The Exploitation of Cockle Shells

The cockle, a delicacy in southern Europe, is harvested with specialized dredgers; however, this method leaves tracks on the seabed. The current draghead was redesigned at the University of Technology Delft to counter this problem. The track depth is caused by the force of jet water; however, this cannot be reduced due to the high pulling forces. Design alternatives included the use of serrated knives to pick up the cockles without the sand, reducing the need for jet spray. Laboratory tests identified a best solution as a serrated knife with straight round bars connected at the back, which optimizes the flow through the knife and eliminates the need for jet water.