| dc.description.abstract | This study presents a comparative age reading on Sebastes marinus from the Icelandic shelf within an otolith
exchange program between institutes in Germany, Iceland and Norway. Out of a series of 212 otolith pairs, one
otolith of each pair was prepared by the break-and-burn technique, while the other otolith was used for crosssections.
Age reading results are compared between readers and otolith preparation methods in terms of bias and
precision, using a set of statistical tests and graphical methods. Significant bias was observed for both the
comparison between readers and between methods, mainly caused by deviations between age scores in the
higher ages (> 20 years). Precision estimates, involving the high longevity of redfish, were relatively good
compared to previous age reading comparisons using other species. In contrast, the age dependent percent
agreement was poor (< 30%) for a tolerance level of ± 0 years, particularly for the age range 21-30 years. A
tolerance level of ± 3 years, however, lead to around 90% agreement for the age range up to 20 years. The fit of
age reading scores with the von-Bertalanffy growth curve was relatively good, providing growth parameters
comparable to S. marinus from the Norwegian shelf. The observed problems in bias and precision of age
readings should to be improved by continuing with similar Sebastes otolith exchange programs and setting up a
further age reading workshop to harmonise the interpretation of growth structures. | en |
