Walking along the beaches of the North Sea coast, one frequently encounters orange and blue fragments of "Dolly Ropes". This is the chafing protection used underneath the demersal trawlers of the Dutch fleets, which are MSC-certified as "sustainable". Since the early 1990s, these robust plastic threads have been used in German, Dutch, and Danish demersal trawl fisheries. Consequently, these extremely durable polyethylene plastic threads, which are deliberately woven under the nets, are repeatedly found on the demersal trawls of ships, tearing off during fishing operations and remaining in the marine environment.
For some time, research has been conducted into alternatives to these plastic threads, which are lethal to marine fauna. One objective of the research at the Thünen-Institut (Johann Heinrich von Thünen-Institut, Bundesforschungsinstitut für Ländliche Räume, Wald und Fischerei), for instance, was to modify the design of the fishing gear to eliminate the requirement for chafing protection. Alternative materials to "Dolly Ropes", such as leather, have also been trialled in the past. The final report of the 2022 project "Verringerungen von Kunststoffmüll aus der Krabbenfischerei durch Netzmodifikationen – Dolly Rope Suspension (DRopS)" states: "The project has demonstrated that sufficient alternatives to the use of Dolly Ropes exist. A large proportion of the German shrimp fishery already utilises at least one of the two aforementioned options and dispenses with the use of Dolly Ropes. This confirms that Dolly Ropes are dispensable. A complete renunciation of Dolly Ropes by the entire fishery could be achieved through the creation of effective incentives or regulatory measures."
Regrettably, the situation in the Netherlands remains different, which is why particularly large quantities of "Dolly Ropes" can be found (and ideally disposed of) on the beaches of Zeeland, Holland, or Texel. The fishing vessels of the Dutch fleet are generally larger and more industrialised than the traditional German "Krabbenkutter". Here, "Dolly Ropes" continue to be used extensively. The Thünen-Institut report states: "It is estimated that within the first few weeks, approximately 10-15% of the newly attached material tears off. In total – according to Dutch researchers for the Dutch fishery – around 25-50% of the Dolly Ropes used end up in the sea."
However, there is also a development in the Netherlands – arising from a context that is perhaps typical for the country: bicycles. This is because bicycle tyres represent a waste material that is significantly more abundant here than in neighbouring European countries. When curved segments of these tyres are attached to demersal trawls with cable ties, they replace the polyethylene ropes. On some fishing gear, leather strips are also used, though still in combination with blue "Dolly Ropes".
Nevertheless, these partly non-natural composite materials will also abrade and remain on the seabed. However, for northern gannets (Morus bassanus) and common guillemots (Uria aalge), these bicycle tyres do make a difference. Approximately 75% of their nesting material on the island of Heligoland consists of "Dolly Ropes" made of polyethylene, which are lethal to these birds. The experiment with bicycle tyres may represent an initial step in the right direction.
It remains to be seen what the outcome will be.
Source: https://literatur.thuenen.de/digbib_extern/dn065718.pdf
