Local acreage in local waterways where shellfish harvesting is not allowed increased from 6,891.1 as of July 1, 2019, to 7,345.2 on July 1, 2020.

Looking back further, the total for that date in 2018 was 5,714.1 acres, according to figures compiled from records in the state’s Division of Shellfish Sanitation, an arm of the Virginia Department of Health.

However, large areas of these waters may be opened in cooler months under a conditional approval program. Waterbodies where such approval may be possible in part or whole are marked with an asterisk on the table that accompanies this article. A map showing condemned areas depicts these portions in green.

In a few cases, no area of a waterbody can be opened to harvesting in a preventive measure taken usually due to a sewage treatment plant outfall.

The state takes water samples at least six times a year from bays, creeks, rivers and coves, measuring for the presence of fecal coliform, according to the DSS website. Waters are...