THE VOYAGE OF THE CHALLENGER
"One of the great accomplishments of the Challenger expedition was the collection of deep and shallow water biological specimens throughout the world. At left is a shallow-water dredge, whereas a deep-sea trawl is shown at right.
Consider the difficulties of sampling: One trawl was put over the side at 9 A.M. in a bottom sounded at 1950 fathoms (11,700 feet or ca. 3,600 meters). "The trawl was hauled in at 5 P.M. The beam was broken through the middle, and otherwise strangely torn and crushed, by the combined action of the of the pressure to shich it had been subjected, and the strain of pulling it up rapidly through three miles of water. The wood was driven in and compressed so as to reduce the diameter of the beam by half an inch, and the knots projected a quarter of an inch on all sides."
The samplers lacked a closing device, which later proved to be a real disadvantage for the deep-sea trawl. Many organisms were washed out, and this led to a mistaken impression that the deep-sea bed was uniformly depauperate of species. Nearly a century later, Howard Sanders and Robert Hessler used better samplers and showed that deep-sea bottoms could be rich in soft-bottom benthic species."
Note: Click HERE for fascinating site.