is present in both male and female urchins, depends on the quality of the macroalgae.

“Aquaculture gives us more control over this process and especially gives us the ability to produce sea urchins with top quality roe and high yield,” he said. 

Morse said sea urchins harvested in Maine have a good reputation among buyers, making the researchers’ work even more potentially lucrative for the industry.

“We have a chance to grow a product that is desired by the market,” he said.

Eddy believes a strong sea urchin fishery can benefit the rest of the aquaculture industry, as well. 

Unlike oysters, which filter water, sea urchins are grazers. 

“You can put them into the same containers (as oysters) and the sea urchins will help keep the containers clean by grazing off the scuzz that’s naturally growing,” he said. 

Or, for seaweed harvesters, instead of discarding or composting leftover or lower-quality seaweed, it can be given to sea urchins.

To Eddy, it’s a win-win situation. 

“It gives crop diversity for your farm – it’s eating leftovers or helping your cages stay clean (while) giving you extra income,” he said. “This isn’t research for the fun of it. The primary focus is economic development.”


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