State-dependent Energy Allocation in Cod (Gadus Morhua)

Joergensen, C. & Fiksen, O. (2005). State-dependent Energy Allocation in Cod (Gadus Morhua). IIASA Interim Report. IIASA, Laxenburg, Austria: IR-05-067

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Abstract

Growth and maturation are processes that are tuned to the external environment an individual is likely to experience, where food availability, the mortality regime, and events necessary to complete the life cycle are of special importance. Understanding what influences life history strategies and how changes in life history in turn influence population dynamics and ecological interactions are crucial to our understanding of marine ecology and contemporary anthropogenic induced change. We present a state-dependent model that optimises life-long energy allocation in iteroparous fish. Energy can be allocated to growth or reproduction, and depends in the individuals age, body length, stored energy, and the state of the environment. Allocation and the physiological processes of growth, storing energy, and reproduction are modelled mechanistically. The model is parameterised for Atlantic cod (Gadus morhua); more specifically for the Northeast Arctic cod stock. Growth and maturation predicted by the model fit well with field observations, and based on a further investigation of cod reproduction in the model we conclude that the model has the ability to recapture complex life history phenomena, e.g. indeterminate growth and skipped spawning, and therefore provides an important tool that can improve our understanding of life history strategies in fish.

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