About the Sardines
Sardines are small epipelagic fish that sometimes migrate along the coast in large schools. They are an important forage fish for larger forms of marine life, according to Wikipedia.
Despite the numbers seen in the schools, stocks globally are dropping, mainly due to overfishing. The population isn’t replacing itself quickly enough, according to NOAA. Stationary sardine balls like the one in Moalboal are usually quickly fished out by local fishermen once the location is known. In Moalboal, the local government managed in cooperation with the fishermen association, the tourist board and the dive centers, to protect the sardine ball for the benefit of everybody. For instance, fishing is allowed, but only with hook and line, so the fishermen get the bigger fish out while the main school remains and continuous to draw divers and tourist to Moalboal. A win-win situation for everybody.
Related: Experience Diving With Millions of Sardines in Moalboal, Philippines