JOURNAL OF PLANKTON RESEARCH | VOLUME 17 | NUMBER 1 | PAGES 183-189 | 1995
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Nauplii of the copepod, Calanus pacificus, off southern California in the El Niño winter-spring of 1992, and implications for larval fish
Marine Life Research Group, Scripps Institution of Oceanography, University of California Sun Diego La Jolla, CA 92093-0218, USA
Received on February 12, 1994; accepted on August 29, 1994 Female and naupliar Calanus were rarer in winter and spring of 1992, an El Niño period, than in 1989. The ratio of abundances, nauplius III (NIII) female-1 (a composite surrogate for reproduction and survival), did not differ between years and was not consistently correlated with concurrently measured chlorophyll (a measure of food). Survival from egg to NIII was negatively correlated with biomass of macrozooplankton (a measure of predators). Survival from NIV to NVI was less variable than that of younger states; it was poorer in winter of 1992 than in winter of 1989, but did not differ in median magnitude between the two springs, although it was least variable spatially in spring of 1992. Survival of these feeding stages was not correlated with chlorophyll. The relative ranty of nauplii was equivalent to a reduction of 30% in this source of food for larval fish.