Anchovies are a boom-and-bust species: Their populations are shrinking and expanding, and scientists aren’t quite sure why. But since a heat wave at sea that ended around 2016, Anchovy population off the coast of California has exploded “orders of magnitude,” said Dr. Santora. It has created a banquet for the birds, sea lions and whales that feast on it, he added.
“These humpback whales are recovering and they are very hungry,” said Dr. Santora, adding that he suspected a group of whales might have driven the anchovies into shallow water. The whales, he said, feed together in small groups by splitting the fish into smaller schools, weakening their defenses.
“Five humpback whales can basically take an anchovy school anywhere they want,” he added, “and scoop everything up.”
The mass die-off of anchovies in the Bolinas lagoon was rare, but not unprecedented. In 2013 anchovies busy in the port of Santa Cruz, which deprive themselves of oxygen. The following year, a massive die-off of the little fish soiled a beach town in Oregon† Earlier this year there were also thousands of fish washed up dead on a beach in Chile†
Rudi Ferris, a fisherman who has lived in Bolinas for more than five decades, said he remembered a handful of deaths in the seaside town, and only one, in the late 1970s, rivaled the carnage he witnessed last month.
“It stank terribly for a very long time,” said Mr Ferris, 71. This time, he added, he viewed the scene from a distance through his binoculars. A flock of pelicans and seagulls were “frantically eating,” he said.