Black abalone (Haliotis cracherodii) once dominated the rocky intertidal zone. The once productive abalone fishery, with densities of 100 abalone per meter, declined and commercial harvests dropped 95% on the northern Channel Islands between 1972 and 1992. By 1993 the entire California black abalone fishery was closed.

Data from the park's monitoring program found massive declines in black abalone in 1986, eventually resulting in over a 99% loss of this valuable mollusk. By 1988 nearly all of the surviving abalone were concentrated at San Miguel Island and densities were reduced to only 0.09 abalone per meter. The primary factors leading to the decline of black abalone were overfishing and disease (withering syndrome). In 2007, the National Marine Fisheries Service petitioned to list the species as endangered under the Endangered Species Act, with official listing in January 2009.

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