The flesh of flatfish should be in a fairly rigid state or feel firm to the touch. Any sticky, gelatinous liquid on the fish should be clear and not congealing. As these fish lose their condition ...
Instead, buy flounder from March to November. To cook whole flounders, trim away the fins, head and blood-line, then grill or bake whole with citrus, herbs and butter as you would cook turbot.
Oita prefecture--A “light farming” technique that stimulates the growth of flatfish varieties is taking hold in Oita Prefecture, one of the nation’s top producers of farmed flounder.