Sea Urchin

Sweet. Briny. Luxurious.

Uni

Spiny on the outside, buttery on the inside, sea urchin, or uni in Japanese, is a delicacy in many coastal communities, and is often consumed raw.

Sea urchins are echinoderms (invertebrates related to starfish and sand dollars) with an armory of spiny, spherical shells that enclose five segments of bright yellow-orange gonads (reproductive organs from either gender) with a bumpy, tongue-like texture.

There are over 950 species of sea urchin worldwide, but only a few that are commercially harvested.

The Atlantic Green Urchin is found in the Northeast United States, Canada, Iceland, Norway, and Russia.

A brief history

“ . . . the best way to get rid of a pest is to eat it . . .”

Maine’s sea urchin fishery experienced a boom and bust cycle in the 1990s that has evened out in recent years. In the 1990s, the overseas markets in Japan became fascinated with New England’s urchin supply. The urchin industry quickly skyrocketed to the second most valuable industry behind lobster. It brought in $35 million alone in 1995. Hundreds of divers and draggers from Maine—and away—were competing to register for urchin licenses with no regulation from the state whatsoever. The sea urchin supply became dangerously overfished, causing the state to impose regulations in an attempt to save the urchin population. 

Today, the sea urchin fishery continues to be closely managed with restrictive harvesting rules. The state is looking to sea urchin farming as a sustainable way to diversify the still-delicate urchin population. 

The average adult size varies between 2 and 3 inches. 

Size

Green sea urchins are echinoderms, a group of marine invertebrates that include starfish. Sea urchins are covered with short, movable spines that are used for locomotion, as a passive defense against predators, and for trapping food particles.

Urchins are filled with five sections of bright yellow-orange reproductive structures called gonads. As the spawning season approaches, which is during the winter in the Gulf of Maine, the contents of the gonads are full of stored nutrient material, just prior to being converted to reproductive cells. At this time the commercial quality of the gonad is highest. If the urchin has been feeding successfully the gonad will be large, the water content low and it will have a yellow to orange color.

Body

diet

Sea urchins graze on kelp, algae, and other invertebrates in the area where they live.

Green sea urchin is abundant in subtidal areas with salinity greater than 15 ppt, just below the algal fringe between 15 and 30 feet, but has been found in depths up to 90 feet. Although found on a variety of bottom types, urchins prefer exposed rocky substrates.

habitat

Sea urchin typically has separate sexes. Fertilization takes place externally. Spawning occurs in the spring and early summer when water and food conditions are favorable. Females will release several million eggs into the water column, which will unit with sperm released from males.

spawn

The key to cooking with sea urchin is you want to buy them fresh.  

Sea urchins are full of sugar, salt, and amino acids, giving them an umami-salty sweetness. Like oysters, they tend to taste like the ocean they come from and the seaweed on which they feed. 

Think of urchin like you think of caviar—they both have a delicate flavor with salty, oceanic notes.

Although urchin is an exciting ingredient to experiment with in soups, sauces, and other dishes as a flavor enhancer, it is arguably at its best when enjoyed in its purest form—raw..

In the Kitchen

High-quality urchin gonads are yellow, gold, or orange in color with a sweet, ocean-like taste and a smooth, buttery texture. If the gonads are brown or gray in color, that could indicate it is no longer fresh, and should be avoided.

The Whole Fish

marinade

Urchin is most commonly served in its raw form to showcase its flavors without any distraction— a lobe placed on sushi rice, as a garnish on pasta, a standout in ceviche, or atop a piece of toast.

raw

Urchin is an emulsifier and can help thicken soups, custards, and sauces, such as mayonnaise, béchamel, and hollandaise

emulsify

Urchin can be added to a barbecue or yakitori marinade—the protein and fat will help with browning meat. 

The East Coast urchin industry continues to be closely managed with restrictive harvesting rules. Current management rules have been designed to encourage harvesters to leave more urchins on the bottom of the seafloor, and to fish for quality instead of quantity.

Examples of current harvesting restrictions include:

  • Minimum (2 1/16 inch) and maximum (3 inches) size requirements;

  • Poundage daily limit;

  • Limit on the number of harvest days per season

Since 2004, Maine has placed a moratorium on the issuance of any new urchin harvester licenses.

Fishing & Sustainability

Harvest Methods

diving. dip nets. baited whelk pots. ring traps. dragging.

Approximately 60% of the Northeast’s urchins are harvested by diving. Some countries allow for dragging, but, although cost effective, is non-selective with respect to urchin harvest size, and disruptive to bottom substrates.

The green sea urchin fishery typically begins in October, when the sea urchin gonads are considered mature and suitable for harvesting and continues until May, when urchins begin to spawn.

Most of the high quality urchins are found in what is called a "feed line", which is a narrow strip of bottom just below a kelp bed. The ideal method of harvesting is to remove the quality urchins from the feed line and allow others to move into the prime feeding area and develop quality gonads for subsequent harvesting.

  • Sea urchins feed on kelps and other macroalgae, and play an important ecological role in determining algal distribution and abundance. Their grazing can reduce kelp beds to “urchin barrens”, dominated by urchins and encrusting coralline algae. When urchins are removed, fleshy algae will recolonize.

    This algal habitat, in turn, may create a hospitable environment for crabs and other predators which feed on newly settling urchins, making it difficult for urchins to become reestablished once they have been removed.

    DMR recognizes that an important goal of sea urchin management should be the avoidance of further flips from urchin habitat to the stable algal state. However, a return to the extensive and less productive urchin barrens (a lot of urchins and encrusting algae and little else) of the 1980s is certainly not desirable. A mosaic of kelp beds and urchin patches is a reasonable objective for productive Maine fisheries.

  • Domestically, the law implemented by the Maine legislature on January 1, 1994 sets limits on the harvest of urchins. The limit includes:

    Harvest Season: August 15- May 15

    Size Limitation: Urchins cannot be harvested if they are less than 2 1/16 inch.

    Night Harvesting: Prohibited

    Lobster Restriction: Sea urchin harvesters cannot possess lobsters while fishing for urchins.

    Management of Maine’s sea urchin fishery is the joint responsibility of the Maine State Legislature and the Maine Department of Marine Resources (DMR), with advice from the Maine Sea Urchin Zone Council, an industry council with representatives from the harvesting, buying/processing, aquaculture, and research communities.

  • Hatchery methods developed in Japan since the 1960s have made full-cycle aquaculture of urchin feasible. The University of Maine Center for Cooperative Aquaculture Research operates a small hatchery for as urchins to encourage commercial development in the Northeast US. However, grow-out methods are still under development. These methods include—free-range esa ranching, tank culture, gonad enhancement, and co-cultured shellfish.

Due to historical struggles with overharvesting, there are a number of significant restrictions placed in New England on the harvest of urchins.

Environmental Impact & Efforts

According to NOAA, the U.S. wild-caught monkfish is a smart seafood choice because it is sustainably managed and responsibly harvested under U.S. regulations.