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MEPS 210:67-83 (2001)
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Abstract
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Prey selection and dietary overlap among zooplanktivorous jellyfish and juvenile fishes in Prince William Sound, Alaska
Jennifer E. Purcell1,*, Molly V. Sturdevant2
1University of Maryland Center for Environmental Science, Horn Point Laboratory, PO Box 775, Cambridge, Maryland 21613, USA
2NOAA/NMFS, Alaska Fisheries Science Center, Auke Bay Laboratory, 11305 Glacier Highway, Juneau, Alaska 99801, USA
*Present address: Shannan Point Marine Center, 1900 Shannon Point Rd., Anacortes, Washington 98221, USA. E-mail: purcell@hpl.umces.edu
ABSTRACT: The potential for competition for food among zooplanktivorous species of gelatinous zooplankton and fishes has been the subject of much speculation. Here, we evaluate the dietary overlaps among 2 scyphomedusan species, Aurelia labiata and
Cyanea capillata, 1 ctenophore species, Pleurobrachia bachei, 1 hydromedusan species, Aequorea aequorea var. albida, and juveniles (Age 0) of 4 forage fish species, walleye pollock Theragra chalcogramma, Pacific
sandlance Ammodytes hexapterus, Pacific herring Clupea pallasi, and pink salmon Oncorhynchus gorbuscha. Zooplankton samples collected in July-August 1995 to 1998 showed great similarity among years (86 to 96%), which allowed valid
dietary comparisons between pelagic coelenterates and fishes collected in different years during that period. The predators fell into 2 groups, one that ate primarily crustacean prey (A. labiata, P. bachei, juvenile walleye pollock, sandlance, and
herring), and another that ate mostly larvaceans (C. capillata, A. aequorea, and juvenile pink salmon). Species within the first group showed significant positive selection for crustacean prey and significant negative selection for larvaceans. The
opposite trends were observed in the second group. Dietary overlaps were higher among crustacean-eating species (63 ± 13%) and larvacean-eating species (66 ± 10%) than when comparing crustacean- with larvacean-eating species (24 ± 14%). Dietary overlaps
among pelagic coelenterate species (41 ± 21%) and among fish species (42 ± 25%) were similar, while overlaps between pelagic coelenterate and fish species averaged 50 ± 21%. These pelagic coelenterate and fish species were collected together in 45 purse
seine sets taken in Prince William Sound in July 1999. We conclude that the diets of pelagic coelenterate and forage fish species overlap substantially, and that the species co-occur spatially and temporally. Therefore, the potential for competition for
prey exists for these zooplanktivores in Prince William Sound.
KEY WORDS: Aurelia · Competition · Ctenophore · Cyanea · Herring · Pollock · Salmon · Sandlance · Zooplankton
Full text in pdf format
Published in MEPS Vol.
210
(2001) on January 26
Print ISSN: 0171-8630; Online ISSN: 1616-1599.
Copyright © Inter-Research, Oldendorf/Luhe, 2001
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