Oyster farmers may have heard the acronym SUMS mentioned in the past year. This stands for Sudden Unusual Mortality Syndrome and is described as high mortalities that happen quickly and cannot be attributed directly to water conditions such as temperature, salinity or dissolved oxygen.
These types of mortality of events are relatively new to the Gulf Coast but have been experienced for decades in other oyster species around the world. For example, farmers that grow the Pacific oyster are likely familiar with Pacific Oyster Mortality Syndrome (POMS), which leads to high mortalities in juveniles and has increased since 2008. POMS has been reported in all continents that raise this oyster species. In Japan, major losses of juvenile Akoya pearl oysters have occurred since 2019. These SUMS events have occurred in the Eastern oyster since 2012 on the East Coast of the U.S., with substantial losses reported on the Gulf Coast in the past three years.
High, sudden mortalities are often reported in spring/summer, although reports on the Gulf Coast have occurred into the fall months. They occur in near market size oysters, across gear types and in both diploids and triploids. Oyster mortality events can lead to losses of over 70% and are a threat to the industry.
What is frustrating is that we have not been able to link them to a single stressful event, such as low oxygen, low salinity or high temperature. It certainly is not from a lack of trying. It is difficult as information suggests these deaths are caused by a combination of stressors or perhaps rapid changes in environmental conditions. What is known is that they are not caused by your typical oyster pathogens (Dermo or MSX, for example) or harmful algal blooms. But this still leaves a number of possible factors, and a few or many of these may interact: genetics, environment, immune function, husbandry, physiology, unknown pathogens… the list goes on.
What is clear is that it will take a village to understand and mitigate these mortalities. A recent NOAA-funded collaboration among researchers and commercial oyster farms across nine states represents the first large-scale effort to gain insight into the causes of these events in the Eastern oyster.
Scientists could use help and information from those dealing with these issues firsthand. We need reports of these events when they happen and in-depth conversations with farmers so we can start to weed through the noise.
What can oyster farmers do? One or more of these things would be extremely helpful in addressing mortality events:
- Call your local Sea Grant agent when you see alarming mortalities, and provide information related to the event. Your observations are vital!
- Participate in the “Waffle House Index” for collaborative monitoring of mortality events. This index is a simple weekly survey where you share a traffic light color that indicates your concern about your crop. A green light means everything is fine, a yellow light means you have some concern, and a red light means things are really bad.
- Write letters of support for and participate in research projects related to these events.
- Track your inventory, as much as feasible, to understand if different oyster groups are more susceptible than others.
It is time to come together, share information and develop mitigation strategies to maintain our oyster aquaculture industry. We know many farmers are already involved, and we thank you! If you would like to become more involved or talk about what you have observed, please reach out to me.
Meet the author
Andrea Tarnecki
Assistant Extension Professor
Andrea Tarnecki is an assistant extension professor at Auburn University's School of Fisheries, Aquaculture, and Aquatic Sciences.She connects with shellfish farmers and stakeholders to identify... Read more
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