Maryland Basin Estimates

For convenience and ease of data presentation, the Chesapeake Bay tributaries in Maryland waters have been grouped into "Basins". The Basins used for Maryland in this project include: the Chester River, Eastern Bay, Choptank River, Little Choptank River, Tangier Sound, the Potomac River, Patuxent River, and the Maryland portion of the Chesapeake Bay mainstem. These basins are shown on the map below.

Maryland Basin Map

Basin estimates are available for Maryland oyster populations from 1994 through 2002. These basin estimates rely on a variety of different data types that are collected by different agencies and institutions. All data used in Maryland oyster population estimates falls into one of three categories: fishery independent, fishery dependent, or restoration. Each of these categories is described briefly below.

A. Fishery Independent data - These data are derived from the annual dredge survey conducted by the Maryland Department of Natural Resources. An oyster dredge, 30 inches wide and 18 inches tall, is deployed from the R/V Miss Kay. Two tows are made with the dredge, averaging about 230 feet in length. A half bushel of oysters is retained from each the two tows, and then measured to provide length-frequency data as well as oysters for disease diagnostics.
B. Fishery Dependent data:
B1. Public/Commercial fishery - These data are based on the annual oyster landings as reported to the Maryland Department of Natural Resources Fisheries Statistics Division. One bushel of oysters was assumed to contain 350, 3.5 inch oysters. A market oyster is 3 inches or 76 mm from its beak to its hinge (shell length).

B2. Private fishery - Oysters harvested from leases are subject to harvest taxes like that of the public fishery. One bushel of oysters harvested was assumed to contain 350 market oysters.

C. Restoration Efforts:
C1. Reefs - unexploited sanctuaries -These data are from dive surveys being conducted on constructed oyster reefs and within oyster sanctuaries by personnel from the University of Maryland.

C2. Replenishment areas - exploited shellplants and reefs - These data are from the annual replenishment reports produced by the Maryland Department of Natural Resources Shellfish Repletion program.

The amount of oysters produced by oyster gardeners in Maryland is small relative to those in Virginia. Thus, oyster gardening efforts have not been included in these calculations for Maryland tributaries.

Annual estimates of oyster populations within Maryland's basins made with these data categories are available for:

1994 1997 2000
1995 1998 2001
1996 1999 2002


Annual basin estimates of oyster population numbers and biomass (g dry tissue) are useful for describing trends in Maryland's oyster population over time. View graph of Maryland oyster numbers and biomass in the period 1994-2002.