Population parameters and dye yield of the purple snail Plicopurpura pansa (Gould, 1853) of west central Mexico

The purple snail (Plicopurpura pansa) is a conspicuous rocky shore species of the intertidal zone of tropical western America. It is considered a potential resource due to the dye it produces. Estimates of population density, sex ratio, growth parameters, mortality, and recruitment were obtained from bimonthly samplings from 1993 through 1995 on a rocky shore of west central Mexico. A different growth rate between sexes was observed. Mortality coefficients for the population are estimated for the first time. Recruitment to rocky shores occurs principally from September through March. The life span (longevity) was estimated as 11 y. Dye production related to size and sex was determined and is described by an exponential relation.