JPR Advance Access published online on November 22, 2005
Journal of Plankton Research, doi:10.1093/plankt/fbi084
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1 NOAA, Southwest Fisheries Science Center, Environmental Research Division, 1352 Lighthouse Ave., Pacific Grove, CA 93950
* To whom correspondence should be addressed. Vertical distribution data seem to indicate that certain species of diel vertical migrating copepods avoid the surface high chlorophyll region within coastal and estuarine environments, even during the night. Copepods may avoid this layer to reduce predation mortality, avoid advective loss, or to avoid consuming too much toxic algae. We hypothesize that copepods make several intermittent feeding "forays" into shallow surface layers during the night, returning to intermediate depths between forays. Using an individual-based model of Calanus pacificus we examined the implications of this behavior on feeding success and mortality risk, and tested whether a practical field-sampling scheme would be able to detect foray-like behavior. In some cases, mortality of the foray-foraging copepods was up to 50% less than that of randomly behaving controls, for a given amount of food ingested. The trapping scheme devised should be able to detect the occurrence of foray behavior in the field, and should show differences in the gut contents of copepods entering and leaving the uppermost food-rich layer. The presence or absence of foray-like behavior significantly altered the relative concentration of copepods within various surface strata, and thus could influence the temporal availability of copepods as prey for the larvae and juveniles of several important managed fish species.
Received June 21, 2005
Accepted October 7, 2005
Article
Copepod foraging and predation risk within the surface layer during nighttime feeding forays
Andrew W. Leising 1 *,
James J. Pierson 2,
Scott Cary 2,
and
Bruce W. Frost 2
2 University of Washington, School of Oceanography, Seattle, WA 98150
Andrew W. Leising, E-mail: Andrew.Leising{at}noaa.gov
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Abstract
Communicating Editor: RP Harris
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