Threats: Bottom trawling

Publication - April 8, 2008
As industrial fishing fleets sweep through the ocean, they are catching much more than what lands on our plates. Fishermen can now locate and track schools of specific fish species and scoop up tonnes at a time with kilometres of nets and hooks. But, due to the indiscriminate nature of many types of gear, targeted species are not the only ones caught in these traps.

The bottom trawl net displayed here is a small example of what is used in the deep sea. The mouth of the trawl net is held open by two steel plate doors that help to keep the net on the seafloor. One company markets what it calls 'Canyonbusters', trawl doors that weigh up to five tons each (our trawl doors here weigh approximately 1.5 tonnes each) and undoubtedly live up to their name. To protect the net from snagging on rugged seafloors, heavy chafing gear is attached to the bottom of the trawl net. A heavy cable is then strung through steel balls or rubber bobbins - known as roller gear or rockhoppers - that can measure a meter or more in diameter (our net also has small rubber rockhoppers which are only approximately 30 cm across). The mouths of the biggest bottom trawl nets are as big as a football field and they are as high as a three storey building.