Rediscovering Sea Urchins: The Ocean's Delicacy in Uni Sushi

Sea urchin with rice, stock.adobe.com

Sea urchins are a delicacy discovered from the sea. Originally an Asian food, they conquered the palate globally with the readily edible orange flesh inside their thorny outer shell. It was the Japanese who perfected the cuisine made of sea urchins, as they prepared tasty rice and sushi recipes out of it.

A sea urchin is an echinoderm, a family of marine invertebrates that includes sea cucumbers, starfish, sand dollars, and crinoids. It lives on seabeds, moving around by using its spines as legs and feeding on algae.

Sea Urchins: Unique Facts

Culinary experts describe the taste of sea urchins (named 'uni' in Japanese) as sweet and salty in an oceanic way. Ocean floors with rocky bottoms are the breeding grounds for sea urchins. Their bodies have a common feature, radial symmetry. Once harvested, the sea urchin is split open, and the golden yellow gonads inside, arranged like the petals on a flower, are extracted. There will be five gonads inside a sea urchin. Mostly, they are eaten raw, especially with sushi in Japan. The sea urchins are playfully called the hedgehogs of the sea. Their thorny outer shell justifies the name. Did you know that as sea urchins grow from larvae, they invert themselves, resulting in their spiky interior (fully developed by that time) becoming their outer shell?

Sea Urchins are Among the Few Food Items, Harvested from the Wild and Eaten Raw

Sea urchins, or uni, live for decades and even centuries if left to themselves. Without any haste, they move upon the rocky bottom of the sea, eat whatever they come across, and grow. They are seen on the seas all around the world. They have to be handpicked by harvesters, as they are very delicate to handle. In Korea, women scuba divers are traditionally the experts in harvesting uni.

Not everyone could love the taste of uni. It smells of the sea, has a briny taste, and a slight sweetness accompanies its creamy texture. Many uni lovers testify that it is an acquired taste.

Sea urchins consume sea algae, and for humans, they provide an excellent source of omega-3 fatty acids. Uni also contains a significant amount of proteins and antioxidants, with the majority of its fat being unsaturated.

Uni Sushi, a popular Japanese dish, is the most common way to enjoy uni. It is cooked rice wrapped in a sheet of seaweed and topped with raw sea urchin gonads. They also form part of salads and sometimes are served in their outer shells.

Cultivation Method of Sea Urchins in Coastal Seas

Uni is plentiful in the coastal waters of California. Sea urchins come in both male and female varieties. They release sperm and eggs into the surrounding seawater, where fertilisation occurs quickly. The embryo swims in the ocean for a period, taking on the peculiar shape of a space lander. Once the spiny adult form has developed inside, it turns itself inside out. Just before this rapid maturation, the embryo attaches to a rock. The result is a well-formed sea urchin with spines and numerous tubular feet.

Sea urchins are found in a variety of colours, including green, pink, purple, red, black, and pale yellow. Some are not suitable for consumption. This marine species is among the most sensitive organisms globally in terms of their response to global warming and climate change.

Japan has been successful in breeding sea urchins on commercial farms. Eggs and spawns are gathered from sea urchins and fertilised in a laboratory environment. Once the embryos hatch, they are grown in artificial tanks until they become mature enough to survive on their own. During this entire period, they are fed sea algae. Sea urchins are voracious feeders, consuming large amounts of sea algae. Occasionally, they are kept on the farm for a year or longer before being harvested, or they are released into natural water enclosures to be harvested later.

Sea urchins sometimes cover themselves with rocks and other materials. It's kind of a camouflage and helps them survive in the hostile environment of an ocean bed where a wolf eel, trigger fish, putter fish, or parrot fish could break open and eat them using their strong jaws. Crabs and lobsters also prey upon them, crushing their outer shells using claws.

California Has A Sea Urchin Problem: Just Eat Them To Solve It

Sea urchins exhibit self-covering behaviour under environmental stress. They tend to cover themselves with pieces of rocks and shells. Scientific studies suggest that this covering helps them protect themselves from predators and physical damage from intense sunlight, and also these covering materials can function as a source of food.

Just like how cattle grazing depletes our terrestrial environment, sea urchin grazing impoverishes the marine environment. The sea urchins destroy the green algae ecosystems by feeding on them. California is facing a serious problem of sea urchins destroying its environmentally valued kelp forests in its coastal marine ecosystem. According to an article in 'The Guardian', the population of sea urchins along the Californian coast has surged by 10,000% since 2014. The destruction of kelp forests devastates the entire marine ecosystem, including the fish that rely on them for food. Areas where over 95% of the kelp forest has been wiped out are known as 'urchin barrens', as they are dominated by a vast expanse of sea urchins covering the ground. Scientists have been urging Californians to include sea urchins in their daily diet to help manage their population.

Now, a quick tip on how to keep sea urchins once bought or harvested. They can be kept fresh in saltwater for many days. They can also be covered in a damp cloth and kept in the fridge.

References

The Solution to California’s Rampant Sea Urchin Problem is to Eat Them: I Gave it a Try. Vivian Ho, theguardian.com

Sea Urchins Pull Themselves Inside Out To Be Reborn, Deep Look, YouTube.