Backdown is a procedure for manoeuvring a vessel to facilitate the escape of dolphins from purse seine nets. After encircling dolphins, net retrieval is suspended whilst the vessel reverses, creating a flow of water which creates an opening to enable dolphins and porpoises to exit the net. To maximise effectiveness, it should be combined with a medina panel – a section of finely-meshed netting in the section of the net that regularly comes into contact with dolphins to reduce entanglement.

Source: Barham et al. 1977


The backdown procedure was primarily developed by tuna fishermen for use in purse seine fisheries, and is used by the Cornish sardine ring net fleet in the UK (Pers. comms.) This method (in combination with additional management methods such as onboard observers, take limits, skipper and crew education, and avoiding dolphin ‘hotspots’) were shown to reduce dolphin mortality by 98% in the eastern Pacific yellowfin tuna purse seine fishery between 1986 and 1998. 

The effectiveness of this mitigation technique in other purse seine/ ring net fisheries is unknown.

This page was last updated on 15.02.21.

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