Oysters Past and Present, and the Future of the Chesapeake Bay

Oyster populations in the Chesapeake Bay have declined massively in recent decades due to overharvesting, disease, and sediment pollution. By the time marine scientists began monitoring bay oysters in the 1940s, oyster reefs were already decimated by 75 years of dredging. One could argue that scientists have never seen a healthy oyster reef in the Chesapeake Bay.

The fossil record, in contrast, provides evidence of widespread, thriving oyster reefs before human settlement. By studying fossils of oysters, we can reconstruct how oyster reefs functioned before human disturbance and develop recommendations for oyster recovery.

For this study, over 4000 fossil oysters, ranging in age from 500,000-80,000 years old, were examined from 11 sites in Maryland, Virginia, and North Carolina. Shell size and lifespan in Chesapeake Bay oysters declined significantly during the last half million years. This pattern occurs because larger oysters, which were common in the past, are more likely to be eliminated due to harvesting and disease in the bay today. These larger, older oysters are important because they are overwhelmingly female, and represent the reproductively most active members of the population.

Although fossil analyses highlight the role that larger, older female oysters play in oyster populations, current management in the Chesapeake Bay focuses almost exclusively on protecting and supplementing young oysters. We recommend four potential management approaches based on data from fossil oyster reefs: (1) implementation of a maximum size limit on oyster harvesting; (2) establishment of large, long-term sanctuaries in the bay; (3) significant decrease in harvesting; and/or (4) prioritizing replanting sites based on predicted sea level rise.

The fossil record provides us with a glimpse into the world of Chesapeake Bay oysters before humans—emphasizing a range of management solutions and providing new hope for the future of the Chesapeake Bay.