SS4.04 The Relevance of Gelatinous Zooplankton to Interdisciplinary Linkages
Date: Friday, June 14, 2002
Time: 10:30:00 AM
Location: Saanich
 
AraiMN, Pacific Biological Station, Nanaimo, CANADA, araim@island.net
Welch, D, W, Pacific Biological Station, Nanaimo, CANADA, WelchD@pac.dfo-mpo.gc.ca
 
DIGESTION OF PELAGIC CTENOPHORA AND CNIDARIA BY FISH
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The diet of chum salmon, Oncorhynchus keta, can range from a primarily arthropod to primarily gelatinous composition. Because there have been no data on the digestion rates of gelatinous prey in any fish, it has not previously been possible to convert data on stomach contents to feeding rates. We measured rates of digestion to address this problem. In freely feeding subyearling chum salmon, the ctenophore Pleurobrachia was digested almost completely within one hour whereas 70% of shrimp sections of similar weight remained in the stomach after 5 hours digestion at 13 degrees Centigrade. To examine the progress of digestion more closely subyearling and yearling fish were also force fed with whole Pleurobrachia or sections of the hydromedusa Aequorea. These data emphasize the necessity of examining fish stomachs very quickly on ship board. Although gelatinous organisms have high water and salt contents relative to organic contents, given the high rates of digestion observed, coelenterates may rival arthropods as energy sources.