Flagtails are fish that are part of the perch family. In fact, some of their other common names reflect this, one example being the flagtail species, also known as the jungle perch. They get their name "flagtail" because of the obvious bars and spots that appear on their caudal fins, which resemble little banded flags. Flagtails superficially look similar to freshwater sunfishes. They have a deep notch in their dorsal fin, so it almost looks like they have two back fins instead of one. This is similar to the wavy dorsal fin of sunfishes. There are other fish that have the name flagtail but aren't related to the fish described in this episode. While they also have a colorful banded tail, they're pretty easy to tell apart just by looking at their dorsal fin. See how this flagtail has a long pointed dorsal fin.
This particular flagtail lives in the Amazon River Basin. The flagtails that are part of the perch family swim in both fresh and salt water around coasts of the Indo-Pacific region. They're found as far into the Pacific as the Hawaiian Islands. Most flagtails swim no deeper than 60 ft below the waves. They live on reefs, but they also inhabit brackish-water estuaries, and some species swim upstream into flowing freshwater rivers so they can tolerate a wide range of salinity. One of the threats they face is the introduction of dams across the rivers and streams they frequent, cutting off their access to vital habitats.
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Flagtails are also caught by humans and eaten either fresh or dried out and salted. It's likely they're also taken by larger fish. Although flagtails at their full size can get pretty big, some flagtails can reach more than a foot long, while others average a few inches shorter. They hunt at night, seeking out all sorts of food. Flagtails eat crustaceans and smaller fish, but they also eat insect larvae and frogs. This is especially worth noting for flagtails native to Australia, where their presence can help reduce invasive cane toad populations. The fish eat cane toad tadpoles. Flagtails also eat adult insects, as well as fruit and flowers that fall into the water. It's not uncommon for flagtails to eat these meals directly from the water's surface. In general, flagtails prefer to stay closer to the waves than down towards the water's bottom.
They often form tight schools with multiple members as they move about. They're described as movement-driven fishes and likely don't ever stay in one place for too long. There's little known about their breeding habits and life cycle. Juveniles can sometimes be found in tide pools where they have some protection from larger predators who can't manage in these shallow habitats. It's likely these ever-moving fish migrate to specific spawning grounds, and it's believed that females lay multiple clutches of eggs during the breeding season.
