Ever wonder what the differences are between Sole and Flounder? Some customers recently asked me the question so I thought I would take a moment to shed a bit of light on the subject.
Here in North America we have no true sole only flounders. When Europeans came to the Americas they called flounders soles because they looked like the fish they knew in the "old world". This has led understandably to much confusion over the years. The only true sole would be Dover Sole, Solea solea.
Lemon sole is one of the names given to winter flounder, Pseudopleuronectes americanus, (also known as black back). Usually at the retail level when multiple flounder sku's are sold; flounder is the name given to the refreshed less expensive product, and sole (or lemon sole) is the name given to the more expensive fresh cut product. Fluke, Paralichthys dentatus also called summer flounder can also be sold as sole fillet. Sometimes there is a distinction between sole and lemon sole with the latter referring to a larger fish or a bigger fillet. All these fresh flounders produce a mild and tender white fillet when cooked, so as long as they are fresh I don't think it matters much what you call them. The refreshed (previously frozen) fillets can be of varying quality, because they usually contain sodium preservative solutions that have you paying for water. Go with fresh when possible.
If you live on the west coast you might even run into something they call "dover sole" a much less expensive and thinner flounder that is a far cry from the Eastern Atlantic flatfish from which it has hijacked the name.
So on one hand the naming of fish has been a bit of innocent mistaken identity and a bit of good marketing. Of course there have been instances when totally different species like Asian catfish have been sold as sole and flounder, so make sure you know and trust your fishmonger.