STABLE ISOTOPE ANALYSIS FOR DETERMINATION OF FEEDING HABITS OF BLUE CRAB Callinectes sapidus IN THE DELAWARE BAY

 Lauren Jescovitch*, Matthew Stone and Gulnihal Ozbay
 Department of Agriculture and Natural Resources
 Delaware State University, Dover, DE 19901 USA
 LJescovitch@desu.edu
 

Stable isotope analysis is becoming a popular method to analyze nutrient cycling which can measure traceability in fisheries. A large, tidal creek - Blackbird Creek - connects to the Delaware Bay and was used to study blue crabs (Callinectes sapidus) and water quality for ecological influences and blue crab fisheries sustainability. A total of 25 blue crab samples were collected in various Delaware Bay sites in 2014. Water samples were monitored for temperature, dissolved oxygen, pH, salinity, conductivity and turbidity at those sites within different marsh habitat (Spartina dominant, Phragmites dominant, mixed, agricultural, non-agricultural). Water samples were further analyzed in the laboratory for ammonia, nitrite+nitrate, total nitrogen, orthophosphate and total phosphorus. Blue crabs were analyzed for δ15N and δ13C isotopic composition using tissues from the legs and gut. Preliminary data that was assessed in 2014 determined that water quality had no influence on isotopic signature; however, the shoreline habitat influenced the δ13C isotope. Preliminary data also discovered that the blue crabs were feeding higher in the food chain, thus changing the fisheries dynamics in this region. Further water and crab samples were taken once every month from July through October 2017 and crab samples are currently being analyzed. Further isotope analysis is being done to confirm our findings in 2014 regarding blue crabs feeding at higher in the food chain. Both years' data will be presented and discussed.