that starved larvae tended to be neutrally buoyant because of a relative increase 
in body water. They speculated that under starvation conditions larvae would 
be relatively inactive, suspended in midwater, and thus more susceptible to 
plankton net sampling than well nourished larvae. Blaxter and Ehrlich’s (20) 
results differ somewhat from Wyatt’s (100), partly because of the different 
criteria used to define activity. 
Behavior of northern anchovy larvae in dense patches of prey, 
Gymnodinium splendens and Brachionus plicatilis, was investigated by Hunter 
and Thomas (49). In dense patches larvae swam slower and covered smaller 
areas. Reversals in swimming direction occurred more frequently in patches of 
food than in non-patch situations. The evidence strongly suggested that 
northern anchovy larvae were able to maintain themselves in suitable patches 
of prey, and that such an adaptation would allow larvae to take advantage of 
prey patchiness in the sea. 
PREDATION 
Predation almost certainly is the greatest direct cause of mortality to marine 
fish larvae, but there have been few attempts to evaluate its impact in 
laboratory studies. The food supply of larval fishes and other environmental 
factors can modify the predation mortality experienced by a cohort. As 
Cushing (29) noted, larvae that have an adequate food supply grow fast and 
swim well. Thus, they presumably avoid predation by growing quickly through 
the larval phase, when they are most vulnerable to a variety of planktonic 
predators. Similarly, pollutants or toxicants that retard larval growth or modify 
behavior could lead indirectly to increased predation mortality. 
Four recent laboratory investigations have examined the potential impact of 
predators on larvae. Three species of pontellid copepods could more than meet 
their metabolic requirements by preying upon yolk-sac larvae of northern 
anchovy (62). Predation in 3500 ml beakers increased as anchovy larvae 
concentration was raised. Two of the copepods, Labidocera jollae and L . 
trispinosa , were only efficient as predators on yolk-sac larvae, but a third 
species, Pontellopsis occidentalism also was able to prey on more developed, 
faster swimming larvae. The presence of alternate prey (Artemia salina nauplii) 
reduced larval mortality caused by Labidocera spp. in direct proportion to the 
numbers of Artemia that were present. In similar experiments, but using the 
euphausiid Euphausia pacifica , as an anchovy larva predator, Theilacker and 
Lasker (94) demonstrated that larval, juvenile and adult stages of the 
euphausiid could meet their daily carbon requirements by preying upon 
northern anchovy yolk-sac larvae. There was no strong evidence that anchovy 
concentration, when above 10 per 3500 ml, or the presence of alternate prey 
(Artemia nauplii) significantly influenced the predation rate on anchovies, at 
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