Population Dynamics and Viability Analysis for the Critically Endangered Ferruginean Limpet

The current study deals with the critically endangered limpet Patella ferruginea (Gastropoda: Patellidae) endemic to the western Mediterranean. The species has been in decline since the early 20th century and is currently restricted to certain locations on the Iberian Peninsula, Corsica, Sardinia, and the North African coasts of Morocco, Algeria, and Tunisia. Its large size and conspicuous shell often makes the species a target of human collection. We describe the results of temporal monitoring conducted on one of the remaining most important P. ferruginea populations in North Africa, and provide quantitative data on growth rates, natural mortality, and harvesting rates. The maximum collection rates were recorded during the summer months, when fishermen most attend the beach. This type of mortality mostly affected medium and large individuals, and increased natural mortality rates up to 37%. All results and previously available data were implemented for population viability analysis. We determined that the species is clearly overexploited in the study area, and may face local extinction within the next 20 y if harvesting activities are not controlled. Even though more precise predictions could be obtained by using a longer time series, our study is the first attempt to model the future viability of the species, and indicates the urgent need of establishing efficient protection measures.