Mass mortality of abalone Haliotis cracherodii or the California Channel Islands: tests of epidemiological hypothesis

Along the coast of the California Channel Islands, USA, the abundant black abalone Haliotis cracherodii began to die in large numbers in 1985. This die-off has spread to most of the islands and still continues. Analysis of the changes in abalone abundance at numerous locations suggests that this is the result of an infectious disease spreading slowly from the south side of Santa Cruz Island. However, this might not be d u e to a directly transmitted disease and w e have found no agent of infectlon As with many diseases, warm temperatures acted to increase mortality rates. Our results were not consistent with other hypotheses for the decline such as over-harvesting, pollution, or factors related to physiological stresses induced by the strong El Nirio of 1983-84, including warm temperatures, starvation and competition.