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GOMTOX: Dynamics of Alexandrium fundyense Distributions in the Gulf of Maine: An Observational and Modeling Study

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Shellfisheries Reopen at Georges Bank, Massachusetts

NASA satellite image showing Georges Bank

NASA satellite image of Georges Bank (center). Cape Cod is on the left.

Something good is happening at Georges Bank, a large area off the coast of Massachusetts that separates the Gulf of Maine from the Atlantic Ocean: After 22 years, some 6,000 square miles of the sea floor recently reopened for surf clam and ocean quahog fishing.

Quahogs collected during a surfclam and ocean quahog research survey.

Quahogs collected during a surfclam and ocean quahog research survey.

Together, the two bivalve species comprise a multimillion-dollar fishery along the East Coast. Surf clams, which are used in clam strips and chowders, are the most important commercial clam species harvested in the United States. Quahogs are typically used in chowders, too.

The area is too large and remote for routine monitoring, so back in 1990, the U.S. Food and Drug Administration (FDA) recommended closing it after clams were found to contain a naturally occurring toxin in levels that exceeded regulatory limits. The toxin is produced by Alexandrium fundyense, a single-celled organism that in high concentrations can form harmful algal blooms such as New England red tide.

Filter-feeding clams concentrate the toxin in their flesh, and when people eat the contaminated shellfish, they are susceptible to the illness called paralytic shellfish poisoning (PSP). For a number of years, NOAA-supported research at Massachusetts’s Woods Hole Oceanographic Institution has played a key role in people’s understanding of the mechanisms of PSP.

The Gulf of Maine Toxicity Project

This image shows cysts of Alexandrium fundyense

The alga Alexandrium fundyense produces a potent toxin that accumulates in shellfish. This toxin can cause paralytic shellfish poisoning in human consumers. This image shows cysts of Alexandrium fundyense.

NOAA supported the research that led the FDA to work with clam harvesters to develop a testing program that determines toxin levels in the two species. Extensive testing showed that the toxin has been consistently below harmful levels in these shellfish, indicating that the clams and quahogs are usually safe to eat. However, since high toxicity has been measured in these clams in the past, a testing protocol was needed to insure that they are safe.

The testing protocol is an outcome of the Gulf of Maine Toxicity Project (GOMTOX), funded by NOAA’s National Centers for Coastal Ocean Science (NCCOS). According to Quay Dortch, PhD, manager of NCCOS’s Ecology and Oceanography of Harmful Algal Blooms (ECOHAB) Program, “The primary purpose is to understand the growth and toxicity of Alexandrium in the Gulf of Maine in order to better predict blooms and shellfish toxicity, and to develop better monitoring methods.”

“The fishing industry was so interested in developing methods of safely harvesting shellfish from Georges Bank that they participated with academic researchers and the FDA in the GOMTOX project,” she continues.

“Early in the project, fishermen were trained in the use of several quick tests, which they then used in a pilot project to test the protocol,” she explains.  “Once the protocol was in place, the Mid-Atlantic Fisheries Management Council requested the reopening of Georges Bank, using the protocol so that this large, untapped resource could be safely harvested.”

The FDA and NOAA’s National Marine Fisheries Service share responsibility for regulating seafood from offshore federal waters.  Consequently, FDA scientists led the effort to test the shipboard screening/dockside testing protocol with financial support from both GOMTOX and the FDA.

Powerful Partnerships

Researchers onboard the Woods Hole Oceanographic Institution vessel R/V Tioga

Researchers onboard the Woods Hole Oceanographic Institution vessel R/V Tioga conducting a survey to map the distribution and abundance of toxic Alexandrium fundyense in the Gulf of Maine. (credit: Woods Hole Oceanographic Institute)

In 2012, the project’s fifth year, the Interstate Shellfish Sanitation Conference, a collaborative effort involving the shellfish industry, regulatory agencies and academic researchers, formally adopted a two-tiered testing approach for PSP. Fishermen conduct initial onboard screening to detect if the toxin is present in harvested clams. Then, scientists at approved laboratories conduct further testing before the shellfish are sold to ensure that toxin levels are within regulatory limits.

The FDA will continue to work closely with NOAA to ensure a safe shellfish harvest, and will prohibit the sale of clams if toxin levels are deemed unsafe.

Dr. Dortch says that close collaboration was the key to reopening these important shellfisheries. Partnerships that involve the shellfish industry with researchers and government officials are powerful in the quest to develop effective tools that protect public health and boost local and regional economies.

And that’s good news for New England.