UC San Diego Library – Scripps Digital Collection

These vertebral counts indicate that sardines from British Columbia to Pt. San Eugenio in central Lower California comprise a mixture of populations, the young of which may have been reared on nursery grounds in any of these localities. For most seasons, presumably, the nursery grounds off California and northern Lower California make the greatest contributions to the population. Sardines living off southern Lower California and in the Gulf of California probably comprise a distinct group which does not mix with the northern fish; or if a mixture occurs, the proportion of southern fish to the total northern population is small. The interchange between nursery grounds begins early, perhaps before the sardines are a year old. The number of vertebrae varies between year-classes, and certain year-classes are characterized by high or low averages in all localities. The average number of vertebrae is approximately 51.7 for all sardines north of southern Lower California and about 51.2 for sardines from southern Lower California.