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RESEARCH PRODUCT

Study of Pinna nobilis growth from inner record: How biased are posterior adductor muscle scars estimates?

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abstract Article history:Received 14 June 2011Received in revised form 19 July 2011Accepted 20 July 2011Available online 17 August 2011Keywords:BivalviaEndangered speciesMediterraneanSclerochronologySpain Previous studies have shown that the external growth records of the posterior adductor muscle scar (PAMS)ofthe bivalve Pinna nobilisareincomplete and donot produce accurate ageestimations. We havedeveloped anew methodology to study age and growth using the inner record of the PAMS, which avoids the necessity ofcostly in situ shell measurements or isotopic studies. Using the inner record we identified the positions ofPAMS previously obscured by nacre and estimated the number of missing records in adult specimens withstrong abrasion of the calcite layer in the anterior portion of the shell. The study of the PAMS and inner recordof two shells that were 6 years old when collected showed that only 2 and 3 PAMS were observed, while 6inner records could be counted, thus confirming our working methodology. Growth parameters of a P. nobilispopulation located in Moraira, Spain (western Mediterranean) were estimated with the new methodologyand compared to those obtained using PAMS data and in situ measurements. For the comparisons, we applieddifferent models considering the data alternatively as length-at-age (LA) and tag-recapture (TR). Amongevery method we tested to fit the Von Bertalanffy growth model, we observed that LA data from inner recordfitted to the model using non-linear mixed effects and the estimation of missing records using the calcitewidthwasthemostappropriate.Theequationobtainedwiththismethod,L=57.3*(1−e