NCEAS Product 3360

Stenseth, Nils; Bjornstad, Ottar N.; Falck, W.; Fromentin, J.; Gjosaeter, J.; Gray, John S. 1999. Dynamics of coastal cod populations: Intra- and intercohort density dependence and stochastic processes. Proceedings of the Royal Society B-Biological Sciences. Vol: 266(1429). Pages 1645-1654. (Abstract)


Skagerrak populations of Atlantic cod (Gadus morhua L.) have been surveyed at several fixed stations since 1919. These coastal populations consist of local stocks with a low age of maturity and a short life span. We investigated 60 time-series of 0-group juveniles (i.e. young of the year) sampled annually from 1945 to 1994. An age-structured model was developed which incorporates asymmetrical interactions between the juvenile cohorts (0-group and 1-group; i.e. one-year-old juveniles) and stochastic reproduction. The model was expressed in delay coordinates in order to estimate model parameters directly from the time-series and thereby test the model predictions. The autocovariance structure of the time-series was consistent with the delay coordinates model superimposed upon a long-term trend. The model illustrates how both regulatory (density-dependent) and disruptive (stochastic) forces are crucial in shaping the dynamics of the coastal cod populations. The age-structured life cycle acts to resonance the stochasticity inherent in the recruitment process.