Flounder
Platichthys flesus
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The flatfish that comes up the river — you can catch one in fresh water miles from the sea.
A flatfish with both eyes usually on the right side, a dull olive-brown upper surface with vague blotches, a white underside, and rough, prickly tubercles along the base of the fins and behind the eyes. Flounder are the flatfish of the Solway's mudflats and estuary, and they are unusual in tolerating fresh water — they run well upstream into the Nith.
Behaviour
Flounder lie half-buried in mud and sand, changing colour to match the bottom, and feed on worms, crustaceans and small molluscs. Like all flatfish they start life as a normal symmetrical larva swimming upright; one eye then migrates across the head as the fish settles onto its side. Adults move out to deeper, saltier water to spawn in late winter and spring.
When to see it
Quick facts
- Family
- Righteye flounders (Pleuronectidae)
- Size
- Commonly 20–35 cm
- UK status
- Native; the flatfish most tolerant of fresh water
Photo by Hans Hillewaert, CC BY-SA 4.0, via Wikimedia Commons