UC San Diego Library – Scripps Digital Collection

Since November, 1919, the California Division of Fish and Game has been gathering data to contribute to the understanding of causes underlying changes in abundance of the sardine,Sardinops caerulea. A knowledge of the relative proportions of the various age groups of fish in the population is an important element in such studies.

Prior to 1924, an attempt was made by Thompson and assistants to read the age marks on the scales and otoliths of this species, but results did not prove satisfactory. However, an indirect method of assessing age by tracing dominant size groups through the fishery was continued. During the period 1928–1933, a study of otoliths of sardines taken in the California fishery was made by H. C. Godsil, but this also proved unsatisfactory. In March, 1938, Walford and Mosher of the U. S. Fish and Wildlife Service started examination of the scales and otoliths of sardines, commencing with the young and later including older fish. This study established the validity of the method of reading scales to determine age in the sardine. The scale method was recommended as more advantageous in some respects than the otolith method, particularly after a rather simple method of mounting scales dry and projecting their enlarged images was developed.

Starting with the 1941–42 season in California a comprehensive program for scale collecting and age reading was undertaken jointly by the U. S. Fish and Wildlife Service and the California Division of Fish and Game. The Fisheries Research Board of Canada, the Washington State Department of Fisheries, and the Fish Commission of Oregon participated in the work by adding the collection of scales from sardines in northern waters. Their collections were included in the age-reading project. This report deals with the first six seasons of age determinations and presents the age composition of the catch without interpretation of the data.