By Paul Rosenberg, Senior Editor
On April 13, federal regulators meeting in Rohnert Park, just outside Santa Rosa, Calif., cancelled the next sardine fishing season, starting July 1, due to a devastating collapse in the West Coast sardine population, which is down 91 percent from 2007. Later that same week, they approved an immediate halt to sardine fishing. It was a drastic response to a drastic situation, but only one small harbinger of the massive changes that may come to our oceans as result of global warming in the decades and centuries ahead, making large portions of the ocean inhospitable to most life, a situation similar to what happened to the oceans when the last ice age ended.
The decisions came from the Pacific Fishery Management Council, a 19-member policymaking organization made up of fishery representatives from California, Oregon, Washington and Idaho.
“While this is a sad day for all those dependent on a healthy sardine fishery, it is actually a good thing that this council is addressing the problem directly, something you don’t always see across the nation or certainly, internationally,” said Council member Frank Lockhart. He then pointed to previous actions: “This council cutback on salmon with extensive closures a decade or so ago, and the Klamath and Sacramento stocks rebuilt fairly quickly. This council also cut back on lingcod and other groundfish catches in the recent past, and those stocks are also rebuilt. This action today paves the way for the sardine population to rebuild as soon as the ocean cycles permit.”
But conservationists, notably the international conservation group Oceana, have been fighting for almost a decade to implement stricter regulations that would pro-actively protect against such drastic collapse in the first place. The sardine population peaked in 2007, according to a March 19 report by scientists at the National Oceanic and Atmospheric Administration. Sardine stocks reached almost a million tons in 1999, but fell to less than 400,000 in 2003. They rebounded to more than a million tons in 2007, but have been declining relentlessly ever since. They reached a low of just under 97,000 tons in the 2015 projection contained in the report. This is the lowest level recorded in six decades, since the period following the industry’s momentous collapse in the 1940s. Prior to that, stocks were estimated to be more than 3 million tons—30 times what they are today.
Yet, even as the biomass plunged below 600,000 tons after 2011, the “exploitation rate” (catch divided by the biomass) skyrocketed. From 2005 through 2011, the exploitation rate varied little from year to year, averaging 7.9 percent for American fishermen, 11.6 percent total. But in 2012, the figures jumped dramatically to 20.6 percent for U.S. fisherman and 26.8 percent total. They inched up even higher the next year, before falling to the mid-teens this past year. When the 2015 projection fell below 150,000 (about last year’s level), that triggered the requirement for the season to be canceled.
Oceana’s California campaign director, Geoffrey Shester called the move “a huge step” when it was announced. “The council’s closure of the directed sardine fishery acknowledges the severe crisis in the sardine population,” Shester said. “Yesterday’s vote is a first step toward recovery of this important forage species.”
A press statement from Oceana went on to stress the systemic ecological effects of the sardine collapse. Sardines—like anchovy and herring—are what’s known as a “forage fish.” They swim in huge schools and play major roles in the diets of a wide range of larger fish and other animals.
“We have been seeing the impacts of a collapsing sardine population on sea lions and seabirds for years now,” added Ben Enticknap, Pacific campaign manager and senior scientist with Oceana. “Sardine are also prey for recreationally and commercially important species like Chinook salmon and albacore tuna, so the effects of a lack of sardine could have much wider impacts.”
Sea lion pups have been dying in large numbers for three years now. In April, the National Marine Fisheries Service reported that a record 2,250 starving and stranded sea lions, mostly pups, have washed up on Southern California beaches so far this year. This is a tally 20 times the average over the past decade, and twice the number documented in 2013, the previous worst year. Lack of prey is the primary cause, but the crash in sardine populations may be only part of the picture, as the shifting of warmer waters farther north—a result of shifting wind patterns that’s also contributing to California’s drought—is also thought to play a role.
This underscores another increasingly important point: the growing need to understand and anticipate complex systemic interactions. The Fishery Council has begun moving in this direction with its April 2013 adoption of its Fishery Ecosystem Plan. According to its website, “The purpose of the FEP is to enhance the council’s species-specific management programs with more ecosystem science, broader ecosystem considerations and management policies that coordinate council management across its Fishery Management Plans and the California Current Ecosystem.”
This year, in a move applauded by Oceana, the council adopted its first amendment to the FEP, protecting unfished and unmanaged forage fish species. Again, its website explained: “The council’s objective is to prohibit the development of new directed fisheries on forage species that are not currently managed by the council, or the states, until the council has had an adequate opportunity to assess the science relating to any proposed fishery and any potential impacts to our existing fisheries and communities.” This reflects a maturing understanding that ecosystems are complex and that human markets for seafood can easily upset balances we don’t even know exist.
One example of this understanding comes from a just-released study showing that over-fishing intensifies, though it does not prolong, normal boom-and-bust cycles in forage fish populations. It’s known from the geological record that forage fish populations go through boom-and-bust cycles naturally—a point that industry advocates repeatedly harp on to argue against over-fishing limits. The new study, conducted by a team led by Timothy Essington, a marine biologist at the University of Washington Seattle, analyzed time-series data for fish populations amounting to almost two-thirds of the global catch of forage fish.
