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NCCOS Project

Uncovering the Mechanisms behind Wintertime Occurrences of Paralytic Shellfish Toxicity in Geoduck Clam Fisheries in Southeast Alaska

This project began in September 2017 and will end in August 2020

Paralytic shellfish toxins (PSTs) from the alga Alexandrium hinder the wintertime geoduck clam fishery in Southeast Alaska. With no winter blooms of Alexandrium on record, scientists hypothesize that the toxins are coming from seed-like Alexandrium cysts in the sediment that are being re-suspended and filtered by geoducks. We are investigating factors to test this hypothesis and provide managers with information needed to reduce the impacts of PSTs to the economically important geoduck fishery.

Why We Care
The Southeast Alaska geoduck clam fishery, worth $4.9 million annually in past years, is an economically and culturally important wintertime fishery. However, the fishery has been plagued by unexplained toxicity from paralytic shellfish toxins (PSTs), resulting in substantial economic losses.

In Alaska, PSTs are attributed to species of the marine dinoflagellate alga Alexandrium and typically threaten shellfisheries during summer months, when conditions support Alexandrium growth. Yet, geoduck clams are showing elevated and erratic patterns of toxicity in fall and winter. The factors that lead to fall and wintertime toxicity in geoduck clams are currently unknown.

While scientists have proposed that benthic resting cysts contribute to the toxicity of certain shellfish through direct cyst ingestion or germination following sediment disturbance, this mechanism for geoduck clam toxicity has not been tested. Further, there is no information about cyst distributions in relation to geoduck harvest areas in Southeast Alaska. Identifying the distribution of cyst populations and the role of cyst resuspension in geoduck clam toxicity will provide managers with critical information needed to mitigate the impacts of PSTs to geoduck fisheries.

What We Are Doing
Our primary objectives are to:

  • Examine the relationship between Alexandrium cyst distributions and geoduck toxicity patterns within commercial harvest areas to identify areas of greater or lower exposure risk to paralytic shellfish toxins.
  • Identify whether cyst ingestion is a mechanism for geoduck clam toxicity to improve understanding of toxin transfer dynamics for geoducks and other shellfish species.
  • Determine if current geoduck harvest and management approaches contribute to the frequent occurrence of wintertime toxicity in geoduck clams.
  • Involve geoduck clam dive industry and resource managers (i.e., Alaska Department of Fish & Game) in research to ensure project outcomes meet stakeholder information needs.

Overall, this project will establish the ecological pathway for algal toxin transfer to commercially important geoduck clams and identify the role of harvest and management approaches in amplifying or mitigating shellfish toxicity.

Dr. Ginny Eckert of the University of Alaska Fairbanks leads this project along with co-investigators Dr. Elizabeth Tobin (University of Alaska Fairbanks), Chris Whitehead (Sitka Tribe of Alaska), and Kate Sullivan (Southeast Alaska Regional Dive Fishery Association). The project is funded through the NCCOS Ecology and Oceanography of Harmful Algal Blooms (ECOHAB) Program.

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