Local Ecological Knowledge & Modeling Insights for Shrimp Abundance in the Pamlico Sound

As environmental changes occur in the ocean, so does overall fish behavior. Species and populations of marine organisms are constantly responding to changes in the ecosystem around them. In turn, this can affect species abundance, distribution, reproduction, and more, which then have implications for fisheries operations and management. This series of chain reactions was highlighted in a recently published study conducted by Drs. Nadine Heck, Lela Schlenker, Samantha Farquhar, and Jim Morley, all of whom have ties to ECU and the Coastal Studies Institute.

The study, Environmental drivers of shrimp abundance: comparing insights from local ecological knowledge and empirical modeling, examines how storms, rainfall, temperature, wind, and offshore reproduction impact the abundance of brown and white shrimp populations in North Carolina. The Pamlico Sound provides critical habitat for these two species which are commercially targeted in the state. Thus, it is important to understand how brown and white shrimp respond to changing environmental variables. Through their research, the scientists use fishers’ local ecological knowledge (LEK) obtained through surveys alongside population models made from long-term datasets to gain a better understanding of observed shrimp response to environmental changes and to make recommendations for future management considerations.

White shrimp (left), commonly referred to as greentails, and brown shrimp (right) are the two focal species of the recent study conducted by Drs. Heck, Schlenker, Farquhar, and Morley. Illustrations courtesy of NOAA.

While many other fisheries population studies are conducted by analyzing trends over time and using computer models to make predictions, this study is unique because it attempts to understand and utilize information and observations from those who interact with the local marine environment regularly. Fishers can often provide “on the ground” insights due to their daily interaction with the local marine environment; however, up to this point, this type of knowledge has been rarely used for management decisions. Heck, Schlenker, Farquhar, and Morley (subsequently referred to as Heck et al.), highlight through their study that LEK in combination with long-term models may provide better information for decision and policy makers in the future.

To arrive at this conclusion, Heck et al. first distributed surveys to commercial shrimp fishers in nine coastal North Carolina communities, as well as in Newport News, Virginia. The survey included questions about observed shrimp abundance and environmental drivers that might affect shrimp populations. The survey also asked respondents for demographic information, including their role in the fishery, how they obtained fishery knowledge, and their livelihood dependency on the fishery. Finally, the survey allowed respondents to qualitatively describe some of their observations in greater detail.

Once survey results were analyzed, they were compared with long-term data about white and brown shrimp in the Pamlico Sound. The ecological data indicated that the general abundance of the two shrimp populations varied across the 33-year time span of the dataset. Specifically, white shrimp trends have increased over time, a fact echoed by almost half of the survey respondents. Furthermore, brown shrimp data indicated no population trend, which was also corroborated by survey results, in which many shrimp fishers reportedly observed a stable population with no clear trend. Interestingly, fishers’ perceptions of shrimp populations were seemingly tied to their experience with the local shrimp fishery based on their respective number of years participating in the fishery.

Furthermore, factors such as storms, rainfall, and temperature were identified by both LEK and the models as influencing brown and white shrimp abundance. However, results from the survey did not always match the model outputs when it came to specific environmental factors affecting shrimp populations. For example, fishers generally felt that storms reduced the abundances of both shrimp populations. However, the models indicated that storms had a positive effect on white shrimp abundance and a negative impact on brown shrimp numbers. On the other hand, both the fishers’ LEK and the models agreed when it came to rainfall, which appeared to have a negative effect on shrimp abundance.

The biggest differences between LEK and the models were highlighted when considering wind. Survey respondents did not typically mention wind as a factor influencing shrimp abundance. However, the models indicated that wind was a strong predictor of increased white shrimp abundance but had a moderate negative effect on the abundance of brown shrimp.

As noted by Heck et al., another result of the survey responses was a better understanding of how the fishers receive or seek out fishery-related information. Those who had participated in the fishery for a longer period of time, and those with a high number of participating family members, had an increased reliance on information shared by friends and family rather than by fishery managers. Those who had participated in the fishery for less time or had fewer family members also participating were slightly more apt to rely on information provided by fishery managers. Overall, however, most fishers learned about shrimp abundances from friends and family, as well as from their own experiences in the fishery.

While the LEK and model results did not always match, and even though the two approaches are based on very different information, the methods “can converge and can be comparable, even in the context of highly variable species such as shrimp,” the authors report. Furthermore, they conclude that “being able to examine lagged environmental drivers is a strength of empirical models, while LEK might attribute annual variation to more proximal drivers.”

Though the new study has many nuances, and this story only highlights a few, the key take away is that LEK can provide valuable insights that correspond to and build upon model outputs. Fishers’ knowledge spans many years and seasons in the fishery, providing valuable details where standardized, long-term data might be lacking. In the future, the best policy and management decisions will be made when both types of information are considered in tandem.

“Fishers are on the water every day and often have a lifetime, and even generations, of knowledge of species and habitats. Incorporating that knowledge base into scientific studies can enhance our understanding of how natural and man-made environmental changes shape species movements and behaviors,” says co-author Dr. Lela Schlenker.

The preceding story first appeared in the Summer/ Fall 2025 edition of CoastLines, published in October.