It may be that the earliest, coming in during the month of March, or early April, when the pond waters are still cold, will go farther than the later arrivals. Their eggs develop more rapidly as the temperature of the water advances, from around the late forties say, at the beginning of the season, to a maximum of 72 or 74 degrees. When the spawn is not ready they may keep going, schooling, roaming in the ponds for days. But there are no hard-and-fast rules about which of the alewife schools goes where, and any generalizations would have to be varied to suit conditions in other localities where they are found. At one extreme they may travel for six or eight miles up a tidal river, or at another they may come into a pond connected with salt water by a waterway or cut only a few feet long. Many of them swim up headwaters as far as they can go, through the last ditch to its stagnant end. I have heard of their going through marshy land in the direction of Pine Pond, a small pond beyond Walker’s, once connected with it I believe. There were cranberry bogs in this land, bordered by wire fences. The alewives would slip sideways under the wire so as to get to the other side. This is characteristic of them. When in very shallow water, inches deep, hardly enough for their bodies, they will skitter on, almost flat on their sides at times, going as far as they can until the water gets deeper. Occasionally they have been known, on their way upstream, to butt their heads against a leaky dam where the flow of the water continued to come rather than go up a fishway to which it had been rerouted. (In one case an old log dam obstructing a stream had enough leaky cracks in it so that fish slithered through them.) Such behavior may not make sense from our point of view, but it is part of a life necessity to them. Returning alewives are not concerned that we bypass a stream or send it off its course. They continue to follow the direction and limits of the flow that is in them, even as it might have been before we came. Behind their persistence, if one term can encompass enough, is the “homing instinct.” This is not only a matter of reacting to environmental waters, but insisting on that area where they were spawned, and where they grew, in the first few weeks or months before they migrated to salt water. In trying to rehabilitate the alewife population, men in fishery management are greatly helped by this powerful drive to return. Sometimes they are hindered by it.