Figure 3. — Vulnerability of white seabass larvae to 

 juvenile white seabass predators as a function of lar- 

 val length. A. Solid circles are percentage of larvae 

 escaping an attack, error bars are 2 x SE, regression 



equation is Arcsine Y = 10.976 e 



 in = 44, r 



0.89), where Y = proportion of larvae escaping and SL 

 = larval standard length (mm); open circles are per- 

 centage of larvae eaten in 10 min trials, error bars are 

 2 X SE, regression equation is Arcsine Y = 81.210 

 ^-o.o48SL (^j ^ 44 ,;! ^ Q 92)^ where Y = propor- 

 tion of larvae eaten in 10 minutes and SL = larval 

 standard length (mm). B. Percentage of larvae re- 

 sponding to an attack, en-or bars are 2 x SE, regi-es- 

 sion equation is Arcsine Y = 16.822 e""^^^^' {n = 44, r 

 = 0.94), where Y = proportion of larvae responding 

 and SL = larval standard length (mm). 



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FISHERY BULLETIN: VOL. 87, NO. 3, 1989 



Predator: Atractoscion nobilis 





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2 4 6 8 10 12 14 

 LARVAL STANDARD LENGTH (mm) 



Table 3. — Avoidance success of responding larvae 

 (numbers escaping/numbers responding). 



escaped white seabass attacks, while a signifi- 

 cantly higher percentage of larvae >7.5 mm SL 

 responded to white seabass attacks (ANCOVA 

 with Least Squares Means, P < 0.05). This in- 

 creased responsiveness to white seabass preda- 

 tors (compared to northern anchovy) translated 

 into significantly reduced consumption rates by 

 white seabass predators on larvae >8.5 mm SL 

 (ANCOVA with Least Squares Means, P < 

 0.05). 



Larval Visual Ontogeny 

 The Retina and Visual Acuity 



Histological examination of the white seabass 

 visual system revealed numerous developmental 

 changes from hatch to juvenile metamorphosis. 

 In yolk-sac larvae, the lens was present, but the 

 retina was unpigmented and undifferentiated. 

 At time of yolk absorption (ca. 3.2 mm SL), the 

 retina became differentiated into distinct layers, 

 the photoreceptive layer contained visual cells 

 and the epithelial (basal) layer became pig- 

 mented. Presumably, at this stage the eye was 

 functional. 



In young larvae (3.5-7.0 mm SL), the retina 

 appeared to be composed of only cone cells and 

 no retinomotor (light-dark) responses were 

 noted by either the photoreceptor cells or the 

 epithelial masking pigment. In larvae >4 mm 

 SL, the posteroventral area of the retina (~15- 

 20° below the horizontal plane) was character- 

 ized by densely packed cone cells, constituting 

 an area temporalis. A lens retractor muscle first 

 appeared histologically at a standard length of 

 4.5 mm (Fig. 4). Seen in sagittal section, the lens 

 retractor articulated posteriad with the ventral 



542 



