Spatial distribution patterns and population structure of the sea urchin Paracentrotus lividus (Echinodermata: Echinoidea), in the coastal fishery of western Sardinia: a geostatistical analysis

• Main Authors: Piero Addis, Marco Secci, Alberto Angioni, Angelo Cau
• Format: Article
• Language: English
• Published: Consejo Superior de Investigaciones Científicas 2012-12-01
• Series: Scientia Marina
• Subjects: paracentrotus lividus; spatial distribution; geostatistics; biomass estimation; management; western mediterranean
• Online Access: http://scientiamarina.revistas.csic.es/index.php/scientiamarina/article/view/1402
• ISSN: 0214-8358; 1886-8134

The identification of appropriate spatial distribution patterns for the observation, analysis and management of stocks with a persistent spatial structure, such as sea urchins, is a key issue in fish ecology and fisheries research. This paper describes the development and application of a geostatistical approach for determining the spatial distribution and resilience of the population of the sea urchin Paracentrotus lividus in a fishing ground of western Sardinia (western Mediterranean). A framework combining field data collection, experimental modelling and mapping was used to identify the best-fit semivariogram, taking pre-fishing and post-fishing times into consideration. Variographic analyses indicate autocorrelation of density at small distances, while the isotropic Gaussian and spherical models are suitable for describing the spatial structure of sea urchin populations. The point kriging technique highlights a generally patchy population distribution that tends to disappear during the fishing season. Kriging maps are also useful for calculating predictable stock abundances, and thus mortality rates, by class diameters within six months of fishing. We conclude that the framework proposed is adequate for biomass estimation and assessment of sea urchin resources. This framework can therefore be regarded as a useful tool for encouraging a science-based management of this fishery.