Radiometric age validation of golden redfish (Sebastes marinus) and deep-sea redfish (S. mentella) in the Northeast Atlantic

Ages of golden redfish (Sebastes marinus) and deep-sea redfish (S. mentella) in the Northeast Atlantic were determined by measurement of natural radioisotopes in their otoliths. Using samples from S. marinus around Iceland as well as S. mentella off East Greenland and in the Irminger Sea, 226Ra and 210Pb activities in otolith cores, pooled by fish length groups, were measured by alpha-spectrometry. The ratio of these isotopes provided radiometric ages for the investigated 20 samples, which in general corresponded well with the expected radioactive ingrowth curves and with annulus-derived age estimates for fish of the same length group. Radiometric ages of S. marinus with 10-55 cm body length ranged from 3 to 31 years, while S. mentella from East Greenland (17-35 cm) exhibited radiometric ages of 8-15 years, and S. mentella from the Irminger Sea (26-45 cm) showed a range of 15-41 years. A slight tendency towards an underestimation of ages by annulus counts could be inferred from the comparison with the derived radiometric ages. Considerable differences between ageing methods were found for Icelandic S. marinus over 40 cm length and pelagic S. mentella from the deeper layers of the Irminger Sea, indicating problematic annulus-derived age estimation for these groups. This study confirms slow growth and high longevity of Northeast Atlantic redfish and delivers the first radiometric age validation for S. marinus.