Species include angelfish, goatfish, butterflyfish, and parrotfish. These predators threaten native reef fish such as parrotfish and goatfish. Species with this condition include parrotfish, wrasses, sea basses, flatheads, sea breams and lightfishes. It requires herbivores including parrotfish and collector urchins that graze on infesting algae. Smaller parrotfish are relatively defenceless herbivores, poorly defended against predators like barracuda. Herbivores include fish such as parrotfish, the urchin "Diadema antillarum", surgeonfishes, tangs and unicornfishes. Most parrotfish species are herbivores, feeding mainly on epilithic algae. On most beaches, the water is shallow with many rays, cuttlefish and parrotfish. Adult green humphead parrotfish may ram its head against corals to facilitate feeding. The carnivorous fish, in turn, preyed on parrotfish that kept the corals clean. Seaweed and algae proliferate given adequate nutrients and limited grazing by herbivores such as parrotfish. Parrotfish are a prime example of reef caretakers. Also visible in the waters surrounding Jamaica are dolphins, parrotfish, and the endangered manatee. This parrotfish mainly feeds on algae. The cheapest was "skaren" (probably parrotfish) whereas Atlantic bluefin tuna was three times as expensive.