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Population dynamics of coastal Cod: The state-space / delay-coordinate equivalence and time series analysis of abundance
Applied Math| Speaker: | Ottar Bjornstad, Penn State |
| Location: | 693 Kerr |
| Start time: | Fri, Nov 15 2002, 4:10PM |
This talk has two interlinked themes. (1) How the age-structured dynamics of fish populations can be understood on the basis of stochastic state-space models and (2) how time-series analysis can be guided by theory: first, through direct estimation of the state-space model; and second, how the delay-coordinate representation of the model motivates particular autoregressive time-series models. After outlining and discussing the statistical / inferential issues, I turn to the interaction between the inherent stochasticity and the dynamic nonlinearities for population fluctuations. The parameterized stochastic age-structured model predicts apparent trends in abundance that are superimposed on the 'deterministic variability' (high-frequency variability) through a cohort resonance effect. I discuss the anatomy of these internally generated trends, and revisit the rule-of-thumb that long-term changes in abundance can be used as indicators of anthropogenic (or other external) forcing.