Growth of the common Cockle Cerastoderma edule : Validation of the periodicity of increment deposition by Calcein marker
|Author(s)||Bellamy Elise, Mahe Kelig, De Rafelis Marc, Lartaud Franck|
|Meeting||2nd International Sclerochronology Conference, 24-28 July 2010, Germany|
|Abstract||Cockle (Cerastoderma edule) growth has not been studied a lot yet and the current approach of counting external ridges in order to make age estimation is limited. Nevertheless, growth is a key parameter for monitoring bivalves populations, which are heavily exploited in French estuaries. The Bay of Somme which is located in the eastern Channel in the north of France, is the first French field of cockles (Cerastoderma edule). In order to improve stock management, it is necessary to increase our knowledge of this species. This study is looking at the growth of the common cockle.
In this way, recapture of shells previously marked under calcein marker and then breed in natural conditions in the Bay of Somme, was performed in order to determine the shell growth patterns. In a methodological point of view, calcein marking has showed a fluorescent increment in shells stayed for only 30 min immersion time at 150 mg.L-1, but also for shells immersed 3 hours at 50 mg.L-1.
High-resolution pictures analysis with the TNPC software (Digital Processing for Calcified Structures) dedicated by Noesis society and Ifremer, performed on several marked cockles permitted to count 23 increments on average between the mark and the ventral edge of the valves, corresponding to the 12 days experience during which 23 tides happened. The periodicity of increment formation is validated for a tidal frequency. This preliminary study give a clue to the understanding of the cockle growth and could be completed by cockles age monitoring, but also by chemical analysis to learn more about biomineralization process of this species.