Bull. Jpn. Soc. Fish. Oceanogr. 81(2), Page 110-123, 2017   Impact of the jellyfish Aurelia aurita on the anchovy fishery stock in Hiuchi-nada, central Seto Inland Sea, Japan Hiromu Zenitani1†, Naoaki Kono2 and Shingo Watari1 1 National Research Institute of Fisheries Science, Japan Fisheries Research and Education Agency, 2-12-4 Fukuura, Kanazawa, Yokohama, Kanagawa 236-8648, Japan 2 National Research Institute of Fisheries and Environment of Inland Sea, Japan Fisheries Research and Education Agency, 2-17-5 Maruishi, Hatsukaichi, Hiroshima 739-0452, Japan † E-mail: zenitani@fra.affrc.go.jp To evaluate the effects of jellyfish on the anchovy fishery stock in Hiuchi-nada, central Seto Inland Sea, we created growth models for anchovy larvae and jellyfish linked with prey-predator dynamics models among nutrients, phytoplankton, copepods, and jellyfish. Fluctuations in copepod (main food items for jellyfish and anchovy larvae) biomass during spring-summer 2001-2005 were simulated with the model to investigate the relationship between the jellyfish abundance and the anchovy growth and survival. Anchovy growth and survival rate from 5.7 mm (first feeding stage) to 40 mm standard length were inversely proportional to jellyfish abundance at the time of occurrence. The simulation revealed that anchovy larvae could not survive by the shortage of food items at first feeding when abundance of the jellyfish of 100-mm bell diameter was >10 ind./100 m3. Mean jellyfish abundance during May-August 2007-2009 reached a maximum of 10 ind./100 m3 when mean bell diameter was 72 mm. These results suggest that jellyfish abundance affected anchovy fishery stock during the late 2000s. Key words: jellyfish impact, anchovy survival and growth, Seto Inland Sea, prey-predator model