A radiological study on vertebral deformities in cultured and wild Atlantic cod (Gadus morhua, L.)

Vertebral deformities are a major challenge in cod culture. To study which vertebral deformities are present in cultured and wild cod, we examined two year-classes (14.4 ± 1.5 cm (mean length ± SD) and 15.8 ± 1.6 cm) of intensively cultured cod, two year-classes (13.9 ± 1.9 cm and 16.3 ± 1.6 cm) of extensively cultured cod, and wild cod caught in the autumn of 2005 and 2006 (17.2 ± 3.4 cm and 23.6 ± 7.7 cm), for vertebral deformities (radiology). The prevalence of individuals with one or more deformed vertebrae was significantly higher in the extensively (37.0 and 30.0%) and intensively (44.8 and 45.0%) cultured cod than in the wild cod (5.8 and 6.1%). Both the intensively (12.5 and 17.2%) and extensively (5.0 and 14.8%) cultured groups had a curvature (lordosis) in the region of the vertebral column, located between the second and third dorsal fin. Furthermore, a group of individually tagged intensively (35.1 cm ± 1.9 cm) and semi-intensively (36.7 ± 2.6 cm) cultured cod was radiographed twice, with one year interval, to investigate how deformities develop with time. In some cases, normal vertebrae became deformed with time; in other cases deformed vertebrae became more severely deformed.