Protecting Blue Crabs and Seagrass in Coastal North Carolina

Why This Project Matters

Blue crab (Callinectes sapidus) is one of North Carolina’s most economically valuable fisheries. However, stocks have been stressed since 1996, due to a combination of environmental and anthropogenic factors including: habitat loss, declining water quality, disease and possible overharvesting. 

Hematodinium, a parasite known for causing high mortality rates in blue crabs, thrives in high salinity waters and spreads more rapidly in areas where habitat degradation forces crabs into closer quarters. While this parasite is not a threat to humans, the high mortality rate significantly impacts the fishery. Understanding the environmental factors that drive disease prevalence is crucial for developing management strategies to protect this essential fishery. Our goal is to find links between these complicated issues and find ways to protect blue crabs, aquatic habitats, and the economic benefit that they bring to our local communities.

Project Overview

Through extensive field surveys, CCRW and its partners are quantifying the prevalence of Hematodinium infections in juvenile blue crabs and examining how habitat and water quality conditions influence disease spread. By linking disease occurrence to habitat loss, this research will inform future conservation and restoration efforts aimed at sustaining North Carolina’s blue crab fishery and protecting coastal ecosystems. 

Blue crabs collected from DMF Trawl Surveys and fisheries-independent sampling are brought back to NC State’s CMAST for processing. There, researchers extract DNA from the hepatopancreas (where the parasite typically aggregates) and utilize qPCR techniques to detect the presence of Hematodinium in the crabs. Juvenile crabs are the main priority of this study as they are observed to have the highest mortality rates, but adult crabs are sampled to detect differences in Hematodinium prevalence in adults versus juveniles. 

The next step of this project is to overlay the Hematodinium data with aerial seagrass survey data to determine whether there are links between areas with declining seagrass and areas with many infected blue crabs. You can learn more about seagrass trends in NC by viewing this comprehensive StoryMap created by the Albemarle-Pamlico National Estuary Partnership (APNEP).

Who is Involved

This project is a joint effort between CCRW and faculty at NC State University’s CMAST. The NC State team consists of Dr. Y Stacy Zhang, a marine community ecologist; Dr. Tal Ben-Horin, an aquatic pathologist; and undergraduate students participating in the Semester at CMAST and CMAST Summer Fellows programs. We have partnered with the NC Division of Marine Fisheries and NC Sea Grant to carry out our research and outreach goals. 

Outreach and Impact

Water quality is an issue that impacts everyone in our communities either directly or indirectly, and it is important that we educate the public about how land use can impact what happens in our sounds and waterways. Seagrass needs good water quality to photosynthesize and grow, and in turn, provide us with many ecosystem services such as carbon sequestration and protection against erosion. Blue crabs are just one of the organisms that rely on healthy seagrass ecosystems to survive, and by learning about the interconnectedness of water quality and fisheries, we can make informed choices that will benefit all parties involved. Through our Seagrass Saturday instagram series, we provide a fun and digestible introduction to seagrass and the threats it faces. As we learn more about Hematodinium and seagrass cover, we will continue to share this important information with the public and stakeholders. Follow along with our journey and learn more about our Water Quality for Fisheries (WQ4F) campaign by subscribing to our newsletter and finding us Instagram and Facebook at @coastalcarolinariverwatch.