Trawls were rugged metal nets used at a variety of depths to collect
larger animals. The Challenger crew found it easier to use trawls,
rather than the heavier and more awkward dredges, when collecting
life from the bottom.
Nets of different size and mesh were the primary tool
aboard Challenger for collecting living samples from all depths
of the ocean. A tow net was attached at various depths on the sounding
line, and collected both floating and slow-swimming life forms.