Effect of the presence of the shore crab, Carcinus maenas, on the burrowing behaviour and clearance rate of the common cockle, Cerastoderma edule

Bivalves demonstrate various morphologicaland behavioural adaptations to reduce the risk of beingattacked by predators. This paper examines how the presenceof the crab Carcinus maenas (L.), a natural predatorof the cockle Cerastoderma edule (L.), affects its burrowingdepth and clearance or feeding rate. Cockles wereplaced in experimental tanks and treated with three levelsof predatory disturbance: (1) unfed crab loose inside thetank, (2) unfed crab inside a cage suspended in the watercolumn and (3) no crab present. Cockles’ burrowing depthwas measured in two sediment types: mud and sand.Cockles burrowed more deeply in treatments with no crabs. Burrowing depth in sand was significantly greater than inmud. Two factors may contribute to the reduction in burialdepth of C. edule in the presence of C. maenas: the changein the vertical orientation of the cockle and the ‘coughresponse’. No significant difference was found in thecockles’ clearance rate among the different levels ofpredator threat.