Cod (Gadus morhua L.) between the Stocks off West and East Greenland in 1984–86 by Means

A method to identify individual cod (Gadus morhua) originating from either of the nurs-ery areas off West or East Greenland is described. The method is based on a visual classi-fication of individual annuli of the cod otoliths (sagitta) into three different types based on the formation of opaque and hyaline zones. The different hydrographic conditions off East and West Greenland probably affected the growth of the cod and were thus manifested as natural tags, in the form of different annuli of the otoliths. The calculation of emigration and immigration rates using the otoliths as natural tags confirmed the cod migration derived from tagging experiments, i.e. a one-way migration from West to East Greenland. In 1984–86, a very strong and rapid emigration of maturing cod from West to East Greenland occurred. The coefficients of emigration of the cod stock off West Greenland increased with age, pointing to a homing phenomenon as the migration factor