The Herring Run area, small center of commerce and history, had been my starting point, but I had hardly begun to follow the alewives on their whole migratory route between salt water and the ponds above. First of all I had some background of local hearsay to bring into question. Did the herrin’ really go all the way down to South America in the wintertime? Was it true that each fish returned to the stream it was born in? Did they come inland on their spawning journey and then die, like the west coast salmon? I overheard a man say, “Poor fish! All that work just to die!” But that was one interpretation I could dispose of early, having seen them go back to salt water the year before. Did they only come in from the Bay at night or on foggy evenings? To find out would take more watching and waiting than I had done so far. You might deduce this much to start with: the alewives, only a few at first, started to come inland in the spring when the brackish waters from the Stony Brook outlet were warmer than the Bay into which they flowed, if only by a few degrees. They responded with sensitivity to the temperature. If the earliest fish were the oldest, it was possible that the later runs also corresponded to age groups, guessing by their size, and that the youngest came last of all. Evidently schools of alewives stay together during their ocean life according to the years when they were spawned. Yet why, between March and June, any given schools would come in when they did would be hard to tell. There are places where you can watch the alewives approach, at the junction between tidal and inland waters. At Damariscotta, Maine, they swim up a wide tidal river until a fresh-water stream flows into it from a height above. I was told that the fish are seen massing and circling, sometimes for days, at this point, until by some communicated decision, or joint response--perhaps to pressure of numbers, combined with the right temperature conditions--they start going up. A cold snap may make them drop back to tidewater. In the same way, cold weather may discourage their coming in from Cape Cod Bay. You can also see them schooling in the Cape Cod Canal at the entrance to the Bournedale run, but not at Stony Brook where the outlet flows into the Bay through low sand dunes, or sand flats at low tide. Whatever the local topography may be, the alewives are evidently attracted to the warmer currents and the lack of salinity in a stream where it flows into salt water.