Now, four decades later, once-abundant winter flounder is difficult to find. The harvesting or possession of the fish is prohibited in much of Narragansett Bay and in Point Judith and Potter ponds. Anglers must return the ones they accidentally catch to the sea. Overfishing is easily blamed, and the industry certainly bears responsibility, as does consumer demand. But winter flounder’s local extinction isn’t simply the result of overfishing. Sure, it played a factor, but the reasons are complicated, from habitat loss, pollution and energy production — i.e., the former Brayton Point Power Station in Somerset, Mass., pre-cooling towers, when the since-shuttered facility took in about a billion gallons of water daily from Mount Hope Bay and discharged it at more than 90 degrees Fahrenheit.