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



Table 2. — Allozyme variation in five population samples of Pacific sardine. 



Tomales Monterey S. Calif. Magdalena 

 Bay Bay Bight Bay Guaymas 



A. Summary statistics 

 No. of fish (N) 



No. of loci 

 P (as percent) 

 Ho (as percent) 

 He (as percent) 



B. Polymorphic enzymes' 



Variants 



5 

 27 

 7.4 



1.5 

 1.5 



29 



27 



14.8 

 1.0 

 1.0 



30 



23 

 8.7 

 0.6 

 0.6 



37 



27 

 7.4 

 0.5 

 0.5 



48 



26 



26.9 

 1.7 

 1.6 



No. of heterozygotes in samples of size (A/) 



'Zymogram banding patterns of presumptive heterozygotes at the loci inferred to encode 

 these proteins conform to those expected on the basis of known subunit structures: letrameric 

 structure for FBP; dimeric structure for GPDH, IDH, LGG, 6PGDH, and SOD; monomeric 

 structure for EST-6, LT and PP (Darnall and Klotz 1975; Harris and Hopkinson 1976; Ruth and 

 Wold 1976; Koehn and Eanes 1978; Utter et al 1987). 



observed and expected average heterozygosities 

 in any of the population samples. For no indi- 

 vidual locus is it possible to test H-W-C expected 

 genotypic proportions in a population sample, 

 owing to the low frequencies of variant alleles 

 and the relatively small sample sizes. 



In addition to the low genetic variation within 

 each of the samples of Pacific sardines, there is 

 almost no variation among populations in the fre- 

 quencies of allozymes (Table 2B). E.xcept for 

 6PGDH, for which a third allozyme was inferred 

 from observation of a single 98/103 heterozygous 

 phenotype in the Guaymas sample, all polymor- 

 phic allozymes are represented by just two al- 

 leles. For each locus that is polymorphic in more 

 than one population, the same rare variant allele 

 is shared at about the same frequency (Table 2B). 



Thus, the five, widely separated populations of 

 Pacific sardine sampled in our study are virtually 

 genetically identical at the 32 loci examined. 



Ageing from Otolith Annuli 



Under the assumption that an annulus rep- 

 resents a yearly gi'owth ring and that fish with 

 one ring are one year old, three age classes, I's, 

 2's, and 3's, predominate in all five population 

 samples. There are no statistically significant 

 differences in distribution of ages among the 

 four larger samples xldf = 10.7083, 0.1 < P < 

 0.5; data in Table 3). Nor is there a difference 

 between the small Tomales Bay sample and the 

 others (Fisher's exact test on Tomales Bay data 

 versus all other data combined, P > 0.90). 



Table 3. — Distributions of ages in five population samples of Pacific sardine. 



658 



