Maryland Department of Natural Resources fisheries biologists have recently finished the 2008 oyster survey, an annual assessment of the health and population of oyster bars in Maryland’s portion of the Chesapeake Bay. It is found that such annual surveys of oysters started from 1939 when at each fall biologists use a dredge to monitor natural oyster bars, seed production and planting areas, dredged and fresh shell plantings and oyster sanctuaries.
Mitch Tarnowski, DNR fisheries biologist, told that preliminary results from 2008 indicate that reproduction was poor throughout most of the bay, with the exception of the lower eastern shore areas of Tangier Sound, Honga River, and the Little Choptank River. He also states that generally, mortalities and oyster disease levels appear to be relatively low again this year.
In all these surveys biologists found some infection during the late 1950’s when they starting seeing the effects of Dermo (Perkinsus marinus) and MSX (Haplosporidium nelsoni) diseases on the bay’s oyster population. While not harmful to humans, these parasitic organisms infect oysters and have lead to the death of up to 90 percent of oysters in some areas.
It is told that disease causes the greatest problems during years with higher than average salinity brought about by lower than normal stream flow. With higher salinity in the bay between 1999 and 2002, MSX, Dermo and oyster mortality was higher than average. In the current survey the biologists assessed more than 1,800 oysters collected from 282 oyster bars.
Mike Naylor, Director of DNR’s Shellfish Program, explained that the dry summer of 2007 did not result in high disease levels similar to previous dry years. The survey found that Dermo increased in 2007, but remained below normal in both prevalence and intensity. It is also states that MSX increased in frequency, but for the fifth straight year observed oyster mortality remained low.
