Jaffe, J. S. Scripps Institution of Oceanography, email@example.com
De Robertis, A. S. Scripps Institution of Oceanography, firstname.lastname@example.org
Ohman, M. D. Scripps Institution of Oceanography, email@example.com
EVIDENCE FOR THE PREDATOR AVOIDANCE HYPOTHESIS IN THE FINE STRUCTURE OF
DIEL VERTICAL MIGRATION OF EUPHAUSIA PACIFICA.
The risk of attack by visual predators increases with prey body size and
with irradiance level. If diel vertical migration (DVM) of zooplankton is
principally a predator avoidance behavior, it follows that the timing of
ascent/descent into/from the surface layer during twilight changes in
illumination should not be identical for all size classes within a
population. Rather, less conspicuous prey should enter surface waters
earlier and leave later than larger, more conspicuous organisms.
The hypothesis of size-class dependent timing of DVM of Euphausia pacifica
was tested in Saanich Inlet, British Columbia, in July-August of 2 years by
deploying the FishTV acoustic imaging system at a fixed depth (40
or 50 m) during times spanning the vertical migration of euphausiids.
Identities of the sonar targets were determined with the OASIS
digital camera. Precise locations of the animals' positions (cms) at high
frame rates (seconds) were derived from the sonar data and used to
determine the distribution of animal sizes passing through the field of
view of the sonar as a function of time of day and irradiance level.
Results from replicated observations over many day/night cycles indicate
that the timing of the vertical migration is a function of body size.
Day: Thursday, Feb. 4
Time: 08:30 - 08:45am
Location: Hilton of Santa Fe