The Hungry Sea Urchin

Auf El Hierro ist das Ökosystem noch im Gleichgewicht. Hier knabbert ein Gallo an einem Diademseeigel.Foto von José Carlos Hernández
Sun, beach, and volcanic rock: the Canary Islands are a paradise – not only for tourists. An underwater sea urchin has made himself really comfortable there. If you have been on the beach, you might have stepped into one of its pointed spines. Ouch, it pricks! The sea urchin called Diadema antillarum has extremely long spines. But the pain they cause is relatively harmless compared to the real problem: there are so many of these sea urchins around the Canary Islands now that they threaten the biodiversity of the ecosystem. I reported on the problem and how marine biologists are trying to contain the plague.

— Reportage translated from German —

Sound bite

Badel: “Hay demasiado!” Friend: “En varios sitios …”

At the harbor of Valle Gran Rey on the island of La Gomera, Badel and his friend are constructing a big cage from wire. Their workshop is part of the vocational school named “El Taller”. Here, the two young men are learning how to fish. With the cages, they plan to catch an infamous animal – the long-spined sea urchin.

Sound bite

Friend: “Cuando está el erizo, no hay vida.” Badel: “Cómo un desierto.”

Where the sea urchin is, not much life survives, they say – like in a desert. By the steep cliffs of La Gomera, the animal devours all of the algae on the ocean floor. Along with the algae – the basis of the food chain – , most of the other creatures in the ecosystem disappear.

Sound bite Badel Cabrera Leon

“Es un problema tan grande …
Voice-over: It is a really big problem. How can we control these sea urchins? The island government had the idea to catch the animals and market them commercially. If the people here fish sea urchins and sell them, the problem can be controlled. It is just this one species, Diadema antillarum, and it’s an invader to this region.
… la Diadema, que es invasor de aquí.”

But the long-spined sea urchin migrated [to the Canary Islands] a long, long time ago. The subspecies “Diadema antillarum b” has been part of the ecosystems along the islands west of Africa for times immemorial. The only thing experts don’t consider to be normal is its strong proliferation. On La Gomera, the black sea urchin with the long pointed spikes already occupies 90 percent of the stony underwater soils. Manuel Machado Fernandez runs the training for which the students build the cages at the harbor, and he is hoping for a commercial solution to the sea urchin plague.

Sound bite Manuel Machado Fernandez

“Los gallegos especialistas que vinieron …
Voice-over: The experts from Galicia who visited us rated the sea urchin as good – the taste, texture, and body. You can use it for decoration or against acidified soils in agriculture.
… la acidificacion de los suelos de agricola.”

Give the sea urchin a value – for Fernandez, a passionate marine biologist, this is the only realistic solution. On the Spanish mainland, in Galicia and Asturias, sea urchins are considered a delicacy. Applied to the Canary Islands, the strategy could solve two problems at once, Machado Fernandez hopes: ease the environmental pressure and put money into the crisis-struck purses of the fishermen.

Lounge Music


“Filled piquillo pepper with blue mussel and sea urchin.
Hake and sea urchin lasagna.
Calamari with sea urchin caviar and Guía cheese.”

Lounge Music down

Recipes from a glossy brochure sponsored by the Spanish Ministry of the Environment. If it was only this simple to turn a plague into a business! But scientists at the University of La Laguna [on the island of Tenerife] claim that the idea won’t work. Marine biologist José Carlos Hernandez and colleague Sabrina Clemente have researched how sea urchins adapt to conditions in their environment. The results suggest that the Canarian long-spined sea urchin is simply not suitable for gastronomic exploitation:

Sound bite José Carlos Hernandez

“La talla de los erizos …
Voice-over: The size of these sea urchins depends on the density of their population. If there are many sea urchins, the individuals are smaller. If there are fewer, they get bigger. If we wanted to commercialize the sea urchin, we’d have to catch the bigger animals. But they live precisely in those areas where the ecosystem is still in a balanced state – and they play an important role within it. So it just doesn’t work out, it’s not profitable.
… no es rentable.”

Agustin Espinoza Diaz, a marine biologist working for the government of the island of Tenerife, has drawn the same conclusion. On his island, the spiny creature occupies almost 70 percent of the rocky coastal ocean floor.

Sound bite Agustin Espinoza Diaz

“A raíz de este gran problema …
Voice-over: Because of this huge problem, we started taking measures eight years ago, first to educate about the issue. We assigned lots underwater and invited divers to come and kill the sea urchins, to clean the floor. The fish returned, ate what was left, and after a few months a lot of algae had returned. With this campaign we wanted to show the divers how the ecosystem there would look in a natural state.
… ecosistema natural que debería estar ahí.”

Espinoza Diaz knows that the mass killing of sea urchins can’t be a sustainable solution. Not only because animal rights activists of such NGOs as the WWF speak out against such measures. Moreover, divers can go down to a limited depth only, and the sea urchin quickly returns. The conditions of the Canary Islands are perfect for the animal, explains Sabrina Clemente, marine biologist at the University of La Laguna.

Sound bite Sabrina Clemente

“Hombre, son muchos factores los que influyen …
Voice-over: There are many factors at play. Our studies show that overfishing the most important predators of Diadema antillarum plays an important role. Here on the Canary Islands and in other parts of the world, huge numbers of animals have been fished from the sea which previously had taken care of limiting the numbers of sea urchins.
… demasiado los numeros de erizos.”

The young scientist is critical of the current measures of the island government.

Sound bite Sabrina Clemente

“Se ha hecho una gran campagna por el gobierno …
Voice-over: The Canary government created a big campaign and paid diving clubs a lot of money to kill sea urchins. We oppose this. Our approach to the solution is that we must protect [predatory] fish, in particular four species around the Canary Islands.
… principalmente a cuatro especies de pesces en Canaria.”

All involved seem to agree on one thing: the best solution by far would be to establish a sufficient number of marine sanctuaries around the islands – zones that could help the predatory enemies of the sea urchin to re-create and re-establish the natural balance. Agustin Espinoza Diaz has just presented these plans in Madrid. The reactions in Spain’s capital have been positive, he says. But unfortunately, there is no money [to realize the plans]. In times of crisis, the sea urchin is last in line.


A report by Anja Krieger – Protected marine areas could help.… If you order fish on or from the islands, avoid choosing ones that control this sea urchin.… An interesting aspect is how the predators overcome the sea urchins. First, they bite off some of their long spines. Then they blow water at them to throw them over. Clever!

Credits + Links
Report broadcast July 23, 2012, on DRadio Wissen, Nature Section
Length: 7:05 minutes
Interviews conducted in Spanish
Report: Anja Krieger
Editor at DRadio Wissen: Lars Westermann
MP3 (German)
Post on my website (German)