Breeding, planktonic and settlement factors shape recruitment patterns of one of the last remaining major population of Pinna nobilis within Spanish waters

Abstract

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.

Recruitment Disruption and the Role of Unaffected Populations for Potential Recovery After the Pinna nobilis Mass Mortality Event

“…Surprisingly, even though P. nobilis populations in the Delta del Ebro remain mostly unaffected, collectors installed in this location have never recorded larval settlement, and according to Prado et al (2019) the local availability of planktonic larvae is very low. These populations seem to rely mainly on sporadic recruitment events and the absence of recruitment inside the bay has been hypothesized to be associated to processes causing larval mortality such as freshwater discharges or even pollution (Prado et al, 2019). Nevertheless, as showed by Wesselmann et al (2018), these populations seem to be exporting larvae, which hints to the fact that even though larval mortality inside the bay might be high, larvae could be transported into the open sea.…”

“…Pinna nobilis populations in this site have survived the MME apparently due to the low salinity conditions in the area, greatly influenced by agricultural discharges from rice cultivation (Prado et al, 2019;García-March et al, 2020) and this area has been already considered as a main source of P. nobilis larvae (Wesselmann et al, 2018). Surprisingly, even though P. nobilis populations in the Delta del Ebro remain mostly unaffected, collectors installed in this location have never recorded larval settlement, and according to Prado et al (2019) the local availability of planktonic larvae is very low. These populations seem to rely mainly on sporadic recruitment events and the absence of recruitment inside the bay has been hypothesized to be associated to processes causing larval mortality such as freshwater discharges or even pollution (Prado et al, 2019).…”

“…All known pen shell populations along the Spanish Mediterranean coast disappeared between 2016 and 2017 due to the MME, with little or no evidence of resistant individuals. There was the exception, however, of two sites with particular environmental conditions (i.e., Delta del Ebro bays -Alfacs and Fangar-, and the hypersaline coastal lagoon Mar Menor) which seem to remain at least partially pathogen-free (Vázquez-Luis et al, 2017;Catanese et al, 2018;Cabanellas-Reboredo et al, 2019;Prado et al, 2019;Giménez-Casalduero et al, in press).…”

“…The closest unaffected site, Delta del Ebro (∼100 km north of the Columbretes Islands), hosts one of the largest P. nobilis populations in the Mediterranean Sea (Prado et al, 2014). Pinna nobilis populations in this site have survived the MME apparently due to the low salinity conditions in the area, greatly influenced by agricultural discharges from rice cultivation (Prado et al, 2019;García-March et al, 2020) and this area has been already considered as a main source of P. nobilis larvae (Wesselmann et al, 2018). Surprisingly, even though P. nobilis populations in the Delta del Ebro remain mostly unaffected, collectors installed in this location have never recorded larval settlement, and according to Prado et al (2019) the local availability of planktonic larvae is very low.…”

“…Most known and studied P. nobilis populations in the Western Mediterranean Sea have almost completely disappeared, with mortality rates exceeding 90% (Vázquez-Luis et al, 2017;Panarese et al, 2019;García-March et al, 2020) and populations in the Eastern Mediterranean and Adriatic Sea are suffering the same fate (Katsanevakis et al, 2019;Kersting et al, 2019;Cižmek et al, 2020;Öndes et al, 2020;Özalp and Kersting, 2020). There is the exception, however, of several sites with very specific environmental settings where P. nobilis populations remain unaffected to date: Fangar Bay (Delta del Ebro, Spain), Mar Menor (Spain), Rhône Delta (France), Etang de Thau (France), Diana and Urbino pools (Corsica, France), Venice lagoon (Italy), inner Kalloni Gulf (Greece) (Catanese et al, 2018;Cabanellas-Reboredo et al, 2019;Kersting et al, 2019;Simide et al, 2019;Prado et al, 2019;Foulquie et al, 2020;Zotou et al, 2020). This worrying scenario has led to the recent inclusion of the species as Critically Endangered on the IUCN Red List (Kersting et al, 2019).…”