Multiple effects of harvesting on populations of the purple sea urchin paracentrotus lividus in north Portugal

We compared patterns of abundance and distribution of the sea urchin Paracentrotus lividus between shores subject to commercial harvesting of this species and unexploited reference shores in north Portugal. Harvesting was associated to a significant reduction in total density and abundance of individuals of commercially valuable size (i.e. larger than 40 mm in test diameter), with patterns, respectively, fully or mostly consistent over a study period of about one year. In addition, the spatial variance in the distribution of the largest individuals was higher under the harvested compared to the reference condition at the scale of sampled shores (i.e. kms apart), while the opposite pattern was documented for the temporal variance of the same response variable. These findings suggest that commercial harvesting has an actual impact on the studied populations of P. lividus, with potential implications for their conservation and for the management of the associated local fishery.