engleski

Age, growth and population structure of the Modiolus barbatus (Linnaeus 1758) in the Mali Ston Bay, Adriatic Sea

Age, growth and population structure of the bearded horse mussels Modiolus barbatus (Linnaeus 1758) was investigated in Mali Ston Bay, Adriatic Sea, in a period between January and December 2004. Samples were collected monthly (N=189-559) by SCUBA at depths between 3 and 5 m. Lengths of 4265 shells were measured to the 0.1 mm using vernier calipers. Mean shell length was 33.73± ; ; 12.68 mm (range from 1.7 to 65.5 mm). Smallest mussels were recorded in a period from May to September. Throughout the study only 0.8 % of the M. barbatus were greater than 55 mm. Length frequency data were analysed using the method of Bhattacharya in the FiSAT statistical package and von Bertalanffy growth equation was constructed Lt = 66.11 (1-e-0.181t+0.013). In addition, age and growth of M. barbatus were estimated from growth rings on the internal shell surface. Total of 200 shells (X=37.69± ; ; 7.76 mm) collected during 2004 were analysed in this way. Growth rings were either not clearly visible or pronounced disturbance rings were present in 25 shells (14%) and these were not included in the analysis. Distances between clearly visible individual growth rings were measured and Gulland-Holt plot was constructed from the obtained data. Modified von Bertalanffy growth equation was Lt = 63.21 (1-e-0.185(t-t0)) and it was similar to the one obtained by length frequency analysis. According to the results of this study M. barbatus attains length of 40 mm in its 5th year of life and that of 50 mm after its 8th year. Majority of population living in Mali Ston Bay is younger than 10 years. However, as this species can grow up to 65 mm it is possible that it can live for over 15 years.

bivalve ; age ; growth ; Adriatic ; Modiolus

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