America's west coast looks set to lose almost all of its wild salmon harvest this year, depriving fish retailers and restaurants around the world of one of their key sources of high-quality fish, and raising troubling questions about the viability of commercial fishing in an age of climate change and increased competition over water use.
United States government regulators have already closed down the early fishing season along swathes of the west coast and are expected to issue a season-long ban in California and Oregon, in response to an unprecedented collapse in the region's salmon population.
The unexpected shutdown will have a devastating effect on the 1,000 or so commercial salmon fishermen who ply their trade between California's Central Coast and the Oregon-Washington state line. It will kill the recreational salmon fishing industry, which attracts millions of anglers each year and generates about $4bn (£2bn) in benefits to the coastal economy.
And it will drastically change the menu at restaurants and private houses on the west coast and far beyond. Wild salmon had, over the past 30 years, slowly changed from a delicacy to a relatively common and affordable menu item. This year, though, anyone wanting to eat wild, as opposed to farmed, west coast salmon is going to have to rely on the solid, but small, harvest of king or chinook salmon from Alaska and Washington state – and pay through the nose for it.
"Brutally expensive," was how one key wholesaler, Paul Johnson, of the Monterey Fish Market in San Francisco, envisaged his wild salmon offerings over the next several months. "Oh man, I'm telling you the king salmon is the icon in the [San Francisco] Bay Area," Mr Johnson told The San Francisco Chronicle. "This is going to be devastating to the economy."
The shortage of fish is so bad that even the commercial fishermen understand there is no point lobbying for a higher quota – or any quota at all – this year.
The most startling data comes from the Sacramento river, the source of more than 80 per cent of all the mature salmon caught off California. Last year, only 90,000 spawning adults returned to the river, the second lowest figure on record, and the projections for this year, based on sightings of two-year-old fish during last autumn's spawning run, are for fewer than 60,000. To put those figures in perspective: the Sacramento River once saw spawning populations of 800,000. The federal government sets a minimum of about 120,000, below which it doesn't authorise any fishing season at all.
The reasons for the drop-off are far from clear. Some scientists blame the whole thing on changes in ocean currents, which in turn disturb the pattern of marine nutrients coming to the surface of the Pacific to supply a food chain that includes the west coast salmon population. It is certainly true that wind and tide patterns have not been favourable to this so-called "upwelling" of ocean nutrients, creating food shortages for many forms of marine life.
Fishermen, though, point to other less immediate causes too: competition over water resources involving big farmers, property developers and big-city water resource managers. Water that comes out of the giant river delta where the Sacramento and San Joaquin rivers meet in California's Central Valley is, they argue, water that salmon cannot use to spawn and thrive in. They also accuse farmers of damaging fish stocks by dumping pesticide-infected irrigation water back into streams and rivers.
Salmon runs up and down the west coast have been affected over the years by everything from the construction of golf courses – a big water siphon, especially in a dry region – to the mass harvest of redwoods and other trees that prevent the silting of rivers.
Up to now the variety most affected has been the coho salmon, a delicate-tasting fish now regarded as an endangered species. King, or chinook, salmon, which is fished in the ocean, has tended to remain plentiful.
Many west coast fishermen are likely to flock to Washington state, which has not suffered the same sort of drop-off. But it is likely to suffer very similar economic hardship because its fishermen will be competing for a limited number of fish with a far higher number of rivals than usual.
Illegal fishing off the California or Oregon coasts is unlikely, however, because the fishermen recognise the scale of the crisis. "I think if we do have fishing, we're shooting ourselves in the foot," said a California fishermen's representative, Duncan MacLean.