Essington’s team found that “Forage fish population collapses shared a set of common and unique characteristics: high fishing pressure for several years before collapse, a sharp drop in natural population productivity and a lagged response to reduce fishing pressure.” They also found that lagged response “can sharply amplify the magnitude of naturally occurring population fluctuations,” making crashes much worse than they would otherwise be—exactly what seems to be happening with West Coast sardines. Consequently, they advise, “A risk-based management scheme that reduces fishing when populations become scarce would protect forage fish and their predators from collapse with little effect on long-term average catches.”
Of course, implementing such practices ought to take place within a broader framework that helps secure the long-term viability of small operators, those who have the smallest share of responsibility for over-fishing, but are least able to survive a suspension in fishing operations. As with the struggle to clean up port trucking, to work properly, environmental protection requires a social justice dimension as well.
But this only takes into account existing conditions, and the one thing we know is that conditions are changing. Perhaps the most relevant large-scale threat to consider is the growth of “oxygen minimum zones” (OMZs), which can profoundly alter ocean environments on a scale spanning thousands of nautical miles. This threat was the subject of a recent article in National Geographic. As that article explained:
These are not coastal dead zones, like the one that sprawls across the Gulf of Mexico, but great swaths of deep water that can reach thousands of miles offshore. Already naturally low in oxygen, these regions keep growing, spreading horizontally and vertically. Included are vast portions of the eastern Pacific, almost all of the Bay of Bengal, and an area of the Atlantic off West Africa as broad as the United States.
Globally, these low-oxygen areas have expanded by more than 1.7 million square miles (4.5 million square kilometers) in the past 50 years.
It’s a matter of debate how much global warming has contributed to this expansion, and how much is simply due to climate variability—a familiar tale. But it’s much more certain that continued global warming will only make this problem get worse—just as OMZs expanded significantly in the past when natural processes were responsible for heating up the planet. This subject was explored in a paper written by a team headed by Sarah Moffitt, a post-doctoral researcher at the University of California Davis, working at the Bodega Marine Laboratory.
OMZs did not exist during the last ice age, around 20,000 years ago, but they appeared as the glaciers melted and the planet warmed. The timing of their expansions was “regionally coherent,” but not simultaneous on a global scale. As the paper explains, “OMZs are tightly coupled to upwelling systems and Eastern Boundary Currents, such as the California Current, the Humboldt Current and the Benguela Current.”
The California Current is the coldwater current running from British Columbia to Baja California, which has a submerged warmwater counterpart, the north/south California undercurrent. A 2008 study headed by Steven Bograd, a NOAA oceanographer, found large declines in dissolved oxygen in the southern California Current System over the period of 1984 to2006, with the OMZ starting as shallow as just 100 meters deep in some places.
A 2010 paper, “Ocean Deoxygenation in a Warming World,” by lead author Ralph Keeling, director of the Scripps CO2 Program at UC San Diego, looked at future projections from a suit of ocean/climate models. “Ocean models predict declines of 1 to 7 percent in the global ocean O2 inventory over the next century,” he wrote, “with declines continuing for a thousand years or more into the future.” He noted that “Significant deoxygenation has occurred over the past 50 years in the North Pacific and tropical oceans, suggesting larger changes are looming.”
Two distinct sorts of processes caused by global warming are reflected in the models, Keeling noted—gross heating of ocean water, which reduces the solubility of oxygen, and “changes in ocean circulation and biology.” Elaborating on the later, the paper continued:
The most important cause of these changes is the effect of global warming on upper ocean stratification, particularly at high latitudes, where reductions in surface density result from both warming and freshening due to an enhanced hydrological cycle.
Even now, Keeling noted, “much of the North Pacific…can be considered an OMZ.” Furthermore, “The relative rapidity of O2 decreases in the subarctic Pacific and in coastal upwelling regions off the west coast of North America raises the specter of imminent impacts on marine habitat and fisheries,” meaning even more of what we’ve already seen, with no end in sight.
“Even if the recent O2 variability in the North Pacific has been partly naturally driven, the implications for the future appear ominous,” the paper said. “The declines over the past 50 years demonstrate that O2 levels in the thermocline [range where temperatures drop with depth] of the North Pacific are highly sensitive to climate changes.”
Furthermore, looking at oxygen declines on the North American shelf, from British Columbia to Baja California, the paper attributes them to “a combination of factors acting in concert,” including “declines observed as far away as the subarctic and equatorial Pacific,” along with local factors as well. “It is worrisome that all of these factors may be amplified in the future by continued global warming,” Keeling warns.
The paper’s summary leaves us with a final warning:
The relative rapidity of O2 decreases in the subarctic Pacific and in coastal upwelling regions off the west coast of North America raises the specter of imminent impacts on marine habitat and fisheries.
Which means that the actions taken so far by the Pacific Fishery Management Council are almost certainly only the beginning. A time for new thinking is at hand.