Research Highlight: Caution to the Wind

John Steinbeck described Cannery Row as “a poem, a stink, a grating noise… a nostalgia, a dream.” The “stink” was the smell of sardines, which were overflowing at the more than a dozen canneries in Monterey, Calif., during the 1930s and ‘40s.

By the late 1940s the sardine fishery off California crashed, leaving the canneries shuttered. The collapse set scientists in search of the ecological mechanisms behind the drop and led to the 1949 launch of the California Cooperative Oceanic Fisheries Investigations (CalCOFI), an ocean dynamics monitoring program initiated by Scripps Institution of Oceanography at UC San Diego, the California Department of Fish and Game and the National Oceanic and Atmospheric Administration’s National Marine Fisheries Service. The program, which continues today, regularly monitors features of the California Current, the eastern portion of the clockwise circulation of the North Pacific Ocean that flows off California’s coast.

The sardine collapse remained a mystery for more than 50 years, until recently when Scripps’s Ryan Rykaczewski and David Checkley formulated a possible explanation.

A fifth-year graduate student, Rykaczewski decided a few summers ago to search for the mechanisms behind sardine and anchovy boom and bust cycles.

He and Checkley, a Scripps professor, combined CalCOFI data compiled in reports dating back to the program’s origin with high-resolution climate models produced by Scripps researcher Masao Kanamitsu, The analysis suggested to Rykaczewski and Checkley that wind may be behind the fluctuations. Their research shows that wind drives ocean upwelling, which brings nutrients to  surface waters, allowing sardines and anchovies to thrive. When winds are strong enough to accelerate upwelling, populations flourish, and the opposite is true when wind conditions change and nutrients dwindle.

Their analysis is published in the Proceedings of the National Academy of Sciences.

“This paper is the first to show a mechanistic relationship between climate variability and the sardine fishery,” said Rykaczewski. “There have been a lot of hypotheses about climate change and sardine and anchovy fisheries, but there has been little scientific support for a mechanism connecting changes in climate to changes in these fish populations.”

Rykaczewski and Checkley’s research also may explain why sardines and anchovies thrive in different locations. Out in the open ocean, upwelling brings up the smallest classes of zooplankton, the prey best suited for sardines and their fine gill-filtering capabilities. Close to the coast, upwelling carries the largest zooplankton to the surface, making them available for anchovies, which are equipped to process larger prey.

Rykaczewski believes the new study could become an important source for marine management, which is increasingly relying on ecosystem-based data for directing fisheries decisions.

Checkley says the research provides evidence that natural processes, as opposed to fishing exclusively, can explain fish booms and busts.

“I think there’s no question that both fishing and natural forcing are responsible for the historical fluctuations in fish not only off California, but off Peru, Japan, South Africa, and Spain,” said Checkley. “It’s important to realize that nature is a large player in this equation, if not the dominant one.”

-- Mario C. Aguilera