Dolly rope (also referred to as ´Chaffe´ in the UK or ‘vahiné rope’ in France) is the name for orange or blue plastic threads that are used to protect (the cod-end) of bottom trawling nets against wear and tear. During fishing, the cod-end usually floats freely in the water. But when stones, sand and/or other material ends up in the cod-end, the cod-end usually sinks and scrapes along the seafloor. In this situation, Dolly Rope acts as a buffer betweethe sea bottom and the cod end of the net, protecting the net from wear and tear. But the effect is that threads or bundles of threads get torn off and end up in the sea.
The use of dolly rope is common amongst different types of demersal fisheries all over the world. In the Dutch part of the North Sea and the Wadden Sea dolly rope is mainly used by bottom trawlers, such as beamtrawlers, pulsetrawlers, shrimping vessels and twin rig otter trawls. Besides Dutch fishermen, the fishing industry in England, Scotland, Ireland, Belgium, Germany and Denmark use dolly rope as well.
Dolly rope consists out of dozens of smaller twisted pieces of rope. These smaller pieces of rope are made out of little polyethylene threads. The diameter of the whole rope varies between 20 to 60mm. It is manufactured in such a way that the little pieces of thread easily loosen when the rope is used.
Fishermen cut the newly acquired dolly rope into pieces of a fixed length. These pieces are folded and attached to the net, often using atie-wrap. The dolly rope is attached to the cod-end, there where the wear and tear is at its highest level.
Dolly rope frays easily and 10 – 25% of the dolly rope ends up tearing off. After two weeks of fishing the strands of dolly rope start to tangle into one another. From that moment onwards, the loss of individual pieces of dolly rope decreases, but at the same time the dolly rope loses its flexibility. The entangled threads cause large amounts of sand and grit to get caught up in the rope, at which point the fishermen often replace the strands of rope with new ones.
The amount of dolly rope used varies per ship and type of fishing, but on average 3-40kg of dolly rope is replaced per month.