A joint effort by three government agencies in American Samoa has so far killed close to 1,000 crown-of-thorn starfish but thousands more are still threatening the territory's corals.
The last time there was an outbreak of the starfish, or alamea, in American Samoa was 1977, when it devoured over 80% of the territory's coral reefs.
The National Marine Sanctuary Deputy Superintendant Michelle Johnston says the starfish feed directly on the coral.
She says runoff and pollution get into the ocean and feed the outbreak.
"Basically, it's an upstream battle, and the things that will help remedy the problem in time, will be reducing those nutrients. Creating buffers so there's not as much runoff, making sure that there aren't any leaky septic tanks."
Michelle Johnston says the sanctuary is working with the Environmental Protection Agence to try to combat some of the problem.