
Conger eels
conger
Ariosoma marginatum

By day the large-eye conger is just a head. The rest of the eel is under the sand, and only the face sticks out, tilted up and watching. Come close and the whole animal drops backwards out of sight in an instant. At night it leaves the bottom altogether and swims in open water. It grows to about 38 cm.
Hawaiian sand flats hold other eels that poke a head out of the bottom, and a head alone gives little away. Wait for the fins to show. This is the one whose long fin is lined with a thin dark edge along its whole length; the others show no such line.
This is a slender eel, very pale brown to pale brown on the back and white underneath. The dorsal, anal and tail fins are joined into one long fin edged with a narrow black border. The eyes are large, each one about as long as the snout, and they sit under a thick, clear layer of flesh that gives the face a glassy look.
The large-eye conger lives only around the Hawaiian Islands and Johnston Atoll. It is a bottom dweller of sandy ground and is common in shallow sandy patches, though it has been recorded from 2 m down to 490 m. Look for it on open sand rather than on hard reef. It is out and active after dark and buried through the day.
Describe what you saw and we name it, then keep every species you find in your Oceandex.