A closed life-cycle model for Northeast Arctic cod

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For Northeast Arctic cod (Gadus morhua), there is much knowledge available concerning the main population dynamics processes (growth, maturation, fecundity, recruitment, natural mortality, fishing mortality). This knowledge is incorporated into a biologically detailed age-length structured population model. The model contains four population groups: EggsandLarvae, 0-group, immatures (age 1-10) and matures (age 4-12+). Recruitment to EggsandLarvae is modelled as a function of the number of mature fish and their population characteristics (length and weight), giving a fully closed life cycle. The model is implemented using the Gadget framework for population models, and the details of the implementation are described here. Results of fitting the population model to observations are presented. The utility of such a model in the assessment of current stock status and the exploration of harvest control rules is discussed.