The DDD and the DiD have been designed by STM Products SrL to limit the interactions between marine mammals and fishing nets.
The goal is to protect both the animal’s safety and the fisheries’ profitability. STMhas developed these products in collaboration with prestigious research centers.
Since the first tests the DDD (Dolphin Dissuasive Device) achieved great success in becoming the first solution that showed persistently positive results.
The DDD employment is very simple - just hang it to the nets. The DDD activates as it touches the water and then starts emitting special random ultrasound sequences. These have been studied to interfere with the cetaceans acoustical perception system in order to disturb the identification of the preys in the nets/lines. The random variation of the signals parameters avoids the mammals habituation. All DDD versions emit the same ultrasound sequences, they differ only by the duration of the intervals.
The last evolution of the DDD is the interactive model, DiD (Dolphin Interactive Dissuasor) . This device produces the same modulated signals as the DDD but only when it detects the presence of cetaceans in the area by perceiving their echolocation signals. This strategy improves the interference adding a surprise effect while it increases the batteries life and the charge duration. The placement of several DiD at a regular distance allows a chain reaction that protects the whole net/line.
STM says that there is scientific evidence demonstrating the DDD and the DiD reduce mammals by-catch and the damage to the nets, while increasing the target catch.
The DDD and the DiD are to be placed at least 10m below the water surface, up to 200m depth, but not too close to the sea bed.
The signals reach 150-200m all around (depending on the ambient conditions) and about 80m under the device.
The model, the number of units to place and the position with respect to the nets depend on the type of net, the kind of fishing operation and the mammal species.
