Feeding patterns and predation potential of scyphomedusae in a highly productive upwelling region

We quantified diet and predation rates for large scyphomedusae from a coastal upwelling region.In the Northern California Current, early stages of euphausiids, gelatinous taxa, and cladocerans were particularly vulnerable to predation by Chrysaora fuscescens, Aurelia labiata, and Phacellophora camtschatica, whereas copepods were not.Moreover, C. fuscescens had the potential to deplete the standing stock of euphausiid eggs where predator and prey overlapped.During August 2002, C. fuscescens ingested an average 32.5% of the standing stock of euphausiid eggs each day at stations close to shore and north of Cape Blanco (42.9°N, 126.6°W) where maximum abundances of the medusae occurred.Ingestion of other vulnerable prey, such as other early stages of euphausiids and gelatinous taxa, reached 10 to 12% d -1 .In contrast, we calculated the maximum removal rate of the standing stock of copepods to be <1% d -1 .Given the importance of euphausiids to fish and other top predators, and the potential for changes in abundance and distribution of both predator and prey taxa with changes in climate, we suggest that gelatinous zooplankton abundance and predation impacts be incorporated within long-term studies and ecosystem models.