``There is significant evidence that fully protected marine reserves are doing what they`re supposed to do, and that they actually can increase fishery yields in adjacent areas,`` Micheli says.

For proof, she need look no further than outside her office window, where she routinely observes sea otters a few yards offshore noisily munching on Pacific sea urchins.

The southern sea otter was hunted to near-extinction by 19th-century Russian fur traders. A tiny population was discovered along California`s remote central coast in the 1930s and has been given complete protection ever since.

Today, the state`s sea otter population has risen above 2,000. As the voracious critters made their comeback, the urchin population rapidly declined. As a result, native kelp forests - no longer threatened by hungry urchins - have returned all along the coast, providing ideal habitat for indigenous crabs, clams, snails and fish.

But protection can have an unexpected downside - especially when the natural ecosystem is totally out of balance. Micheli is evaluating the effects of no-take reserves along the west coast of Italy. Several species of fish targeted by recreational and commercial fishers enjoy eating sea urchins - spiny invertebrates that, in turn, dine on seaweed. A dramatic change in the size of one population can have a cascading effect on the other two species - a phenomenon known as a trophic cascade.

``In the marine reserves of the Medes Islands, Spain, the number and sizes of urchin predators has increased within protected areas, which seems to have resulted in greater predation on the sea urchin population,`` Micheli notes. The subsequent sea urchin decline appears to have resulted in the spread of invasive species of algae that choke off the natural habitat for a variety of native species.

``I am testing this idea of a trophic cascade occurring in the marine reserves of the Tuscan Archipelago, off the weste
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Contact: Mark Shwartz
mshwartz@stanford.edu
650-723-9296
Stanford University
13-Jul-2001