Timing and determination of fecundity and skipped spawning: implications for stock-recruitment theory of determinate spawners

To forecast stock size is an integral part of responsible and sustainable management of marine resources, and requires intimate knowledge of stock-recruitment relationships. Models that accurately depict these relationships have therefore long been sought . These models have evolved in complexity from models using correlations between spawning stock biomass and recruitment, to models incorporating the individual state of the spawning females. Incorporating basic biological knowledge is fundamental for cons truction of realistic population dynamics models. However, in determinant spawners, emerging evidence suggest that there may also be a critical time window during early vitellogenesis, which is highly influential for potential fecundity. This time window is likely also linked to the decision to skip spawning, a common occurrence among many mature fish. The energy reserves of the mature population during this time window may therefore have considerable important implications for stock recruitment theory, y et this has never been tested. We will use Northeast Arctic cod (NEA) and Norwegian Spring Spawning (NSS) herring as the study species in a combined laboratory, field and modeling approach, to test the hypothesis that there are sensitive periods where ene rgy levels of individual females are either directly linked to the decision to skip spawning or the potential fecundity of spawning females. All data obtained will be implemented into existing life history and stock recruitment models for these species to improve the models explanatory power. If the same general decision rules for skipped spawning and potential fecundity applies for NEA and NSS, this indicates that similar relationships may be relevant to a large number of commercially important species.