Temporal and spatial distribution of the cannonball jellyfish Stomolophus meleagris in the South Atlantic Bight, USA

The cannonball jellyfish Stomolophus meleagris is one of the most abundant scyphozoan jellyfish in the South Atlantic Bight (SAB) of the southeastern USA. Like many scyphozoan jellyfish, cannonball jellies have high interannual variability and little is known about the environmental drivers of their distribution and phenology. To better understand the ecology of this commercially targeted species, we used fisheries-independent abundance and biomass data of S. meleagris from 2001 to 2019 collected by the Southeast Area Monitoring and Assessment Program (SEAMAP) throughout the coastal zone of the SAB. Average biomass of S. meleagris is highest in the spring off Georgia and southern South Carolina, and on average, the largest jellyfish were collected during the spring months. The lowest biomass was observed in the summer months when smaller jellyfish were caught at lower abundances in the coastal zone. These patterns suggest that mature S. meleagris medusae occur in the offshore area in the spring and move inshore toward estuarine habitats to sexually reproduce in the summer. Juvenile S. meleagris medusae move out of the estuaries as they mature throughout the summer and fall, and finally the surviving adults occur offshore again the next spring. The seasonal and spatial variability across the region is not correlated with local differences in temperature, salinity, chlorophyll a concentration, or river discharge, but is perhaps influenced by distance from the presumed source estuarine habitats and prevailing currents. While interannual variability in jellyfish biomass is high, no long-term trends or strong correlations with the tested environmental parameters were detected.