FISHERY BULLETIN: VOL. 69, NO. 3 



Table 3. — Vertical distribution of Labidocera trispinosa 

 adults and anchovy larvae at 32°55.1' (Station 1 at 0100) 

 June 3, 1970, and 32°45.8' (Station 2 at 2340) June 3. 

 Volume of water filtered for each discrete depth sample 

 in oblique tows were: Station 1, 6 m^; Station 2, 

 4.35 m^. No L. jollae or Pontellopsis occidentalis indi- 

 viduals were caught in these samples. 



Depth (m) 



Number of 



L. trispinosa 



adults 



Number of 



En^raulis mordax 



lorvaa 



is the area which should be examined for further 

 elucidation of this predator-prey relation- 

 ship. 



The observations presented in this paper in- 

 dicate that marine copepods may be effective 

 predators on larval fish, at least in the sense that 

 a predator need not devour its prey but is equally 

 effective if it injures it mortally. Younjj pelagic 

 fish larvae are particularly susceptible to biting 

 zooplankters because they have an extremely 

 thin skin and are unable to survive once the skin 

 is punctured. Pontellid copepods, in particular 

 Labidocera spp., appear to have a well-developed 



Table 4. — Numbers of Labidocera jollae, L. trispinosa, 

 Pontellopsis occidentalis, and Engraulis mordax eggs and 

 larvae taken in 463 m^ within 30 cm of the surface simul- 

 taneously with the oblique tows described in Table 3. 



Species 



Station 1 



Station 2 



L_ trispinosa 



L. jollae 



P. occidentalis 



E. mordax 



1152 

 336 

 112 

 226 

 (5-10 mm long) 



6400 



104 



128 



36 



(10-12 mm long) 



vibration sense which serves to orient the cope- 

 pod toward its swimming prey although this is 

 preceded by random searching. A fish larva 

 with its beating tail provides the right stimulus 

 to the copepod to initiate an attack when the 

 latter is close enough to detect the beat. 



We have called attention to the vertical distri- 

 bution of Labidoceru in the sea and the apparent 

 co-occurrence of larval anchovies in the same 

 depth stratum. Unfortunately, quantitative 

 data on the density of predatory copepods or 

 other zooplankters as related to fish larvae have 

 yet to be made. It is our opinion that pontellid 

 copepods and fish larvae are concentrated in the 

 upper few meters and probably the ui)i)er few 

 centimeters of the sea and that observations of 

 this oceanic fine structure may reveal densities 

 of fish larvae to copepods which would implicate 

 predatory copepods (and possibly other zoo- 

 plankters) as important causes of larval fish 

 mortality. 



666 



