Fish, jellyfish, and Killing the Winner

Killing the Winner (KtW) is a generic model of competition involving a defense specialist and a competition specialist that is controlled by a predator. It has previously been proposed that this model might predict how mass is channelized between fish and jellyfish as a function eutrophication and water clarity in the Baltic Sea. The main finding from this approach is that above a certain eutrophication threshold, all added mass to the system will channel directly to jellyfish. Here we analyze observations from several areas where major jellyfish blooms have been reported. In systems where jellyfish have a relatively large footprint, like the Black Sea, our results suggests that the abundances of fish and jellyfish are consistent with the KtW predictions previously described for the Baltic Sea. However, in systems like the northern Benguela and the Bering Sea, jellyfish, although present in comparable biomasses to fish, appear to leave a relatively small footprint, consuming only a moderate part of the available mass in the system. Thus, these systems could be considered as dominated by fish, not jellies.