Deep-sea Smelt Identification Guide
Recognize deep-sea smelt by their silvery bodies, large eyes, and small fleshy adipose fin.
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Key identification features
- Small, slender, silvery body, often just a few centimeters to about 20 cm long
- Large eyes adapted for capturing faint light
- Single soft dorsal fin roughly at mid-body
- Small fleshy adipose fin present near the tail, just before the caudal fin
- Forked caudal fin
- Thin, delicate scales that shed very easily when handled
- Fine black speckling (melanophores) often visible along the belly and lower flanks
Common look-alikes
- Slickhead: lacks an adipose fin entirely and has a bare, scaleless head, unlike the scaled head and adipose fin of deep-sea smelt
- Lanternfish (myctophids): show rows of distinct light-producing photophore spots along the body and head that deep-sea smelt do not have
- Herring and anchovy relatives: lack an adipose fin, which is a reliable mark present on deep-sea smelt
Where you'll see one
Deep-sea smelt inhabit the mesopelagic to bathypelagic zones of the open ocean worldwide, often migrating upward at night to feed near the surface before descending again by day.
Frequently asked questions
How do I distinguish a deep-sea smelt from a lanternfish?
Lanternfish have obvious rows of light-organ spots along the body and head, while deep-sea smelt lack these photophore rows and instead show fine dark speckling on the belly.
How do I know a small silvery deep-sea fish is a smelt and not a slickhead?
Look for a small adipose fin just before the tail and scales on the head; slickheads lack both of these features.