On the stock estimation for a harvested fish population

Area of Science:

• Ecology
• Population Dynamics
• Fisheries Science

Background:

• Harvested fish populations require accurate stock assessment for sustainable management.
• Stage-structured models are crucial for understanding population dynamics.
• Estimating stock state, especially with nonlinear recruitment, presents significant challenges.

Purpose of the Study:

• To develop a robust observer for estimating the stock state of a stage-structured fish population.
• To address the challenge of unknown recruitment functions in population models.
• To provide a dynamical estimation of stock state for each stage class.

Main Methods:

• A discrete-time, stage-structured population model with a nonlinear recruitment relationship was employed.
• An auxiliary dynamical system (observer) was designed to estimate the stock state.
• The observer utilizes catch data from each time interval for estimation.

Main Results:

• The developed observer successfully provides dynamical estimates of the stock state for each stage class.
• The observer demonstrates effectiveness even when the population's recruitment function is not well-defined.
• The approach is validated for its ability to handle uncertainties in population dynamics.

Conclusions:

• The proposed observer offers a reliable method for estimating fish stock status in stage-structured populations.
• This technique is valuable for fisheries management, particularly when recruitment dynamics are uncertain.
• The study extends previous work on age-structured models to stage-structured systems.