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Fishery Bulletin 90(4). 1992 



in both years, due to the peaks in abundance of YOY 

 observed in both 1988 and 1989, although monthly 

 differences were significant only in 1988. In 1989, a 

 significant spatial pattern of catches was detected, 

 related to distance from the mainland and depth of cap- 

 ture over months. 



Both the distance block ANOVA from 1989 data and 

 the overall correlation analyses strongly suggest that 

 the abundance of YOY white seabass decreases rapid- 

 ly with distance from the mainland. Other factors 

 are less important. Nonetheless, the combination of 

 distance, temperature, and biomass of drift algae pro- 

 duced a highly significant canonical correlation with 

 distance and temperature contributing most heavily to 

 the relationship. 



The large amount of unexplained variation in the 

 multivariate model suggests that important factors 

 may be missing from the analysis. We believe that one 

 such factor is the initial availability of presettlement 

 larvae in the plankton. A dearth of premetamorphic 

 larvae at a potential settlement site results in low 

 settlement, no matter how favorable the environmen- 

 tal conditions. Population sizes off southern California 

 might be limited largely by number of settling larvae 

 rather than site-specific environmental factors or 

 density-dependent survival of YOY. Only when larval 

 input is constantly high, as we suspect is the case in 

 Mexican waters, could the influence of environmental 

 factors on settlement success be determined with any 

 precision. 



Factors affecting larval availability are not well 

 known. Spawning of white seabass occurs in the sum- 



mer and may be related to lunar periodicity (moon 

 phase) (Franklin and Allen, unpubl. data) early in the 

 reproductive period. Lunar periodicity of spawning ac- 

 tivity coupled with adult stock size, larval transport 

 mechanisms, and larval growth dynamics could all 

 ultimately influence the availability of white seabass 

 larvae. 



Distance from the mainland, the strongest correlate 

 with YOY abundance, probably reflects larval avail- 

 ability which may decrease with distance from coastal 

 stocks occurring in both southern and Baja California. 

 Island populations of adults were either not repro- 

 ducing or their larvae were being carried away from 

 settlement sites. Long-term settlement success of 

 white seabass to islands may be sporadic and highly 

 variable. For example, Cowen (1985) found that Cali- 

 fornia sheephead (Semicossyphus pulcher) settled only 

 sporadically to the offshore islands. The pattern of 

 settlement success of sheephead over a 7-9 year period 

 in areas without larval sources "upstream" of typical 

 current direction was highly variable and dependent 

 on episodic events, such as the El Nino climatic anoma- 

 ly (Cowen 1985). 



Warm water currents may be important to white 

 seabass settlement for two reasons: (1) Large num- 

 bers of larvae carried northward from more southern 

 waters by warm water currents may settle after meta- 

 morphosis and locate suitable habitat; and (2) the warm 

 water itself may induce locally spawned larvae to 

 settle. On a larger scale, major water movements such 

 as the California Current, gyral circulation ("eddies"), 

 and other mesoscale flows (e.g., internal waves) may 



