(Presented at AGU/ASLO Ocean Sciences meeting, January 24-28, 2000, in San Antonio, Texas)
Sean R. Avent1, Stephen M. Bollens1, Jeffrey Cordell2, and Bruce W. Frost3
1Romberg Tiburon Center for
Environmental Studies and Department
of Biology, San Francisco State University, 3150 Paradise Dr., P.O.Box 855,
Tiburon, CA 94920, USA
2Wetland
Ecosystem Team, School of Fisheries, University of Washington, Campus Box
357980, Seattle, WA 98195-7980, USA
3School of
Oceanography, University of Washington, Campus Box 357940, Seattle, WA
98195-7940, USA
No less than six Asian estuarine and marine copepods have been introduced to
the Pacific coast estuaries of North America. The changes that these
introductions have on the ecosystems are not yet fully understood and can have
implications on both a local and global scale. The genus Pseudodiaptomus,
an epibenthic, omnivorous copepod and potentially important prey item that has
been established in several North American west coast estuaries, was
studied. Vertical migration behavior and prey selection by fishes in
addition to broadscale temporal and spatial distributions were
conducted. Pseudodiaptomus inopinus was studied in the
Chehalis River estuary, WA with a vertically stratified pump sampling field
design for assessment of tidal and diurnal vertical migrations, while the
vertical migration behavior of Pseudodiaptomus marinus from the San
Francisco Bay estuary was investigated using a video-microscope/minitower
system in the laboratory. Prey-selection experiments for both P.
inopinus and P. marinus with respective indigenous fish
predators and indigenous copepods as alternate prey were also conducted in the
laboratory. We will discuss the results of these studies and apply them
to the question of why this genus tends to be a productive nonindigenous
zooplankter.