engleski

Age and growth determination of Pinna nobilis L. from the Croatian Adriatic Sea using Mg/Ca, Sr/Ca ratios and stable oxygen isotopes

The fan shell Pinna nobilis L. is the largest Mediterranean bivalve and has been protected in the Croatian Adriatic since 1977. However, little is still known about its population structure at different locations. Richardson et al. (1999) used inner shell adductor-muscle scar rings to estimate the age of fan mussels from the Spanish Mediterranean and using stable oxygen isotopes (d18O) demonstrated that the rings were deposited annually during a period of increasing sea water temperatures. In this study we examine potential use of Mg/Ca and Sr/Ca ratios for estimating age of P. nobilis collected at three sites in the Croatian Adriatic; Mali Ston Bay, and Veliko jezero and Malo jezero on island of Mljet. Our results show that variations in Mg/Ca and Sr/Ca ratios are closely correlated with d18O variations. Recorded variations reflect seasonal differences in shell growth rate and can therefore be used to estimate the number of winter-summer growth cycles. Growth rings on adductor-muscle scar form in the winter and early spring as a result of slow shell growth, first clearly visible ring forms when fan mussels reach 20-30 cm length and probably represents the second winter of growth. The oldest Pinna nobilis collected was 9 years old.

bivalve; Pinna nobilis; age; growth; stable oxygen isotopes; elemental ratios; Adriatic Sea

nije evidentirano