The End of American Abalone Diving?

Usually, the first weekend of April is when abalone divers pack up their wetsuits and fins and head off to campsites along Northern California's Sonoma and Mendocino counties coast. It's a unique delicacy that cannot be commercially sold, so restaurants pay as much as $125 a pound for farm-raised abalone.

However, this year's recreational abalone season -- only free diving is permitted -- is closed because the abalone population is on the brink of collapse, thanks mainly to the purple sea urchin, an overpopulated species that has laid waste to the struggling kelp forests, home to abalone, the commercially viable red sea urchin, small fish and the invertebrates that other larger fish feed on.

In response, recreational abalone divers are paying professional divers to vacuum up the purple sea urchins -- which have little commercial value -- from select areas of Northern California with a fiberglass pipe that empties into a big net.

The once-great underwater fields of bull kelp shrank by 93 percent between 2008 and 2014. One cause was the 2014-15 El Niño, which raised ocean temperatures and discouraged new growth.

The purple urchin has few natural predators. The sea star that normally eats them disappeared after suddenly dying off from disease in 2013. The North Coast sea otter population, decimated decades ago, hasn't recovered. Unlike abalone, the hardy purple sea urchins reproduce well, even under starvation conditions.

"This is a nightmare," said retired commercial urchin diver Jon Holcomb, 72, of Fort Bragg, who said he never witnessed such bad kelp conditions in his 37-year career. One of a handful of professional divers taking part in the urchin removal program, Holcomb created the urchin-sucking device they're using based on an airlift, a tool used to clear sand and other small objects from the ocean floor. Rather than scuba gear, the divers use hookahs attached to small fishing boats for breathing and then dive down with the airlift. After scraping the urchins off the rocks, they suck the animals through the pipe and into a waiting net.

Each diver can clear around 1,500 square feet a day of urchin barrens, the vast areas of the seafloor that have been stripped of kelp by the purple-spined creatures.

By having Holcomb and company remove urchins from specific areas, starting with Caspar Cove near the town of Mendocino, Catton wants to see if they can create a few kelp "oases." Bull kelp is an annual plant -- it's actually algae -- that depends on spores released by the previous year's kelp to grow. The hope is that a few small, thriving kelp forests could create enough spores to encourage growth elsewhere on the coast.

"We don't know how many of those there will be, or how far the spores will travel," she said.

The larger goal, Catton said, is to create a market for the purple urchins, which are not meaty enough to sell as seafood. One potential use is to augment compost.

"The kelp is the bottom of the ecosystem," Russo said. If the urchins "get rid of all the kelp, there'll be no crabbing, there'll be no salmon, there'll be no nothing."

From an article by Tara Duggan
in the San Francisco Chronicle