A recent study conducted by Nofima and the Norwegian University of Life Sciences, funded by the Norwegian Seafood Research Fund, has revealed that rib fractures and deformities, not feed or genetics, are the primary cause of dark melanin spots in farmed salmon fillets. The research followed a group of fish from their freshwater phase to slaughter and compared their findings with wild fish, discovering an average of four rib defects per fish in both freshwater smolt and wild salmon, which increased to 10 defects per fish after transfer to sea. The study suggests that improving the fish's conditions during this period could help prevent these issues, and further research is needed to explore the possibility of muscle tears contributing to melanin spots. The findings have been peer-reviewed and published in the journal Aquaculture.