USM Professor Receives Funding to Research Blue Crab Discard Mortality

Wed, 09/20/2023 - 09:54am | By: Gabriela Shinskie

Since 2004 Dr. Zachary Darnell, an associate professor in The University of Southern Mississippi’s (USM) Division of Coastal Sciences in the School of Ocean Science and Engineering (SOSE), has been studying blue crabs. Now his new research project, funded by the National Oceanic and Atmospheric Administration (NOAA), is set to begin in January 2024 when he will analyze strategies to reduce discard mortality in the blue crab fishery.

“Not all crabs can be harvested- for example, crabs under the minimum size limit or females carrying eggs. We are interested in what happens to those crabs when they are released and whether or not they survive,” said Darnell. “We are trying to get an idea how their fate, and the likelihood of mortality, depends on the season, water temperature and salinity.”

Funding for the project began at the beginning of September 2023, titled “Quantifying and Reducing Discard Mortality of Undersized and Ovigerous Crabs in the Gulf of Mexico Blue Crab Fishery” in a collaborative effort with Mississippi State and the University of South Alabama. USM will lead the project and work with the local fishing community to determine the likelihood of mortality among discarded crabs and to find a solution to the growing concern of discard mortality.

Dr. Darnell wants to make recommendations for fisheries management and industry on strategies they can use to reduce mortality. “We want to make sure that these crabs that are released continue to grow and reproduce,” he said. “It doesn’t do any good to release them if they are not going to survive.”

Blue crabs are extremely valuable in the northern Gulf of Mexico, with Louisiana known for being the largest crab-producing state in the country, making it a an economically valuable species for coastal areas. These crabs are also ecologically important to keeping the estuary food web in balance because of their abundant population.

“I think they are a fascinating species,” Dr. Darnell said. “They have interesting behaviors and complex life strategies. They are very resilient.”

Dr. Darnell plans to work with local crabbers on their boats and access their catch, with the goal of identifying the conditions of the catch and analyzing what portions of their catch will be discarded. He will also distribute a survey to better understand fishing practices of the commercial crabbers and identify how they handle their catch when they load the crabs on their boat.

Field experiments will also be conducted with crabbers, and traps will be installed with various sensors to measure water conditions, temperatures and other factors that might affect crab survival. Dr. Darnell will handle the catch from the traps and access the best way to obtain the highest crab survival rate.

“With this project, we have a nice combination of approaches and collaboration with the local crab industry to better understand this issue and work toward potential solutions,” he said.

Learn more about the School of Ocean Science and Engineering along with Dr. Darnell and his team’s research at the Craboratory.