Equivalence of Stock-Recruitment Functions and Parent-Progeny Relationships in Discrete-Time Multi-Stage Models

Area of Science:

• Ecology
• Population Dynamics
• Fisheries Science

Background:

• Fisheries management relies on understanding the relationship between adult fish populations (stock) and new individuals (recruits).
• Traditional stock-recruitment (SR) functions simplify this by directly linking stock size to recruitment, often ignoring complex life-stage dynamics.

Purpose of the Study:

• To evaluate the accuracy of traditional stock-recruitment functions in representing fish population dynamics.
• To develop and apply a more comprehensive multi-stage, age-structured population model.
• To determine conditions under which simplified SR functions may still be applicable.

Main Methods:

• Utilized a multi-stage, age-structured discrete-time population dynamic model.
• Accounted for all life stages and transitions between them.
• Analyzed mathematical conditions for equivalence between multi-stage models and univariate SR functions.

Main Results:

• Demonstrated that a single, closed-form stock-recruitment function often fails to accurately capture recruitment dynamics when multiple life stages are considered.
• Identified specific mathematical criteria where a simplified SR function can be equivalent to a multi-stage model.

Conclusions:

• Conventional stock-recruitment models may oversimplify complex population processes.
• Multi-stage population models offer a more robust framework for understanding recruitment.
• Findings advocate for the adoption of multi-stage approaches in fisheries management for improved decision-making.