California has a remarkable diversity – 32 species – of native salmon and trout, thanks to our long coastline and high mountains. However, the disappearance of bull trout in the 1970s may foretell a series of salmon and trout extinctions in the near future, including our coho salmon and golden trout.

In collaboration with my colleagues at UC Davis and with support from California Trout, I recently completed a two-year research study that indicates 65 percent of California's salmon and trout species face extinction within this century, if not sooner.

These are not just obscure species that only a few people care about, but species that support fisheries, that are extraordinarily beautiful, and that are emblematic of California's diverse streams, rivers and lakes.

For example, silvery spring Chinook salmon once ascended streams of the Central Valley in the hundreds of thousands. Today, just a few thousand spawn in three small streams in the shadow of Mount Lassen. Lahontan cutthroat trout, a spotted bronze trout that was once found throughout the northeastern Sierra, is now fighting to survive in a few protected localities. And just a handful of oceangoing steelhead remain to struggle up the damaged streams of Southern California.

For most species, the major cause of decline is degraded habitat, either through water removal or through watershed conditions that allow temperatures to warm, silt to cover spawning gravels and shade-providing riparian trees to disappear. In the Klamath River, for example, most of its nine varieties of native salmon and trout are in serious trouble, in part because there is not adequate cold water to support spawning and rearing during the warmer months of the year.

This doesn't have to happen. The Goose Lake redband trout, in remote Modoc County, is thriving because of watershed restoration projects resulting from cooperation among ranchers, agencies and diverse citizen groups. Restoration projects on important streams such as Clear Creek and Battle Creek in the Sacramento Valley are increasing habitat for the four runs of Chinook salmon. A court settlement has ordered restoration of Chinook salmon to the San Joaquin River. Major efforts are under way to protect the three kinds of golden trout in the upper Kern River basin, funded by water users.

Providing a future for our iconic native fishes and their waters is not easy. It requires a fundamental shift in the way our society treats its streams and natural lakes. We have to leave more water for fish while protecting their diverse habitats. We need to engage in more large-scale restoration projects, following the example of the San Joaquin River.

To start this effort, we must re-energize, fund and empower the fisheries, water protection and landscape management agencies so they can do their jobs and lead efforts to re-create healthy streams and landscapes. Water is California's most valuable commodity, and the environmental costs of its heavy use by humans need to be repaid, through a combination of better management of our natural systems and creating stable funding sources for fish and wildlife conservation programs. Above all, we need to teach the public how to better live in a world of limited resources.

Our fish are telling us that we are using our water and watersheds in an increasingly unsustainable fashion. If we lose our native salmon and trout, we will have created environments much less suitable for humans, and we will leave our grandchildren an unfortunate legacy of water shortages, poor water quality and degraded landscapes. The drastic decline of California's native fish is symptomatic of a much larger water crisis that, unless addressed, will severely impact every Californian in the future.

Peter Moyle and study co-authors Joshua Israel and Sabra Purdy are associated with the Center for Watershed Sciences at the University of California, Davis. To see the report "SOS: California's Native Fish Crisis," go to www.caltrout.org.