Strongylocentrotus purpuratus (Stimpson, 1857), commonly known as the purple sea urchin or Pacific purple sea urchin, inhabits the eastern Pacific coastline from Baja California, Mexico, to British Columbia, Canada. It is particularly abundant along the coast of California, where it is an important herbivore in kelp forest ecosystems.
As its name suggests, this species is distinguished by its deep purple test and spines. Adults typically reach around 10 cm in diameter and may live for several decades, with some individuals estimated to survive for more than 70 years.
The purple sea urchin is a herbivorous species that feeds primarily on kelp and other marine algae. In recent decades, population outbreaks have occurred in parts of its range due to a combination of factors, including declines in key predators—particularly the sunflower sea star (Pycnopodia helianthoides)—marine heatwaves, and large-scale losses of kelp forests. Dense populations can overgraze kelp habitats, transforming them into so-called “urchin barrens,” where little seaweed remains.
For sushi and seafood markets, the edible portion is the gonad, known in Japanese as uni. Although commercially harvested, the species is generally considered less valuable than the larger Giant red sea urchin (Mesocentrotus franciscanus) because of its smaller gonad yield. However, high-quality specimens can offer a rich sweetness, a clean ocean flavor, and a creamy texture. The gonads typically range in color from yellow to golden orange.
In California, purple sea urchins are increasingly harvested as part of ecosystem restoration efforts, helping to reduce grazing pressure on kelp forests while providing a sustainable source of uni for seafood markets. This approach has attracted growing attention from both fisheries managers and the culinary industry.
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