The migration of a massive school of Northern anchovies off the coast of La Jolla took place on Tuesday afternoon. Scientists are flabbergasted as it is the first time when they have seen something like this in more than 30 years.

In a video of the school, the fish can be seen swimming with graduate students from the Scripps Institution of Oceanography at UC San Diego and a Leopard shark.

Robert Monroe, a communications officer with Scripps, said people gathered in large numbers at the Scripps pier around mid-morning to watch the anchovies.

Monroe initially thought that it was a red tide and ran down to the pier with a GoPro camera. "It was remarkable. From a distance it looked like an oil slick and you think 'What happened?' and then you get up close and it's amazing. It's like watching the motion of a lava lamp", he said.

Immediately after getting down to the pier, he threw the camera to three grad students already in the water with the fish

Scientists were not aware of the number of fish in the school. Samples have been collected by members of the Scripps Marine Vertebrate Collection for studies, said Scripps in a news release.

Researchers with the Scripps Institution of Oceanography spotted the biggest school of California anchovies in three decades off La Jolla. The announcement for the same was made on Tuesday.

Such an aggregation has not been seen in past 30 years and they have yet not been able to ascertain the reason behind why the large school moved into shallow waters off the coast.

The school travelled to north and mostly disappeared this evening, said Phil Hastings, a marine biology professor and curator of the marine vertebrate collection at the UC San Diego-connected Scripps.