The changes will affect everyone from the weekend angler to the industrial trawler, and will hit coastal communities hard, but biologists say the restrictions are the only way to rebuild one of California's most important, and most endangered, fisheries.

Sport fishermen will see smaller bag limits, draggers must modify their gear to avoid productive rocky reefs, and hook-and-line fishermen will be allowed catches of roughly one-third the current quota. For recreational and most small-scale commercial operators, fishing will be closed in March and April.

``These are more drastic than anything we expected,'' said Alec MacCall, a veteran fisheries biologist with the National Marine Fisheries Service in Tiburon. ``We're in uncharted territory in terms of regulations. We have to cut allowable catches to below what most fishermen need to make a living.''

Although the causes of the population crash are somewhat mysterious, scientists believe a combination of environmental changes and overfishing has led to the decline of three spiny species that can live 100 years but reproduce slowly.

Meeting in Sacramento earlier this month, the North Pacific Fisheries Management Council declared three West Coast species ``overfished,'' a designation that requires managers to give them special protection and plot their long-term recovery.

They include two rockfish species, bocaccio and Pacific Ocean perch, and lingcod, which also are ``ground fish'' that inhabit rocky ocean floors. Scientists say the bocaccio population, for example, is 98 to 96 percent smaller than its historic levels. Two other rockfish species, canary rockfish and cowcod, are expected to be placed under rebuilding plans next year.

Rockfish, which are typically called red snapper in West Coast fish markets and on menus, are California's fifth-largest fish harvest by volume, according to the state Department of Fish and Game. In 1997, California commercial fishermen landed 16 million pounds of rockfish, worth $8.3 million.

In anticipation of the cuts, Gov. Gray Davis last month asked the U.S. secretary of commerce to declare a federal disaster in the West Coast ground-fish industry to provide relief to fishing and processing workers.

Sport fishing operators such as Bill Beckett of Huck Finn's point out that the cutbacks will hurt not only charter fishing boats but also the restaurants, stores and hotels that cater to them.

``You just can't take everything. There's got to be a tomorrow,'' he said.

There is disagreement over who, or what, bears primary responsibility for the rockfish decline. But most scientists, environmentalists and fishermen agree that a combination of heavy fishing pressure and a warming trend in the North Pacific that began in 1976 conspired to ravage the colorful, spiny, long-lived creatures that once inhabited every underwater rock crevice between Baja California, Mexico, and the Gulf of Alaska.

``The water's been warm and lacking in food and plankton, so the little ones starve,'' said Milton Love, one of the world's leading rockfish experts. ``At the same time, people are pruning down the populations. So you have the old double whammy.''

Until recently, neither fisheries managers nor the public paid much attention to rockfish stocks, added Love, a researcher with the Marine Science Institute at the University of California-Santa Barbara.

``In last couple of years, people all of a sudden are going, `Where are the rockfish?' ''

Some scientists believe the rockfish crisis is on the same order of magnitude as the great sardine collapse chronicled by John Steinbeck in ``Cannery Row.'' Studies suggest that warm ocean temperatures favorable to sardines led to a boom in the fishery in the 1930s. By the '40s, the temperatures were headed down, causing a natural decline in the population, but fishing pressure remained high.

``Thirty years ago, sardines were down to nothing,'' said MacCall, who helped write sardine laws for the government. Now, after more than 20 years of warmer water and better management, there is an estimated million tons of sardines in the Pacific Ocean.

Fishermen and environmentalists say there have long been indications that rockfish were in trouble and that the North Pacific council has been slow to act. The council sets fisheries policy for the West Coast and includes fishermen, scientists and government representatives.

``We've had indications of changes in these groundfish for years and years, and we've largely ignored them,'' said Josh Sladek Nowlis, a scientist at the Center for Marine Conservation in San Francisco.

But Barbara Stickel, who fishes commercially for rockfish out of Half Moon Bay, argues that too little is known about how the fish react to changing conditions to establish responsible regulations, although she said she has seen declines in some species.

``The sad part is, a lot of the cuts (in fishing) are because there's inadequate data,'' she said.

``It's immoral, isn't it? Should you eat anything older than your grandma?'' asked Love. ``That also makes them very susceptible to overfishing. Many live 50, 60, 70 years and only reproduce successfully one year.''

Rebuilding rockfish populations is also expected to take decades. The cuts in fishing quotas are designed to give these slow-growing creatures the ability to reproduce and replenish.

``I'm very optimistic that given enough time we'll see recovery of these stocks,'' MacCall said. ``We are talking about a long, long time. Meanwhile, it's going to take a terrible toll on the fishing industry.''