Warming Seas and Red Tides: Why Japan’s Sea Urchin Delicacy Is Slipping Out of Reach

Japan’s Sea Urchin Crisis: A Delicacy Under Threat

Japan’s beloved sea urchin, known as uni, has long been a symbol of luxury and culinary excellence. But in recent years, this prized delicacy has become increasingly scarce and expensive, with prices soaring to record highs. On Hokkaido’s Rishiri Island, a bowl of rice topped with just 100 grams of bafun sea urchin now costs between 15,000 and 18,000 yen (roughly $100–$120), double what it was only a few years ago. The sticker shock is so severe that groups of diners often share a single bowl, supplementing their meal with cheaper dishes like ramen. For many Japanese households, uni is now off the menu—even for special occasions.

This dramatic price surge is not just a story of luxury gone out of reach. It is a warning sign of deeper environmental and economic challenges facing Japan’s seafood industry, driven by a combination of climate change, extreme weather, and ecological disruptions.

What’s Driving the Price Surge?

Several factors are converging to push sea urchin prices to unprecedented levels. While policymakers often cite the weak yen and rising import costs as primary culprits behind Japan’s broader food inflation, scientists and industry experts point to a more insidious threat: warming seas and ecological upheaval.

Warming Waters and Shifting Species

Research shows that average sea temperatures around Japan have risen by about 5 degrees Celsius in recent years. This warming trend is particularly pronounced in northern regions like Hokkaido, historically known for their cold, nutrient-rich waters that support species such as salmon, squid, saury, and sea urchin. As the waters warm, these cold-water species are struggling to survive, leading to sharp declines in their populations and, consequently, their availability in markets and restaurants.

According to a Reuters report, the catch of sea urchins on Rishiri Island has halved compared to the previous year, continuing a multi-year downward trend. The price for 10 kilograms of Rishiri’s bafun sea urchin has surged to 90,000 yen—more than double the price just two years ago. Similar patterns are seen with other cold-water seafood, whose prices have jumped nearly fivefold over the last two decades.

Red Tides: A Deadly Phenomenon

Compounding the problem are increasingly frequent and severe red tides—harmful algal blooms that can devastate marine life. In 2021, a series of red tides off the coast of Hokkaido caused mass die-offs of both salmon and sea urchins. The Hokkaido prefectural government estimated the damage to the local seafood industry at 7.6 billion yen (about €58 million), with losses from 2,300 tonnes of sea urchins alone accounting for 6.84 billion yen (€52 million). These events not only wiped out adult sea urchins but also likely decimated juvenile populations, threatening future harvests.

Red tides are not new to Japan, but their appearance in Hokkaido—once considered too cold for such blooms—signals a worrying shift. Warmer waters, possibly linked to climate change, create favorable conditions for the proliferation of phytoplankton species like Karenia selliformis, which can be deadly to marine animals. Researchers from Hokkaido University and other institutions are still investigating the precise mechanisms, but the consensus is clear: climate-driven changes are making red tides more frequent and more destructive.

Economic and Social Impacts: More Than Just Seafood

Seafood is a cornerstone of Japanese cuisine and culture, but the economic effects of these environmental changes ripple far beyond the dinner table. Fish and seafood make up less than 10 percent of the average Japanese food basket, yet their scarcity and rising prices are emblematic of broader inflationary pressures. In July, food prices in Japan rose 7.6 percent year-on-year, the fastest pace in decades. Household spending on food now accounts for nearly 30 percent of total expenditures—the highest in 43 years.

For many consumers, especially the elderly and those on fixed incomes, these increases are painful. Salaries have not kept pace with inflation, and the cost of traditional foods like uni is now prohibitive. Even tourists at Tokyo’s famous Tsukiji seafood market are opting for cheaper street foods instead of expensive seafood bowls.

Implications for the Fishing Industry

The fishing industry, already grappling with labor shortages and rising utility costs, faces an existential threat. The loss of key species like sea urchin and salmon undermines the livelihoods of fishermen, wholesalers, and restaurant owners. The crisis is particularly acute in regions like Hokkaido, where seafood is both an economic mainstay and a cultural identity.

Hokkaido Governor Naomichi Suzuki described the red tide crisis as “unprecedented in scale” and warned that its effects could last four to five years, urging the national government for urgent aid to protect fishermen’s livelihoods.

