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Simple equipment
Drop-trap
A drop-trap is a tool that is used to catch mobile epifauna, organisms
that live and move on top of the sediment on soft bottoms. Such organisms
are small flatfish, whelks, shore crabs, periwinkles, gobies and shrimps.
A drop-trap is easily made out of aluminium plate. A box is formed,
but without a bottom or top (a walled square). It should cover an
area of 0,5 sq. metres, which means that each side should be 0,71
metres in length. Surveying is accomplished when two people carry
the drop-trap on a pole (figure below) above the water surface. When
the drop-trap is over an area that is to be surveyed, it is lowered
onto the bottom. Care should be taken not to tread on the area to
be surveyed. Therefter the edges the drop-trap are controlled so the
sides go against the bottom and no organisms can escape. Afterwards
a net is used to catch all the enclosed organisms which are placed
in jars.
A suitable net is an aquarium or butterfly net, but will probably
have to be reinforced with plastic tubing around the opening so as
not to be worn out to quickly.
A drop-trap standing on the bottom
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