Enhancement of jellyfish (Aurelia aurita) populations by extensive aquaculture rafts in a coastal lagoon in Taiwan

<jats:title>Abstract</jats:title> <jats:p>Lo, W-T., Purcell, J. E., Hung, J-J., Su, H-M., and Hsu, P-K. 2008. Enhancement of jellyfish (Aurelia aurita) populations by extensive aquaculture rafts in a coastal lagoon in Taiwan. – ICES Journal of Marine Science, 65: 453–461. Blooms of the moon jellyfish, Aurelia aurita, often occur in coastal waters that are heavily affected by human construction, such as harbours. Tapong Bay is a hypertrophic lagoon in southwestern Taiwan that was studied between August 1999 and September 2004. The removal of extensive oyster-culture rafts in June 2002 provided a “natural” experiment to examine the effects of aquaculture on processes and communities in the lagoon. The removal caused many changes in the ecosystem, including increases in flushing, light penetration, dissolved oxygen, salinity, chlorophyll a, primary production, and zooplankton, but decreases in nutrients, periphyton, and dramatically reduced populations of bivalves, zooplanktivorous fish, and jellyfish (A. aurita). We conclude that environmental and trophic conditions were favourable for jellyfish throughout the study period. Therefore, we believe that aquaculture rafts enhanced jellyfish populations by three probable mechanisms: the rafts provided substrate and shading for the larval settlement and polyp colony formation, and the rafts restricted water exchange in the lagoon. Aquaculture is increasing rapidly in Asia, and the problems associated with jellyfish may also increase.</jats:p>