A state commission will consider placing part of the ocean surrounding the Channel Islands off limits to fishing Wednesday, creating one of the nation's largest marine protected areas.

Fishing would be outlawed in state waters making up about 10 percent of the 1,500-square mile Channel Islands National Marine Sanctuary under the proposal before the state Fish and Game Commission. Eventually, federal action could increase the size of the reserve so it covers 25 percent of the waters surrounding the chain of five islands south of Santa Barbara.

The five-member commission, meeting in Santa Barbara, has before it five alternatives that could either shrink or increase the size of the proposed marine protected areas. It can also defer making a decision or take no action.

If passed, the first reserves could be established as early as Jan. 1.

Environmentalists cite the project as essential for preserving the biodiversity of the Channel Islands ecosystem, home to hundreds of species of wildlife. It is also vital for maintaining the fisheries that operate in and around the sanctuary, they said.

The proposed reserve is akin to setting aside land ashore, said Gregory Helms of the Ocean Conservancy. "We just haven't afforded our oceans that kind of protection, even though protecting areas on land has proven its value," he said.

Fishermen are not universally opposed to the idea of creating no-take reserves. There is dispute, however, over the size and speed with which they are to be implemented.

"We don't know what will happen, so let's do it in stages and that will allow for the social changes that will happen," said Jim Marshall, who dives off the Channel Islands for sea urchin, a delicacy mostly exported to Japan.

Fishing advocates have submitted their own proposal for a more limited protected reserve they said would lessen the economic impact on those who make their living from the ocean. The waters are commercially fished for lobster, squid, sea urchin, shellfish and various species of fish.

The process to create the reserves, four years in the making, is being closely watched as a test case of the 1999 state Marine Life Protection Act. The act mandates the development of a plan to establish networks of marine protected areas throughout California waters.

Currently, the only no-take area in the Channel Islands sanctuary is about a square mile in size; statewide, only about eight square miles of waters are off limits to fishing.

The proposal would add another 132 square miles of marine reserves.

The only areas with larger marine protection are in waters in Florida and the northwestern Hawaiian Islands.

"This will be the first network of marine protected areas of any scale and with meaningful protection in ... California," said Richard Charter, a marine conservation advocate for Environmental Defense.

Through what biologists call "spillover," advocates of the proposal say the areas will allow fish and other species to flourish and repopulate even surrounding waters. Overall numbers of fish, as well as the size of individual specimens, are expected to begin increasing in as little as four or five years, said John Ugoretz, a senior biologist with the state Department of Fish and Game.

"The results from around the world are extremely consistent. The amount of increase can be fairly amazing," he said.

Critics of the proposal have said that many species would not benefit from the reserves, since they migrate in and out of the areas. Many of the overfished species in the region already have management plans in place as well.

"The idea of a marine reserve as a catchall that can fix the whole thing is a tad simplistic," Marshall said.

If the proposal is adopted by the commission, it would be the second major fishing restriction imposed this year. In August, it adopted the Nearshore Fishery Management Plan, which regulates commercial and sport fishing of 19 species of fish near the California coast.

"We've seen the pound of cure. What we're talking about is the ounce of prevention," Helms said of the marine protected areas.

The proposed marine protected areas touch a portion of each of the islands in the sanctuary: San Miguel, Santa Rosa, Santa Cruz, Anacapa and Santa Barbara. The islands themselves form the Channel Islands National Park.

The Channel Islands Marine Sanctuary was created in 1980, primarily to limit the spread of offshore oil drilling in the Santa Barbara Channel. It does not restrict fishing.