December 21, 2023 — New research from Scripps and NOAA scientists has discovered ecological correlations that could help explain the booms and busts of California’s anchovy population. If the correlations hold up to further research, they could one day help inform management of California’s anchovy fishery and improve conservation.
The Northern Anchovy (Engraulis mordax) is a crucial food source for much of California’s most conspicuous marine life—including droves of sea lions, pods of dolphins, lucrative tuna fisheries, and throngs of whales. But one of the hallmarks of the anchovy population off California is the cycle of booms and busts that can last for more than a decade. These ups and downs reverberate through the entire marine ecosystem, with busts at times contributing to starving sea lion pups or leading brown pelicans to abandon their chicks.
Exactly what drives these booms and busts has remained elusive despite decades of scientific study, notably by the CalCOFI research program which is cooperatively run by UC San Diego’s Scripps Institution of Oceanography, the National Oceanic and Atmospheric Administration (NOAA), and the California Department of Fish and Wildlife. The program surveys marine ecosystems up and down the California coast and is one of the largest and longest ocean monitoring programs in the world.
The study, published in Nature Communications and funded by NOAA and the National Science Foundation, points to the marine ecosystem surrounding newly hatched anchovies known as larvae. The researchers analyzed 45 years-worth of anchovy larvae collected during CalCOFI surveys and found that the length of the food chain supporting the larvae strongly correlates with anchovy population booms and busts. Specifically, shorter food chains preceded booms and longer ones preceded busts. Shorter larval food chains have fewer steps of one animal eating another between the photosynthetic phytoplankton harvesting the sun’s energy at the base of the food chain and the larvae, which eat mostly zooplankton.
Read the full article at ECO Magazine