Swimmers in La Jolla, California were in for a shock on the 8th after the waters were swarmed by a huge shoal of anchovies bringing a strange addition to a balmy summer’s day. The group, the biggest seen in 30 years, measured around 50 feet wide by 325 feet long, adding a harmless yet daunting-looking shadow to the Pacific waters. It is estimated that there could have been anywhere from 1 million to 100 million fish contained in the shoal. By the evening, most of the school had swam north. A video of the swarm, taken by a staff member from La Jolla’s own Scripps Institution of Oceanography, can be viewed above. It is unknown why the fish, which normally live further out to sea, came so close to the shore. David Checkley, a professor of Oceanography at Scripps, said, speaking to Livescience, that it is unlikely the fish were in search of their normal food of zooplankton. California’s anchovy population has been on the rise recently, and it is believed that the Pacific Ocean’s cooling due to an effect known as the Pacific Decadal Oscillation is responsible. via Science Recorder.