A new benthic macrofauna and sediments sampler for attaching to otter trawl nets: comparison with the Van Veen grab

Most bottom trawling around the world occurs in shelf areas covered by unconsolidated sediments, which can negatively affect bottom communities in several ways. We present a new bottom sampler device that can be attached to trawl nets or other bottom fishing gears. This device consists of a steel tube with a piston positioned in the interior to slide the material collected after the trawling and two lateral supports for fixing the device to the footrope of the trawl. Sampling design consisted in comparison two distinct sites, in each of them were conducted three tows with the sediment sampler device and at the begin and final of each tow it were collected sediment samples with Van Veen grab. PERMANOVA test on macrofauna composition indicated no significant difference in relation to both sampler devices. During the experiment, was not detected any problems in relation to positioning and using the new sampler. The addition of extra weight to the ballast cord did not unestablished the net and the device returned to the surface full of sediment in all the trawls, thus enabling the analysis of macrofauna and sediment particle size. Since this device does not interfere with the operation of the vessel or fishing performance, suggest a promising use of this equipment to collect samples in soft bottoms, as well as analysis of macrofauna and determining the size and composition of sediment.