The Food Web Supporting Forage Fish Populations
Prince William Sound, Alaska
Summary:
Forage fish, such as sand lance (Ammodytes hexapterus), herring (Clupea
harengus), capelin (Mallotus villosus), and juvenile walleye pollock
(Theragra chalcogramma), on which many
sea birds depend for food, feed on zooplankton. A variety of jellyfish species
also consume zooplankton as well as the egg and larval stages of fish. APEX
researchers have explored how the seasonal abundance's and distributions of
zooplankton relate to the population patterns of forage fish and jellyfish.
We have evaluated the extent of dietary overlap between forage fish and jellyfish
and their potential for food competition using several data, including aerial,
acoustic, and net surveys, from the APEX and SEA programs from 1994 to 1997,
with an emphasis on comparisons among years that showed marked differences
in environmental variables. As predicted, different species respond to interannual
and regional environmental variability, in which competition and environmental
condition determines abundance's of forage species.
Principal Investigators:
J.E. Purcell, University of Maryland, Center for Environmental Science, Cambridge,
MD
J. Thedinga and L. Hulbert, Auke Bay Laboratory, NMFS, Juneau, AK
E.D. Brown and K.O. Coyle, University of Alaska Fairbanks, IMS, Fairbanks,
AK
T.C. Shirley, University of Alaska Fairbanks, School of Fisheries and Ocean
Sciences, Juneau, AK
R.T. Cooney, University of Alaska Fairbanks, Institute of Marine Science,
Fairbanks, AK
M.V. Sturdevant, National Marine Fisheries Service, Auke Bay Laboratory, Juneau,
AK
Tracey Gotthardt, University of Alaska Anchorage, Department of Biology, Anchorage,
AK
L.A. Joyal, U.S. Fish and Wildlife Service, Anchorage, AK
D.C. Duffy, University of Hawaii Manoa, Department of Botany, Honolulu, HI
many
sea birds depend for food, feed on zooplankton. A variety of jellyfish species
also consume zooplankton as well as the egg and larval stages of fish. APEX
researchers have explored how the seasonal abundance's and distributions of
zooplankton relate to the population patterns of forage fish and jellyfish.
We have evaluated the extent of dietary overlap between forage fish and jellyfish
and their potential for food competition using several data, including aerial,
acoustic, and net surveys, from the APEX and SEA programs from 1994 to 1997,
with an emphasis on comparisons among years that showed marked differences
in environmental variables. As predicted, different species respond to interannual
and regional environmental variability, in which competition and environmental
condition determines abundance's of forage species.