The Purple Hinged Rock Scallop, a Promising Aquaculture Species with a Toxic Algal Problem

Investigators are examining rock scallops to help establish an approved, reliable assay for evaluating biotoxins and to improve growout methods for the purple hinged rock scallop.

Principal Investigator

Bobbi Hudson, Pacific Shellfish Institute

Co-Principal Investigators

Jerry Borchert, Washington Department of Health

Dan Cheney, Pacific Shellfish Institute

Jonathan Davis, Puget Sound Restoration Fund

Steve Morton, NOAA/National Ocean Service, Marine Biotoxins Program

Sandy Shumway, University of Connecticut

Brent Vadopalas, University of Washington, School of Aquatic and Fishery Sciences


Washington Sea Grant-supported researchers investigated the uptake and depuration of biotoxins by rock scallops. They examined individuals and their tissues, comparing where toxins, such as saxitoxin, might be held within the animal. They also examined growout methods and continued to develop National Shellfish Sanitation Program (NSSP) marine biotoxin testing methods for scallops. Investigators will address regulatory and industry needs by improving understanding of biotoxin uptake and depuration in rock scallop species and by helping to establish approved National Shellfish Sanitation Program lab tests for detecting marine biotoxins. Research results are also anticipated to help improve understanding of optimal growout methods for purple hinged rocks scallops in Washington State.

Research Updates


The market demand for purple hinged rock scallops has encouraged research on the viability of aquaculture production. However, rock scallops sometimes ingest marine biotoxins created by algae, which can cause illnesses such as Paralytic Shellfish Poisoning (PSP). Understanding where biotoxins accumulate in the animal—and how long the toxins remain there—is crucial to developing rock scallop farming in Washington.


In 2018, rock scallops were monitored for growth and effects of naturally occurring biotoxins at four pilot research sites: the scallops thrived at all sites. The researchers examined uptake and accumulation of PSP toxins in rock scallops. In 2018–19, 180 individual samples were analyzed following PSP occurrences. Tests confirmed the presence of saxitoxins in both the viscera and the adductor muscles and showed high variability of toxicity across individuals and sites. This is the first data to discriminate between two parts of the animal. The data showed that the toxins stayed in both the viscera and the adductor muscles for longer periods than previously thought.