As winter chills the rivers and streams of California and Oregon, a beleaguered batch of chinook salmon has finally finished its long trip home from the Pacific Ocean. In the gravel of gentle rapids and shaded pools, eggs laid by a decimated group of females are growing, starting the next generation of chinook on their turbulent journey to the ocean and back.
For their part, Pacific fishermen can only hope for the best. After all, it would be tough for things to get worse. In 2008, both commercial and sport fishing for the salmon was completely shut down along the coast from Southern California to northern Oregon for the first time in history.
"This was the first time that I sat around San Francisco and wasn't out there catching wild California king salmon," says Larry Collins, one of roughly 1,500 commercial fishermen forced to spend summer on dry land.
Collins and his fellow anglers blame debased rivers for the collapse of one of the country's prime salmon fisheries. An onslaught of dams and diversions that channel water to suburbs and subsidized crops has depleted fresh water for the fish. The Central Valley river system has historically produced one of the largest runs of chinook in the continental United States. Yet in 2008 roughly 90 percent fewer salmon returned to spawn than in 2004.
"The cities, farms and all the other users have over-drafted the river," says Collins. "Every time you take another acre-foot out of the delta, you put another nail in the coffin of the commercial fishermen of California."
For decades, fishermen and environmentalists have directed their ire at the degradation of rivers. But in the last year, marine biologists have focused on increasingly stressed oceans as the cause of the crash. Yet surprisingly, as 2009 dawns, salmon experts see signs that idle fishermen can start firing up their boats again in the coming year.
Bruce MacFarlane of the National Oceanic and Atmospheric Association (NOAA) Salmon Ecology Team in Santa Cruz explains that the historic 2008 crash begins with the fact "that ocean conditions weren't good when the salmon went to sea." Salmon need the right food in the right places to thrive to maturity in the ocean. Those needs weren't met for 2008's salmon run, whether the cause is global warming, as many scientists suggest, or simply the natural variability of the environment. And, of course, the rivers are still a major player. If the salmon population wasn't already in a weakened state, there would have been more survivors left to spawn the next generation.
"A natural period of poor ocean conditions hurts the salmon more than it did historically," says Peter Moyle, a fisheries biologist at the University of California Davis. "Under normal circumstances, you would have so many fish coming out that they could more or less overwhelm the poor ocean conditions."
Yet the common thread in the failure of the salmon seems to be the sea. Coho and chinook salmon from up and down the coast -- not just from one river or river system -- all declined. "When you start looking at what they have in common, it is that they share the same ocean at the same time," says MacFarlane.
The unfavorable conditions weren't in 2008 and 2007 when adult salmon failed to return from the sea -- but three years earlier, when the fish were only a few months old and the ocean's food chain fell apart.
"Salmon went to sea expecting the usual bountiful harvest, and they found a desert instead," says Bill Peterson, a NOAA fisheries biologist based at Oregon State University's Hatfield Marine Science Center who has been studying the local oceans for 30 years. "I think they were dead within a couple of weeks."
A signal of distress came in 2005, says Bill Sydeman, chief scientist with the Farallon Institute. The Cassin's auklet, a seabird that feeds on the same prey that young salmon do, failed to produce a single chick on the ecologically vibrant Farallon Islands. Located nearly 30 miles off the coast of San Francisco, these rocky islands are a well-studied seabird sanctuary. Around the same time, fisherman also noticed the lack of krill -- a favorite food source for juvenile chinook, and an important part of the oceanic food chain.
"There were a couple of years when we saw hardly any krill at all," says veteran California fisherman Chuck Wise. "When there's a lot around you'll see big clouds of it on the surface. The water will almost be red and it will come up on your trolling wires."
The ocean is vastly changeable -- having ups and downs is par for the course. So what exactly went so terribly wrong in the last few years?
The Pacific Fishery Management Council, one of eight regional councils of federal and state officials whose task is to oversee conservation and management of marine fisheries in the country, developed a list of 64 different factors, such as wind direction and water temperature, that could have contributed to the collapse.
While marine biologists say the salmon crash can't be blamed on any single factor -- "That's not how it works in ecology," says Sydeman -- the key problems stem from oceanic processes called "upwelling" and "retention." Upwelling refers to the process in which winds from the north push water away from the coast every spring and summer. The warmer surface water is then replaced by cold water that comes up from the depths and carries abundant nutrients such as nitrates, phosphates and silicates.
These nutrients feed the plankton, which then bloom into massive populations. Because the process happens on a relatively regular schedule, many animals -- such as salmon and Cassin's auklets -- have evolved to depend on these massive, seasonal influxes of food.
Juvenile fall-run chinook salmon migrate into the open ocean from the relative stability of their home streams and estuaries between April and June. They almost always find abundant food waiting for them, given that upwelling begins in March and April, and lasts all summer. But in 2005 and 2006, the ocean broke the rules. In 2006, upwelling started early -- in February -- and then it stopped, occurring only sporadically throughout the summer. In 2005, the upwelling simply didn't start until mid-summer.