Ecological Dynamics: Sea Urchins, Kelp, and Changing Oceans

Sea urchins are not just a delicacy—they play a crucial role in marine ecosystems. In healthy numbers, they help maintain the balance of kelp forests, which are vital habitats for countless marine species. But when their populations boom or crash, the consequences can be dramatic.

Sea Urchin Barrens and Kelp Forest Collapse

In some parts of the world, overpopulation of sea urchins has led to the creation of so-called “urchin barrens”—rocky reefs stripped of kelp and other seaweeds, resulting in low biodiversity and productivity. This phenomenon is well-documented in places like Australia and New Zealand, where warming seas have allowed invasive urchin species to thrive, devastating kelp forests. In these cases, managing urchin populations—sometimes by harvesting them for food—has become a tool for ecological restoration.

In Japan, however, the problem is the opposite: declining sea urchin numbers threaten both the ecosystem and the economy. Long-term studies in southern Japan have shown that rising water temperatures and red tides are major factors influencing sea urchin abundance and species richness. The loss of sea urchins can disrupt the balance of marine communities, potentially leading to overgrowth of algae or shifts in species composition.

Species on the Move: Mesocentrotus nudus and Beyond

Not all sea urchin species respond to warming in the same way. Recent scientific studies have documented the northward expansion of Mesocentrotus nudus, a commercially valuable species, into new areas of Hokkaido as water temperatures rise. Field surveys in Akkeshi Bay found that surviving urchins were older, having lived through recent harmful algal blooms, and that warming trends could make conditions more favorable for their future growth. However, overall densities remain low, and it is unclear whether these populations are self-sustaining or reliant on larvae from other regions.

Meanwhile, other herbivores like the top shell Turbo sazae are increasing their feeding pressure on kelp as temperatures rise, potentially altering the dynamics of seaweed beds and further complicating ecosystem management.

Climate Change: A Structural Challenge for Japan’s Food Security

The crisis facing Japan’s sea urchin industry is a microcosm of the broader challenges posed by climate change. Extreme weather events, rising average temperatures, and shifting ocean currents are disrupting traditional food systems and threatening the country’s goal of raising its food self-sufficiency ratio to 69 percent by 2030. Even with aggressive efforts to cut greenhouse gas emissions, scientists warn that further warming is inevitable, making adaptation strategies essential.

Regulation, Diversification, and Innovation

Experts suggest a range of responses to these challenges:

• Regulating fishing to prevent overharvesting and allow depleted populations to recover.
• Diversifying diets to include more resilient species, such as sardines, which are thriving in warmer waters.
• Investing in aquaculture and regenerative technologies to supplement wild catches. Japanese companies are even exploring sea urchin farming in places like Tasmania, Australia, to secure a stable supply of uni for export and domestic consumption.
• Restoring kelp forests and managing herbivore populations to maintain healthy marine ecosystems.

Scientific research into the gut microbiomes of sea urchins and their feeding behaviors is also providing new insights that could inform sustainable aquaculture and ecosystem management.

Global Lessons: Contrasts and Comparisons

Japan’s sea urchin crisis stands in stark contrast to situations elsewhere, such as Australia, where exploding urchin populations are destroying kelp forests. There, the challenge is to control urchin numbers—sometimes by encouraging their harvest for food—to restore ecological balance. In both cases, climate change is the underlying driver, but the local impacts and solutions differ dramatically.

This highlights the complexity of managing marine resources in a rapidly changing world. What works in one region may not be suitable in another, and adaptive, science-based approaches are essential.

In Summary

• Japan’s sea urchin prices have doubled in recent years, with a 100g bowl of uni now costing up to $120 in Hokkaido.
• Warming seas and frequent red tides, linked to climate change, are causing sharp declines in sea urchin populations and other cold-water species.
• Mass die-offs from red tides have devastated the fishing industry, with billions of yen in losses and long-term impacts on marine ecosystems.
• Rising food prices are straining Japanese households, with seafood inflation outpacing overall price increases.
• Ecological shifts are altering the balance of kelp forests and herbivore populations, complicating restoration efforts.
• Japan is exploring regulatory, dietary, and technological solutions, including aquaculture and ecosystem management, to adapt to these changes.
• The crisis underscores the broader challenges of climate change for food security and marine biodiversity worldwide.