An illustrated manual for macroscopic determination of Baltic cod reproductive status

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The manual has been elaborated with the purpose to improve determination of Baltic cod ( Gadus morhua L.) reproductive status and thereby the data basis for estimation of spawning stock size and reproductive potential. The macroscopic determination is based on a 10-level index scale applied by the Danish Institute for Fisheries Research (DIFRES) and the Institute for Marine Sciences (IFM) onboard research vessels. The method considers that macroscopic staging is a rapid method in the field, but that validation by more accurate measures is a necessity to ensure data quality. The photo documentation of the various stages aims at reducing deviations caused by subjective judgement and thereby further improving the quality of data.