A beam trawl is used for collecting megafauna, that is to say large benthic fauna (invertebrates and fish bigger than 2 cm). Samples give information on the structure and size of the fauna, and provide the basis for estimations of density and biomass.
A beam trawl comprises a fixed beam which has a metal skid at each end. This rigid structure keeps the mouth of the trawl-net open. Chains are fixed to the underside of the net.
The chains scrape the sea floor and force the benthic fauna into the trawl-net. The aim is to harvest as many animals as possible while collecting the least amount of sediment and rock.
Two trawl nets are available, one with a 6 m beam, the other with a 4.4 m beam.