Demographic regulation processes in Pinna nobilis populations of the Balearic Islands: implications for restocking

Abstract

[eng] A mass mortality event (MME) impacting the endemic Pinna nobilis in autumn 2016 across the Mediterranean Sea. This event affected specimens of all sizes, depth ranges and habitat types, so that populations of the species have suffered a drastic decline of close to 100%. Actually the consequences in the distribution, potential recovery, and therefore in the viability of the endangered endemic species Pinna nobilis are unknown. In order to determine optimal areas for future reintroduction programs; the population dynamics is essential knowledge to develop an ecological model for the reintroduction of the species. The demographic processes of Pinna nobilis subpopulation were investigated in two areas with different environmental conditions, in the Cabrera National Park (protected area) and San Telmo (non-protected area), both in Balearic Islands. A total of 259 individuals were tagged and monitored annually between 2011 to 2014, before the MME. Leslie matrix models have been used to reduce the complexity of agestructured population dynamics and address the question of population persistence. The elasticity of population growth rate was also calculated to measure changes in survival and maturation rates. The subpopulation of Pinna nobilis from San Telmo showed highly variable values of demographic rates suggesting that it is an area where the population does not tend to persist. In contrast, in Cabrera NP populations are more stable regardless of depth being a more suitable site for future reintroduction programs.