 Mature adults (excluding those on Georges Bank) generally migrate in two phases, where adults enter shallow estuaries in the late fall and early spring to spawn in late winter or early spring before returning to deeper parts of the estuary or offshore waters.However, these migration patterns may be altered or individuals may stay inshore year round if temperatures remain at 15 °C or lower or if enough food is available.Genetic analyses and tagging studies indicate that there is little mixing between the Winter flounder populations in the Gulf of Maine, South of Cape Cod, and on Georges Bank.