Do you know what you’re eating?

When in doubt, ask the restaurant to show you the harvest tag

The penalties levied against a Morgan Hill restaurant for serving tilapia and trying to pass it off as the pricier petrale sole has diners wondering about the differences between the two mild white fishes, both considered “lean” varieties.

Here’s some consumer information about the two. But if you’re ever in doubt, Bay Area culinary experts say, don’t hesitate to ask to see the supporting tag. Reputable fishmongers will provide restaurants and retailers with harvest tags that list the species and location of harvest.

Petrale sole is a Pacific flounder with a fine texture and delicate flavor, one of the many flounders found widely along American coastlines. Wild sole caught in West Coast ocean waters by the California Groundfish Collective, using bottom trawls, is rated a “best choice” by the Monterey Bay Aquarium Seafood Watch, which oversees sustainability issues.

“The fisheries are managed well, and the stock is rebuilding.” Sole caught elsewhere along the coast and in British Columbia is rated a “good alternative.” Sole can also be farmraised.

According to the UC Berkeley Wellness website, “If you see Dover sole on a restaurant menu, it may be imported from England (and will be priced accordingly) or it may be a type of Pacific flounder that is sometimes called by this name in the United States.”

Tilapia is a farm-raised variety of freshwater fish that once was largely imported into this country, the UC Berkeley Welllness site says. In terms of texture and taste, UC calls it a “firm-fleshed, mild-tasting fish.” Its texture is firmer than that of sole.

The Seafood Watch rates tilapia raised in closed tanks in the United States and Canada as a “best choice,” noting that “closed tanks often have less effluent, disease, escapes and habitat impacts than other aquaculture systems.” Tilapia farmed in Mexico and Indonesia is assessed as a “good alternative,” but tilapia farmed in net pens in Colombia is on the group’s “avoid” list.