eel

Eel is a common name for a broad group of elongated fish in the order Anguilliformes. True eels have long, snake-like bodies; their dorsal, anal, and caudal fins are often fused into a continuous ribbon, and they typically lack pelvic fins. They occur in fresh, brackish, and marine waters around the world. The term eel is also used for some non-eel fish such as morays (family Muraenidae), which are not true eels and belong to a different evolutionary lineage.

Most true eels are catadromous, meaning they live in freshwater or brackish habitats as juveniles and migrate to the sea to spawn. Their life cycle begins with free-swimming leptocephalus larvae, which drift across oceans and later metamorphose into glass eels as they reach coastal areas; glass eels become elvers when they enter rivers, where they grow into adults. Reproduction is difficult to study in the wild, but many species are believed to migrate back to the open ocean to spawn and likely die after breeding.

The best-known true eels are the freshwater eels of the genus Anguilla, including the European eel (Anguilla anguilla), American eel (Anguilla rostrata), and Japanese eel (Anguilla japonica). They are distributed widely in temperate and tropical waters and often inhabit rivers, estuaries, and coastal lagoons. Eels are opportunistic carnivores, feeding on crustaceans, fish, and invertebrates.

Conservation and management concerns: eel populations have declined in many regions due to overfishing, construction of dams and other barriers, pollution, invasive species, and climate change. Several species, notably the European eel, are subject to stringent protection and management measures in parts of their range.