Skipped spawning is common for the Northeast Arctic cod in a life-history energy allocation model

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That iteroparous fish reproduce every year after they have become sexually mature is a common assumption in fisheries science. Experimental and field studies suggest, however, that mature fish commonly skip spawning, often but not only in relation with failing food resources. This study presents a life-history model based on optimal energy allocation for the Northeast Arctic cod. Ingested energy can either be allocated to growth or to storage for the next spawning period. This trade-off embodies lifelong patterns of growth, maturation, and reproduction. The allocation decision was optimised based on five individual states: age, length, size of energy stores, month of the year, and the current food availability. The model showed that skipped spawning was partly related to periods of low food intake (there was not sufficient energy to spawn), but that it also played a central role in life-history: spawning should be omitted because of the benefits that come from growth to a larger size. Skipped spawning was most common in the years just following maturation. The influence of several parameters was tested, and skipped spawning was more common when: 1) juvenile mortality was high; 2) mortality at the spawning grounds was low; 3) the energetic cost of migration was high; and 4) food intake was low.