SS4.04 The Relevance of Gelatinous Zooplankton to Interdisciplinary Linkages
Date: Friday, June 14, 2002
Time: 10:15:00 AM
Location: Saanich
 
PurcellJE, Shannon Point Marine Center, Bellingham, USA, purcelj@cc.wwu.edu
Sturdevant, M, V, NMFS, Auke Bay Laboratory, Juneau, USA, Molly.Sturdevant@noaa.gov
 
PREDATION ON ZOOPLANKTON BY JELLYFISH AND THE POTENTIAL FOR COMPETITION FOR FOOD WITH COMMERCIAL FISHES
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Zooplanktivorous jellyfish and fishes potentially compete for food resources, which may detrimentally affect commercial fish populations. Large jellyfish (Aurelia labiata, Cyanea capillata, Aequorea aequorea) and young-of-the-year fishes (walleye pollock Theragra chalcogramma, herring Clupea pallasi, pink salmon Oncorhynchus gorbuscha, Pacific sandlance Ammodytes hexapterus) were sampled in July-August in Prince William Sound, Alaska. The jellyfish and fish species overlapped spatially and temporally. Small copepods, larvaceans and cladocerans were the most important shared zooplankton prey, and dietary overlap between jellyfish and fish species averaged 50%. Consumption of zooplankton by jellyfish was estimated from gut contents, digestion rates, and densities of jellyfish and prey in 1998 and 1999. Because of the low jellyfish densities (< 2.0 per 100 cubic meters) and high prey densities, predation on copepods and cladocerans was low (< 0.2% and < 2.5% of the standing stock daily, respectively). Predation on larvaceans, the principal food of pink salmon, was greater at < 17% per day. During our sampling, these jellyfish were unlikely to limit or reduce populations of crustacean prey, but may have affected larvacean populations at times.