Local News
Parasites Keep Raritan Bay Shellfish Off-limits in 2004
By Pat Camuso
Mar 10, 2004, 3:21pm

RARITAN BAY- The New York State Department of Environmental Conservation (DEC) has announced a decision to extend the closure of the Raritan Bay Shellfish Transplant Program for 2004 due to the continued presence of the hard clam parasitic disease Quahog Parasite Unknown (QPX) in hard clam populations in the transplant harvest area in Raritan Bay off Staten Island, New York.

DEC administered a hard clam transplant program in the uncertified state waters of Raritan Bay during the period 1987 through 2002. The program involves the harvest of hard clams from uncertified (polluted) waters and their relay to certified (clean) waters for bacterial cleansing and eventual marketing as a food product. Raritan Bay represented one of the most productive hard clam resources in the State.

According to the DEC, QPX is a protozoan parasite that infects the soft tissue of hard clams causing an inflammation in the tissue which prevents the clams from closing their shell and pumping food and water to the gills. The disease is normally observed in the mantle and gills of the clam.

QPX is not harmful to humans and does not represent a public health concern but is fatal to hard clams, causing significant mortalities in an infected clam bed. There is no known treatment or cure for QPX in hard clams.

In 2002, DEC received reports from shellfish harvesters of dead and dying clams in the transplant harvest area in Raritan Bay. DEC sampled clams from Raritan Bay for analysis in August 2002 which were confirmed to display QPX-positive infections. DEC immediately terminated the Raritan Bay transplant program on September 6, 2002 in order to prevent the potential introduction of the parasite to the cleansing sites and waters of Peconic Bays. This was the first time QPX had been found in hard clams in New York waters.

During 2002, DEC conducted extensive monitoring of the transplant harvest area in Raritan Bay in order to determine the extent and distribution of the QPX disease. The diagnostic analysis of the clam samples was performed by the Marine Animal Disease Laboratory at Stony Brook University (MADL). The final pathology report released by the MADL in 2003 documented the finding of QPX positive infections at 16 out of 20 sampling sites covering the majority of the harvest area. Based on this report, DEC announced the closure of the shellfish transplant program for 2003 on March 13, 2003.

In May 2003, DEC conducted additional and follow up surveys of hard clam populations at four sites in Raritan Bay in order to determine the potential for making new areas of the bay available for transplant harvest. The diagnostic analysis was conducted by the MADL and a pathology report issued in July 2003 reported the detection of QPX positive infections in three out of four samples with a low prevalence of 3.3 percent. The most significant observation in this report was the drop in QPX from 23.3 percent (November 2002) to 3.3 percent (May 2003) at the focal point of the infected area. The report further indicated the observation of dead/dying QPX cells in positive clams which was a sign of a healing process and improvement in clam health.

Based on these results and in order to evaluate the potential for re-opening the program for 2004, DEC completed an extensive monitoring program in August 2003. The QPX sampling involved the collection of 360 clams from 12 designated sampling sites in Great Kills Harbor and Raritan Bay. The MADL completed a histopathology report in 2004 that indicated the finding of QPX positive infections at nine out of 12 sites examined with prevalences ranging from 3.3 to 33.3 percent. The central part of the fishery displayed the highest prevalence of QPX positive infections accounting for almost 60 percent of the infected clams. Although prevalences at most of the sites were relatively low, between three to 10 percent, they were adjacent to sites displaying more significant infections which exceeded the recommended thresholds for safe movement of product.

DEC is working in partnership with the Marine Animal Diagnostic Laboratory at SUNY Stony Brook to develop strategies for monitoring clam beds in Raritan Bay, Peconic Bays and other areas of the state in order to reduce the risk of transfer of QPX to non-infected beds and obtain more comprehensive information on the status of QPX in New York. There is still much unknown about transmission of the disease and the long-term impacts of the disease to an area once it is infected. DEC is working with researchers to help answer these important questions on QPX disease which are vital to management of these important shellfish resources.