Sebastian Glindtvad, Master Student

Thesis title: Morphometric Analysis of Cod (Gadus morhua) Otoliths

Four genetically different populations of cod (Gadus morhua) inhabit the waters along the coast of Greenland. These populations share habitats on the west coast, and current available fishery management tools for population separation are restricted to Genetic classification. As genetic classification is both time consuming and expensive, alternative classification methods are need. In this study, the use of otolith outline shape analysis as a tool for population separation was investigated. Both Discrete Wavelet Transform and Normalized Elliptic Fourier were used. The whole outline of the otolith, as well as the outline of the 1st and 2nd year increments were used for shape analysis. Normalised Elliptic Fourier showed more potential than the Discrete Wavelet Transform for populations classification. Two out of the three populations could be classified with a high mean classification rate (>70%). The 1st and 2nd year increments provided a lower mean classification success (<65%) than the whole shape of the otolith. Neither genetics nor environment were found to have a significant influence on the whole otolith shape. Age group separated shape analysis indicated a possible migration from inshore areas to offshore areas by the West Greenland Offshore cod population. Further studies should be done to investigate a combination of shape analysis and other population classification methods for fishery management purposes.

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