Why the Entire Reef Is Terrified of the Giant Trevally

On a remote atoll in the Seychelles, young terns learn to fly over a calm, shallow lagoon. Underneath them, a fish the size of a child is following their shadows, and when a bird drops too low, it comes straight up out of the water and takes it. This is the giant trevally, the ulua of Hawaii, and it's why so much of the reef has learned to fear it. It's built like a battering ram, it starts life in rivers (and in one volcanic lake it never left), it hunts in gangs, it follows monk seals to steal their food, and it has been seen ramming reef sharks to death without eating them. On untouched Hawaiian reefs it once made up most of the top-predator weight. Then comes the twist: what the giant trevally fears, and the poison it carries out of the reef. Sources: Parrish et al., Endangered Species Research 2008 (Crittercams on 42 Hawaiian monk seals, French Frigate Shoals); McPherson, Blaiyok & Masse, Pacific Science 66(3) 2012 (lethal ramming of sharks by large jacks, Palau); Friedlander & DeMartini, Marine Ecology Progress Series 230, 2002 (apex predators, NW vs main Hawaiian Islands); BBC Blue Planet II 2017 (Farquhar Atoll); Save Our Seas Foundation, Amirantes acoustic tracking from 2016; Alphonse Foundation catch-and-release research (*Fisheries Research* 2022); Hawaii Department of Health 2018 (ciguatera cases from ulua, Kohala coast); Hawaii Seafood Council (ciguatera species). Chapters: 0:00 The lagoon at Farquhar 2:04 Reason 1 · It's built like a battering ram 3:23 Reason 2 · It starts out in a river 4:52 Reason 3 · It hunts in gangs 5:45 Reason 4 · It follows seals 7:37 Reason 5 · It kills sharks 9:00 Reason 6 · It eats nearly everything 9:47 Reason 7 · It used to run Hawaii 11:12 Reason 8 · It hunts birds 13:32 What the giant trevally fears 15:13 The reef bites back #gianttrevally #fish #animals