Age, growth, and population structure of the smooth clam Callista chione in the eastern Adriatic Sea

Abstract

The age, growth, and population structure of the smooth clam Callista chione were determined from samples collected by hydraulic dredge and SCUBA at four locations in the eastern Adriatic during 2007 and 2008. The age of 436 clam shells was determined from internal growth lines present in shell sections, and the timing of growth line formation was ascertained from monthly collections of clams to occur between August and September when sea water temperatures were maximal. In addition, age of 30 older individuals was verified with acetate peels of polished and etched shell sections. Differences were apparent in the age structure and growth rates of clams collected from the four locations studied. Von Bertalanffy growth (VBG) curves obtained for clams from these locations were Lt = 72. 4 (1-e-0. 25(t - 2. 68)) (Rab Island), Lt = 74. 5 (1-e-0. 15(t + 0. 57)) (Pag Bay), Lt = 79. 3 (1-e-0. 34(t - 0. 97)) (Cetina estuary), and Lt = 82. 5 (1-e-0. 11(t + 2. 88)) (Kaštela Bay). The age of the clams ranged between 3 and 44 years; median clam ages were similar at three of the four locations (14, 12, and 12 years, respectively), but was significantly lower in the Cetina estuary (4 years). The VBG growth constants recorded from clams were within the range of values obtained for this species by previous authors. The observed local differences in population structure indicate different levels of exploitation and illustrate the need to establish long-term strategies for a sustainable exploitation of smooth clams in the Croatian Adriatic. © 2010 Springer-Verlag and AWI.