Influence of water depth on growth and mortality of Chlamys varia (Linnaeus, 1758): implications for cage culture in Mali Ston Bay, Croatia

Abstract

This study investigated growth and mortalities of juvenile variegated scallops Chlamys varia (Linnaeus, 1758) grown in suspension at Mali Ston Bay in the Adriatic Sea. Juveniles collected from the previous year’s natural breeding, mean length of 14.58 mm, were placed in cages at three depths (1, 3 and 5 m), for 21 months. We compared results on shell heights at the end of growth period in relation to seawater temperature and salinity. Shell lengths averaged 45.30 ± 4.10 mm (range 39–54 mm) at 1 m depths, 42.48 ± 2.40 mm (39–48 mm) at 3 m, and 41.90 ± 4.25 mm (37–50 mm) at 5 m. Average monthly growth of shell height throughout the experimental period was 1.7 (1 m), 1.6 (3 m) and 1.7 mm (5 m). Total mortality throughout the experimental period was 25.0 % (1 m), 16.6 % (3 m) and 71.4 % (5 m). Furthermore, we estimate von Bertalanffy growth parameters from growth increment models, where extensions of the von Bertalanffy model that allow growth rate to vary with changing body size and with periodic (seasonal) changes in the growth parameter K are presented. The goal of this research was to evaluate the potential for commercial aquaculture of C. varia (growth rate, degree of survival and quality of the soft tissue) caged at different depths. Based on a combination of mortality and growth rate, we found that the most suitable depth for culture was at 1 m, but culture at all three depths is viable and the main issue is being the source of mortality at 5 m, seasonally. We conclude that Mali Ston Bay has good potential for variegated scallop mariculture.