Status and trends of black abalone (Haliotis cracherodh): Apreliminary approach to modeling population viability

摘要

Black abalone, Haliotis cracherodii, was added to the National Marine Fisheries Service (NMFS) species of concern list in 1999 because of documented large declines, known threats and uncertainty regarding the future course of those threats. Although efforts have been made to protect surviving populations in California, USA through closure of the commercial fishery in 1993, the species continues to decline and a >90% reduction in abundance has been observed throughout >50% of the species range since the late 1980s. Heavy fishing pressure and disease have contributed to the observed decline. Expanding coastal development may increase human traffic in the intertidal and may intensify enforcement problems. Pollution, warming temperatures, and biological interactions with competitors/predators may also threaten remaining populations. NMFS must determine whether the rate and extent of black abalone population decline and the severity of risk are high enough to warrant a listing under the United Stated Endangered Species Act. In order to do this, a variety of tools are employed using the best available data to predict the probability distribution of long-term population trends. A population viability model is one tool that is being developed to assess species vulnerability through the analysis of the interplay of specific demographic parameters over a spatial array of habitat suitability and other possible forcing factors. Our scientific challenge is to identify important gaps in our understanding of this species' ecology that will allow us to deter-mine what data needs to be collected for improving the estimates of the most influential parameters.