During the annual “hareed” festival in the Farasan Islands — an archipelago in the Red Sea off the coast of Saudi Arabia — hundreds of people run into the water to catch parrotfish, which aggregate there annually since time immemorial.Science cannot yet explain this annual phenomenon, but there are clues in traditional ecological knowledge and cultural history, a new op-ed explains.“Only by weaving [traditional] knowledge together with science can we begin to understand what we are trying to protect,” the author writes.This article is a commentary. The views expressed are those of the author, not necessarily of Mongabay.

“Al Dhiwaini!” HRH the Prince of Jazan called in the traditional way that spurred hundreds of people to sprint toward the water, carrying around nets and shouting.

Standing on the shores of the Farasan Islands, I watched participants in the annual parrotfish festival pull fish from the sea en masse, with catches reaching up to 78 kilograms (more than 170 pounds) of parrotfish per person. Known locally as hareed — or generally as longnose parrotfish (Hipposcarus harid) — the scale of extraction immediately triggered my instincts as a scientist, as the question asked itself: How is this sustainable? How do the fish keep coming back, year after year?