PS 47-158 - The nature of the symbiosis between the cannonball jellyfish Stomolophus meleagris and spider crabs Libinia spp. and its impacts on the cannonball jellyfish fishery operating in Georgia's territorial waters

Friday, August 12, 2016
ESA Exhibit Hall, Ft Lauderdale Convention Center
David J. Stasek1, Jeffery E. Tailer1, Jim Page2 and Patrick J. Geer3, (1)Department of Natural Sciences, College of Coastal Georgia, Brunswick, GA, (2)Wildlife Resources Division, Georgia Department of Natural Resources, Waycross, GA, (3)Coastal Resources Division, Georgia Department of Natural Resources, Brunswick, GA
Background/Question/Methods

The cannonball jellyfish (Stomolophus meleagris) is a common Cnidarian species commercially harvested in state and federal waters adjacent to Georgia. In 2013, the cannonball jellyfish fishery transitioned from an experimental fishery to an official state fishery governed by the rules and regulations established in Georgia law. Given this distinction, it is important fishery managers understand the factors which could potentially impact the sustainability of the fishery including the interactions of other species with the cannonball jellyfish. Juvenile spider crabs of the genus Libinia inhabit the bell of the cannonball jellyfish. There is no known benefit for the jellyfish in this symbiosis, but it is unknown if the crabs are parasitic on the jellyfish or are commensals. If the relationship is parasitic, this may result in smaller jellyfish which could lessen the value of a fisherman’s catch. To determine the nature of this symbiosis, jellyfish were randomly sampled via dip netting from a commercial fishing vessel at multiple sites along the Georgia coast. For each jellyfish, the number of juvenile spider crabs inhabiting the bell was recorded along with jellyfish bell diameter, crab carapace width, and the presence of other symbiotic species.

Results/Conclusions

It was found that 41% of jellyfish had a juvenile crab symbiont with no crab being over 29mm in length. There was no correlation between bell width and crab carapace width. There was also no difference in bell width among jellyfish with crab symbionts and those without symbionts. This suggests that while juvenile crabs consume food collected by the jellyfish and feed on jellyfish tissues, they do not hinder jellyfish growth. It is likely that the relationship between the cannonball jellyfish and juvenile spider crabs is a commensalism and not parasitism. Therefore, it is unlikely that the value of the fishermen’s catches is being lessened due to this symbiosis. This knowledge will allow fishery managers to focus their attention on other factors which might affect the sustainability of the fishery such as cannonball jellyfish reproductive effort, growth rates, and interactions with protected species such as sea turtles.