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



mechanoreception, which are presumed to be 

 important components of predator detection and 

 larval escape responses (Blaxter 1986). The 

 ontogeny of avoidance/escape responses and 

 other larval behaviors of white seabass were 

 then analyzed in relation to the structural and 

 functional development of their sensory 

 systems. 



Very little is known of the early life history of 

 the white seabass, even though it is the largest 

 sciaenid occurring in coastal waters of California 

 and Baja CaHfornia and has historically been a 

 favored sport and commercial species (Feder et 

 al. 1974; Vojkovich and Reed 1983). White sea- 

 bass spawn in spring and early summer in near- 

 shore coastal waters of southern California, and 

 produce pelagic eggs. Abundance and distribu- 

 tion of young-of-the-year in southern California 

 waters have been reported by Allen and Frank- 

 hn (1988). Larval morphological development 

 has been described by Moser et al. (1983), but 

 larval ecology, predator-avoidance behaviors, 

 and sensory system development have not been 

 described. 



METHODS 



Larval Rearing 



White seabass larvae used in the experiments 

 were hatched from eggs obtained from brood- 

 stock adults maintained at the Hubbs Marine 

 Research Center at Sea World in San Diego. 

 Eggs were transported to the aquarium at the 

 Southwest Fisheries Center La Jolla Laboratory 

 and stocked in 76 L aquaria at stocking densities 

 of 6 L~^ During the culture experiments 

 water temperature ranged from 17° to 19°C, and 

 a constant photoperiod of 13 h light: 11 h dark 

 was maintained. 



First-feeding white seabass larvae were fed 

 rotifers, Brachionus plicatilis, cultured on the 

 green alga Tetraselmis. Older larvae were se- 

 quentially fed diets ofArteniia nauphi, a mixture 

 of Artemia nauplii and wild copepods, and adult 

 Artemia. The developmental size range of white 

 seabass tested ranged from hatching (2.6 mm 

 SL, day after hatch) to juvenile metamorphosis 

 (15.0 mm SL, 42 days after hatch) (Fig. 1). 



Experimental Predators 



Adult northern anchovy and juvenile white 

 seabass were used as predators. Both of these 

 predator groups occur in nearshore waters of 



southern California and are potential natural 

 predators of white seabass larvae. These two 

 predator groups represent different types of 

 raptorial predatory behavior (Table 1). Adult 

 northern anchovy are pelagic, cruising predators 

 that attack prey at relatively high speeds and 

 often from obhque angles. Juvenile white sea- 

 bass attack at much slower speeds and have a 

 somewhat discontinuous mode of attack that in- 

 volves an approach, glide, and then engulfing of 

 prey. Northern anchovy also initiate attacks 

 from much greater distances. 



Predators were held in laboratory holding 

 tanks and fed adult Artemia, minced euphausiids 

 and occasionally white seabass larvae. To mini- 

 mize predator learning behavior, after comple- 

 tion of predation trials on a given date, predators 

 were transferred to separate holding tanks; this 

 ensured that no predator was used more than 

 twice during the 6 wk experimental period. 



Experimental Methods 



The predation experiments were conducted 

 following the methods of Folkvord and Hunter 

 (1986), with several modifications. Predation 

 trials were carried out in rectangular fiberglass 

 tanks, 1.4 m^ in volume, with a clear glass win- 



10 20 30 40 50 



LARVAL AGE (days after hatch) 



Figure 1. — Sizes, ages, and developmental stages of 

 larval white seabass prey used in predation trials. 



538 



