LB 11-109 - Evaluating Temporal Shifts of Size at 50% Maturity for the North Carolina Blue Crab Stock

Blue crabs (Callinectes sapidus) play a key role in North Carolina estuaries and commercial fisheries. However, blue crabs are often overfished because of the high demand for seafood, which can be detrimental to their population, along with the estuaries as a whole. A full understanding of the blue crab’s life cycle is crucial in the process of writing well-informed policy that will be effective in properly managing blue crab fisheries and protecting the blue crab population. My research aims to provide information about temporal shifts in North Carolina blue crab size at maturity which may aid in the future development of management strategies in North Carolina. Blue Crabs were collected from two locations in the Newport River estuary near Beaufort, North Carolina. Standard crab pots, peeler pots, and minnow traps were used to ensure a collection of blue crabs of all sizes. The female blue crabs collected were checked for sponge, weighed (g), and their carapace width was measured (mm). Since female blue crabs do not molt after reaching their reproductive form, this allows for easy and accurate measurement of their size at maturity. From this data, the female individuals were compiled by carapace width and were fit to a logistic regression curve to the proportion of mature individuals at each given size to estimate the approximate L50 value. The estimated size at fifty-percent maturity for blue crabs in Haystack and Prytherch Creek was 167 mm. This value was compared to previous research conducted by NCDMF from 1988-2016 and we found that there was an increase in carapace width by 43 mm. It is probable that the size at fifty-percent maturity for North Carolina blue crabs has increased due to the observed changes in other blue crab populations. However, it is not probable that they are increasing as quickly as the results indicate. With further research, we would expect to collect more female crabs in sponge and as a result we would expect to calculate an L50 value closer to the mean. Further research is necessary to help us better understand the shifts of size at fifty-percent maturity for the North Carolina blue crab stock over time.