German Federal Agency for Nature Conservation (BfN)


Chart description: Hyrophone and POD placement

The chart shows the marking and anchoring system for an underwater microphone (a hydrophone). The entire system is marked by a large buoy. A cement-filled truck tire serves as an anchor on the sea bed and is attached to the buoy by a nylon rope. About 10 metres above the anchor, a click detector which records sounds made by harbour porpoises is attached to the rope. The hydrophone is attached to the anchor by another nylon rope. The hydrophone is placed in a yellow box called a trawl shield which protects the hydrophone from getting caught up in fishing nets or from being damaged.