“Ocean Urchins”

    Anyone who fishes the coastline of New England notes the differences north and south of the Cape. While anglers may still be chasing the same species—bluefish and striped bass, for instance—the environment is rather different. To the north, the water is much colder and the coast becomes mostly rocky. To the south, sandy beaches and warmer waters are more the norm.

   With that change to rock-studded coastlines and colder waters comes a different set of echinoderms. The sea star is the most commonly known member of the rough-skinned phylum. While sea stars are quite common both north and south of the Cape, sea urchins, brittle stars, and sand dollars are all much more common in cold, boreal waters. The sea urchin, particularly, has an interesting ecology—and an equally interesting history.
   Sea urchins have a rounded “test” – or shell – about the size of a tennis ball, which is much more rigid than the shells of sea stars. While at first glance a sea urchin may not seem related to a sea star, it’s apparent once you take a closer look. With urchin in hand, flip it over and look at the bottom. You should be able to make out ten sections, from which five distinct “arms” can be arrayed. If you peeled the arms out and laid them flat, the urchin would very much resemble a sea star.
   These five arms are filled with holes, and from those holes run the tube feet (often called suckers on a sea star), which are used for locomotion, to hold the urchin onto rock and other substrates it crawls on, and to move food to the mouth. In the water, the tube feet can extend well beyond the spines seeking food or a place of attachment, giving the urchin a Medusan appearance.
   The spines of sea urchins are their most noticeable characteristic, and they’re used for defense and locomotion. If you watch an urchin the water, you’ll see the spines “waving.” The spines the near the bottom and in contact with the substrate will dig in and slowly move the urchin along. There is a delicate dance ongoing between the tube feet and the spines. They work together to move the urchin along; while keeping it in place, despite currents set up by waves and tides.
   The green sea urchin (Strongylocentrotus droebachiensis) is one of the most common sea urchins in New England and can also be found along the Pacific Coast and in European waters. They live in tide pools along the coast north of Cape Cod and range into deep waters as well. The spines on the green urchin are not poisonous, and you would be hard-pressed to impale yourself on them, unlike some of the longer, sharp-spine varieties found in tropical waters (e.g., the long-spined urchin). Sea urchins creep along the sea floor and the rocky sub-tidal shoreline. They subsist mainly on seaweed, though they can and will eat fish and other animal flesh, given the opportunity.
   Fish, crabs, and sea stars are the main marine predators of the green sea urchin, though a new predator—man—has entered the scene. Apparently, someone once flipped over a sea urchin, opened the shell, and decided to eat the bright yellow or orange reproductive organs – and found them quite tasty.
   In Japanese cuisine, sea-urchin roe is called uni. It’s buttery or custard-like in texture with an enticing flowery bouquet. Uni has a sweet, briny taste that varies depending on the urchin’s origins. As with the terroir assigned to certain wine grapes and the particular soil in which they were grown, or oysters and the particular characteristics of the water in which they were raised, uni’s aqueous origins add another dimension to its intrigue. This makes uni even more of a treat for those who develop a taste for it, and, like highly sought-after oysters and wines­, it commands a steeper price tag.
   Each urchin produces five little strips of uni, which must be carefully removed and then thoroughly cleaned before they get to the consumer. Uni is highly perishable and doesn’t freeze well; therefore, it must be handled carefully while getting from source to consumer rapidly. Uni’s fragility adds to its cachet—and to its hefty price tag.
The highest demand for sea-urchin roe for consumer markets is in Japan, where fresh uni often commands a very high price. When any commodity hits top dollar, there will likely be a rush to cash in on the action. This is what has happened with green sea urchins in New England.
   The green urchin is not much of a challenge for a predator to catch. They amble slowly along the bottom, and while the spines may deter a fish or two from taking a serious bite, it’s not much of a defense against the gloved hand of a diver who can readily and rapidly pluck urchins off rocks and pop them in a bag to go to market.
   Say that every urchin might yield about 10 percent of its body weight for uni, and an average urchin weighs about 3 to 4 ounces. That would mean that each urchin yields about 1/3 of an ounce of uni, or three urchins to the ounce. Given that several-thousand tons of uni are consumed annually, you can imagine how many urchins it takes to feed a sushi-loving, uni-hungry population.
   Because of high demand and high prices, urchins have been overharvested in some areas, including Maine. Rules are now in place to better manage the urchin fishery and move toward sustainable harvest. Some of the “seafood cards” out there still give Maine urchins an “avoid” status, though there does appear to be some rebound in stocks, suggesting the start of a recovery. Green urchins are now being raised in aquaculture operations, and this will likely take some of the pressure off the need to harvest wild stocks to meet demand.
   The lot of the green sea urchin seems a rather unlikely tale, indeed. Maybe someone on a Pacific coastline saw sea otters lazing on their backs in the water, munching urchins, and decided to give it a try. And with that, the urchin—basically a spine-covered tennis ball that scrapes algae off sub-tidal rocks in chilly waters—went from obscurity to notoriety, oddity to delicacy.

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