Age and growth of the bivalve Arca noae L. in the Croatian Adriatic Sea

Abstract

The Noah's Ark shell Arca noae is a widely distributed and locally abundant bivalve in the coastal waters of the eastern Adriatic Sea where it is commercially exploited. Information regarding its basic biology is lacking, and little is known about its population structure, recruitment, reproduction, growth and longevity. We estimated the age of three populations of A. noae collected from the Croatian Adriatic using external surface growth rings, pallial line scars on the inner shell surface, and growth lines in acetate peel replicas of sections of the umbo and outer prismatic shell layer. All the age determination methods used were successful in estimating the age of A. noae, however counts of the prismatic growth lines provided a less ambiguous estimate of the age of the shells. Arca noae is a slow-growing species reaching a size of 70 mm and an age of up to 16 years. Croatian populations might be vulnerable to over-exploitation.