Progress 05/15/24 to 05/14/25

Outputs
Target Audience:There has been an effort to promote shellfish aquaculture in the USA, particularly along with Southeastern, Mid Atlantic and Northeastern seaboards, as a means to fill the trade deficitbetween imported seafood and US-raised seafood. The state of North Carolinaboasts a growing shellfish aquaculture market, primilarily focused on oysters and clams.In 2016, an advisory team generated a report on Shellfish Mariculture and identified key recommendations for the expansion of the NC shellfish market to match national competitors. However, growth of the industry has been stifled because ofoyster mortality events, exacerbated by extreme weather events,that have impacted productivity and generation of profit. Our team has been using a multi pronged approach to study oyster mortality, with the ultimate goal of understanding the drivers of oyster mortality, identifying genetic lines of oysters who are more resilient to mortality events, identifying farm practices that can be used to reduce the magnitude of mortality events, and working with the shellfish industry to promote communication for this and other issues that hamper economic growth. Our direct audience for this work is the shellfish farmers of NC, including the NC Shellfish Growers Association, as well a regional audience ofthe East Coast Shellfish Growers Association (ECSGA). Our work is globally relevant to reduce shellfish mortality events across a range of different species and markets. Changes/Problems:The only significant change for this project has been a request for a no cost extension to extend our project funding window to May 2026. This no cost extension will not require a re-allocation of budget, and it does not change the scope or aims of the project that have been outlined. Since mortality largely occurs in the spring/summer months, this no cost extension will give us an additional season over which to test genetic lines of oysters that have been produced at the hatchery, so that we can select genetic lines of oysters that are resilient to mortality events. This no cost extension also gives us an opportunity to work more effectively with our shellfish growers during periods of time that are best for their schedules. That is, in fall of 2024, even though we had active funding, we were not able to schedule our initial shellfish farmer industry open forum events, because there were too many farmers who were still actively dealing with on-farm losses associated with mortality events, and the timing was not appropriate. Finally, the no cost extension will give us an opportunity to listen to the industry, and identify on farm practices that might play a role in reducing the overall losses associated with the industry. What opportunities for training and professional development has the project provided?This project has provided an opportunity for training of 1) post doctoral, graduate and undergraduate scientists in the areas of dPCR based tracking of shellfish pathogens, 2) post doctoral and graduate studentscientists learning traditional shellfish pathology based histological analysis, 3) training for undergraduate, graduate students and postdoctoral researchers in social science approaches for gathering information on perceptions and behaviors of the industry (surveys/interview), 4) this project has also provided an opportunity for training across our collaborative research team and the research team at Virginia Institute of Marine Sciences. How have the results been disseminated to communities of interest?We have been working closely on this project for the entire duration in collaboration with Chris Matteo and the NC Shellfish Growers Association. We have interacted with the NCSGA on the interviews and surveys that have been conducted on farmer behaviors and farm practices, and we have worked directly with farmers themselves on studies related to shellfish mortality (5 different farms). We have also collaborated directly with the UNC Wilmington Shellfish Research Hatchery for the work on genetic lines of oysters, and we continue to work with Dr. Ami Wilbur and collaborators to identify resilient lines of oysters for future deployment. As part of our project, we have also conducted events, and have attended events (Aquaculture/NSA 2025, Oyster South, NC Aquaculture Development Conference) where we are broadly supporting and listening to the national shellfish aquaculture community and we have received feedback from our work at these events indicating that folks across the country are impressed with our work to mitigate the losses associated with oyster mortality. There is broad sense that much of what we are working on in NC will be applicable to the Northeast, Gulf, and Pacific Northwest shellfish farming industries. What do you plan to do during the next reporting period to accomplish the goals?The NC Shellfish industry continues to grow and produce a high-quality product, but mortality events are a significant issue across the industry. Growers could beutilizing a range of potentially farm-level adaptive behaviors, including stocking densities, flipping rates, genetic line selection, gear choice, and location. We are currently working with industry partners to understand the local successes andefficacy of these behaviors. For the next reporting period, we intend tocomplete tasks related to streamlining shellfish pathogen quantification, and continued selection, deployment and experimentation with resilient genetic lines. Now that we have completed our shellfish farmer interviews and have assembled and are near release of our on line survey tools for understanding drivers of mortality and shellfish farm levels best practices. So the next step will be to distill that information and select a few farm-level Best Practices that we can then test using deployment of oysters in select farm locations. We will also conduct additional open dialogue forums with the NC Shellfish Industry over the next reporting period, and capture the information that has been gathered from the NC Shellfish Farming community into flyers about reducing oyster mortality that can be shared across NC, but also across other regions.

Impacts
What was accomplished under these goals? There are three main aimsof this project which is focused around the characteristic of drought periods driving windows of high salinity The accomplishments are stated in the context of each of the aims below, with the aim in italics and the accomplishments following.Aim 1: Characterization of archived samples collected during recent drought conditions using molecular and histological approaches, followed by a summary available to farmer stakeholders.We have completedanalysis of archived samples collected from two previous mortality seasons in 2023 and 2024, and are assembling that data in the context of quantitative molecular results (digital PCR for Vibrio species) as well as traditional microscopy based histological outcomes. We have presented some of this information at the Aquaculture/NSA 2025 Conference, and are in the process of distilling the messages for our farmer audience. Aim 2: Deployment and active assessment of 4 genetically distinct oyster lines (available spring 2024) at two farm sites that have historically experienced devastating oyster mortality events.We have completed a limited amount of testing on genetically different oyster lines to determine their resilience to mortality. We hope to complete additional tests of genetic lines in spring/summer 2025 based upon selected "survivor" populations that will be deployed under a range of conditions. We are summarizing the patterns of oyster mortality that have been observed over multiple locations in NC over the last 4 summers and working to assess this data in the context of shellfish loss and drought or other described condition so that we can understand drivers of shellfish mortality. Aim 3: Implementation of mitigative farm-level practices, including testing patterns of oyster planting, site selection, and harvesting in NC estuaries that will alleviate losses experienced by farmers during large-scale mortality events.We completed a study that involved movement of oysters from a farm experience mortality (high salinity) to a location that was not experiencing mortality (low salinity) and we are summarizing those results for hte industry and in the form of a publication. The experiment worked well, and we observed no further mortality at the low salinity site, showing that there are candidate farm practices that might be helpful in mitigating the extent of any given mortality event. We are in the process of conducting a survey that will help us identify other farm practices that might be helpful in reducing mortality. Once that survey is complete, we will identify a select number of practices and will conduct experiments on those practices in collaboration with shellfish farmers. Aim 4: Develop materials to share collaboratively with oyster farmers to promote industry-wide knowledge and active response to mortality eventsWe have already completed one outreach event on January 13, 2025, and we have another one planned in Wilmington, NC on April 1. We have engaged with the shellfish farming community in NC through interviews and now distribution of the survey regarding oyster mortality, and we will summarize those outcomes into a cohesive package of information that can be shared across the whole shellfish industry of NC to reduce the losses associated with oyster mortality events.

Publications