Evaluating the Role of Large Jellyfish and Forage Fishes as Energy Pathways, and Their Interplay With Fisheries, in the Northern Humboldt Current System

Luciano M. Chiaverano, University of Southern Mississippi
Kelly L. Robinson, University of Louisiana at Lafayette
Jorge Tam, Instituto del Mar del Perú
James J. Ruzicka, Oregon State University
Katrina T. Aleksa, University of Southern Mississippi
Frank J. Hernandez, University of Southern Mississippi
Richard D. Brodeur, NOAA Northwest Fisheries Science Center, Hatfield Marine Center
Robert T. Leaf, University of Southern Mississippi
Shin-ichi Uye, Hiroshima University
Mary Beth Decker, Yale University
Marcelo Acha, Instituto Nacional de Investigación y Desarrollo Pesquero
Hermes W. Mianzan, Instituto Nacional de Investigación y Desarrollo Pesquero
William M. Graham, University of Southern Mississippi


Large jellyfish are important consumers of plankton, fish eggs and fish larvae in heavily fished ecosystems worldwide; yet they are seldom included in fisheries production models. Here we developed a trophic network model with 41 functional groups using ECOPATH re-expressed in a donor-driven, end-to-end format to directly evaluate the efficiency of large jellyfish and forage fish at transferring energy to higher trophic levels, as well as the ecosystem-wide effects of varying jellyfish and forage fish consumption rates and fishing rates, in the Northern Humboldt Current system (NHCS) off of Peru. Large jellyfish were an energy-loss pathway for high trophic-level consumers, while forage fish channelized the production of lower trophic levels directly into production of top-level consumers. A simulated jellyfish bloom resulted in a decline in productivity of all functional groups, including forage fish (12%), with the exception of sea turtles. A modeled increase in forage fish consumption rate by 50% resulted in a decrease in large jellyfish productivity (29%). A simulated increase of 40% in forage fish harvest enhanced jellyfish productivity (24%), while closure of all fisheries caused a decline in large jellyfish productivity (26%) and productivity increases in upper level consumers. These outcomes not only suggest that jellyfish blooms and fisheries have important effects on the structure of the NHCS, but they also support the hypothesis that forage fishing provides a competitive release for large jellyfish. We recommend including jellyfish as a functional group in future ecosystem modeling efforts, including ecosystem-based approaches to fishery management of coastal ecosystems worldwide.