Urchin predators converge on Mendocino beach
The two main predators of the purple urchin have been removed from the ecosystem. That leaves humans.
June 20, 2022 — The first annual urchinfest took place this weekend, with opportunities to learn about urchins and their environment, and to eat them raw on the beach at Van Damme State Park in Little River.
A woman named Juanita described the flavor as “someone sweet and buttery. It just slides down really easily. Maybe it’s a softer texture than raw fish, but I love it.” She had just sampled some of the red urchin uni harvested by Greg Fonts, a freediver and spear fisherman who was wearing a shirt that said “Meateater” as he cracked into the spiny creatures.
About 120 people showed up on Saturday morning to watch the demonstration, hear about the urchin, and have a chance at a taste.
Not that there’s much to eat out of the spiny purple shell. A mysterious illness has killed off most of the sunflower sea stars, which were the urchins’ main predator. The purple urchin have overpopulated and devoured the kelp, and now they hang out in a dormant malnourished state. Unlike the red urchin, the purple urchin have no marketable value.
Joshua Russo is president of the Watermen’s Alliance, a recreational divers association that’s part of an effort to remove the urchins from some small areas. The idea is to create a few refugia for kelp so it can re-seed itself if ocean conditions start to balance out again. In 2019, the recreational limit for purple urchin was doubled from the previous year’s limit, to forty gallons per diver in Mendocino, Sonoma, and Humboldt counties. And in Caspar Cove, there is no recreational limit and divers are allowed to crush the urchins in the water.
“What we’re doing is under a scientific collection permit,” Russo explained. “Part of the project is to see if divers will voluntarily report their activity. Reef Check (a non-profit that trains citizen scientists to collect data on California’s kelp forest ecosystems) has a website set up where divers can report their activity. It basically asks how many you think you culled in a dive, how many people were with you, how many dives you made, were you scuba or free-diving…it’s not a legal requirement, but we are hoping that everyone will report, because if people are doing it and not reporting, the department (California Department of Fish and Wildlife) will let the regulation expire. Part of the program is to see if people will voluntarily provide that information so we can use it to prove that what we’re doing is effective and it doesn’t harm anything.”
The purple urchin has another missing predator, in addition to the sunflower sea star. The otter was hunted out of the area by fur trappers in the 19th century. Russo says there are several shortcomings to any plan to reintroduce the otter to clear out the purple urchin. “The problem with that is these urchin are void of much material, so even if they were full, there’s a study that shows that otters are taught what to eat by their parents. So if you brought an otter up here that was not shown how to eat urchin, it wouldn’t even see them as a food source. So you would have to bring the right otters up here, and very quickly, they would open up a few urchin and learn there was nothing in them, so very quickly, they would move right over to anything else. Abalone, crab, anything they could get their hands on.”
Warm ocean conditions from 2014-2019 didn’t help the kelp at all. In the past couple of years, the ocean has been cooling off a little, and the kelp is showing some signs of recovery, but Tristin McHugh, the kelp project director with the Nature Conservancy, says it’s still historically low.
There is some money available for studies like the one Russo is involved in. Starting in 2020, Reef Check received a half-million dollar grant from the Ocean Protection Council to work with the Department of Fish and Wildlife and a variety of non-profits and commercial fishermen to figure out how to reduce urchin to what McHugh calls, “this magical threshold value that would potentially facilitate kelp growth.” That is about two urchin of any species per square meter. The challenge, McHugh says, “is trying to understand what to do when red urchin are also grazers, but also have commercial uses, as opposed to the purple urchin at this point.” Commercial divers are effective at culling urchin, but unlikely to do so without grants or other economic incentives. “What other tools for restoration can we test on top of that?” McHugh asked. “So one thing we are starting here in 2022 is evaluating urchin traps at Noyo Harbor, with hand harvesting of urchin, and we’re also looking at Albion, with Moss Landing Marine Labs, looking at out-planting kelp in addition to hand harvest.”
There was a promising sighting of a sunflower sea star in Mendocino last year, but for now, the known remnant populations of the once-mighty predator are in British Columbia and Alaska. “Typically, sunflower stars are pretty amazing predators,” McHugh said. “We know that they eat young purple urchin, or sometimes even adult purple urchin. We also know they eat snails, sometimes other stars. I’ve seen them eat fish underwater, I’ve seen them eat anemones, oddly enough. Back when I first started diving, I remember seeing them just cruise on the bottom of the ocean so fast, just nailing everything in its way.” As for the cause of the disease that has devastated them, “That’s still a mystery. We’re working right now to figure out what that is. Because it’s still in the system.”