FISHERY BULLETIN: VOL. 74. NO. 4 



development; the 10-12 mm group, most charac- 

 teristic of the southern California area in Figure le, 

 was of a cohort which remained locally dominant 

 from its inception in July 1955 until January 1956. 



The 7-8, 9-12, and 15-16 mm modes are described 

 below as being common to E. pacifica because they 

 are at body lengths at which life-phase changes 

 and growth slows; therefore frequencies of those 

 sizes increase, particularly during fall-winter 

 periods of reduced food supply. 



L-F curves for individual stations show the clear 

 7-8 mm mode along an "offshore" north-south 

 track (Figure 2a, c) in the axis of the fastest part 

 of the current (Figure la). It dominates the 9-10 

 mm mode as the transect, following the steam- 

 lines, angles shoreward along the southern edge of 

 the southern California area, until lat. 35.5°N 

 (station 97.50) where the 7-8 mm mode becomes 

 inconspicuous and the 9-10 mm mode assumes 

 dominance. Thus offshore, where southerly 

 population transport would be expected on the 

 basis of the observed current, dissipation of the 

 L-F characteristic of the northern population 

 takes place along the western limit of the study 

 area. This is considered evidence that such trans- 

 port then contributed little to the area's popula- 

 tion, relative to more nearshore, local 

 contributions. 



Individual stations along a "nearshore" north- 

 south transect (Figure 2b) showed a dense heter- 

 ogeneous population of E. pacifica off San 

 Francisco (station 63.55, lat. 37°N). Off central 

 California (stations 70.55, 77.55), 7-8 mm juveniles 

 became conspicuous (cf. Figure 3). Farther south, 

 particularly in the southern California area 

 (stations 83.51-90.28), 7-10 mm individuals were 

 much reduced in numbers, while the frequency of 

 the 11-12 mm size increased, appearing as a clear 

 L-F mode. In October, larvae were few off north- 

 ernmost Baja California where oceanic water 

 typically moves eastware compressing shoreward 

 the faunistic connection of the southern California 

 area to more southern upwelling centers. To the 

 south along the Mexican coast, the 11-12 mm mode 

 characteristic of the study area reappeared, coin- 

 cident with areas of production of larvae. Farthest 

 south (off Punta Eugenia; stations 120.45, 123.40), 

 modes were at 9-10 mm and at 3-mm larvae. These 

 9-10 mm specimens may be poorly nourished 

 individuals, corresponding in age to 11-12 mm 

 individuals occupying the area immediately to the 

 north— an area which appears relatively fertile 

 with respect to production of larvae. The same 



738 



relationship was observed locally off northernmost 

 Baja California; there the population having a 9-10 

 mm mode included few larvae (Figure Ic) and 

 occupied an easterly incursion of oceanic water 

 (Figure la), being bounded on the north and south 

 by cooler and presumably more fertile areas in 

 which both 11-12 mm and larval modes were again 

 conspicuous. 



At this time (October 1955) the range of E. 

 pacifica terminated near Punta Eugenia, but it 

 can extend to lat. 23°S (Brinton 1967b). These 

 far downstream parts of the population appear 

 reproductive, but to the south of southern Califor- 

 nia they are impermanent (Brinton 1967b, 1973). 

 Mature or maturing individuals are expected to be 

 intermittently injected from the north, par- 

 ticularly during the March-June period when 

 southerly flow is intensified. These individuals 

 may find local places of refuge in cool, slowly 

 moving, productive coastal waters from Point 

 Conception southward in association with up- 

 welling centers. The southern California eddy is 

 the largest such refuge, serving also as a major 

 population center which has both coastal and 

 oceanic dimensions. 



Spawning and Recruitment 



Spawning intensity was estimated indirectly 

 since free-floating eggs were not sampled. 

 Females bearing ripe eggs provided a means of 

 estimating incipient spawning. All females hav- 

 ing an attached spermatophore also carried ripe 

 eggs in the ovary. From the several thousands of 

 these counted, 373 of different body lengths were 

 examined with respect to number of ripe eggs 

 carried. The relationship between body length and 

 mean number of ripe eggs was linear between 11 

 and 20 mm length (means were encompassed by 

 95^ confidence limits of regression line), with the 

 mean number of eggs extending from 20 to 212 

 across this range (Figure 3). Disproportionately 

 small numbers of eggs were observed in the 

 largest (>20 mm) females. Mean values for each 

 body length were applied to the numbers of each 

 length of ripe female counted in the plankton 

 samples to estimate the spawning potential for 

 each sampling period. These are underestimates 

 since, for 60% of the surveys, the predicted values 

 are not high enough to have produced the density 

 of larvae found at the time of the next 

 surv^ey— even presuming only 50% mortality 

 between surveys (Figure 4c). Evidently some eggs 



