Brook Silverside Identification Guide
How to recognize the pencil-thin, beak-jawed Brook Silverside of North American lakes and streams.
Read the full Brook Silverside encyclopedia entry →
Key identification features
- Extremely slender, elongated, almost pencil-shaped body
- Nearly transparent body with a fine silvery midlateral stripe
- Distinctive protruding lower jaw giving a small beak-like snout
- Two dorsal fins, the first tiny and easy to overlook
- Large eyes relative to head size
- Deeply forked tail fin
- Faint dusky stripe running from snout to tail base
- Delicate, almost see-through fins
- Long, low-set anal fin base
- Small, usually under 10 cm
Common look-alikes
- Hardyhead silverside: stockier bodied and lacks the beak-like protruding lower jaw.
- Mosquitofish: an unrelated, stouter, rounder-bodied fish without the elongated beak snout.
- Mummichog and other killifish: much deeper, stouter bodied with a blunt, not beaked, head.
Where you'll see one
Common in freshwater lakes, ponds, and slow rivers of eastern and central North America, typically seen skimming and leaping just below the surface in open water far from shore, often in loose, actively moving schools that scatter when disturbed and are easy to overlook against sun-glare on the water.
Frequently asked questions
What's the single best field mark for a brook silverside?
Its small, beak-like protruding lower jaw combined with an unusually slender, nearly transparent body.
How do I avoid confusing it with a mosquitofish?
Mosquitofish have a stout, rounded body and a normal small mouth, while brook silversides are pencil-thin with the distinctive beaked jaw.