Page:Popular Science Monthly Volume 52.djvu/814

792 and used these fisheries long before the first white settlers found them at work with their rude seines. In the early part of this century, before canals and the dams which supply them were made, there were forty fishing stations beyond the forks of the Susquehanna in northern Pennsylvania, and some of them were worth from one thousand to twelve hundred dollars a year to their owners. There is a record of the capture, at a single haul, of ten thousand shad at one of these fisheries on Fire Island, near Wilkesbarre. Dams across the river have excluded the shad from more than two hundred miles of the course of the Susquehanna, and the profitable fisheries now reach for only a few miles above the boundaries of Maryland, while the shad are cut off from many of the best breeding grounds, which are the sandy flats near the shores of streams and the sand bars which lie in their course. The fishes run up into these places in pairs in the early evening after sunset, and the eggs are thrown into the water while the fishes are swimming about, but they soon sink to the bottom and develop very rapidly. The number of eggs is about twenty-five thousand, but a hundred thousand have been obtained from a single large shad. Few adult shad escape all the dangers of their journey, and these few are so battered and emaciated that they have no value as food, and are unknown in our markets, which are supplied with those that are captured on their way upward. The young fish remain in the rivers until late in the fall, feeding upon small crustacea, the larvæ of insects, the young of other fishes, and minute active animals, and they grow to a length of two or three inches by November, when they leave our waters for the ocean. The shad is a marine fish which has acquired the habit of laying its eggs in fresh water, out of reach of the innumerable enemies that abound on the shoals and sand bars of the seashore. Since the eggs are abandoned by their parents soon after they are laid, prolonged residence at the breeding grounds is not necessary, and the shad has thus been able to utilize safe places which supply no proper food and are unfit for prolonged residence. If it were compelled to incubate its eggs and to guard and protect and feed its nestlings like a bird, it would have been restricted to some breeding place fitted for more prolonged residence, and we should then feel something of the same tendency to call its birthplace its true home that we experience in our study of birds. We should refer the migration to this place as the starting point, and we should try to discover some reason why they spend part of the year elsewhere.

Most animals owe their existence to the occurrence, in their natural home, of all that their life requires, but the power to traverse great distances at great speed, and to pass over all the barriers of land and water, joined to their comparative indifference to changes