Slickhead Identification Guide
Identify slickheads by their smooth, scaleless heads and single rear-set dorsal fin.
Read the full Slickhead encyclopedia entry →Key identification features
- Elongated, moderately compressed body
- Smooth, naked, scaleless head, often mucus-covered, which gives the family its common name
- Large eyes suited to low-light deep water
- Single soft dorsal fin set well back on the body, near the tail
- No adipose fin present
- Small, weak mouth with fine teeth
- Coloration ranges from silvery to dark brown or black depending on species
Common look-alikes
- Deep-sea smelt: has a small adipose fin near the tail and a fully scaled head, unlike the slickhead's naked head and lack of adipose fin
- Cusk-eels: have dorsal and anal fins that merge continuously with the tail, whereas the slickhead's dorsal fin is short and separate
- Bristlemouths and other small mesopelagic fish: typically have photophores (light organs) that slickheads lack
Where you'll see one
Slickheads live in bathypelagic and deep benthopelagic waters of oceans worldwide, generally between about 500 and 4,000 meters, often swimming slowly just above or within the water column near continental slopes.
Frequently asked questions
How do I tell a slickhead from a deep-sea smelt?
Check for an adipose fin and head scales: slickheads lack an adipose fin and have a bare, scaleless head, while deep-sea smelts have both an adipose fin and a scaled head.
What is the easiest feature to spot on a slickhead?
Its head looks smooth and almost slimy compared to the rest of the body, since it is completely bare of scales.