California Sea Grant College Program

In the 1970’s, white abalone populations in California suffered catastrophic declines due to over-fishing, and the species has been listed under the Endangered Species Act since 2001. Genetic diversity of a modern population of white abalone was estimated to be significantly lower than similar Haliotis species, but the effect of the recent fishery crash on the species throughout its range was unknown. In this investigation, DNA was extracted from 39 historic and 27 recent dry abalone shells from California, and 18 historic dry shells from Baja California, Mexico. The DNA from the shells was of sufficient quality for the reproducible amplification of 580 bp of the mitochondrial COI gene and 219 bp of the nuclear Histone H3 gene. Two COI haplotypes were distinguished, and no difference (p>0.05) was found between the nucleotide or haplotype diversity of California’s recent (π=0.0010; Hd=0.501) and historic baseline (π=0.0010; Hd=0.505) wild populations of H. sorenseni. However, COI diversity in the historic Baja population (π=0.0004; Hd=0.209) was significantly lower (p<0.05) than in California. This study demonstrates the importance of appropriate historic reference groups for threatened or commercially important species, and can aid captive breeding programs manage broodstock and re-introduction design. Stringent controls and treatments to eliminate surface DNA advocate an endogenous source for DNA extracted from shells, but the hypothesis that abalone DNA in shells was remnant of trapped epithelial cells during shell formation could not be verified by histological and fluorescent staining of decalcified abalone shell.