Relative growth and reproductive cycle in two populations of Bolinus brandaris (Gastropoda: Muricidae) from northern Tunisia (Bizerta Lagoon and small Gulf of Tunis)

A study on the relative growth and reproductive cycle of the purple dye murex (Bolinus brandaris) was performed from March 2007 to February 2008 in two populations with contrasting imposex levels (Carthage Byrsa — CB in the small Gulf of Tunis and Menzel Abderrahmane — MA in the Bizerta Lagoon). Both populations presented balanced sex ratios. Comparison of allometric relationships established between linear and ponderal variables (sexes confounded) revealed higher growth in CB than in MA. Mature individuals were found throughout the year, except for September in MA. Spawning periods occurred from March–April to May and from June to August in both sites. Spawning was associated to an increase in seawater temperature. Besides increasing the current knowledge on the biology of B. brandaris from the southern Mediterranean, the information gathered in the present study constitutes a useful baseline for the sustainable management of local wild stocks, namely by prohibiting collection of snails during the spawning season.