Battle of the urchins

I remember the first time someone told me that sea urchins were edible. It was at a party hosted by my high school marine biology teacher, at which he served a variety of snacks from the local marine ecosystem. I don’t think I tried the sea urchin on a cracker that evening, in part because I was vegetarian and in part because the orange blob did not look very appetizing to me.

“Sea Urchin Roe” by Ron Dollete is licensed under CC BY-ND 2.0

I could not have imagined then that I would be living on the West Coast many years later, and that an abundance of sushi restaurants would have made uni or sea urchin seem a lot less unusual. I also could not have imagined that the ocean floor would see a veritable battle of the urchins.

A recent news article recounts how “tens of millions of voracious purple sea urchins that have already chomped their way through towering underwater kelp forests in California are spreading north to Oregon.”1 The purple sea urchin, Strongylocentrotus purpuratus, has eaten its way through so much kelp that other species depending on that same kelp, including the red sea urchin, Mesocentrotus franciscanus, are in decline. The kelp forests were already struggling due to “warmer-than-usual waters in the Pacific Ocean.”2 On top of that, one of the purple urchin’s main predators, the sunflower sea star, Pycnopodia helianthoides, has seen a sharp decline due to a wasting disease that is yet to be fully explained but thought to be due to a combination of a pathogen and the same warmer ocean water affecting the kelp forests.3

“File:Strongylocentrotus purpuratus California.JPG” by 99of9 is licensed under CC BY-SA 3.0

It is a good reminder of the tight interconnections between species in an ecosystem, with the most unpredictable factor in the ecosystem still being Homo sapiens. That species is now deciding how to respond to the out-of-control population of sea urchins, so that the kelp forests may have a chance to recover (even as Homo sapiens is doing far too little to stop the climate crisis that also affecting the kelp.) In September 2018, a project to remove and destroy large numbers of sea urchins began in the Gwaii Haanas, further north along the BC coast. The Parks Canada webpage providing information about that project does not specify whether it is a proliferation of purple or red sea urchins, or perhaps a combination of both, that is threatening the kelp forests.4 In the Gwaii Haanas project, the sea urchins are raked off the rocks and smashed with a hammer, which is labour intensive and generates no direct revenue.

“Red sea urchin” by brewbooks is licensed under CC BY-SA 2.0

In the explosion of purple sea urchins in California, one of the proposed solutions is to make them commercially viable. Interestingly, the purple urchin can survive well in conditions of food scarcity, but there is little to eat in a skinny urchin. While the edible part of the urchin—the orange blob I describe above—is commonly called urchin “roe,” suggesting it consists of eggs, uni is actually the gonads that produce the eggs.5 For these gonads to be worth harvesting, the sea urchin has to be well fed. So,

conservationists, commercial urchin harvesters, scientists and private interests are coming together with an unusual plan: Pay underemployed red sea urchin divers to collect the shrivelled, but living, purple sea urchins and transfer them to carefully tended urchin “ranches” to be fattened up for sale to seafood markets around the world.6

Next time someone offers me an orange blob on a cracker, it won’t be a novelty anymore. Instead, it may be, as one of the commercial urchin harvesting companies puts it, a way to “help the kelp.”7

  1. Associated Press, “Sea Urchin Explosion Decimates Kelp Forests Off Pacific Coast,” CBC News, October 24, 2019,
  2. Associated Press, “Sea Urchin Explosion Decimates Kelp Forests Off Pacific Coast,” CBC News, October 24, 2019,
  3. Jason Daley, “Why Almost All of the West Coast’s Sunflower Sea Stars Have Wilted Away,” Smithsonian Magazine, January 31, 2019,
  4. Parks Canada, “Chiix̱uu Tll iinasdll: Nurturing Seafood to Grow,” August 2, 2019,
  5. Michelle Persad, “Uni Is Gonads. Go Chew On That,” Huffington Post, March 30, 2016,
  6. Associated Press, “Sea Urchin Explosion Decimates Kelp Forests Off Pacific Coast,” CBC News, October 24, 2019,
  7. Urchinomics,