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

Abstract

SUMMARY: 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.Keywords: Paracentrotus lividus, spatial distribution, geostatistics, biomass estimation, management, Western Mediterranean. RESUMEN: Modelo de distribución espacial y estructura poblacional del erizo de mar Paracentrotus lividus (Echinodermata: Echinoidea) en la pesquería costera de Cerdeña occidental (Mediterráneo occidental): aplicación de un enfoque geoestadístico. -La identificación de modelos de distribución espacial apropiados para la observación, análisis y ordenación de los stocks con estructura espacial constante, como los erizos de mar, son temas clave en la ecología de los peces e investigación de pesquerías. El presente trabajo describe el desarrollo y aplicación de un enfoque geoespacial para determinar la distribución espacial y resistencia de la población del erizo de mar (Paracentrotus lividus) en un área pesquera al oeste de Cerdeña (Mediterráneo occidental). Se utilizó un marco que combina la recolección de datos de campo, modelos experimentales y mapas, para identificar el mejor ajuste en el semivariograma, teniendo en cuenta tiempos antes y después de la pesca. Los análisis variográficos indican una autocorrelación para la densidad a pequeñas distancias, mientras que los modelos isotrópicos Gaussianos y esféricos son apropiados para describir la estructura espacial de las poblaciones del erizo de mar. La técnica del kriging puntual destaca una distribución desigual de la población que tiende a desaparecer durante la temporada de pesca. Los mapas que utilizan kriging son también útiles para calcular una abundancia fiable del stock, y por lo tanto tasas de mortalidad por clases de diámetro en un período de s...

Habitat traits and patterns of abundance of the purple sea urchin, Paracentrotus lividus (Lamarck, 1816), at multiple scales along the north Portuguese coast

“…between quadrats and between sites) as the most relevant for the variability of the distribution of almost all size classes of Paracentrotus lividus, though the distribution of the largest individuals varied considerably also between shores located some kilometers apart. The small-scale patchy distribution of present populations of sea urchins, particularly of relatively small individuals, agrees with previous studies which have demonstrated the main variability of the distribution of sea urchins at spatial scales from centimeters to meters rather than at larger scales (Hereu et al, 2004;Ceccherelli et al, 2009Ceccherelli et al, , 2011Addis et al, 2012;Bertocci et al, 2012b). Several biological and abiotic factors and processes, separately or possibly through complex interactions, can be responsible for such patterns, including competition (Guidetti et al, 2004), predation (Sala and Zabala, 1996;Hereu et al, 2005;Guidetti, 2006), recruitment (Tomas et al, 2004;Rius and Zabala, 2008) and topographic complexity (Benedetti-Cecchi and Cinelli, 1995;Barnes and Crook, 2001b;Hereu et al, 2005).…”

Geostatistical analysis and spatial modeling of population density for the sea cucumbers Isostichopus badionotus and Holothuria floridana on the Yucatan Peninsula, Mexico

“…Patches of different sizes and shapes may result, some with higher densities than others. Some of these patches can occupy dozens of square kilometers; therefore identification of appropriate spatial scale is a key issue for the experimental design (Orensanz et al, 2006;Ciannelli et al, 2008;Addis et al, 2012). In order to identify the spatial scale, a pilot study was carried out before the main sampling.…”

Effect of two different habitats on spine and gonad colour in the purple sea urchin Paracentrotus lividus

“…Our study was conducted on the sea urchin population of Sardinia (Southern Italy), where fishing for P. lividus plays a significant socio‐economic role (Addis et al . , ).…”

“…The aim of this study was to evaluate the colour of the spines and the gonads of P. lividus using colorimetric methods. Our study was conducted on the sea urchin population of Sardinia (Southern Italy), where fishing for P. lividus plays a significant socio-economic role (Addis et al 2009(Addis et al , 2012.…”