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Stochasticity and determinism: how density-independent and density-dependent processes affect population variability.

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Environmental stochasticity and density dependence impact fish populations. Density-dependent survival in juveniles is key to regulating Northeast Arctic cod abundance and resilience.

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Area of Science:

  • Ecology
  • Population Dynamics
  • Fisheries Science

Background:

  • Population variability is driven by environmental stochasticity and density dependence.
  • The timing of density regulation influences stochastic effects on population abundance.
  • Understanding these factors is crucial for managing exploited fish populations.

Purpose of the Study:

  • To develop a life-cycle model for Northeast Arctic cod.
  • To disentangle density-independent and density-dependent processes in early life stages.
  • To quantify compensatory density dependence and its role in population dynamics.

Main Methods:

  • Life-cycle modeling of Northeast Arctic cod.
  • Incorporation of survey and commercial harvest data.
  • State-space approach to account for observation error and stochasticity.

Main Results:

  • Density-dependent survival in juveniles is critical for population regulation.
  • Juvenile stage largely determines the population's compensatory capacity.
  • Density regulation at the juvenile stage dampens earlier stochastic impacts.

Conclusions:

  • The timing of stochastic and regulatory processes significantly affects adult abundance variability.
  • Quantifying environmental stochasticity and compensatory mechanisms is vital for predicting population responses.
  • This research provides insights into cod population dynamics under climate change and fishing pressure.