Twenty years is a long time to wait for a fish to find its way back home, but that is what happened with the shad of the Susquehanna River. Dams on the river, which feeds the Chesapeake from a watershed reaching all the way to Binghamton, N.Y., blocked access to the migratory foodfish's spawning ground early in this century. The worst effects of that ++ were not seen until 1980, when a harvest 91 percent smaller than formerly recorded prompted a ban on shad fishing.
Maryland and Pennsylvania authorities had been struggling to convince Philadelphia Electric Co., principal owner of the Conowingo Dam, and other utilities farther up the Susquehanna to provide ways for the shad and herring, another migratory foodfish, to get past their dams. That effort started well before the 1980 ban, and Philadelphia Electric installed a small fish lift at Conowingo during the 1970s. Starting with 182 fish caught at the base of the dam, the spawning population built up to 16,000 by 1990.
That slow buildup may surprise some observers, but it must be remembered that it took half of a century to choke off the shad runs in the first place. Shad move up and down the East Coast, running in the Delaware and other rivers as well as the Chesapeake Bay. And there were other factors inhibiting the shad runs, notably silting from construction along the bay and riversides, pollution from chemical wastes, fertilizer runoff and poorly treated sewage. Finally, the turbines pulling hydroelectric power from the stored waters behind the dams themselves added to the problem, moving water but providing little aeration, depriving fish of oxygen to breathe.