As a consequence, auklets and other marine life that depend on the same food as salmon simply starved to death. Scientists think the same thing happened to the chinook, says Brian Wells, a NOAA scientist based out of the Southwest Fisheries Science Center in Santa Cruz.
In addition to the sparse and ill-timed upwelling, intense winds pushed what little food there was far offshore, according to Wells, who has spent the past few years studying ocean conditions in the California Central Coast region. He modeled the production rates of krill, seabirds and rockfish for up to 30 years and correlated them with staggering quantities of data on environmental conditions, looking for a relationship with how the salmon population relates to changes in the ecosystem from year to year. He found that in 2005 and 2006, remarkably low amounts of food were retained near the shore.
"Just because food is out there doesn't mean it's accessible," Sydeman says. "Predators such as salmon seem to do best when the krill are in very large patches, even if there are fewer patches. And they have to be in the right place."
Some scientists -- such as Peterson -- also suggest that the vagaries of the Pacific Decadal Oscillation (PDO) correlate with the hardships confronted by the salmon. The PDO describes sea surface temperatures for a vast swath of the Pacific Ocean, north of Mexico. As a result of winds, the ocean will sometimes be warm near the coast and cold in the middle, and then flip-flop so water near the coast is cold instead. "When the ocean is in cold phase, salmon do really well, and when it's in warm phase, salmon do horribly," says Peterson. But in the last decade, he added, the PDO has "gotten all goofy."
Based on more than 100 years of data, scientists say each PDO phase generally lasts for 20 or 30 years. Now, instead of multi-decadal cycles, the flip-flopping has been happening every few years. A 20-year warm phase ended in 1999, followed by three years of cold phase. From 2003 to 2006, during the time when the salmon were suffering, it was warm again. Since then, it has returned to a cold phase. Whether these changes indicate a temporary variation or a long-term trend won't be known for years, says MacFarlane.
The warmer sea surface temperatures that are inherently an aspect of poor upwelling are also a problem for salmon. The fish need much more food to survive in warm waters, whether or not they are associated with the PDO, MacFarlane adds. Some say this is due to plankton, the tiny plants and animals that myriad sea creatures -- including salmon, squid, seabirds and whales -- rely on for food. Some eat the plant plankton directly; some eat the animal plankton, such as krill, that feed on the plant plankton; others eat the small fish that feed on the krill, and so on.
However, not all plankton are created equal. "The species in Alaska are like bears," Peterson says. "They're quite big and they pile on the fat so they can hibernate through the winter." When local coastal waters are chilly, Alaska-type plankton thrive off the west coast of Oregon. Some researchers hypothesize that ocean currents carry both cold water and fatty plankton down from Alaska and this is what feeds the salmon.
When the ocean is warm, the plankton are skinny and so are the fish, Peterson says. Lean plankton frequently found in the tropics take the place of the fatty, northern variety. "They're not going to be as strong, not as feisty and they won't grow as much," says Peterson. "For best salmon conditions, you have to have the right kind of water, with the right kind of plankton -- and you also have to have some upwelling."
Many scientists suggest that climate change is part of the problem. For over a decade, research has predicted that global warming could lead to upwelling that was strong, but occurring late -- as well as less food retention along the coast. "They actually suggested we would see a trend like we have been seeing in the last few years," says Wells.
"I'm confident that climate change is leading to changes in the environment, and starting to affect lots of food webs in a lot of different ways," says Sydeman. He adds that 2002 saw the highest levels of both salmon and Cassin's auklet reproduction on record, while the lowest rate for both came just a few years later in 2005. "Things are getting more and more variable, which is one of the predictions of global warming -- that the systems are going to get less predictable," he says.
Yet other scientists say there is not yet any clear evidence that upwelling, retention or the PDO are being affected by climate change. "We don't have a long enough time series to see if there's a relationship between oceanographic conditions and greenhouse gases," explains MacFarlane. Predictive models disagree widely about how specific places in the ocean are going to fare in the future, he adds.
Whatever their cause, the ocean conditions triggering the 2008 crash have eased up -- at least for now. Fortunately for fish and fishermen alike, conditions improved in 2007, and 2008 yielded abundant upwelling, cold waters and vibrant life in the sea. Krill were abundant; whales and porpoises fat and feeding; and seabird colonies thrived.
"The ocean looks in better condition now than I've seen in 25 years, except for the salmon," Collins says. "There's more rock cod, more marine mammal predators, and the sardines are back. The ocean is full of life."
It looks like this is going to be "a great year to be a baby salmon," says MacFarlane. "I hope that turns out to be true; we really need good ocean conditions and low predation to start rebuilding that stock."
Still, say the scientists, the future of the salmon, and the seas, remains precarious. Oceans worldwide face the long-term problems of acidification, pollution and hypoxia. Freshwater rivers are increasingly stressed. And regions of the ocean that are still generally healthy, such as those off the California and Oregon coast, have proved how vulnerable they are to short-term variability.
"It's kind of a cheat out to say that it's all better, because I'm not sure that it is," says Wells. "Just because 2008 was OK doesn't mean that 2009 will be."