In spite of marked improvements in some places, the total acreage of local waters condemned to shellfish harvesting has risen in the past 12 months.

Total area of waters in Gloucester and Mathews under the prohibition, as of July 1, 2012, was 4,199 acres. The total at this point in 2011 was 3,942 acres.

The largest change for the worse, and accounting for all the increase of acreage and more, was in the Piankatank River, where the prohibited area rose from 542 to 1,104 acres.

While the oyster industry is just a shadow of its former powerful profile in the local economy, the health of the waters where shellfish live is a consistent indicator of pollution levels.

The Virginia Department of Health, through the Division of Shellfish Sanitation, takes monthly water samples in bays, rivers and creeks. The purpose is to test for the presence of fecal coliform; and areas where levels are too high are put off-limits to gather oysters and clams.

The division, on its website, notes t...