Flounder Identification Guide

Key identification features

• Strongly flattened, disc-like body with both eyes positioned on the same (upper) side of the head
• Mottled brown, gray, or sandy pattern on the eyed (top) side that closely matches the seafloor, with a plain white underside
• Ability to shift shade and pattern slightly to blend with different substrates
• Large mouth with sharp teeth for an ambush predator, positioned asymmetrically
• Sizes range from small, dinner-plate-sized fish to over half a meter depending on species
• Long dorsal and anal fins running nearly the full length of the body

Common look-alikes

• Halibut: grows far larger and shows a more elongated, diamond-shaped outline rather than a rounder disc shape
• Sole species: smaller, more strictly oval body with a distinctly smaller, more downturned mouth
• Turbot and other flatfish: differ mainly in which side the eyes sit on (left- versus right-eyed) and in the texture of the skin, which can be smooth or studded with bony tubercles

Where you'll see one

Flounders live on sandy or muddy seafloors in coastal and estuarine waters worldwide, typically lying partially buried with only the eyes exposed while waiting to ambush passing prey.