Does inter-annual variability in recruitment affect the abundance, biomass and size of stalked barnacles (Pollicipes pollicipes)?

Antonia Porz¹, Joana N. Fernandes¹, Maria Inês Seabra¹, Nélia Penteado¹, David Mateus¹, Alina Sousa¹, Teresa Silva¹, Francisco Neves¹, João J. Castro¹, David Jacinto¹, Teresa Cruz¹

¹University of Évora - MARE - Centro de Ciências do Mar e do Ambiente, Portugal

Temporal variability of recruitment might affect population dynamics of sedentary temperate reef species, particularly the ones exploited. The edible stalked barnacle Pollicipes pollicipes occurs on very exposed rocky shores along the Atlantic coast from France to Senegal. It has, especially in Portugal and Spain, a high economic and cultural value, being one of the marine intertidal resources that is most exploited by humans. P. pollicipes is a simultaneous hermaphrodite species that produces planktonic larvae of which the last stage (cyprid) settles heavily on the peduncle of adult conspecifics and metamorphoses into a juvenile. The main recruitment season is between summer and autumn. Interannual variability of recruitment at Cabo de Sines, SW Portugal, has been associated to variation in sea surface temperature and to an upwelling index. Here, we test if interannual variability of recruitment (summer/autumn of different years) at Cabo de Sines has an effect on the abundance, biomass, and size of benthic P. pollicipes in the following spring seasons. Low recruitment years are expected to lead to a reduced number of juveniles and a shift in size structure towards larger/older size classes and high recruitment years to an increased proportion of smaller individuals. Recruitment was measured by counting cyprids and juveniles on conspecifics sampled at Cabo de Sines during summer and autumn from 2011 to 2021. At the same site, the density, biomass, and size structure of barnacles were estimated during the following spring seasons (2012-2022) by destructive sampling of 15x15 cm quadrats. We will analyse the relation between mean annual recruitment of P. pollicipes during summer and autumn and its benthic density, biomass, and size structure in the following spring seasons. Investigating how natural processes (recruitment) affect the abundance, biomass, and size of an exploited species is crucial for management and important to predict shifts due to climate change.