| Summary: | That sexually mature fish skip reproduction, especially in response to poor condition, has been documented in many species. We present results from an energy-allocation life history model that shed light on the underlying logic of skipped spawning, based on the Northeast Arctic stock of Atlantic cod (Gadus morhua). The model predicts that skipped spawning is a regular phenomenon, with up to 30% of the sexually mature biomass skipping spawning. Spawning should be skipped if the expected future gain in reproductive output, discounted by survival, more than balances the expected reproductive success the current year. Skipped spawning was most common (i) among potential second-time spawners and (ii) early in life, (iii) when fishing mortality at the spawning grounds was high, (iv) when fishing mortality at the feeding grounds was low, (v) when natural mortality was low, and (vi) when the energetic and mortality costs associated with migration and spawning were high. Cod skipped spawning more often when food availability was both increased (opportunities for better growth) and decreased (too little energy for gonad development), and this pattern interacted with mortality rate. We conclude that skipped spawning may be more widespread than appreciated and highlight potential consequences for the understanding of stock-recruitment relationships.
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