FISHERY BULLETIN: VOL. 84, NO. 1 



one-half of the stations, comparisons of weight and 

 water content between specific regions were diffi- 

 cult. Although the average weight of adults of both 

 euphausiid species were greater in the northern area 

 (nearshore and offshore combined), water content 

 of both species was similar in all areas. The weight 

 and biochemical composition of adult euphausiids 

 may be less susceptible to short-term changes in food 

 concentration than copepods because of their larger 

 size and longer life cycle (>1 yr, Ross 1982). 



Thus far, it is apparent that processes which oc- 

 cur in relatively small areas along the California 

 coast, in particular the area near Point Conception, 

 have a considerable influence on the nutritional state 

 of two common herbivorous zooplankters, E. paci- 

 fied, and C. pacificus. What are the long-term im- 

 plications of this mesoscale patchiness? 



The regions of high phytoplankton standing crop 

 found in April 1981 appear to be relatively predict- 

 able from year to year. Although upwelling events 

 in these areas are episodic and seasonal, previous 

 studies have shown similar patterns. CalCOFI sur- 

 veys (Owen 1974) and recent satellite imagery (Smith 

 and Baker 1982; Pelaez and Guan 1982) indicate that 

 in past years Point Conception and the area off 

 Monterey Bay have consistently been regions of high 

 phytoplankton production during the spring and 

 summer months. This enhanced production has un- 

 doubtedly influenced zooplankton populations in pre- 

 ceding years in much the same way that was found 

 during the present study. Previous investigations 

 concerning zooplankton distributions and grazing ac- 

 tivity along the California coast support this conclu- 

 sion (Fleminger 1964; Brinton 1976, 1981; Cox et 

 al. 1982, 1983). 



Although reproduction was not estimated, it is like- 

 ly that well-fed zooplankters in the California Cur- 

 rent produce more eggs than poorly fed animals. 

 This has clearly been demonstrated in the laboratory 

 for copepods (Marshall and Orr 1955; Checkley 1980) 

 and has been suggested for euphausiids (Brinton 

 1976). Larger individuals of a species also produce 

 more eggs (Brinton 1976; Nemoto et al. 1972; Ross 

 et al. 1982). Thus, the larger, better fed copepods 

 and euphausiids near Point Conception and off Mon- 

 terey Bay probably have a higher reproductive out- 

 put than animals from other areas. There is some 

 evidence which suggests that enhanced reproduction 

 of zooplankton takes place near Point Conception. 

 Arthur (1977) noted that the highest densities of 

 copepod nauplii in the Southern California Bight 

 were located in a cold-water upwelling plume extend- 

 ing south from Point Conception. In addition, eggs 

 and larvae of E. pacifica are more abundant in the 



Southern California region following periods of up- 

 welling (Brinton 1976). 



In summary, our results show that upwelling and 

 phytoplankton variability have a significant impact 

 on the herbivorous zooplankton in the California 

 Current. Not only did we find patchiness of zooplank- 

 ton abundances, but more importantly, zooplankton 

 nutritional states were also highly variable (i.e, meso- 

 scale and larger scale patchiness of trophic inter- 

 actions). Zooplankton in upwelling regions appear 

 to experience better feeding conditions for periods 

 of up to several weeks. Prolonged periods of better 

 feeding conditions in specific areas should influence 

 secondary production as well. This implies that the 

 relatively small, productive regions along the Cali- 

 fornia coast, south of San Francisco Bay and par- 

 ticularly the area near Point Conception, have a 

 disproportionally large impact on the biology of 

 marine organisms within the California Current 

 System. 



ACKNOWLEDGMENTS 



We thank M. Page, T Bailey, L. Haury, D. Morse, 

 and R. Trench for critical review of the manuscript. 

 We also thank P. Smith and the research staff at the 

 Southwest Fisheries Center in La Jolla for support 

 during CalCOFI cruise 8104 and for providing ac- 

 cess to preserved samples. This work was supported 

 by NSF grants OEC 79-9317 and OEC 81-09934 and 

 by the Marine Science Institute at the University of 

 California, Santa Barbara. 



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