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Long-Lining Versus Trawling


Long-lining has several advantages over trawling, according to researchers at Nofima and stfoldforskning. The project Fra bunn til munn (From Seabed to Mouth) has been looking at the entire value chain of line-caught white fish.

Whiter and firmer fish fillet

“We have analysed and compared fish caught by long-lining and fish from trawler catches. This has shown that line-caught fish has a whiter flesh and gives a firmer fillet. The most important reasons for the better flesh quality of line-caught fish are better bleeding out and less compression damage,” says researcher Bjørn Tore Rotabakk of Nofima Mat.

Both the compression damage and the poor bleeding out are caused because trawling brings up from five to twenty tons of fish onto the deck each time, while with long-lining the fish are brought on board one by one. Researchers and sensory assessors at Nofima Mat in Stavanger have carried out chemical, technical and sensory analyses in order to assess fish quality.

Taste assessors have judged the fish on colour, texture, smell, splitting and surface, while chefs at the Gastronomic Institute have assessed the flavour. The conclusion of both groups is that line-caught fish has a much higher quality.

Lower CO2 consumption

Østfoldforskning has been responsible for creating a complete environmental audit for line-caught cod. Their analyses show the carbon audit for finished products, which indicates that for each kilo of fish products sold to the consumer there are emissions of 2.35 kilos of CO2 equivalents.

“We have made thorough analyses of line-caught fish and these have been compared with previous data from trawler fishing, including from a recent Icelandic study. This study shows that trawler-caught cod accounts for more than three times the greenhouse gas emissions and energy consumption of line-caught cod. We see that even with very careful estimates, the energy consumption of long-line fishing in Norwegian waters is half that of trawling in the same waters,” explains researcher Erik Svanes of Østfoldforskning.

A survey from Norwegian waters shows that in terms of fuel consumption, an autoline vessel uses 0.32 litres of diesel per kilo of round fish, a normal trawler 0.58 litres and a factory trawler 0.72 litres. All three examples are for fishing far offshore. Coastal fishing with shorter transport distances will naturally have a lower diesel consumption. Coastal fishing using seines, nets or jigs gives a diesel consumption of 0.21 litres per kilo of round fish. Coastal long-lining gives an even lower consumption, about 0.18 litres of fuel per kilo of product delivered to the consumer.

“But the big problem for coastal fishing is that the coastal cod is a threatened species, so it is primarily deep sea fishing that has been assessed in this project,” says Mr Svanes. He adds that another problem with fishing with nets is that it is not unusual to lose the gear, which then remains lying on the bottom. This means that fish continue to swim into the net, causing a great deal of fish mortality over a long period.

More selective fishing and intact sea bed

Lower greenhouse gas emissions are just one of the benefits of long-lining. Other advantages are that the seabed is not damaged, as it is when trawling, and that long-lining is a very selective method. Which means less unwanted bycatch.

“When it comes to selective fishing, long-lining has many advantages. A number of fish, such as spawning cod, are rarely taken on a hook, thus improving conditions for reproduction. If you use big hooks and baits, the small fish do not take them. We are now working on developing baits that are only taken by specific fish species. We already have bait that is only taken by haddock, which is particularly interesting for long-lining in areas where, for example, cod stocks are threatened and fishing for cod is illegal. Developing baits is also interesting from an environmental point of view because fish waste is an important ingredient in the specially designed bait,” explains Mr Svanes.

Eco-certified fish - a good selling point

The Domstein fish group has chosen to buy line-caught fish precisely because of its quality and environmental benefits compared with trawl catches.

“We have long been focusing on the environment at Domstein and through this project we now have scientific evidence of both the environmental and the quality benefits of line-caught fish. This in turn has given us the opportunity to eco-certify this type of fish, which is also an important selling point. Others will follow the trend eventually, so it is an advantage for us to be ahead,” says Bengt Gunnarsson, consultant and former production manager of Domstein.

Domstein’s increasing sales income shows that customers like the sound of selling points linked to the environment and quality. Now the partners in the project wish to go on to look at wider catching methods, as well as how they can develop specially designed bait that, for example, cod of the required size will take.

The project “Fra bunn til munn” is mainly financed by The Research Council of Norway, with contributions from participating industry.

May 2010