Question: How did Purple Sea Urchins become such a big problem?
Answer: Strong Urchin recruitment in 2011, Warm water conditions in 2013 known as the "Blob", Sea star wasting disease decimating 20 species of starfish, and poor kelp recruitment all combined to allow urchin populations to explode.
Question: How extensive are the urchin barrens in Monterey?
Answer: I estimate there are about 2,000 acres of urchin barrens containing about 160 million purple urchins. This is based on Reef Check data and personal observations. There is an effort in this project to map urchin barrens. The density of purple urchins doubled in 2019 to 21 urchins per square meter. There is a new 2 cm cohort in play and the trend is towards more urchins.
Question: Won't the sea otters eat them?
Answer: No, at least not starving urchins. Sea otters are a land animal struggling to survive in cold water and must consume 25% of its body weight in a day. Openly grazing urchins do not have gonad reserves and have little nutritional value. Sea otters eat a wide variety of foods and some specialize in eating urchins, but they are clever enough to not rely on starving urchins for food. More info
Question: Don't people eat them as sushi?
Answer: Uni comes from harvested red sea urchin gonads. Purple urchins are smaller and not harvested commercially. The purple urchins in the urchin barrens have eaten all edible seaweeds and are starving. Their tissues and gonad is reduced to basically a hollowed out test (shell). Unfortunately, it can take them years to die of starvation,
Question: Won't they just go away on their own?
Answer: Urchin barrens are an alternative stable state. Unless there is some perturbation in the stable state it will remain that way for decades. Possible perturbations are: cold water, pollution, predation (California sheephead, spiny lobsters, sun stars), and disease. Disease seems the most possible when the urchins are in such high densities. A disease was thought to have occured in Southern California in the 70s that reduced their numbers and there is evidence that urchin disease is effecting urchins again in SoCal.
Question: Can I just smash them when I dive?
Answer: No, it is illegal to smash urchins. Killing critters without a purpose is considered "wanton waste". With a fishing license you can take 35 urchins per day, but that excludes the urchins in the Marine Protected Areas where the accessible urchin barrens are located. Plus, there are so many urchins that removing 35 a day is simply not enough. Efforts to remove urchins must be coordinated so that entire area is cleared to a low urchin density where kelp has a chance to establish. Randomly smashing them is ineffective and unlawful.
Question: Are divers removing them up north?
Answer: Smashing purple urchins is allowed at Caspar Cove in Mendocino County. CA Fish & Game Commission has changed the regulatory language to permanently increase the bag limit of purple urchins to 40 gallons of purple urchins in Sonoma and Mendocino Counties only.
Question: Will smashing them create a spawning event and make matters worse?
Answer: Maybe, but it doesn't matter. There is no peer reviewed scientific publication that proves that smashing purple urchins causes a spawning event. The urchins are starving and lack reproductive material. Before culling, random samples of urchins are cut opened and a Gonad Index test is performed to ensure that they are starving and lack gonads for reproduction. The amount being culleded is statistically insignificant relative to the enormous amount of urchins spawning at their most effective time in spring. We have found that smashed urchin remains are eaten by fish and red urchins. Two weeks after culling urchins only the bare shells remain.
Question: Have purple urchins been a problem in other areas and what was done?
Answer: Purple urchins have been successfully removed in Palos Verdes California. Until Marine Protected Area restrictions were put in place, urchins were removed in Orange County 3 days a week for 12 years by volunteer divers. On the California north coast, frustrated abalone divers are removing urchins bi-monthly at organized events.
Question: Will removing urchins bring back kelp?
Answer: When we removed urchins on the Lovers Urchin Experiment on reefs to reduce their density giant kelp recruited and lived persisted to the next year. The Tanker's Reef project will study removal to determine how this dynamic works in Monterey Bay to inform a larger removal effort.
Question: What's the hold up? When can we get started?
Answer: Now. The project is open to volunteer divers. Register here! When classes are available we will post them on this website.
Please contact me to ask any other questions. There may be other people with the same question.