Population structure and morphometric relationships of Paracentrotus lividus (Echinodermata: Echinoidea) in the South Aegean Sea

Abstract

The gonads of the common sea urchin Paracentrotus lividus are a pricey gastronomic delicacy, and so the species is intensively harvested. Considering the recent collapse of its Populations in many Mediterranean areas and the lack of information for the Aegean Sea, a three-year survey was carried out focusing on population structure, morphometric relationships and reproductive status of P lividus in Astypalea, a South Aegean island, where the species is traditionally commercially exploited. Population density showed significant inter-annual variability, while its distribution pattern was contagious. P lividus individuals had larger size at the most sheltered site. Nevertheless, a significant interaction was detected among sites and years or seasons confounding the effect of these factors on the urchin's biometry. All the examined morphometric relationships followed negative allometry. The body diameter appeared to be a good predictor of its biomass. Voluminous gonads were present in several specimens of P lividus in all temporal samples; the gonad-somatic index peaked in early spring, particularly at the most sheltered site. Size-frequency distribution analysis revealed the presence of one mode of large sized individuals, implying that P lividus stocks have not been heavily fished yet in this area.