To glue or not to glue? Reassembling broken otoliths for population discrimination
The Marine Research Institute in Iceland has a valuable sample of otoliths from DST tagged Atlantic cod (Gadus morhua). This sample has been used in several studies that have increased the knowledge of the cod stock around Iceland. An ongoing study of the otolith shape differences between Coastal and Frontal cod in Iceland employs the otoliths from the DST tagged cod. One problem exist with the sample, which is that many of the otoliths have been broken for aging. Twenty five randomly sampled cod otoliths were, therefore, measured using 8 shape measurements along with Fourier analysis of their outlines to test whether gluing broken otoliths affects morphological analysis. The effects were significant in seven of the eight shape measurements, but not in the Fourier Descriptors. The effect is however so small that it has no effect when applying discriminant analysis such as Cluster Analysis.