Results from longlining research project

Every aspect of line fishing is considered; from seabed to plate. The project has two objectives: first, to document the relative benefits on the environment using longline gear, and second, to find the quality benefits on the actual product fished by longline compared to other gear.

The project began in January 2006 and is due to be completed at the end of this year. The partici¬pants are Mustad Longline (project owner), Domstein, TraceTracker, Nofima and Østfold Research Foundation. The project is part of the BIA program financed by the Norwegian Research Council.

Østfold Research was responsible for the study of environmental impacts. This is a unique study because it takes into account the whole value chain from catch to final product.

The research found the fishery to be the most important phase due to energy use and environmental impact, but the potential for improvement has been identified on the boats and through the whole value chain. For example, better control of cooling systems on the boats can give up to 30% reduction of climate gas emissions, better temperature control in processing, and might be used for reduced use of ice in transport.

Different studies say that passive catching methods are more energy efficient than active and this project supports that. Also, less energy leads to less climate gas emissions, relatively.

Quality assessment of cod caught by trawling and longlining was carried out by Nofima. A total of 47 headed and gutted cod were analysed for pH, texture, colour, sensory quality, water binding capacity, drip loss and catching injuries. The cod was caught in the southern part of the Barents Sea in the end of May 2009, frozen onboard the fishing vessel and stored frozen until use.

The research shows a clear difference between the two groups. All the responses, except for drip loss, made it easy to distinguish between the two catching methods. Both sensory analysis and catching injuries had a significantly higher quality score on longlined cod compared to trawled cod, showing an increased amount of blood in the fillets. Colour analysis confirmed these findings, concluding with a significantly redder fillet from trawling. Texture analysis evaluated the longlined cod to have a firmer flesh than trawled cod. Both blood in the fillet and a softer fillet can be related to the stress on the cod during trawling. This stress is not present during longlining.

The pH was increased in longlined cod compared to trawling, resulting in increased water holding capacity, which can be related to stress while soaking on the line. The project concludes that longlining gives a better quality than trawling. All the quality parameters indicated higher quality, with less blood, firmer fillet, and better water holding capacity and higher sensory score on cod caught with longline in contrast to trawling.

The effects of the catching method on stress and quality of saithe were studied by Nofima. In the autumn of 2008, 77 saithe with a mean (SD) size of 1.89 (0.43)kg were caught at 80-110m depth in Lofoten, Norway. The different catching methods were longline and hook and line. In addition, one group of longlined fish was chased to exhaustion for 15 minutes. The blood of these three groups was analysed for pH, sodium (Na+), potassium (K+), hematocrite (Hct), hemoglobin, glucose, Lactate, partial pressures of blood gases of carbon dioxide, oxygen and bicarbonate (HCO3-). The pH, colour, texture and water holding capacity were measured seven days after slaughtering to assess the quality of the muscle.

The results showed that hooking caused an acute stress reaction accompanied by increased lactate levels and disturbed acid-base balance. Longterm effects of stress were observed in longlined fish with increased blood glucose levels, high Na+, K+, Hb content and Hct. Longlined fish had however restored their acid-base balance, having significantly higher blood pH and HCO3 levels, reflecting hyperventilation. Hypoxia occurred only in one case. The project concluded that angling causes a release of primary and secondary stress responses in saithe associated with acute stress and flight reactions fatiguing the animal. This species has the physiological capability to restore its acid base balance during soaking and thereby staying alive until hauled onboard 6-12 hours later for slaughter. From a welfare perspective, hook and line is recommended, but from a commercial standpoint longlining saithe is applicable from food safety and quality reasons.

Nofima concludes that stress had no effect on the flesh quality and none of the investigated quality parameters revealed differences between the groups.

Christian H. Engh, Managing Director of Mustad Longline sums up the project as follows: “We started out as a group of people in companies representing the entire value chain of longline caught fish who all felt very passionately about our the quality and sustainability of this product. Now we have very strong evidence that both the environment and the quality conscious market will benefit from more longlining in the future.”