Nofima, the Norwegian research institute, has released a study examining the status and challenges of pigmentation in salmon fillets among Norwegian fish farmers.

According to Nofima scientists, the mapping also provides insights into some solutions that can be pursued further.

The research, led by senior scientist Trine Ytrestoyl and her team, sheds light on factors affecting fillet color, particularly the negative impact of repeated mechanical delousing, a previously undocumented connection.

The study reveals that repeated mechanical delousing significantly diminishes fillet pigmentation, likely due to stress-induced increases in antioxidant consumption, such as astaxanthin, and reduced feed intake. This reduced feed intake may lead to lower slaughter weights, exacerbating the color issue. The findings suggest that fish slaughtered at lower weights to avoid further delousing treatments show even poorer pigmentation.

The investigation, funded by the Norwegian Seafood Research Fund, is based on industry questionnaires from 2023, fillet color data from commercial productions between 2012 and 2023, and data from Nofima's research. According to Ytrestoyl, the strong correlation between the survey responses and the data analysis supports the study's validity, using a realistic picture of the current situation.

The study highlights the variability in how fish farmers experience pigmentation issues. While some report pigmentation problems in only 2% of their fish, others face challenges in 20-40% of their production. There is also variation in the acceptable minimum color standard, with targets ranging from 24 to 27 on the SalmoFan scale and between 5 and 7 milligrams of astaxanthin per kilogram of fillet.

Historical data indicate that the intensity of salmon fillet color in Norway decreased between 2012 and 2021, with a slight recovery after that. However, the variation in fillet color has increased, echoing the survey results that some farmers struggle more with pigmentation than others.

Most fish farmers have addressed pigmentation issues, including increasing astaxanthin levels in feed and incorporating more omega-3 fatty acids and vitamins. Although these measures have had positive effects, they are costly, prompting further investigation into the underlying causes of pigmentation challenges.

The study also points to seasonal variations and rapid growth as factors affecting pigmentation. The researchers were surprised by the significant difference in color at slaughter between suppliers of hatchery fish, suggesting that the hatchery phase may have a substantial impact on final pigmentation. This aspect will be explored further in future research.