FISHERY BULLETIN: VOL. 75, NO 3 



densities required for larval survival in the 

 laboratory may be that present microplankton 

 sampling techniques do not detect small but dense 

 aggregations of nauplii which, however, can be 

 found by fish larvae. It, also, may be that present 

 rearing techniques do not approximate oceanic 

 conditions sufficiently to permit assaying of 

 actual prey concentrations required to allow sig- 

 nificant larval survival. Blaxter (1965) reported 

 that the condition factor of herring larvae living 

 in the ocean is worse than that of larvae which 

 died presumably of starvation in the laboratory. 

 This may attest to greater ability of larvae to 

 survive poor rations in the usual oceanic environ- 

 ment than in the laboratory. 



Maximum of Naupliar Biomass Spectrum 



The abundance of copepod nauplii decreases 

 exponentially with increasing size of individuals 

 (Figure 9), whereas the volume of an individual 

 nauplius increases exponentially with increasing 

 size (roughly by the cube of width). When the 

 naupliar size range is divided into 10-/xm wide 

 size classes and the average volume per nauplius 

 is multiplied by numbers of individuals per class 

 (calculated from the equation for combined data, 

 Figure 9) it is seen that the naupliar biomass 

 is at a maximum at about the 70 yum width 

 (Figure 10) even though there are many more 

 nauplii of smaller sizes. 



Figure 10 includes, also, the food-particle size 

 range at first feeding of larvae of Pacific sardine, 



RANGE OF FOOD WIDTH AT FIRST FEEDING 



• SARDINE 



• OVERLAP 



ANCHOVY 



JACK 

 MACKEREL 



= o 



if 



< Q 

 z 5 



9 2- 



J I l I i I i i_ 



50 



J I I I l_ 



100 150 



WIDTH OF NAUPLII ( jim ) 



200 



FIGURE 10. — Biomass spectrum of naupliar size range compared 

 with food size at first feeding of the larvae of three fishes in 

 the California Current system. 



610 



northern anchovy, and jack mackerel (Arthur 

 1976). It is interesting to note that these ranges 

 overlap at the 50- to 80-/xm width range which 

 brackets the naupliar biomass spectrum maxi- 

 mum. This suggests that larval feeding habits of 

 these three fishes have evolved to take advantage 

 of this important food resource at first feeding. 



ACKNOWLEDGMENTS 



I express my appreciation to Martin W. John- 

 son, Reuben Lasker, and Paul E. Smith for their 

 helpful comments and criticisms during the prep- 

 aration of the manuscript. 



LITERATURE CITED 



Allen, w. e. 



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ANONYMOUS. 



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Arthur, D. k. 



1956. The particulate food and the food resources of the 

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Beers, J. R., and G. L. Stewart. 



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1970. Numerical abundance and estimated biomass of 

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 BERNER, L., JR. 



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Blaxter, J. H. s. 



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