“The sea-fish come into our rivers in March...great schools of herring come first; shads of a great bigness follow"—A. Whitaker, Jamestown Colony, 1613
VIMS professor John Olney has worked for more than a decade to help restore American shad to Chesapeake Bay. These fish, once as iconic to the Bay as blue crabs or oysters, are now largely unknown except by scientists, commercial netters, and fly fishermen.
In George Washington’s day, anyone living near the Bay was likely to be intimately familiar with shad. Great torrents of these large, silvery fish ran up local rivers each spring, heralded by the snow-white blossoms of the shadbush. In fact, Washington was himself a shad fisherman, part of the Bay’s largest commercial fishery during the 18th and 19th centuries. The “poor man’s salmon” was prized for both its meat and roe, as hinted by its scientific name Alosa sapidissima, or "most delicious shad.”
As late as 1896, commercial shad landings on the Atlantic coast exceeded 48 million pounds. But that fishery is now all but gone, victim to over-harvesting, pollution, and dams that block historic spawning grounds. Nearly all of the Bay and its tributaries are now closed to shad fishing. Olney and colleagues are striving to help reverse this long decline. “Our focus,” he says, “is to gain the basic population and ecological data that managers need to restore this fish to sustainable levels.”
Each spring since 1998, Olney’s team has partnered with local watermen to monitor the shad run up the James, York, and Rappahannock rivers. Their latest sampling shows that populations have yet to recover, despite annual releases of millions of hatchery-reared fry into Bay rivers each spring. These hatchery fish are chemically marked and can be identified in scientific samples.
Olney’s team also measures the ages of sampled fish, an important part of understanding shad population dynamics. Aging is traditionally based on growth rings in scales, but the method needs validation. VIMS graduate student Sally Upton is using natural isotopes of oxygen to test scale-based ages and reveal annual patterns of recruitment to the York River.
Recently, former graduate student Joel Hoffman used natural isotopes to show that the shad’s diet incorporates materials from both the river and the surrounding forest. As Hoffman puts it, “In a sense, American shad are growing on trees! If we are to bring back American shad… we need to conserve the ties between the land, the river and this marine fish.”