MOUNT SINAI - A ban on lobster fishing is set to begin next year for the Long Island Sound. According to the Atlantic State Marine Fisheries Commission, local lobster populations have steeply declined in recent years and need to be rebuilt. Officials say the main cause of the dwindling populations is not overfishing, but warm water temperatures and an increase in predators. Officials say the ban, set to take effect after Labor Day 2013, will likely be in place for three months.