A project in Norway has examined pelagic/semi-pelagic trawling for cod which could lead to lower fuel consumption for fishing vessels. Photo: istock
A project from the University of Tromsø (UiT) – The Arctic University of Norway, has examined pelagic/semi pelagic trawling for cod which could lead to lower fuel consumption in trawling for the fish stock.
Fishing with pelagic trawls in the Barents Sea (north of 64o N) was banned over 40 years ago. Changes in fleet and operating structure, changed quota basis, together with demands for cost-effective fishing without too large a climate footprint, lead to demand for changes to trawl technology in Norway.
Cod, haddock and pollock are largely fished with bottom trawls in the sea fishing fleet. Over the past 20 years, bottom trawl technology has been developed into a double trawl arrangement for fishing trawls and the size of modern trawlers requires considerable machine power. The technology, which entails both relatively large climate emissions and stress on benthic fauna from the trawl fleet, is under constant criticism. This project was initiated to obtain a knowledge base to simplify the process of searching for basic information for the selection of technical solutions.
Opening will be able to provide environmental benefits
This report has been compiled from input from business operators with experience from bottom pelagic and semi-pelagic trawl fishing in Norwegian waters. Several of the users, partly supported by research reports, believe that it is justifiable to allow the use of pelagic/semi-pelagic trawls in fishing for cod, haddock and pollock north of 64°N and that the principle of free choice of gear should apply. This is justified by the fact that fuel costs per kilogram of fish are reduced, damage to benthic fauna is avoided and by-catch of unwanted species is avoided. All in all, fishing becomes more rational.
Other fishermen express scepticism about free choice of gear and believe that the use of pelagic/semi-pelagic trawls should be tested to a greater extent over several seasons before a final conclusion is drawn. Challenges in avoiding undersized cod are particularly pointed out. Several research reports show that pelagic trawling for cod and haddock in northern waters has produced highly variable results. Opening up the possibility of using pelagic/semi-pelagic trawls will provide an environmental benefit in the form of lower fuel consumption and less wear and tear on the gear and a reduction in marine litter. Several players specify that an opening for pelagic/semi-pelagic trawl fishing must not lead to a ban on bottom trawling.
The main findings of the research:
- Pelagic trawling can exploit good deposits of cod and haddock that are pelagic. Cod and haddock only occasionally have a pelagic distribution, which provides catches of commercial size with pelagic trawls. Bottom trawling must therefore still be allowed, while pelagic trawling should be allowed as a supplement and not be prohibited as it is today.
• The rope resistance for semi-pelagic trawls is on a par with the bottom trawls used in the Barents Sea. Larger opening enables higher catch rates, shorter towing time and lower fuel consumption compared to bottom trawls. Bottom trawls with pelagic trawl doors can reduce fuel consumption by 12-17%.
• The selection properties of existing sorting grids are reduced at high fish density in pelagic trawls because the grid area is too small. Handling problems make it challenging to increase the area of existing grates. Exit Window or T90 meshes in pelagic trawls provide very good selection for cod. Shorter lead rope in the trawl bag keeps the meshes open and increases selection. Mesh selection and shortened leader lines can be used in the Barents Sea to replace or supplement other selection devices. Good experience has been gained with Excluder for selection and bycatch reduction in industrial trawling. This can have transfer value and can be adapted to pelagic trawling for whitefish. There is less bycatch in pelagic trawls compared to bottom trawls.
• Catch limitation in pelagic trawls can prevent large hauls. Different systems for catch limitation in pelagic trawls have been tested and there are several current systems, such as thin wire and catch limitation systems from seine seines. New selection systems and catch limitation systems must be tested and developed further before they can be used in commercial fishing. New trawl designs can contribute to a more gentle fishing operation and a higher quality of raw material for both pelagic trawls, semi-pelagic trawls and bottom trawls.
• Semi-pelagic trawling can reduce bottom impact by lifting the trawl doors from the bottom and can be as effective as bottom trawling for large concentrations of fish. At the same time, it will be possible to achieve reduced tool costs due to less wear and tear. This results in less litter in the form of macro and microplastics. Semi pelagic trawling techniques do not require changes to the current technical regulations.
Conclusion and recommendations from the project
- A further dispensation is granted from the ban on the use of pelagic/semi-pelagic trawls in fishing for codfish (cod, haddock and pollock) north of 64°N.
- Carry out controlled trials to document time and energy consumption per kilogram of fish using pelagic/semi-pelagic trawls.
- New trials are carried out at different times of the year to map selection characteristics in pelagic/semi-pelagic trawls for the species cod, haddock and pollack. Selection and catch limitation must have a special focus.
- It would be desirable to survey the quality of fish caught with pelagic/semi-pelagic trawls (external/internal crush injuries, barotrauma, etc.)
FHF believes that the results provide a good basis for the industry and administration to introduce measures that contribute to improving bottom impact and energy consumption in bottom trawls.