Biometric relationships for the bivalve Ark shell Arca noae(Bivalvia; arcidae) from the Bizerte lagoon (Northern Tunisia)

Abstract

Bivalves are known to exhibit wide morphological variations, which are closely linked to their ecology and reproductive activity. Therefore, the study of growth is necessary to model population dynamics, which, in turn, is crucial to support the exploitation and management of the stock. The current study aimed to analyze the shell morphological variations in the bivalve Ark shell Arca noae collected monthly from the Bizerte lagoon (northern Tunisian coasts) from October 2013 to September 2014. Allometric relationships established between linear variables (shell length and height); weight variables (total weight) and the relative growth between variables (isometry vs allometry) were analyzed. All morphometric relationships were highly significant with high correlation coefficients (R2: 0.604-0.903). Seasonal monitoring of the linear and weight relationship of the A. noae population suggested the presence of a negative allometric growth during the seasons which indicated that Ark shells are growing faster in length than in height and weight. Overall, linear and weight growth in A. noae from the Bizerte lagoon was found to be uniform and synchronous over the seasons and seems not to be influenced by the species’ reproductive cycle. This preliminary study will be useful for further research studies in biology, ecology and stock management of this non-exploited marine resource.