The lower jaw projects beyond upper jaw. One small gill slit is found in front of each pectoral fin. Coloration is variable with maturity level, the larval stage is called a leptocephalus, or glass eel. This stage is transparent and leaf-shaped with a prominent black eye. Sexually mature adults, silver eels, are dark brown and gray dorsally, with a silver to white ventral side.
Large eyes are prominent in silver eels.
Feeding habits of A. rostrata vary with level of maturity. Yellow and Silver eels are primarily nocturnal carnivorous feeders, consuming insects, crustaceans, clams, worms, fish and frogs. Eels at this stage will also eat dead animal matter. Sexually mature adults migrate to the Sargasso Sea, to spawn and supposedly die. Eels may reside in freshwater systems for up to 20 years before leaving to spawn at sea.