Scripps Scientists Peg Wind As The Force Behind Fish Booms And Busts

The mid-20th century crash of the sardine fishery off California for decades has vexed marine ecologists searching for the root causes of large fluctuations in the sardine population. Before its collapse, the fishery was one of the world's most productive and formed the setting of John Steinbeck's "Cannery Row" in Monterey, Calif.

Scientists at Scripps Institution of Oceanography at UC San Diego have now shed light on the puzzle by proposing a plausible mechanism behind the mystery: wind.

Writing in the online early edition of the Proceedings of the National Academy of Sciences, Scripps researchers Ryan Rykaczewski and David Checkley propose that atmospheric wind forces can determine the availability of microscopic organisms that sardine and anchovy feed upon. When wind causes nutrient-rich waters to rise to the surface, plankton levels increase and sardine populations flourish. Conversely, sardine numbers crash when plankton become scarce as wind conditions change.

The scientists say their findings may explain the sardine and anchovy booms and busts off California's coast and could explain similar population cycles elsewhere around the world.

"This paper is the first to show a mechanistic relationship between climate variability and the sardine fishery," said Rykaczewski, a Scripps graduate student researcher. "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."

After a sardine collapse that began in the late 1940s, scientists sought a greater ecological understanding of the California Current, the eastern portion of the clockwise circulation of the North Pacific Ocean that flows off California's coast. This need led to the 1949 launch of the California Cooperative Oceanic Fisheries Investigations (CalCOFI), a unique ocean dynamics monitoring program initiated by Scripps Institution, the California Department of Fish and Game and the National Oceanic and Atmospheric Administration's National Marine Fisheries Service, which continues today.