Marine reserves can't be all things to all species, a new study suggests. Researchers found fewer red abalones in areas of the California coast with sea otters--evidence, they say, that marine protected areas can't protect both big predators and the animals we like to eat.
Red abalone are tasty to sea otters and humans, too. Abalone populations soared in the late 19th and early 20th centuries after almost all the sea otters in California were killed for their fur. Then the abalone populations crashed after the otters' return and years of human overfishing. The commercial abalone fishery in California has been closed since 1996, but the population's recovery has been negligible. One factor might be hungry otters, which are also protected under state and federal law.
To look at the effects of otters on abalone, University of California, Santa Cruz, graduate student Samantha Fanshawe went scuba diving to count red abalone in areas with and without sea otters along the central and northern California coast. She found fewer, smaller abalone in sea otter habitat, and most were wedged in crevices where otters couldn't reach.
The work makes an important point about marine protected areas--that they can't make everyone happy, says Glenn Vanblaricom, a marine biologist at the University of Washington, Seattle, and the U.S. Geological Survey who advised Fanshawe on her project and helped with the abalone surveys. "If you love sea otters, everything's fine, but if you're in it for the abalones, having a marine protected area that includes sea otters pretty much puts you out of business," Vanblaricom says. The work appears in the February issue of Conservation Biology.
Marine reserves are intended to protect an ecosystem, but they might not protect all denizens of the ecosystem equally, says Stephen Palumbi, a marine biologist at Stanford University's Hopkins Marine Station in Pacific Grove, California. "They might generate ecosystems that have low numbers of particularly luscious and juicy species that you'd like to eat yourself." The problem may be unavoidable, Palumbi says, but a better understanding of marine ecology may help scientists predict what a reserve will do.
The California Department of Fish & Game's Draft Abalone Recovery & Management Plan 
All about sea otters, from the Monterey Bay Aquarium 
Abalone from UC Davis's Seafood Network Information Center 
How to cook abalone steaks