Potential Impact of Jellyfish Blooms on Forage Fishes from Diverse Ecosystems

Increases in the frequency and size of recurrent jellyfish blooms in a number of coastal areas worldwide have intensified concerns these ecosystems are shifting from fish to jellyfish. Ecosystems supporting major forage fish fisheries are believed to be particularly vulnerable given the considerable harvest pressure exerted on wasp-waist species and evidence of jellyfish- forage fish replacement cycles in recent decades. Jellyfish are indisputably major consumers of plankton production and shifts in bloom frequency and size can be a sign of ecosystem transformation, yet they are often not included as main components of ecosystem-based fisheries management (EBFM) production models. We review how heavily-fished ecosystems can potentially transform from forage fish to jellyfish, ostensibly through fishing providing a competitive release for jellyfish. Responses of functional groups to changes in energy transfer pathways in a scyphozoan jellyfish- versus forage fish-dominated food web are compared for several oceanographically distinct ecosystems (the Northern California Current, Gulf of Mexico, and Bering Sea) using ECOTRAN analysis techniques. These modeling efforts will improve EBFM of forage fish and their predators by increasing our understanding of trophic interactions between forage fish and large jellyfish, an important, but overlooked component in most ecosystem models to date.