FISHERY BULLETIN: VOL. 71, NO. 2 



r'2 



Table 1. — Comparison of CV^ values and character means (v^^^) of barred sand bass from southern Cahfornia and 



' Variances for dentories / cranium and lateral epiotic projections 

 (LEP) /cranium X lOl 



2 Mean standard length 288.4 ± 6.1 mm (SE). 



3 Mean standard length 293.7 ± 6.5 mm (SE). 

 * Mean standard length 292.9 ± 6.8 mm (SE). 



5 Mean standard length 287.0 ± 4.9 mm (SE). 



6 Mean standard length 293.6 ± 6.5 mm (SE). 



7 Mean standard length 193.6 ± 3.2 mm (SE). 



8 Mean standard length 193.3 ± 4.4 mm (SE). 



Table 2.- 



Locaiity 



-Locality designation and approximate straight- 

 line distance to Point Fermin. 



Miles to 

 Point Fermin 



Son Simeon 



Santo Rosa Island' 



Carpinteria 



Point Fermin 



Belmont Shore 



San Clemente 



San Diego 



California-Mexico border 



Bahia Son Quintin (Mexico) 



Bahia Sebastian Vizcaino (Mexico) 



Turtle Boy (Mexico) 



Southern Baja California (Mexico) 



210 



100 



85 







9 



53 



101 



116 



270 



435 



475 



550-750 



' Santa Rosa Island is 26 miles to sea from the nearest point 

 of land, which is itself 100 miles from Point Fermin. 



grouped into size classes (Table 3). From these 

 data it would appear that in small individuals 

 (< 100 mm) pectoral fin ray asymmetry may 

 decrease as size increases, while gill raker 

 asymmetry may decrease. For gill rakers the 

 trend is probably an effect of incomplete develop- 

 ment, character means are always lowest in 

 smaller size classes (Tables 3, 4, 5). 



Southern California barred sand bass were 

 likewise grouped into size classes (Table 4). 

 Comparing the data in these two tables (3 and 

 4) will illustrate three notable differences. First, 

 small southern California fish (0.0-49.9 mm) 

 have higher asymmetry levels than do their 

 Mexican counterparts. Second, pectoral fin ray 



asymmetry increases with size in southern 

 California barred sand bass, instead of decreas- 

 ing and plateauing, as in Mexican barred sand 

 bass. Third, the largest southern California 

 fish have asymmetry levels four to five times 

 higher than do Mexican fish. (In southern 

 California barred sand bass the association of 

 asymmetry in both characters with standard 

 length is highly significant, P < 0.01, using 

 Kendall's coefficient of concordance; Snedecor, 



1956.) 



Further analyses of these data suggest that 



these geographic differences in asymmetry are 

 the consequence of both ontogenetic and his- 

 torical processes that have been occurring in 

 the southern California population. The possible 

 ontogenetic change is an increase in asymmetry 

 with size (age). The possible historical process 

 is a secular increase in asymmetry. Both hy- 

 potheses are sufficient to account for the 

 observed trends. Unfortunately, data are lacking 

 to resolve this problem by straightforward 

 regression analyses. Nevertheless, the following 

 analyses suggest that both processes are 

 operating. 



First, the ontogenetic theory is examined 

 by following cohorts (cohort, in this case, being 

 defined as specimens spawned in the same year, 

 regardless of the size or age of the fish at the 

 time of capture). Our only collections containing 

 enough specimens to perform such an analysis 

 are those hatched in 1957, 1958, and 1959 



360 



