I was wondering the same thing. I first noticed it a few weeks ago on the night of the new moon while fishing in front of Bridgeport Harbor. A week later, the water was still full of clouds of them in Smithtown bay too. This weekend we saw them at the Triangle. None of the oldtimers that I fish with have ever seen anything like it. I hope they are not a dangerous species from overseas that hitchiked here in the bilge of a freighter.