Understanding the determinate–indeterminate fecundity dichotomy in fish populations using a temperature dependent oocyte growth model

• We modeled the fecundity type in fishes based on the relationship between oocyte growth period and duration of spawning.
• Simulations showed that stocks with OGP longer than the SP are predicted to exhibit determinate fecundity and vice versa.
• Oocyte size frequencies and time trends in fecundity match descriptions for determinate and indeterminate spawners.

The fecundity type (determinate vs. indeterminate) is still uncertain for many commercially important fish populations affecting accuracy in fecundity estimations and hindering the selection of appropriate egg production methods for stock assessment purposes. It is broadly considered that boreal fish populations living in colder habitats are determinate spawners whilst populations residing in warmer habitats tend to be indeterminate spawners. In the present study we modelled the determinate–indeterminate fecundity type in batch spawning fishes, i.e. fish that spawn several batches of eggs per spawning season, based on the relationship between oocyte growth period and the duration of the spawning period considering that both variables can be affected by water temperature and latitudinal distributions. Individual based models (IBMs) were developed to explore how the interaction of these variables can result in a series of patterns along the continuum from extreme determinacy, i.e. annual fecundity being recruited long before the onset of the spawning period, to indeterminacy. Model simulations showed that fish stocks with oocyte growth periods longer than the spawning period are predicted to exhibit determinate fecundity which provides a fair justification for why cold water species with slow oocyte growth and limited spawning periods are determinate spawners and vice versa.