The development of aquaculture activities has posed an alternative solution for the preservation of some overexploited shellfish fisheries worldwide. In the same way, endemic Mediterranean bivalves such as Pinna nobilis, highly threatened by habitat loss and coastal pollution, could found in aquaculture a solution for preserving the continuity of the species. Given the endangered status of the species, the biological and ecological processes regulating natural populations have been well studied, but there are still important knowledge gaps preventing the development of viable artificial cultures. This study describes for the first time the larval development of P. nobilis (from fertilization until pediveliger larval stages) in captivity conditions. Moreover, different rearing tanks of 5, 16 and 80 L, larvae density from 1 to 600 larvae mL −1 , light conditions, food doses, were tested in order to establish the bases for the optimal rearing of the species and provide a source of individuals for restoring field populations. Results showed that 16 L tanks with a concentration of 2 larvae mL −1 , constant temperature of 21 °C, 12/12 h photoperiod and fed with an "optimal" mixture of 25 cells per μL of Chaetoceros calcitrans + 33.3 cells per μL ofPavlova lutheri + 100 cells per μL of Isochrysis galbana" appear to be the best conditions to rear larvae of P. nobilis. Different captivity conditions such as lower or higher tank volume, larvae density, or food doses; light privation did not report better results for larval development.

Knowledge of the feeding habits of marine species is fundamental for a better understanding of their relationship with the environment. Although phytoplankton has traditionally been reported as the main food source consumed by the Mediterranean fan mussel Pinna nobilis, recent studies have revealed that detritus represents an important food source for this species. We analysed the degree of acceptance of muddy detritus and the utilisation of its organic matter (OM) by P. nobilis on a group of 21 individuals [30.3-59.7 cm of total shell height (Ht)]. The specimens were collected between July and September 2012 in two areas (43°04´25" N; 5°46´7" E and 43°04´34" N; 5°47´32" E) of the Embiez archipelago, north-western Mediterranean (France). Our studies show that P. nobilis retains high quantities of OM from muddy detritus (47.50 ± 11.23% of filtered OM) irrespective of shell size. Smaller individuals, however, actively filter more detritus than large ones. The values of retained OM, together with previous studies on stomach contents, suggest that muddy detritus is a more important OM source than phytoplankton for this species.

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Acknowledgements The authors thank the Zoo Barcelona Foundation for an Antoni Jonch grant 2015. JR García-March and J Tena were funded by the Albert II of Monaco Foundation to develop the age study within the project "The study, protection and possible breeding of the pen shell (P. nobilis) in the Boka Kotorska Bay". Additional funding was obtained from a 2017 INIA grant for project EMERGER (E-RTA2015-00004-00-00). We thank Department of Territory and Sustainability for granting us a permit for the collection of P. nobilis (Ref.: SF/030). Environmental factors were obtained from the project "Programa de seguiment de la qualitat de les aigües, mol•luscs i fitoplancton toxic les zones de producció de marics del litoral català de la DGPAM". IRTA acknowledges support from the CERCA Program from the Catalonian Government. Authors thank Dr. Miguel Alonso García-Amilivia for help with the separation of bivalve larvae, and to Pep Cabanes, Lluis Jornet, and Jose Luis Costa for fieldwork assistance.

Pinna nobilis is an endangered species of fan mussel found along coastal Mediterranean waters requiring special attention for conservation. Populations are restricted in number, due to anthropogenic disturbances, disease, and in some areas, low rates of recruitment. To date, the difficulties associated with the identification of planktonic stages have prompted the use of benthic collectors as a proxy for quantifying larval supply, despite important information being lost regarding planktonic processes. We present evidence of spawning utilizing a qPCR assay developed for detecting genomic DNA of P. nobilis to enable specific identification of planktonic stages to augment knowledge of P. nobilis life history. In the Ebro Delta, Spain, it has been used to study what might be limiting their reproduction locally. We demonstrate the ability to differentiate DNA of P. nobilis from other bivalve mollusks and distinguish between fertilized and unfer-tilized eggs of P. nobilis, which may be a crucial point for understanding the low level of recruitment seen in this natural population. We also show evidence of larval presence during the expected spawning period, although abundance in positive samples were so low that they pose new questions about factors controlling the availability of planktonic stages of P. nobilis.

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