Novel aquaculture methods include deepwater cages supported by pillars operated by Snapperfarm, Inc., off Puerto Rico to grow cobia. With this open-ocean system, currents disperse excrement from the fish, but with farms in coastal shallows, waste builds up, polluting the waters. Aquaculture companies usually feed carnivorous fish smaller fish of other species, but Snapperfarm raises its cobia from fingerlings to 12-pound (5 kilograms) adults in a year on a diet of half grain, half fish meal and hopes eventually to eliminate fish from the feed. Aquaculture now contributes nearly 50 percent of the world's seafood, filling the void left by declining stocks in the wild.