Effects of harvesting on distribution and size structure on intertidal grazers. A comparison among different species of the genus patella
Author(s)
Marra, Stefano
Date Issued
June 15, 2017
Type
Doctoral Thesis
Abstract
Harvesting is considered the main anthropogenic pressure threatening marine biodiversity and Marine Protected Areas (MPAs) are a key tool to counteract biodiversity declines. This thesis was carried out in the Sinis Peninsula (Sardinia, Italy) to quantify the effects of harvesting on intertidal limpets and to assess the efficacy of the management measures in the “Penisola del Sinis-Isola di Mal di Ventre” MPA, where limpet collection is forbidden. Time series of abundance and population size structure data were analysed for four Patella species with different life-history traits (Patella ferruginea, P. caerulea, P. rustica and P. ulyssiponensis) to assess differences in mortality rate among levels of legal protection and site accessibility. Declines in abundance and mean size were observed for all species, with the higher survival rate recorded in sites where the number of harvesters is limited by the physical features of the shore and by the presence of stricter protection regulations. The local population of P. ferruginea is dramatically declining and close to extinction, whilst the other three species that have faster maturation periods resulted more resilient to harvesting. This thesis demonstrated that in the study area harvesting is an important stressor for limpet populations. The effectiveness of the MPA on preventing harvesting of intertidal species was limited, and the physical accessibility of the shore played an important role on providing protection.
Additional information
Dottorato di ricerca in Ecologia e gestione sostenibile delle risorse ambientali