Sink-source connectivity for restocking of Pinna nobilis in the Spanish Mediterranean Sea

Abstract

[eng] Critically endangered and endemic bivalve Pinna nobilis from the Mediterranean Sea has suffered from the declining of its population, concluding in a mass mortality event from 2017 to the present time. These occurrences have led to several conservation actions in order to avoid the extinction of the species. Among the various conservation initiatives currently underway some very important aspects are still unknown to achieve the establishment of a breeding plan of Pinna nobilis, such as the closure of the larval cycle, the cycles of hermaphroditism or the existence of genetic resistance factors of the surviving individuals. The management of resistant individuals is fundamental because they can be the element contributing with new breeders. It is necessary to have a broad breeding plan to be able to close the captive breeding of Pinna nobilis; however, in parallel with the breeding plan, it is necessary to identify optimal places to make the first releases/regrouping resistant individuals. The use of larval dispersion models can help to select reintroduction areas, prior to making efforts in different areas. In this study, biophysical modelling, connectivity metrics and graph analysis were used to select optimal repopulation points to begin with the reintroduction of resistant animals in the Western Mediterranean Sea. These tools were used for different pelagic larval duration due to the current knowledge gap regarding this factor. Nevertheless, the results obtained were solid for the different scenarios, allowing identifying repopulation key points able to maintain themselves but emit larvae for the rest of populations, repopulating the whole network that existed in the Spanish Mediterranean Sea prior to the mass mortality event. Overall, the results highlighted the repopulation points located in Isla Grosa, Tabarca, Columbretes, Espalmador-Llevant, Cabrera and Addaia as the optimal ones to begin with reintroduction efforts in the Spanish Mediterranean Sea.