State officials and fisheries managers are monitoring an explosion of purple sea urchins along the Oregon and California coasts.
“We haven’t seen this change in populations or levels of purple sea urchins before,” said Scott Groth, an Oregon Department of Fish and Wildlife (ODFW) project manager. “With surveys extending back to the 1980s, we’ve never seen many purple sea urchins at deep sites. Now, they dominate those areas.”
According to reports cited by the ODFW, the purple sea urchins have devoured much of the giant bull kelp forests in northern california and are now moving north along Oregon’s sea floor, threatening the local marine ecosystems.
Groth said the purple sea urchins are in competition with other species for the grazing of kelp beds. “Most concerning would be their competition for food and space with abalones,” he said.
“These urchins have become more numerous (because of) good environmental conditions for recruitment events, such as temperature and currents, and the lack of their primary predator, the sunflower star, which went from very common to effectively absent following the 2014 sea star wasting event.”
It’s unclear, according to reports, whether climate changes have triggered the purple sea urchins explosion.
Dr. Cynthia Catton, a scientist for the California Department of Fish and Wildlife, said the impact of the purple sea urchin explosion has significantly impacted the California recreational red abalone fishery, which was closed last year. That fishery contributed an estimated $44 million annually to the California coastal economy.
In Oregon, the ODFW has suspended abalone driver permits for three years.
Catton said due to the decline of the kelp forests, the red urchin fishery also has been hit hard, and she expressed concern about other species that will be affected by the decline in bull kelp, such as rockfish.
“We are seeing the impact to red urchins and red abalone right away. Those are not subtle,” she said. “But if we go too long without nursery habitat for rockfish species, we will be seeing those impacts as well.”
According to Catton, human intervention could be one solution. For the past three years, she has been working with the commercial red urchin industry and local recreational fishermen to develop a program for harvesting purple urchins.
This project examines whether human intervention can play a role in helping shift the balance of the ecosystem back in favor of the kelp.
“The idea is that if there are fewer urchins in strategic locations along the coast, the kelp may have an opportunity to recover and replenish bull kelp spore availability more broadly,” she said.
But human intervention might be questionable, according to Cal Poly University marine ecologist Benjamin Ruttenberg, who said there are other factors besides purple urchin predation that can limit kelp.
So even with extensive urchin harvesting, a recovery of the kelp ecosystem might not happen. At best, it might work on a small scale, but that would require continuous urchin harvesting and monitoring.
Catton said the efforts to control the purple sea urchins will need to be a long-term investment.
For more details, contact the ODFW at 503-947-6000. To volunteer to help monitor coastal ecosystems, contact Reefcheck at http://reefcheck.org/california/ca-overview.