Preferential prey and attacking strategy of the purple dye murex (Bolinus brandaris) on three common bivalve species from Tunisia (Central Mediterranean Sea)

The purple dye murex (Bolinus brandaris) is an active predator that feeds mainly on bivalves, barnacles and other gastropods, further supplying its generalist diet through scavenging and cannibalism. The present study investigated B. brandaris feeding behaviour on three bivalves commonly found in the Bizerte lagoon (northern Tunisia): the unexploited lagoon cockle (Cerastoderma glaucum), and the harvested and commercially valuable carpet shell (Ruditapes decussatus) and Mediterranean mussel (Mytilus galloprovincialis). The purple dye murex showed a clear preference for feeding on C. glaucum and R. decussatus, distantly followed by M. galloprovincialis. Signs of attack were clearly visible in R. decussatus shells, but not in the other two bivalve species. Overall, B. brandaris attacked bivalves mainly by chipping and/or drilling their shells, but opening the valves was the most common feeding strategy. The present study provides a brief description of the predatory behaviour of the purple dye murex, together with the quantification and illustration of the attack patterns (chipped, drilled and/or broken valves) on these bivalve prey. Besides improving the current knowledge on the feeding ecology of the purple dye murex, this study provides helpful information for small-scale fisheries targeting this species and to further assess the aquaculture potential of B. brandaris.